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City of Tamarac Resolution R-89-097
Temp. Reso. #5387 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 125 26 27 28 29 30 3 3" 33 34 35 CITY OF TAMARAC, FLORIDA RESOLUTION NO. R-89-__YZ A RESOLUTION AUTHORIZING THE APPROPRIATE CITY OFFICIALS TO ACCEPT THE SAFE DRINKING WATER ACT STUDY AS PREPARED BY HAZEN AND SAWYER DATED JANUARY, 1989, TAMARAC UTILITIES WEST PLANT EXPANSION, PHASE III, PROJECT #88-53; AND PROVIDING AN EFFECTIVE DATE. WHEREAS, on May 11, 1988, the City Council authorized Addendum #15 to the Agreement with Hazen and Sawyer to provide an evaluation of the effects of new regulations under the Safe Drinking Water Act and develop an implementation plan for phased facility improvements that will allow adaption to regulations as they are developed. NOW, THEREFORE, BE IT RESOLVED BY THE COUNCIL OF THE CITY OF TAMARAC, FLORIDA: SECTION 1: That the Safe Drinking Water Act Study as prepared by Hazen and Sawyer dated January, 1989, Tamarac Utilities West Plant Expansion, Phase III, Project #88-53, a copy of said study being attached hereto as "Exhibit 1", is HEREBY ACCEPTED. SECTION 2: This Resolution shall become effective upon adoption.' PASSED, ADOPTED AND APPROVED this/ day Of 1989. ATTEST: �y CAROL A. EVANS CITY CLERK I HEREBY CERTIFY that I have approved this RESOLUTION as to form. , l 7'C 1dn oAi RICHARD DOODY CITY ATTORNEY u NORMAN ABRAMOWITZ MAYOR RECORD OF CUUNCIL VOTE MAYOR ABRAMOWITZ X DISTRICT 1: C M ROHR DISTRICT 2: C/M U_WR__ DISTRICT 3: C/M HQFFMAN DISTRICT 4: V/M B It KX Nit 51 r-1 �► �_. SAFE DRINHING WATER ACT EVALUATION CITY OF TAMARAC, FLORIDA T.U.W. PROJECT NO.88-53 TAMARAC UTILITIES WEST JANUARY, 1989 HAZEN AND SAWYER, P.C. UAL Engineers TAMARAC UTILITIES WEST SAFE DRINKING WATER ACT EVALUATION JANUARY, 1989 HAZEN AND SAWYER, P.C. ENGINEERS 0.1 � I 0 R- 97-'77 � HAZEN AND SAWYER, P.c. ENGINEERS ffi 5950 WASHINGTON STREET • HOLLYWOOD, FLORIDA 33023 • (305) 987.0066 (305) 625.4101 January 25, 1989 Robert Foy, P-E. = Director of Utilities/Engineering TAMARAC UTILITIES WEST 7805 Northwest 61st Street Tamarac, Florida 33321 Final Issue Tamarac Utilities West Safe Dri-n-kjno haler Act Evaluatlon Dear Mr. Foy: • We are pleased to submit ten copies of this final Safe Drinking Water Act Evaluation following incorporation of review comments from Tamarac staff. We thank you and your staff for your cooperation and your assistance in obtaining the information necessary to successfully conclude this study. very truly yours, HAZEN AND SAWYER, P.C. Patrick A. Davis, P.E. Project Manager George C. Budd, Phd., P.E. Project Engineer Brett P. Samuels . Principal Investigator 4337 1541L/kf NEW YORK NY . HOLLYWOOD FL - MIAMI FL - CHARLOTTE N C - RALEIGH. N C - MT KISCO. N Y . JUPITER FL - NEWPORT NEWS VA l�- Sy- 97 L� • L� EXECUTIVE SUMMARY CHAPTER 1 — INTRODUCTION Report Purpose and Scope ........................... Authorization ........................................ 1-1 Background ........................................... 1-1 CHAPTER 2 — DRINKING WATER REGULATIONS RegulatoryAgencies .................................. 2-1 Current Standards .................................... 2-1 Future Standards ..................................... 2-5 CHAPTER 3 — DESCRIPTION OF EXISTING FACILITIES AND PROJECTED NEEDS FOR FUTURE DEMANDS General..... •.................................... 3-1 Future Demand Requirements ........................... 3-1 RawWater Wells ...................................... 3-1 Upflow Clarifiers .................................... 3-5 Lime Silos/Lime Slakers .............................. 3-5 Chlorinators.. ................................... 3-6 Existing Rapids and Filters .......................... 3-6 LimePond ............................................ 3-6 Clearwell............................... ............. 3-6 Pumps and Piping ..................................... 3-6 Storage.. .......................................... 3-7 PlantNeeds .......................................... 3-7 CHAPTER 4 — EXISTING TREATMENT PRACTICES General.............................................. 4-1 Lime Softening ....................................... 4-1 Filtration........................................... 4-1 Fluoridation ......................................... 4-5 Chlorination....... ...... 4-5 Effect of Future Standards of Treatment Practices.... 4-6 Hwd:1518R/01-24-89 TC-1 ABLE OF -CONTENTS (continued) CHAPTER 5 - BENCH -SCALE AND PILOT TESTING Objectives........................................... Testing Results Methods of Analysis.... ............................ Characterization of TTHM and ................... TOX Formation Characteristics..... .......... Calibration of Bench Scale Test Methods......... Evaluations of Removal of Color, Trihalomethane Formation Potential and TOX Formation Potential by Ferric Chloride and Potassium Permanganate. Evaluations of Chlorine Dioxide as an Alternative Disinfectant. ...... ........... Evaluations of Ozone an an Alternative Disinfectant .................................. Conclusions..................................... CHAPTER 6 - EVALUATION OF SOFTENING WITH LOW PRESSURE RESERVE OSMOSIS CHAPTER 7 - ASSESSMENT OF ALTERNATIVES AND RECOMMENDED IMPLEMENTATION PLAN Treatment Needs.. ... Evaluation of Alternative Treatment �Plans ............ .. Recommended Implementation Plan ...................... APPENDIX A - PRESENT WORTH COST SUMMARY OF ALTERNATIVE WATER TREATMENT SYSTEMS Hwd:1518R/01-24-89 TC-2 PH 5-1 5-3 5-3 5-5 7-1 7-3 7-6 C_J1 0 []I R- 97- C1 IAble Nos _ Title Pa 2-1 Primary Drinking Water Standards 2-2 2-2 Secondary Drinking Water Standards 2-4 2-3 Contaminants to be Regulated by EPA, by June 1989 = 2-6 2-4 Identified Disinfection By Products 2-10 2-5 Disinfectants and Disinfectant By Products Listed in the First Drinking Water Priority List (January, 1988) 2-12 3-1 Water Treatment Plant Design Criteria 3-2 3-2 Potable Water Demand Projections 3-4 4-1 Chemical/Physical Water Charactoristics 4-2 4-2 Water Regulation Compliance 4-3 4-3 Historical TTHM and Chlorine Residual in Distribution 4-7 5-1 Summary of Analytical Procedures 5-4 5-2 Jar Test Calibration 5-7 5-3 Bench Scale Tests for Ferric Chloride Addition After Lime 5-9 5-4 Bench -Scale Tests for Addition of Ferric Chloride and Potassium Permanganate Prior to Lime 5-10 5-5 Chlorine Dioxide Residual Versus Dose and Time 5-13 5-6 Bench -Scale Test for Chlorine Dioxide in Combination with Chloramination 5-14 5-7 Ozone Disinfection of Raw Water 5-18 11 Hwd:1518R/01-24-89 TC-3 • LIST QF TA (continued) 5-8 Ozone Disinfection of Unchlorinated Lime Softened Water 5-20 6-1 Typical Raw Water Characteristics for Reverse Osmosis Evaluation = 6-2 7-1 Alternative Water Treatment Systems Cost Summary 7-5 • Hwd:1518R/01-24-89 TC-4 E Figure No, 3-1 TUW Water Treatment Plant 3-2 Raw Water Well Locations 4-1 Existing Chemical Treatment Process 4-2 Four Treated Water Sampling Points for TTHM's 4-3 Historical TTHM's in Distribution 4-4 Historical Free Chlorine Residual in Distribution 5-1 Chlorine Dosage Effect on Chlorine Residual 5-2 Chlorine Concentration vs. Time Effect on Raw Water TTHM Formation Potential • 5-3 Chlorine Concentration vs. Time Effect on Raw Water TOX 5-4 pH versus Lime Dose 5-5 Ferric Chloride Chemical Treatment Alternative 5-6 Potassium Permanganate Chemical Treatment Alternative 5-7 Ferric Chloride Chemical Treatment Alternative 5-8 Chlorine Dioxide Chemical Treatment Alternative 5-9 Chlorine Dioxide Chemical Treatment Alternative 5-10 Ozone Pilot Plant 5-11 Effect of Ozone Dosage on Ozone Residual in Raw Water 5-12 Effect of Ozone Dosage on Color in Raw Water 5-13 Ozone Chemical Treatment Alternative 5-14 Ozone Chemical Treatment Alternative • Hwd:1518R/01-24-89 TC-5 /?- 4??-? Figure No. Title 5-15 Chlorine Dosage Effect on Chlorine Residual 5-16 Effect of Ozone Dosage on Ozone Residual in Lime Softened Water 5-17 Effect of Ozone Dosage on Color in Lime Softened Water 5-18 Ozone Chemical Treatment Alternative 6-1 Process Schematic of Reverse Osmosis Hwd:1518R/01-24-89 TC-6 r� L L EXECUTIVE SUMMARY The objective of this study is to evaluate effects of new regulations of the Safe Drinking Water Act on planning for water treatment facilities by Tamarac Utilities West (TUW). This planning is necessary to provide a basis for imminent decisions for improvements to the existing water treatment plant. If the existing lime softening system is to be retained in service, the addition of standby softening facilities has been recommended to provide an appropriate level of reliability. A major consideration in electing to provide these standby facilities at this time is the effect of new regulations on future acceptability of the lime softening system and the advisability of continued investment in -this system. Therefore, basic questions addressed in this report are: 1. What degree of flexibility exists within the existing lime softening system for meeting new regulations? 2. What is the most economical course of action for TUW to meet both new and potential future regulations? Because regulations are not fully developed at this time, evaluations were directed towards assessment of capability to meet a broad range of criteria. Pilot and bench -scale testing was . performed to assess capability for modifying plant performance by incorporating new treatment technologies into the existing lime softening treatment facilities at the TUW Water Treatment Plant. Results from these evaluations provided the basis for addressing general process feasibility and siting information for economic evaluations of potential strategies to meet future standards. Basic economic evaluations were also performed to assess low pressure reverse osmosis (RO) as an alternative softening technology. This technology could offer advantages by removing organic matter that can potentially react with chlorine to form undesireable byproducts that are projected for regulation under the Safe Drinking Water Act. The approach to disinfection, presently used at the TUW water treatment plant, involves the addition of chlorine in a manner that results in reactions with background ammonia in the raw water to form chloramines. This method of chlorination, which avoids the higher chlorine dosage range that will form free chlorine as opposed to chloramines, has been effective for limiting the formation of trihalomethanes below presently regulated levels. A critical factor for continued use of chloramination is the extent to which criteria for strong (or primary) disinfection at the water treatment plant will be met under the forthcoming groundwater treatment regulations. Regulations may prohibit the use of chloramine for achieving these criteria. Chloramines may still be appropriate in conjunction with another strong disinfectant for providing a necessary disinfecting residual in the water distribution system downstream of the initial disinfection process at the water treatment plant. Hwd:1565R/01-24-89 S-1 Chlorine application dosages required for free chlorine are not • likely to be acceptable within the existing lime softening system due to concern for formation of trihalomethanes and other halogenated byproducts. Therefore, ozone and chlorine dioxide were evaluated as the most likely alternative disinfectants for meeting primary disinfection criteria. Uncertainties due to present health -related concerns for chlorine dioxide residual make ozone the more logical choice for planning at this time. However, knowledge of disinfection byproducts for alternative disinfectants is evolving and chlorine dioxide may prove to be acceptable within future regulations. Testing performed under this study indicates that_ significant flexibility exists for using ozone and chlorine: dioxide in combination with chloramines to reduce trihalomethanes and other halogenated organics. Therefore, use of these disinfectants has a good potential for allowing the existing lime softening system to be adapted to meet these future standards. However, given the uncertain status of future regulations at this time, no final commitment to an alternative is appropriate until these issues are further resolved by the U.S. EPA. Economic evaluations were performed over a planning period from 1988 to 2008. Three basic alternatives for treatment to meet future regulations were evaluated: 1. Construct a new a mad_-Accelator in 1989 andi inf i • lLrar,tices within the limg sofieningm in 1required for new _regulgtions. A range of outcomes are possible under this alternative. If new standards are not highly restrictive in terms of disinfection and disinfection byproduct requirements, little change in plant processes may be necessary and present disinfection methods may be applicable with slight modification. In the extreme, ozone may be required in conjunction with pre -formed chloramines to meet stringent requirements for primary disinfection, while achieving low levels of disinfection byproducts. Costs are presented for this extreme case. 2. Eliminate addition of-Ahe 8 mgd Accelator and reglaLe existing "m softening facilities With reverse m i R n 1989, A phased approach is assumed involving initial installation of four 2 mgd RO trains and appurtenant facilities in order to provide an initial RO capacity of 8 mgd. Subsequently, 2 mgd trains are assumed to be added in 1996 and 2007, respectively, bringing the overall capacity to 12 mgd by the end of the planning period. This is less than the projected maximum daily demand of 14.6 mgd, reflecting the desirability for avoiding extreme variations in RO operating conditions. This requires that additional storage be provided to meet excess flow requirements under, extreme demand conditions. For the •' Hwd:1565R/01-24-89 S-2 � 1 purpose of this cost evaluation, it was assumed that 10 million gallons of additional storage would be provided to meet this need. This corresponds to approximately 4 days of operation at an incremental flow difference of 2.6 mgd between the 12 mgd production capacity and the 14.6 mgd peak daily demand. Disposal of the waste brine from RO was assumed to require deep well injection. 3. ConstrUCt a new 8 mad Accelato-r--in 1989 and dgfer--con5truction f a rgyerse osmgsis--(RO)r futurerg"tions in 1992. Under this alternative, the new 8 mgd Accelator unit would initially be installed to meet immediate plant needs for redundancy in the existing lime softening system. Replacement of the lime softening system by RO would then be deferred until 1992. At that time, a phased implementation of RO would be initiated resulting in the construction of four 2 mgd trains in 1992, with subsequent 2 mgd additions in 1996 and 2007. Estimated capital, operation and maintenance and total present worth costs for these alternatives for the 20 year planning period are presented in the following table. For comparison purposes, all costs are expressed in terms of a common 1988 dollar base. An interest rate of 8 5/8% was used for computing present worth. CITY OF TAMARAC ALTERNATIVE HATER TREATMENT SYSTEMS COSI SUMMARY (Cost in $1,000) INTERIM 1988 ACCELATOR REVERSE ACCELATOR AND PRESENT CONSTRUCTION OSMOSIS IN CONSTRUCTION OF WORTH_ KLOZOATION IN 1992 _ 1982 RO IN 1222 CAPITAL $ 4,747 $ 12,822 $ 10,977 0&M _ 4.295 14,429 11,785 TOTAL $11,042 $ 27,251 $ 22,762 These analyses indicate that continued use of lime softening, at least on an interim basis, is the most economical approach for TUW. Even if RO is ultimately selected as the treatment technology for meeting future needs, plant rehabilitation and addition of an Accelator unit for interim use of lime softening is more economical than abandoning these facilities in favor of immediate plant modification to RO. Also, by deferring a potential conversion to RO, it is possible to take advantage of any improvements to this technology that might occur during the interim period. Hwd:1565R/01-24-89 S-3 • Maintaining the lime softening system for the interim period retains the option for use of lime softening in conjunction with alternative disinfection methods if such an approach is determined to be capable of meeting future needs. Retaining this option is extremely valuable to TUW since the results in the above table indicate that a significant reduction in present worth costs can be achieved even for relatively conservative assumptions for alternate disinfection methods using ozone as compared with either RO alternative. Even greater savings are possible if future standards allow lower ozone doses or eliminate the need of ozone. A primary reason interim use of lime softening is favored in this case is because most of the facilities for this process already exist, thereby substantially reducing capital cos4s for this alternative. Additionally, raw water available to TUW is more readily treated by lime softening for removal of color and other constituents of concern than are many Florida groundwater sources. Therefore, added costs for modifications to further control these constituents are unnecessary. Given the possible outcomes under these alternatives, the most practical approach is to continue use of lime softening on an interim basis. Subsequently, a decision to modify the existing lime softening system with alternative disinfection approachs or to replace it with RO can be made based on regulatory requirements as they become established. Modifications to provide a standby . Accelator and other necessary rehabilitation measures should proceed as soon as possible so that reliable operation can be maintained for the interim period. Hwd:1565R/01-24-89 S_4 • CHAPTER 1 INTRODUCTION REPORT PURPOSE AND SCOPE (New regulations under the Safe Drinking Water Act and its amendments will affect future water treatment facilities required by the Tamarac Utility West (TUW) Water Treatment Plant. The intent of this study is to provide an evaluation of the effects of these regulations and develop an implementation plan for phased facility improvements that will allow adaptation to regulations:as they are developed.) A need for this type of planning information derives from decisions that are required on near -term improvements to the existing water treatment plant for adding standby facilities and capacity expansion. If the existing lime softening system is determined to be incapable of accommodating modifications necessary for forthcoming regulations, treatment systems to replace existing facilities could be considered. Softening by low pressure RO is being considered by several Florida water systems as such an alternative. Because regulations are not fully developed at this time, . evaluations were directed towards assessing a capability for meeting a broad range of criteria using different treatment technologies. Pilot and bench -scale testing was performed to assess capabilities for modifying plant performance by incorporating new treatment technologies into the existing lime softening treatment facilities at the TUW Water Treatment Plant. Results from these evaluations provided a basis for assessing general process feasibility and sizing information for economic evaluations of potential strategies for meeting future standards. Additional experimentation may be required in the future in order to optimize processes for meeting specific standards as they are developed. AUTHORIZATION On May 11, 1988 the City Council authorized Addendum No. 15 to the Agreement to provide City Consulting Engineering services to prepare these Evaluations for the Safe Drinking Water Act. BACKGROUND The City of Tamarac operates two separate utility systems, known as Tamarac Utilities West and Tamarac Utilities East. R207/4340/122088 Hwd:1003T 1_1 Tamarac Utilities West (TUW) provides service to all of the City west of US 441. This area is growing at a fast and steady pace and is expected to reach build out land use capacity near the beginning of the next century. TUW owns and operates a water treatment plant located in Tamarac near the intersection of University Drive and N.W. blst Street. The plant currently consists of two lime softening units and rapid sand filters. Raw water is supplied via 13 operating supply wells. TUW physical facilities are described in more detail in Chapter 3. Tamarac Utilities East (TUE) serves a very limited portion of the City that is situated on both sides of Commercial Boulevard in the vicinity of Prospect Road and east of N.W. 31st Avenue. TUE residents rely upon the City of Fort Lauderdale to 4supply their water. The City of Tamarac purchases water from Fort Lauderdale through a large user agreement. The focus of this report is on facilities planning at TUW. U R207/4340/122088 Hwd:1003T 1-2 • DRINKING HATER REGULATIONS REGULATORY AGENCIES In 1974 the Federal government enacted the Safe Drinking Water Act to assure that public water systems supplying drinking water meet minimum requirements. Primary responsibility or primacy was to be held at the state level for those states capable of implementing programs within designated guidelines. To meet requirements for primacy, the State of Florida enacted the "Florida Safe Drinking Water Act" as part of Chapter 17-22, Public Drinking Water Systems of the Florida Administrative Code. Drinking water regulations were adopted to meet national primary and secondary requirements of the Federal government. The State of Florida gives the Department of Environmental Regulation (DER) general supervision and control over all public and private water systems that are subject to regulations contained in Chapter 17-22. The DER oversees all such public and private operations throughout the state of Florida and enforces associated public drinking water standards. In counties such as Broward, where the DER has limited manpower to provide supervision and control over public and private water systems, the Department of Health and Rehabilitative Services (DHRS) is given the power of enforcement. In these instances the DHRS takes over the rule of the DER and enforces public drinking water standards. Under this arrangement, DHRS is given general supervision and control authority, while the DER still retains the ultimate power of enforcement. CURRENT STANDARDS U.S. EPA Primary Drinking Water Standards, which are health related criteria that require mandatory enforcement by the State primacy agencies, encompass a broad range of categories. Specific primary standards that have been adopted by the State Florida are listed in Table 2-1. In addition to these standards, the State of Florida has developed regulations requiring that either 0.2 mg/1 of free chlorine or 0.6 mg/l of combined chlorine be maintained as a disinfecting residual in the water distribution system. Similar requirements for disinfecting residual are under consideration by the U.S. EPA for future Federal standards. U.S. EPA Secondary Drinking Water Standards are applied to community systems such as the City of Tamarac for control of aesthetic factors. Unlike primary standards, parameters developed as secondary regulations were established as guidelines for states that did not require enforcement. The State of Florida has adopted these secondary standards and regulates treatment activity in order to maintain parameters below specified maximum contaminant levels. Table 2-2 summarizes regulations for these contaminants. R194/4340/122088 Hwd:1004T/01-17-89 2-1 R, 7 - C� 11 TABLE 2-1 STATE OF FLORIDA INORGANICS: Arsenic, As Barium, Ba Cadmium, Cd Chromium, Cr Fluoride, F Lead, Pb Mercury, Hg Nitrate, N Selenium, Se Silver, Ag Sodium, Na ORGANIC PESTICIDES: Chlorinated Hydrocarbons: Endrin Li ndane Methoxychlor Toxaphene Chlorophenoxys: 2,4-D 2,4,5 TP,Silvex DISINFECTION BYPRODUCT: Total Trihalomethanes TURBIDITY: Turbidity MICROBIOLOGICAL: Total Coliform Bacteria: Median Maximum (allowed in less than 5% of monthly samples) RADIONUCLIDES: Radium-226 & 228 Gross Alpha Radioactivity Beta & Photon Radioactivity R194/4340/122088 Hwd:1004T/01-17-89 2-2 Maximum mum ContaminantLevel 0.05 mg/1 1.0 mg/1 0.01 mg/l 0.05 mg/l 4.0 mg/1* 0.05 mg/l 0.002 mg/l 10. mg/l 0.01 mg/l 0.05 mg/l 160. mg/l 0.0002 mg/l 0.004 mg/1 0.1 mg/l 0.005 mg/1 0.1 mg/l 0.01 mg/l 0.10 mg/l (4 quarter average) 1.0 NTU 1/100 ml 4/100 ml 5 pCi/l 15 pCi /l 4 mrem/yr** R-5'i-9 7 TABLE 2-1 (Continued) STATE OF FLORIDA VOLATILE ORGANICS***: Trichloroethylene Tetrachloroethylene Carbon Tetrachloride Vinyl Chloride 1,1,1—Trichloroethane 1,2—Dichloroethane Benzene Ethylene Dibromide .003 mg/l .003 mg/l .003 mg/l**** .001 mg/l**** .200 mg/1 .003 mg/1**** .001-mg/l**** . 000-02 mg / l *A Secondary Standard for fluoride exists at a level of 2.0 mg/l. **The contribution of this category of radionuclides is to be computed. Tritium at 20,000 pCi/l and Strontium-90 at 8 pCi/l, respectively, are computed to give 4 mrem/yr. ***New U.S. EPA drinking water standards will result in p—Dichlorobenze and 1,1 Dichloroethylene at levels of 0.015 and 0.007 mg/l, respectively. ****These standards are more stringent than existing U.S. EPA drinking water standards. Note: Lower standards are presently being evaluated for lead, arsenic and turbidity. R194/4340/122088 Hwd:1004T/01-17-89 2-3 C� C� C11 j��Y7- ? I • TABLE 2-2 SECONDARY DRINKING Contaminant WATER STANDARDS Maximum Contaminant Level Chloride 250 mg/1 Color 15 color units Copper 1 mg/l Corrosivity neither corrosive nor scale forming Fluoride 2.0 mg/l Foaming Agents 0.5 mg/l Iron 0.3 mg/l Manganese 0.05 mg/l Odor 3 threshold odor number PH 6.5. minimum (no maximum) Sulfate 250 mg/l Total Dissolved Solids 500 mg/l . Zinc 5 mg/l R194/4340/122088 Hwd:1004T/01-17-89 2-4 R-91-77 Cl FUTURE STANDARDS The U.S. EPA is presently in a process of modifying and expanding drinking water regulations in response to the Safe Drinking Water Act (SDWA) and its subsequent Amendments. Extensive development of new provisions are contemplated over a time period extending through 1991 and subsequent regulations are contemplated every 3 years thereafter. Contaminants for which standards are presently being developed due to recent 1986 Amendments are listed in Table 2-3. While this list is extensive, most of these contaminants do not occur at significant levels in the source waters available to TUW. Therefore, evaluations of future requirements should be focused on specific areas that will have an effect on facility planning. In evaluating potential effects of the recent 1986 Amendments on treatment processes, the major areas of concern are for adequate disinfection to control microbiological contaminants and for the occurrence of lead and copper due to corrosion of plumbing systems. Although not included under specific contaminants required for evaluation under the 1986 Amendments, the U.S. EPA is also evaluating new regulations for disinfection byproducts. New regulations for corrosion control to reduce lead and copper will probably require some adjustments in treatment, however, major facility modifications are not contemplated. The required adjustments are most likely to consist of the addition of chemical additives within an existing plant configuration to reduce the effects of corrosion. These will not have a major effect on long-term planning for major treatment systems. The most complex problems are likely to occur in attempting to simultaneously add disinfecting chemicals to meet criteria for controlling microbiological contaminants while trying to limit the formation of undesirable disinfection byproducts. Presently, the U.S. EPA is developing new disinfection standards that will apply to treatment of surface water' systems. Under these standards, specific dosages and contact times are being established for application of disinfecting chemicals to achieve primary disinfection goals for removing water -borne pathogens that might be present in raw water. Specific criteria are being established for use of chlorine, chloramines, chlorine dioxide and ozone. With the exception of chloramines, these criteria are based on dosage requirements for disinfection of Giardia, a protozoan pathogen that has occurred in surface water supplies. Chloramines have stringent criteria for enteric viruses due to relatively low efficiencies for disinfecting this category of pathogens. These criteria are so severe that they essentially eliminate chloramines as a viable method for meeting primary disinfection criteria in water sources that are considered to be at risk from viruses. R194/4340/122088 Hwd:1004T/01-17-89 2-5 R- ff9- 97 11 0 • TABLE 2-3 CONTAMINANTS TO BE REGULATED BY EPA BY JUNE 1989* Microbiological Contaminants Turbidity* Viruses Total Coliforms* Standard Plate Count Giandi .Lublin Leaionella Trichloroethylene* Tetrachloroethylene Carbon Tetrachloride* 1,1,1-Trichloroethane* 1,2-Dichloroethane* Endri n* Li ndane* Methoxychlor* Toxaphene* 2,4,-D* 2,4,5-TP (Silvex)* Total Trihalomethanes* Aldicarb Chlordane Dalapon Diquat Endothall Glyphosate Arsenic* Barium* Cadmium* Chromium* Lead* Mercury* Nitrate (as N)* Selenium* R194/4340/122088 Hwd:1004T/01-17-89 Volatile Organic Chemicals Vinyl Chloride* Methylene Chloride Benzene* Chlorobenzene Dichlorobenzene(s)* Synthetic Organic Chemicals Carbofuran 1,1,2-Trichlorethane Vydate Simazine PAHs (Polynuclear Aromatic Hydrocarbons) PCBs(Polychlorinated Biphenyls) Atrazine Phthalates Acrylamide QBCP (Dibromochloropropane) 1,2-Dichloropropane Inorganic Chemicals Trichlorobenzene(s) 1,1-Dichloroethylene* cis-1, 2-Dichloroethylen trans-1, 2-Dichloroethylen Pentachlorophenol Picloram Dinoseb Alachlor EDB (Ethylene Dibromide) Epichlorohydrin Dibromomethane Toluene Xylene Adipates Hexachlorocyclopentadiene 2,3,7,8-TCDD (Dioxin) Silver* Vanadium Fluoride* Sodium Aluminum Nickel Antimony Zinc Molybdenum Thallium Asbestos Beryllium Sulfate Cyanide Copper 2-6 C� TABLE 2--3 (Continued) CONTAMINANTS TO BE REGULATED BY EPA BY JUNE 1989* Radiological Contaminants Radium 226 and 228* Beta Particle and Photon Natural Uranium Gross Alpha Particle Radioactivity Radon Activity* * Asterisked substances are currently regulated; all exicept the VOCs may be revised. Source: Environmental Protection Agency CJ R194/4340/122088 Hwd:1004T/01-17-89 2-7 /3-89- 97 • Although the primary disinfection criteria for surface water provide insight to potential regulations for utilities that use groundwater sources, such as TUW, they will only apply to surface water supplies. Disinfection regulations for treatment of groundwater sources are not scheduled to be promulgated until 1991. Because of a lower exposure to microbiological contaminants in groundwater, less stringent regulations may result. In particular, Giardia may not be a significant contaminant category in groundwaters. However, enteric viruses may still be a concern and restrictive requirements may still limit use of chloramines for primary disinfection. Because no guidelines have been established for groundwater, surface water criteria are used in this study as a indicator of_ "worst -case" potential for future disinfection needs. - In addition to meeting primary disinfecting goals, surface water treatment regulations will require that a residual concentration of a disinfecting chemical be maintained at all locations in a water distribution system. The most likely chemicals for reliably achieving the required residuals are chlorine and chloramines. Chlorine dioxide is another possibility, but greater uncertainty exists for its applicability in a secondary disinfecting role. Although the U.S. EPA has not finalized a secondary disinfection standard regulation, the State of Florida presently has secondary u�sinfection standards that require minimum levels of either 0.2 mg/l of free chlorine or 0.6 mg/l of combined chlorine (chloramines) throughout the distribution system. With respect to existing standards for disinfection byproducts, total trihalomethanes (TTHMs), which are byproducts of reactions between chlorine and naturally occurring compounds found in source waters, are the only compounds that are regulated. These regulations have required changes in chlorination practices to comply with an existing limitation of 0.10 mg/l averaged over four quarters of sampling. More restrictive regulations are under consideration by the U.S. EPA and flexibility to further reduce levels of trihalomethames and other disinfection byproducts, while maintaining adequate disinfection, is an important aspect of planning for future regulations. A wide array of disinfection byproducts have been identified as indicated in Table 2-4. This subject was reviewed in 1987 by the Safe Drinking Water Committee of the National Academy of Sciences and, in January, 1988, the U.S. EPA published a preliminary list of disinfectants and disinfectant byproducts to be considered for regulation under the first Drinking Water Priority List. These are shown in Table 2-5. Formation of most of the disinfection byproducts that are being considered for regulation can be minimized by elimination of free chlorine as a disinfectant. This can be achieved by substitution of ozone or chlorine dioxide as alternative primary disinfectants and chloramines as an alternative for secondary disinfection. R194/4340/122088 Hwd:1004T/01-17-89 2-8 l?-89-97 Uncertainty exists for future applicability of chlorine dioxide due to concerns for suspected health effects of chlorine dioxide and its degradation products, chlorate and chlorite. This chemical will be less reliable as a potential future disinfection alternative until more information becomes available resolving these issues. Although some concern also exists for ozone byproducts, they are presently of much less concern and much greater planning flexibility can be achieved if ozone can be established as a viable approach for meeting disinfection criteria for concentration and time of contact. R194/4340/122088 Hwd:1004T/01-17-89 2-9 • 0 R_ 97- 17 7 TABLE 2-4 IDENTIFIED DISINFECTION BYPRODUCTS Chlorine TTHMs TOX Inorganic Chloramines Chloride Hypochlorite Chlorophenols N-Chloroorganics Haloacetonitriles Chlorinated Benzenes Chlorinated Toluene Chlorinated Xylene Chlorinated Aldehydes Chlorinated Ketones Chlorinated Alkanes Chlorinated Alkenes Chloroacetic Acids Unchlorinated and Chlorinated Dicarboxylic Acids .Unchlorinated and Chlorinated Monocarboxylic Acids Halogenated Aromatic Carboxylic Acids Halogenated Thiophenes Epoxides Chlorohydrins Tri (2-chloroethyl) Phosphate Halogenated Propenenitriles Non -halogenated Polycarboxylic Acids Chlorofuranones 0 Chlorine iByproducts Chlorine Dioxide Chlorite Chlorate Chlorine Chloride Chlorinated and Unchlorinated Chlorinated Aromatics Chlorinated and Unchlorinated Carboxylic Acids Epoxy Compounds Chlorophenols Ketones Cyanogen Chloride Aldehydes Quinones R194/4340/122088 Hwd:1004T/01-17-89 2-10 R- ff�- 77 TABLE 2-4 (Continued) IDENTIFIED DISINFECTION BYPRODUCTS h 1 orami Inorganic Chloramines TOX N-Chloroorganics Chlorophenols Quinones Aldonic Acids Aldehydes Haloacetic Acids Cyanogen Chloride Aldehydes Ketones Epoxides Peroxides Carboxylic Acid Quinones Phenols Oxides of Bromine Brominated Organics R194/4340/122088 Hwd:1004T/01-17-89 2-11 0 9 R-g9-g7 0 0 TABLE 2-5 DISINFECTANTS AND DISINFECTANT BYPRODUCTS LISTED IN THE FIRST DRINKING WATER PRIORITY LIST (JANUARY, 1988) P siof t : Chlorine, Hypochlorite Ion, Chlorine Dioxide, Chlorite Ion, Chlorate Ion, Chloramine, and Ammonia -Four Tri hal ometanes Chloroform, Bromoform, Bromodichloromethane, Dichlorobromomethane, Haloacgtonitrilec: Bromochloroacetonitrile, Dichloroacetonitrile, Dibromoacetonitrile, Trichloroacetonitrile HaluenatedAlc n s. andr i r Chloropicrin (trichloronitromethane), Cyanogen Chloride, Ozone Byproducts R194/4340/122088 Hwd:1004T/01-17-89 2-12 R-Y9- 9 7 11 If future groundwater regulations for primary disinfection do not restrict the use of chloramines, chloramination may be the most cost effective alternative for reducing the formation of regulated disinfection byproducts. In any event, chlorimination is the most likely candidate for secondary disinfection. Issues regarding concern for toxicity of chloramines and its byproducts may also need to be considered and uncertainty in this area should be resolved before its applicability can be confirmed. Given the present status of these regulations, no completely reliable approach can be selected at this time. Specific information will not be available until the U.S. EPA publishes requirements for disinfection of groundwater and for.:disinfection byproducts. Therefore, evaluations in this study are intended to assess general flexibility for modifying treatment to meet a wide range of possible regulations. More specific evaluations will become appropriate when the specific regulations have been developed for determining treatment requirements. 0 C� R194/4340/122088 Hwd:1004T/01-17-89 2-13 r-, 11iiL12*1W DESCRIPTION OF EXISTING FACILITIES AND PROJECTED NEEDS FOR FUTURE DEMANDS GENERAL The TUW Water Treatment Plant is located near the northwest corner of University Drive and NW 61 Street. This facility presently has a 12 MGD rated plant capacity. Groundwater from the surficial Biscayne Aquifer is the sole source of raw water. Treatment includes lime softening in upflow clarifiers and subsequent filtration to remove residual suspended solids. Within the treatment train, chlorine is added for disinfection and hydrofluosilic acid is added as a source of fluoride. Filtered water is routed to a clearwell where it is pumped to either City-wide distribution or on -site and off -site storage. Rehabilitation of the existing water treatment facility is presently under way with the addition of an 8 mgd Automatic Backwash Filter and the rehabilitation a number of existing features, including yard piping, switchgear, motor control units, electrical distribution system, emergency power, polymer feed, filters and production wells. Specific treatment components and projected needs to meet future demands are described in the following sections. A site layout is shown in Figure 3-1 and design criteria for existing unit processes are summarized in Table 3-1. FUTURE DEMAND REQUIREMENTS Projections of future demand for the TUW Water Treatment Plant are summarized in the study, Tamarac Utilities We„5t: LQ,pg Term Water SugplyI n___.(AuguSJ, 19M. These projections, as tabulated in Table 3-2, have been used as the basis for developing alternatives under the study described herein. Two sets of demand projections have been developed: average demands and peak daily demands. Average demands are used as a basis for developing annual costs of operation. Peak demand establishes the maximum size requirement for treatment facilities, thereby establishing the plant design capacity. RAW WATER WELLS TUW operates thirteen (13) raw water supply wells. Six of these wells (Nos. 1, 2, 3, 7, 8 and 9) are located on the plant site and are operated from the plant main control console. The remaining seven wells are located off -site and are operated manually. Well Nos. 4, 5 and 6 are located directly to the west, along the canal which runs parallel to NW 61 Street. Well Nos. 10, 11, 12 and 13 .are located directly to the east, at a location one block east of University Drive. Well locations are shown on Figure 3-2. R195/4340/122088 Hwd:1005T/01-24-89 3-1 --, w 3 0 0 Z _<'� P •- may �%� � o a�a�4 E3 O <�t5 � bW W aO U PJU_,� OJvw 07 1V sa3.L-ILd 00'1LANI aNLLSIX3 i i m i m i am u L LXD*'f4 . R-- 97 9 % • TABLE 3-1 CITY OF TAMARAC WATER TREATMENT PLANT pFSIGN CRITERIA ITEM„ -DESCRIPTION ACCELATOR (Dimensions) (Loading Rate) - Existing 8 MGD 64.5' DTA.xl7.5'HT 2.20 GPM/SF - Existing 4 MGD 46.5' DIA.xl7.5'HT 1.85 GPM/SF - Proposed 8 MGD 64.5' DIA.xl7.5'HT 2.20 GPM/SF FILTER (Dimensions) (Loading Rate) - Existing (6) 1.2 MGD 36'LTx8'WTxl3'HT 2.89 GPM/SF - 8 MGD ABF 51'DIA.xl7.5'HT 3 GPM/SF CLEARWELL (Dimensions) (Volume) 65'xl2'x8'HT +38'xl3'x8'HT 75,000 GAL LIME POND (Dimensions) (Volume) . 140'xl00'x10'HT 1,000,000 GAL STORAGE TANK (Dimensions) (Volume) - On -Site 85'DIA.x23.5'HT 1,000,000 GAL - Off -Site 85'DIA.x23.5'HT 1,000,000 GAL - Off -Site 100'DIA.x34'HT 2,000,000 GAL BACKWASH SYSTEM (Dimensions) (Volume) -- Conctructed Recycle 8'DIA.x8.5'HT 3,200 GAL Pump Station - Proposed Recycle Basin 105'x50'x9'HT 350,000 GAL LIME SYSTEM (Capacity) (Rate) -. Existing Silo No.l 100 Tons ---- - Existing Slaker No.l ---- 4000 lb/hr - Existing Silo No.2 50 Tons ---- - Existing Slaker No.2 ---- 1000 lb/hr Hwd:1521R/01-24-89 3-2 /R-89-97 TABLE 3-1 (Continued) CITY OF TAMARAC WATER TREATMENT PLANT DESIGN CRITERIA ITEM _DESCRIPJION PUMPS (HP) (Flow) (TDH) Wnit) - High Service No.1 30 500 GPM 162 FT Vertical Turbine - High Service No.2 50 1000 GPM 162 FT Vertical Turbine - High Service No.3 100 1500 GPM 162 FT Vertical Turbine - High Service No.4 100 1500 GPM 162 FT Vertical Turbine - High Service No.5 150 3000 GPM 162 FT Variable Speed/Vert. Turb. - High Service No.6 200 3000 GPM 162 FT Variable Speed/Horiz. - High Service No.7 100 1500 GPM 162 FT Horizontal Splitcase - Transfer No.l 100 5500 GPM 55 FT Vertical Turbine - Transfer No.2 100 5500 GPM 55 FT Vertical Turbine - Backwash No.l 25 1500 GPM 40 FT Vertical Turbine - Backwash No.2 25 1500 GPM 40 FT Vertical Turbine POWER SUPPLY - Primary 13.2 kv - 277/480 Volt Transformer - Secondary 900 kw diesel engine generator I II Hwd:1521R/01-24-89 3-3 f?- 89- 97 • 0 TABLE 3-2 CITY OF TAMARAC Projected Average Yam[ DeMand. No 1986 5.0 1990 6.4 2000 9.2 2010 10.3 R195/4340/122088 Hwd:1005T/01-24-89 3-4 Projected Peak Daily 6.5 8.9 12.9 14.6 = t?—eF9-97 -t UUU U UU U P12 P11 P10 Z _ _��• a co 3 Li a UNIVERSITY DRIVE W18 W119 4pLJ NW 77th AV. NW 80th AV. P5 MIDWAY PLAZA JujuuLc� LEGEND P1 ■ EXISTING PUMPS Wl0 rROPOSED WELLS EXISTING PIPELINE — --- PROPOSED PIPELINE (12"0) C� 9 *I 7X1 �r R-97-77 Cl The oldest of the existing wells, Nos. 1-9, were drilled about fourteen years ago. More recently, wells 10 and 11 were drilled in 1983 and wells 12 and 13 were drilled in 1985. The well casings have been set at depths of approximately 110 feet. Each well consists of a vertical turbine pump with original design capacities of 800 GPM for wells 1-9, 750 GPM for wells 10 and 11, and 725 GPM for wells 12 and 13. Sustained capacity of the existing wellfield, which is dependent upon pump characteristics, aquifer characteristics and aquifer recharge, indicates a 7 MGD best case production for a nine well system. This production is adequate for the City's existing water demand along with a 25 percent standby requirement. However, additional wells will be required to meet future demands. UPFLOW CLARIFIERS Raw water is initially treated by upflow clarifiers (Accelators). As raw water enters an Accelator, flow is routed to a primary mixing and reaction zone at the center and bottom of the unit. Lime solution is introduced at this location. This mixture is continually circulated in the primary mixing zone by a circular rotor impeller. The lime and water mixture flows upwards into the secondary mixing and reaction' zone (located on the top center portion of the Accelator). Water exits the secondary mixing zone and enters the clarification portion of the unit where the clarified effluent is decanted into troughs located at the surface of the unit. Settled sludge is accumulated at the bottom of unit, which is segregated into two areas. The first area collects a portion of the sludge which settles in hoppers and is removed as waste sludge. The second area, known as the return flow zone, allows for recycle of the remaining lime slurry to the primary mixing and reaction zone. This recycled slurry acts as a catalyst in the lime softening reaction between new lime and raw water. TUW presently has a 4 mgd steel Accelator and an 8 mgd steel Accelator (20 years and 17 years old, respectively). If the 8 mgd unit must be removed from service, the 4 mgd unit does not have adequate capacity for meeting existing average demands shown in Table 3-2. The addition of a new 8 mgd Accelator has been recommended in past planning documents as a means for achieving plant reliability and expanded capacity. LIME SILOS/LIME SLAKERS The treatment facility maintains two (2) lime silos, one having a 100 ton capacity and the other a 50 ton capacity. Quick lime (rice size) is transported from the silos on a conveyor belt to lime slakers where the dry lime (90% - 95% pure) is mixed with water to form a slurry. The lime slurry is then further diluted to a solution and pumped into the Accelators at a rate necessary to maintain the appropriate pH. R195/4340/122088 Hwd:1005T/01-17-89 3-5 R-97-57 11 CHLORINATORS The TUW water treatment plant has a newly constructed chlorination facility located on the plant property adjacent to the lime pond (see Figure 3-1). The facility consists of a loading dock, a chlorine cylinder hoist, two cylinder bays and chlorinators. Pressurized one ton chlorine cylinders are brought to the facility at the loading dock where they are hoisted into the building and stored in bays. Chlorine feed is typically split between feed locations in the raw water piping and into the Accelators. EXISTING RAPID SAND FILTERS Clarified Accelator effluent flows by gravity to six (6) rapid sand filters. These are dual media filters which have operating capacities of 1.2 MGD, each, resulting in a combined capacity of 7.2 MGD. Filtered water flows by gravity through the filter effluent lines into the plant clearwell. A new Automatic Backwash Filter, with four (4) separate dual media cells, is being constructed. This will increase the plant filter f,anarity by 8 mgd, resulting in a total plant capacity of 15.2 mgd in combination with the existing filters. • LIME POND Lime softener blowdown and filter backwash water are disposed in an nn-site settling pond. Wastewater accumulates in the pond and solids are allowed to settle. Clarified water is decanted to an adjacent off -site canal. Periodically, accumulated sludge is removed with a clamshell (crane) and piled in an area adjacent to the pond. It is subsequently hauled by truck and used as fill material. CLEARWELL Treated filter effluent flows by gravity to the finished water clearwell located below the pump room in the main control building. The clearwell has a depth of 8 feet and a volume of approximately 75,000 gallons. PUMPS AND PIPING Finished water is removed from the clearwell by three (3) different sets of vertical turbine pumps: transfer pumps, backwash pumps and high service pumps. The transfer pumps (two pumps with 100 hp motors) send finished water from the clearwell to the on -site storage tank via a 16-inch transfer main. Piping is also arranged so that the transfer pumps are capable of supplementing the backwash pumps. High service pumps transfer flow directly to the finished water distribution system. R195/4340/122088 Hwd:1005T/01-17-89 3-6 • • C� STORAGE An overall storage capacity of four (4) million gallons is maintained by a two million gallon storage tank located at Tract 27 in the northwest corner of the city, a one million gallon tank at Grants Plaza near the intersection of Commercial Blvd. and the Turnpike, and a one million gallon tank on the east most portion of the plant site. PLANT NEEDS Current TUW planning calls for a near term expansion of the lime softening system (new 8 mgd upflow clarifier), the addition of 4 million gallons of storage capacity, a backwash recovery system and additional production wells. R195/4340/122088 Hwd:1005T/01-17-89 3-7 0 101,112I41all EXISTING TREATMENT PRACTICES GENERAL A treatment schematic for the TUW Water Treatment Plant is shown in Figure 4-1. General quality characteristics for raw and finished water are summarized in Table 4-1 and specific criteria are compared with existing standards in Table 4-2, indicating that these standards can be met with existing treatment methods. With respect to conventional treatment needs, the raw water has relatively high levels of hardness and color that mus-t be treated. Low concentrations of iron and manganese occur in the TUW wells and removal to levels below the secondary standards for these constituents is not a concern. Treatment by lime softening in Accelator units has proved effective in controlling these parameters at desired levels to meet existing treatment goals as shown in Table 4-1. Disinfection is provided within the process train through two -stage addition of chlorine, consisting of pre -chlorine addition to the raw water- pipeline and post -chlorine addition within the Accelator units. Typical pre- and post -chlorination dosages of 3 mg/l and 6 mg/l, respectively. have provided adequate disinfection, while maintaining total trihalomethane (TTHMs) concentrations at levels that meet existing standards. Downstream of the softening process additional treatment is provided by filtration which removes residual solids. Fluoridation is also provided. LIME SOFTENING Lime softening is achieved by the addition of a slaked dry lime slurry that is derived from bulk pebble lime. Polymer (Drewfloc No.3) is also added to enhance flocculation and settling. A dry lime dosage range of 140 to 200 mg/l is typical and higher dosages are periodically used. Hardness is reduced by this process from 260 to 310 mg/l as CaCO3 in raw water to finished water levels of 70 to 80 mg/l as CaCO3. Color is typically reduced by this process from a approximately 30 color units to a finished water level of approximately 5 color units. The process is controlled based on a target finished water pH of 8.9 to 9.1. The addition of chlorine tends to lower the pH and an allowance for this effect must be made in controlling the lime dosage. FILTRATION The existing filters are operated at a loading rate of 3 gpm/square foot and normally achieve finished water turbidities of 0.1 to 0.3 NTU. Filter runs of 80 hours are typical. R196/4340/122088 Hwd:1006T 4-1 R-e9-97 i • C� LALl XT r1 L tA r H c �i c t f- H LL � }C? F- C P4 b" •� u F E ea Ln v L7 n %D qw M co M Ln n o 1..1 N N N N CV N '1� N m o ri o 0 0 0 0 0 0 o a o M C N O qr O M C N O m C I" O N O N O cn 9 m C? en C Iy C O C O C2, 4? C� L7 © CL Cl Q in in M Ln Ln Ln Ln 0 Ln Ln Ln Ln i.� .J W Z OG O [I O n n Ln qr LL'1 N Q d ►w FN C M M M M N N M N N N N N W cC ton L2D LD � 2 i. n It si LD n Ln Ln n oL Ln r► 4 H n n n n n rn n r► r% r%lir L� i o c M N N M N M cl � or! .- 0% Ct C• CL 0% C• OL at OL C+ CL µNµA� C? M « LA A Cl N LV O CL O Cl 0 C7 O CL C+ •5 M en eq M N M M N M m N N A W -y4V M � 11 t! 19 V? M M N e� M r+ N `I o o Q 6 Q 'D Q Q o © o o a M M qtr MD co LD ^ LO rF LP LD Ln N L.1 L. •L N N wn- r to r L W OD m P. W n C co CL Ur H d _ n LLD L1D � n n %0 Ln to Ln -W LD .0 00, N N N N N N N N N N N N LF O. N �CpD b H M M N N N N N N N N N ENE C � G d C N LD qtr el C• r► N N r Ln O M Lam. 0,r n r% r%Ln Ln Ln M v w M 0 c. w N N N N LV N N N N N N N x H L LU Ll L_ x k 'a W c0 SI N N N N N M N N N N of (+f L a p WI n I,- r% n n n n n n n I,.r. O' N O 7. 0 Y w�j 9w cc C en to x W cc co x J L~/1 m S� 1 O cc wd Cied Y LWj M u Z C n n Q LW/f ¢ a k 4-2 TABLE 4-2 CITY OF TAMARAC PARAMETER RAN NATERI+2 FINISHED NATER1 Arsenic 0.05 mg/L 0.003 0.003 Barium 1.0 mg/L 0.09 0.01 Cadmium 0.01 mg/L 0.01 0.01 Chromium 0.05 mg/L 0.03 0.03 Lead 0.05 mg/L 0.01 = 0.01 Mercury 0.002 mg/L 0.0005 0.0005 Selenium 0.01 mg/L 0.002 0.002 Silver 0.05 mg/L 0.019 0.016 Nitrate 10.0 mg/L 0.05 0.05 Flouride 1.4 mg/L 0.31 0.23 Endrin 0.0002 mg/L 0.00007 0.00007 Lindane 0.0004 mg/L 0.0002 0.0002 Methoxyclor 0.1 mg/L 0.005 0.005 Toxaphene 0.005 mg/L 0.001 0.001 2,4-D 0.1 mg/L 0.02 0.02 2,4,5-TP Silvex 0.01 mg/L 0.002 0.002 Turbidity 1.0 NTU 2.415 0.515 Total Trihalomethane 0.1 mg/L -- 0.037 Chlorides 250 mg/L 40-62 53.5 Color 15 PCU 15-32 10 Copper 1 mg/L 0.012-0.038 0.015 Corrosivity -0.6 - +0.3 + 1.0 Foaming Agents 0.5 mg/L 0.05-0.07 0.05 H2S 0.05 mg/L 0.025-0.506 0.01 Iron 0.3 mg/L 0.04-0.46 0.03 Maganese 0.05 mg/L 0.01 0.01 Odor 3 TON 1 1 pH 6.5-8.5 6.8-7.4 9.5 Sulfate 250 mg/L 3.7-37.4 24.1 Total Dissolved Solids 500 mg/L 290-460 205 Zinc 5 mg/L 0.01-0.08 0.01 • R196/4340/122088 Hwd:1006T 4-3 /?-89-97 • TABLE 4-2 • CITY OF TAMARAC N& LATION COMPLIANCE (Continued) PARAMETER _ RAWj8TERI.2 EINISHEQ WATERI Total Hardness* -- 198 — 350 66.0 Total Alkalinity* -- 169 — 327 32.0 Non —Carbonate* -- 3 — 41 34.0 BiCarbonate* -- 169 — 327 - 23.4 Carbonate* -- 0.1 — 0.4 _ 7.0 Hydroxide* -- 0.0 1.6 Bicarbonate, HCO3 -- 103 — 199 14.3 Calcium -- 45 — 134 22.4 Magnesium __ 0.5 — 28 2.5 Carbon Dioxide -- 12 — 124 0.0 Sodium -- 21 — 34 26.2 * as CaCO3 1 Samples collected on April, 7, 1988 2 Individual values represent an average as tested from a composite of operating wells. Paired values represent a low to high range of operating wells (Nos. 1-13). R196/4340/122088 Hwd:1006T 4-4 FLUORIDATION Background fluoride levels of 0.2 to 0.3 mg/1 typically occur in the TUW raw water supply. These levels are significantly lower than the existing Maximum Contaminant Level (MCL) of 1.4 mg/l for fluoride and present no problem with respect to this standard. Operationally, an allowance for these background levels is taken into account in selecting fluoride dosage in order to prevent excessive fluoridation. CHLORINATION Chlorination practices have been significantly _gffected by adjustments required to meet existing standards for total trihalomethanes (TTHMs). Monitoring for TTHMs has been required on a quarterly basis since the beginning of 1984. Four treated water sample points, shown on Figure 4-2, are located within the distribution system: Sample Point 1 - 10500 NW 70th Street Sample Point 2 - Fire Station No. 1 Sample Point 3 - 8100 NW 70th Avenue Sample Point 4 -- 4801 Commercial Boulevard TTHM analyses for these sample points are summarized in Table 4-3 for the required sampling period that began in 1984. These results indicate that TTHM levels have typically been maintained below 0.10 mg/l and at no time during this period has the required standard of 0.10 mg/l for an average of four consecutive quarters been exceeded. TUW has collected samples for TTHMs since 1981 as shown in Figure 4-3. These indicate a general trend of reduced TTHM levels since 1982, reflecting adjustments in chlorination practices by plant personnel. Most significantly, chlorine dosage has been controlled to minimize free chlorine levels as indicated by the trends shown in Figure 4-4. Adjustments have also been made in the points of chlorination and optimum results have been achieved by pre -chlorinating raw water followed by post -chlorination in the Accelators. Both chlorine feed locations are near the head of the plant. A major effect of this approach is that a much lower pH profile can be maintained through the plant as a result of placing the acidifying effect of chlorine at these upstream locations. Because a lower pH reduces the rate of TTHM formation reactions, reduced levels of TTHM result from this approach. C� 0 R196/4340/122088 Hwd:1006T 4-5 21 IV wpolall, YBiXOKV :i'p Z UO QF �Q J zz o U lz U u WLn a u c f..> Wz Wo W LL J Q N Q 4J C) Q a < Nw W W p L 7 J m � J n� W 3 J ZU a ao N o i W W W in ¢ r� 3F r g to o� r i r D C t 0 C p " fli C (vbw) ivnalS38 3NI401HO 33W • 'I �-A EFFECT OF FUTURE STANDARDS ON TREATMENT PRACTICES K ~ w The presence of significant levels of background ammonia in the raw • water is a critical water quality characteristic for limiting the formation of TTHMs under the present approach to chlorination. At proper dosages, the presence of free chlorine is minimized in the presence of ammonia due to the formation of chloramines. At the present chlorine dosages, chloramines predominate and free chlorine is typically present only in trace quantities. Because free chlorine is the predominant cause of TTHM formation, TTHMs are reduced by this approach, thereby allowing existing standards to be met. A wide range of variability in TTHM concentrations is indicated by the data in Table 4-3. This probably derives from a variable extent of chloramination, with periodic overdosing of chlorine beyond the chloramine range. While these methods have been adequate for meeting existing standards for TTHM, improved results to meet more stringent standards may require greater control of the ratio of chlorine to ammonia in order to assure minimal presence of free chlorine during treatment. Additionally, if future standards for disinfection of groundwater require a strong disinfectant to meet primary disinfection criteria, chloramines might not be acceptable for meeting these requirements. Stronger disinfectants, that minimize the formation of TTHMs and other disinfection byproducts, may be required for primary disinfection. Ozone and chlorine dioxide may be required for this primary disinfection criteria. Chloramines are still likely to be applicable for meeting secondary disinfection criteria for maintaining residuals in the distribution system. C� . R196/4340/122088 Hwd:1006T 4-6 • �I N N M M M W th M M LA M M LA Ll') O� 4.7 Ln Ca r 0 r M N fW M r r M r W Z L.1 � M M M LO t0 LA M M co L19 O M M M Li! co N C? W N N N M N N M .+ N r M r J N LA M co n M co W N M f. M Ln M Ch M N P. O w r N N N N M N N M r r r M 0 I r C� M O CD a! Llf N9 M-1� M M^ N n M Ln CO N- N M N O r O r N 0 rtl O M N N N N M M N N N N N O v N N N N O 0 0 0 6 6 6 6 6 0 6 6 6 0 O O O yM� M V N N M V M N N M N N N O LD M N 1..1 NI N LA M Ll"1 M N N M N M M N N M N N M N N O N N O= O O O O O= O O O CD Q O O O Cl! M P► M M V N'It N N N N N N r MO N N Q O N Ca C? Ca O O O O O O O O O O O O O A 0 a O N Q Ch O N M A �p O kn N OL O P+ n ►n N O� M M 0 4 m Ch qrqjr N M M v N n r LA W r V! � 4 U W 1► 0 a .p w K! v 0 LA Ln M Ln M! W n LL'f M OD n M L4 %D qr qW N M OL M N N Ch N u7 1A r r UDDD LU O r p ��pp {p M LA co OL P+ O kn M 1► m m C go qr p� N CO OL 4A N LO g M M O N h r M v J F� fp N CL O O 4� t0 L'T O Lil O N M s�p gp W W 01 N CV r tt N CO r r a W r- qr n r 40 N N LO A a +1 A a I a a.d a.i 7 C Ln W W pp pp pp N N l0r! N O© P O Lp O� Orc _ L�•L W 01 M e0+1 O . IA C? N M CD O O O O O a w r v O O Pm m 0 C f- G co U ++ N O b Z +� N C u L/1 Cl r J C? O a O H qT kG LU 411 L l+l O py�� tlp ap pp pp �p pp qp Cp pIp 2 I 1 I L V f- 1 t- O G ^ O V « N 4-7 . • CHAPTER 5 BENCH --SCALE AND PILOT TESTING OBJECTIVES. The major objective of this testing program was to evaluate the capability to modify the existing treatment train in order -to meet possible future drinking water standards. Capability to implement these types of modifications is critical to planning future needs for the existing lime softening facilities. Based on a review of potential regulations, key areas selected for evaluation were disinfection and disinfection byproducts. As discussed in Chapter 2, standards for disinfection of groundwaters and disinfection byproducts have not yet been formally proposed by the U.S. EPA. Although a number of regulatory options have been informally discussed within U.S. EPA, firm conclusions relative to these standards cannot be drawn at this time. As a consequence, testing was oriented towards screening alternative treatment methods for meeting a range of possible standards. Important aspects of evaluation were as follows: 1. Capability to maintain disinfecting residuals while reducing theformation of TTHMs i inf i n bygroducts. . TTHMs are regulated under present standards and the potential exists for more stringent regulations in the future. Therefore, they were specifically assessed in this study. Because no final list is available for other disinfection byproducts that will be regulated in the near future, the Total Organic Halide (TOX) measurement was used as a general surrogate for these byproducts. Halogenated species, which are measured as a general class by the TOX analysis, dominate the list of disinfection byproducts to be considered for regulation under the first Drinking Water Priority List shown in Table 2-5. C� Testing was performed to determine capability for reducing the levels of TTHMs and other disinfection byproducts as indicated by TOX. Approaches for achieving these goals fall into two genera :� categories: 1) removal approaches and 2) avoidance approaches. Removal approaches involve treatment techniques to remove either disinfection byproducts or background organic materials that occur in raw water and react with disinfecting ch#"micals to form disinfection byproducts. These approaches include 'the use of ferric chloride to precipitate organic materials or the use of oxidizing agents such as potassium permanganate, ozone and chlorine dioxide for oxidizing these materials. A more extreme removal approach, adsorption on R202/4340/122088 Hwd:1007T/01-17-89 5-1 activated carbon, can also be considered, but this is typically not competitive on a cost basis. Another removal approach involving reverse osmosis will be presented in Chapter 6 of the report. The applicability of removal approaches depends on the concentration of organic materials. Where high levels of TTHM and TOX formation potential are encountered, it is more difficult to achieve removal down to low levels unless high process efficiencies can be achieved. Under these conditions, avoidance strategies may be more appropriate. Avoidance strategies involve the replacement of chlorine with alternative disinfectants that do not form as many disinfection byproducts of concern. Chlorine dioxide and ozone are potential alternatives for achieving primary disinfection goals. A critical characteristic in assessing these disinfectants is capability for achieving residual concentrations that are adequate for meeting potential concentration and time of contact criteria (CxT criteria) for primary disinfection. Neither of these chemicals are likely to achieve a lasting residual as would be required to meet secondary disinfection goals for maintaining a disinfection residual in the distribution system. To meet these criteria, a second disinfection step is likely to be required, using either chlorine or chloramines to provide more stable disinfecting residuals. Unless TTHM formation potential can be removed to low levels prior to addition of the secondary disinfectant, secondary disinfection will probably have to be accomplished by use of chloramines instead of free chlorine. Chloramines can be formed either by separate addition of chlorine to react with ammonia in the main process stream or by prior reaction with ammonia to pre —form chloramines prior to addition to the process stream. The use of pre —formed chloramines minimizes opportunities for exposure of the process stream to free chlorine and its associated byproducts. Therefore, its use may be advantageous if byproducts must be reduced to extremely low levels. 2. ili i i 1 _chlorin treatment r In addition to disinfection, chlorine serves an important function as an oxidizing agent in many water treatment plants, providing removal: of color, iron, manganese, tastes and odors, and control of other characteristics of concern. Of these, color is the most critical parameter for control at the TUW Water Treatment Plant. Iron and manganese occur at low levels in the raw -water and do not present a significant concern, and tastes and odors have not been a problem. Reduction in color can be achieved by lime softening. However, at many water treatment plants, it has been necessary to supplement this removal by using chlorine. If chlorination R-507-97 C� CJ R202/4340/122088 . Hwd:1007T/01-17-89 5-2 R 9?- 9 7 • is eliminated, alternative chemicals such as potassium permanganate, chlorine dioxide, and ozone can be considered for replacing its role in oxidizing color. Also, ferric chloride can be added to precipitate color. The need and applicability of these alternatives was evaluated in this study in order to assess need to compensate for possible changes in chlorination practice within the plant. • TESTING RESULTS Methods of Analysis A summary of analytical procedures used in the testing program is provided in Table 5-1. With the exception of analyses for trihalomethanes and total organic halides, all analyses were performed at the time of testing. Samples for trihalomethanes and total organic halides were taken in accordance with the prescribed methods indicated in Table 5-1. Analyses of trihalomethanes were performed by the TUW laboratory. Analyses of TOX were performed by Thornton Laboratories. Independent analyses of trihalomethanes were also performed by Thornton Laboratories and these analyses were used whenever the TUW laboratory load for performing TTHM analyses became excessive. Characterilation of M and TOX-Formation CbAr_acteristicS TTHM and TOX formation evaluations were performed using raw water at a pH in the range of 6.8 to 7.4. Initially, chlorine demand tests were performed to establish the effect of chlorine dose on the distribution of chlorine between combined and free forms and to determine the chlorine demand at "breakpoint". Results from this testing are shown in Figure 5-1. These results take the form of a classic "breakpoint chlorination" curve in which there is an initial increase in total chlorine content as chlorine reacts with ammonia to form a combined residual, followed by a region of decline as the combined residual is oxidized upon further addition of chlorine. As a result of these oxidation reactions, a minimum chlorine residual occurs at a chlorine dose of approximately 9 mg/l. Beyond this point the oxidation is complete and further chlorine addition results in an increased residual that is predominantly in the free chlorine for*. R202/4340/122088 Hwd:1007T/01-17-89 5-3 Rr V ! - I 7 E TABLE 5-1 PARARETH STANDARD HETHOD IYPE OF TEST Alkalinity 403a Acid Titration Chlorine Residual 408a Titrimetric, DPD-FAS Chlorine Dioxidel --- Titrimetric, Phenylarsine Oxide Color 204a Visual Comparison Hardness 314a Titrimetric, EDTA Ozone Residual2 --- Indigo Spectrophotometric pH 423a Electrometric Total Organic Halide3 450.1b Microcoulmetric-Titration Total Trihalomethane4 502.1b Liquid/Liquid Extraction . 1 Reference - "Determination of Chlorine Dioxide, Chlorine, Chlorite and Chlorate in Water" Paul Roberts,, E. Marco Aieta and Marguerita Hernandez-Esparza, Journal, AWWA (January, 1984). 2 Reference - "Determination of Ozone in Water by the Indigo Method, a Submitted Standard Method", H. Boder and J. Hoigne, Ozone: Science and_Engineering (1982). 3 Standard detection limit 0.005 mg/l 4 Standard detection limit 0.001 mg/1 a Standard7Metho s r the EXaminatiQnw r, 16th Edition, 1985 b U.S. EPA, "Methods for Chemical Analysis of Water and Wastes", EPA - 600/4 - 79 - 020 R202/4340/122088 Hwd:1007T/01-17-89 5-4 2.5 2.0 cr E J a W W z 1.0 O J 49.0m'g/I U 0.500 -2 4 6 8 10 12 14 16 18 20 CHLORINE DOSAGE (mg/1) CITY OF TAMARAC S.D.W.A. EVALUATION N CHLORINE DOSAGE EFFECT ON CHLORINE RESIDUAL HAZEN AND SAWYER, P.C. FiG. 5-11Engineers I BREAKPOINT/DEMAND I CHLORAMINE DECOMP051110N H JFC ORAM RMATI NE N FREE CHLORINE RESIDUAL I I R- B9- 9� Because formation of TTHMs occurs primarily in the presence of free chlorine, the region beyond the breakpoint was selected for subsequent evaluations of the effects of chlorine dose and time of contact on formation of TTHMs and total organic halides (TOX). These evaluations were performed at chlorine dosages of 2.5, 5.0, 10.0, and 15.0 mg/l beyond the "breakpoint" demand of 9 mg/l, resulting..ln total chlorine dosages of 11.5, 14, 19, and 24 mg/l, respectively. Samples were obtained at 1 day, 3 day, and 5 day intervals. Results for TTHM formation, shown in Figure 5-2, demonstrated a progressive increase in formation with increased dose. However, time did not have a significant effect between 1 and 5 days. Total formation potentials for these experiments ranged up to 0.284 mg/l. In contrast with the TTHM results, results for TOX formation, shown In Figure 5-3, exhibit a significant effect due to time. Because the data show no indication of leveling off with continued time of reaction, it was decided that future evaluations of TTHM and TOX formation potential would be performed for a common 5 day period and that results would be reported in relative terms that are not intended to indicate ultimate formation potential. It should also be noted that TTHM and TOX are affected by pH. As such, pH was controlled at a common level within a given experiment so that comparable formation conditions would be maintained. Based on capability for reliably maintaining a free chlorine residual at a level greater than 1 mg/l over a 5 day period, a chlorine dosage of 15 mg/l beyond the "breakpoint" demand was selected for future evaluations. All samples were incubated in the dark at a laboratory temperature of approximately 20"C. Sample bottles were filled to minimize the presence of an air space in which TTHM and other volatile organics (compounds which tend to desorb into gaseous forms) could accumulate and thereby be lost from the sample. Calibration f n h Bench scale simulations of the lime softening process were performed using 2 liter, square beakers made of acrylic plastic (Phipps and Bird B-KER 2 jar test beakers) and a jar test apparatus was used for mixing. Reagent grade calcium hydroxide (Ca(OH)2) was used in place of dFy lime because of greater ease in control under laboratory conditions. Out of necessity, chlorine was added in the form of dilute reagent grade sodium hypochlorite (NaOCI). In all cases, 1 mg/l of Drewfloc No. 3 polymer was added to simulate the use of coagulant aids in the full scale plant. Figure 5-4, shows the results of tests performed to assess the effect of hydrated lime dose on pH in the 8.9 to 9.1 range that is the operating goal for the full scale plant. This figure is typical of the relationships that were derived throughout the testing period. As indicated by these results, the target pH of 8.9 to 9.1 R202/4340/122088 Hwd:1007T/01-17-89 5-5 4q 5or 40( 9111 200 u81 1 2 3 4 5 REACTION TIME (DAYS) NOTE: pH RANGE WAS 7.2 TO 7.4 LE.GENQ 11.5 mgA A 14.0 mg/I ■ 19.0 mg/I #24.0 mg/I 24.0 mg/I 19.0 mg/I 14.0 mg/I 11.5 mg/I CITY OF TAMARAC S. D. W. A. EVALUATION CHLORINE CONCENTRATION VS. TIME EFFECT ON RAW WATER MM FORMATION POTENTIAL m HAZEN AND SAWYER, P.C. FIG. 5-2 Engineers 1?-K7-?7 .�- 50( 14J Z 200 Lf O J H 100 qs n mg/I 19.0 mg/I 1 2 3 4 5 REACTION TIME (DAYS) NOTE: pH RANGE WAS 7.2 TO 7.4 LESENQ • 11.5 mg/I ♦ 14.0 mg/1 ■ 19.0 mg/I * 24.0 mg/I 14.0 mg/I 11.5 mg/I I� CITY OF TAMARAC S.D.W.A. EVALUATION i CHLORINE CONCENTRATION VS. TIME EFFECT ON RAW WATER TOX HAZEN AND SAWYER, P.C. FIG. 5-3Engineers r2- g9 - ? corresponds to a relatively narrow band of dosage, requiring careful is control of lime dose. From a plant operating standpoint, raw water quality varies to an extent depending on the combinations of wells in service. Sensitive adjustments in lime dose are frequently required when these variations occur. Operating personnel also report that similar adjustments may be required due to variation in the quality of lime when new dry lime deliveries are received. Due to the highly sensitive nature of the relationship between lime dose and pH, pre-screening testing of raw water was necessary in order to determine the precise relationship between lime concentration and pH prior to each bench -scale test. Also, because the Accelator units provide internal recirculation of sludge as a means of catalyzing the softening reactions, recycle of sludge was practiced in bench -scale experiments. Recycled sludge was generated by a process of lime addition at the selected dose for a 20 minute reaction time followed by a 20 minute settling time. Supernatant was decanted and the remaining sludge was retained and added to the next sample which was then dosed with lime and other treatment chemicals. Three cycles of sludge accumulation were employed in each test. Best results were obtained in these experiments by stirring throughout the mix period at a rate of 80 rpm. With respect to chlorine dosage, a slightly lower dosage in the bench scale yielded the best approximation to the full-scale Accelator in terms of total chlorine residual. The method of chlorine dosing consisted of an addition of one half of the chlorine dose prior to the addition of lime and the remainder following lime addition. This simulates the sequence of addition in the full scale plant. Results shown in Table 5-2 indicate that the bench scale test gives a relatively close approximation to full scale Accelator performance for most parameters. Although the total chlorine residuals are relatively close, a somewhat higher free chlorine residual is observed in the bench -scale tests. However, this does not appear to have a significant effect on the formation of TTHMs or TOX when results from the bench scale experimentsi are compared with those obtained from the full scale Accelator for the same time period. Because color removal at other water treatment plants has proven to be a significant problem in treating groundwater from the Biscayne Aquifier, especially when chlorination practices are modified, evaluations were performed to assess the use of ferric chloride and potassium permanganate as alternative means of color removal. Such approaches are sometimes beneficial in this respect in cases where chlorination practices have been modified to reduce TTHM formation. R202/4340/122088 Hwd:1007T/01-17-89 5--6 0 L-1 Chlorine Dose Lime Dose" pH Free Chlorine Residual Total Chlorine Residual Color Total Hardness Calcium Hardness Total Alkalinity Initial TTHM TTHM Formation Potential TOX Formation Potential TABLE 5-2 JAR JESI CALIBRATION Bench -Scale Test 8.0 mg/1 220 mg/1 9.1 0.8 mg/l 3.3 mg/1 15 color units 66 mg/l as CaCO3 62 mg/1 as CaCO3 42 mg/l as CaCO3 0.048 mg/l 0.319 mg/l 0.520 mg/1 Full -Scale Accelator 8.8 mg/l 240 mg/l 8.9 0.0 mg/l 3.4 mg/l 10 color units 76 mg/l as CaCO3 76 mg/l as CaCO3 42 mg/l as CaCO3 0.038 mg/l 0.287 mg/1 0.400 mg/l " Lime is expressed in terms of equivalent calcium hydroxide- Ca(OH)2. An allowance is also made for approximately 10% impurfities in the bulk dry lime used in the full-scale Accelator. R202/4340/122088 Hwd:1007T/01-17-89 5-7 Use of ferric chloride was evaluated in the lime softening process .. which is operated at a pH of approximately 9. Table 5-3 shows the results for a series of bench —scale experiments in which ferric chloride was added at different dosages to the lime softening process (pH9). The sequence of chemical addition for a full scale plant is represented schematically in Figure 5-5. These results do not demonstrate any significant benefits of the use of ferric chloride -for the removal of color. Although significant reductions in TTHM formation potential (TTHM—FP) can be achieved at some dosages, these reductions are not adequate to justify the use of ferric chloride as a means of controlling disinfection byproducts to very low levels. Results are presented in Table 5-4 for bench —scale experiments performed with potassium permanganate and ferric chloride, both added prior to lime addition at a raw water pH of approximately 7. A contact time of approximately two minutes was provided between the addition of either potassium permanganate or ferric chloride and the addition of lime. In the case of ferric chloride, this method of addition is intended to take advantage of more favorable conditions for color removal at pH 7 prior to subsequent increase to pH 9 by lime addition. The sequences of chemical addition for these tests are represented schematically as they would occur for a full scale plant in Figures 5-6 and 5-7. A major objective of these experiments was to evaluate the capability of potassium permanganate and ferric chloride for removing color if chlorination was eliminated or altered. Therefore, chlorine was not added in these bench —scale experiments and results were compared with parallel bench scale simulations of the existing softening process with and without the addition chlorine. No significant reductions in color are achieved as compared with the existing method of treatment with or without chlorine. Results from the softening simulation without chlorine also indicate that softening alone can achieve significant reductions in color and that the role of chlorine for supplementing these reductions is not significant at the TUW Water Treatment Plant. This finding was confirmed by subsequent full—scale evaluations when the point of chlorination within the plant was moved downstream of the Accelator. Under this condition lime softening was capable of removing color from 25 color units in raw water to 10 units in the Accelator effluent. Results for --TTHM of TOX formation potential do not indicate that these constituents can be removed to low levels with the addition of either potassium permanganate or ferric chloride prior to lime addition. Therefore, no subsequent evaluations were performed with these chemicals under this study. As more becomes known regarding specific standards for disinfection byproducts, the benefits of these chemicals might be re—evaluated as supplemental approaches for optimizing disinfection byproduct control in conjunction with other methods. 12 R202/4340/122088 Hwd:1007T/01-24-89 5-8 x 0 O pp OA �- O� �O 1 O Ln eD CO D tp O c M •C « � O O O O « « Fgy N 1h N M N +� V O O O Q L w 0 a) K a M A v � N C d 2 « « CA CD �O at N Q t AJ ►pi c © N U O O b vs a ro d n W ++ W w I--1 n n n n o 11 A N N N N a ' W Jga�Gr,b r O �'' '•. •N ce o r- LLI 0 o rr LL .� O © n ^ a b n o, ah co co .40+ a �. w 6 r b o vLU 1 I N � L. EE N M C 41 S LL b b « N c I Ill CDLO Ln w 7 J O N N N N O �p d V N N a G d N d O C x � a A 1 co co CD eo �•+� a N A d N 31 it •^ N Yl A lr d a �+ N •O .-. L c I n C x •� i a c c 's s o Y ` N x E E F L •p t u+ o c .+ b do 4- G •i M �! M •� e7 a Q w O A L) d of i LU c� +• a �- u 5 a oLL o� o� c x L. 00V a d C r L. a •q ME A •C A N A do �p1 S S H M N Ln « it« OC Vf N cm V! M N 1OA « Mil 0 C1 n a. LLI i O '►f Ln N %Q M N ff! O (•7 a c KI K -j q er sf er u 1 v H K Im H I— Z W pppp b H ce d x lam► N In 41Y PN+ C W H K K L a o Ln Ln Ln Ln Ln LO .•► N N O F C b N 0 I I I 1 t a Ix li9 cm a d � u C d Y f • p0� I O� �r•• U 1• co w vh ao ao I+ C /h .r d[ I I I I O I N A W W �x 7 qr 1 I N I 1 O O b Y M ram► Ky� {M ( N •F•I N N N N J F t Co t t I 1 W H W _ J d c Im m ro C U ro r .e N b N 0 d C 7 X d r r L •�• r•'- X IV L W M ,C t O .Z Gc L O W a+ x O d w d . •� d 0 OG IA O con N s Y N X Y Vf W L? N O N U I* 5-10 11 Tvxvrrt U O <F i QQ LLJ J =z U aC C-i v a: q H> o� )p wLL O i OQ UW Q U W a z z > r W� Z 0 U O = U 72 O LLI J LE m LY a 3 3 a 89xo*v* �3rz-��9�97 Evaluati n f lorine Dioxi e %is an-AlterMtive Oisinfectantan-Alter Approximately 15 gallons of raw water from the TUW Water Treatment Plant were transported to the Hillsborough Water Treatment Plant in Tampa, Florida for experiments to evaluate chlorine dioxide. This facility applies chlorine dioxide (C102) on a full scale basis, using a Rio Linda, vacuum -type, chlorine dioxide generation system. This system consists of a chlorine injector that applies a vacuum to draw both chlorine gas and sodium chlorite (NaC102) to a point where they are mixed and reactions take place to form chlorine dioxide. An idealized representation of this reaction is as follows: 2 NaC102 + C12(gas)•2C102(gas)+2NaC1 In practice, some excess chlorine is added and free chlorine will occur in full scale chlorine dioxide feed streams as an impurity. As such, free chlorine is not entirely removed from the process stream by converting to chlorine dioxide and its potential effects as an impurity in the feed stream are an important consideration. Because of the effects of impurities on full scale application of chlorine dioxide, use of a chlorine dioxide stream generated at a full scale facility such as the Hillsborough Water Treatment Plant is more representative of phenomena that might be anticipated from commercial generation equipment. Bench -scale evaluations were performed to assess capability for maintaining a chlorine dioxide residual and for using chlorine dioxide in conjunction with chloramines to minimize the formation of TTHMs and TOX. Analytical methods that have been developed for process control at the Hillsborough Water Treatment Plant were used to assess chlorine dioxide residuals in these bench -scale studies. These methods involve titrations of combinations of residual oxidants with a phenylarsine oxide titrant in the presence of potassium iodide and a starch indicator. Two titrations were preformed: 1. Titration ri n h i Dioxide JpH7 r i - A pH7 buffer was added to the sample to control the pH for this titration. ' Chemical constituents titrated at this pH include free and combined chlorine and chlorine dioxide. 2. Ti r Tgtal i hl ril rini Dioxide (02 T r i n) - This is actually a two stage titration in which a pH4 buffer is initially added to the sample and the phenylarsine oxide titrant is added to achieve a color change in the- starch indicator. This is the initial step of titration that is intended to eliminate interferences that might occur as a result of chloramines. For the second step, 4 Molar hydrochloric acid is added to further reduce the pH to 2. R202/4340/122088 Hwd:1007T/01-24-89 5-11 /F— acl9- 97 �J �J Subsequent titration at this pH indicates the quantity of chlorine dioxide plus its major degradation product, chlorite (C102). This combination is termed total oxidants and typically represents the major residual products which should to be limited to meet health -related criteria for chlorine dioxide and its degradation products. While these methods of analysis are not rigorous for firmly establishing chlorine dioxide and chlorite concentrations, they provide order of magnitude assessments that were suitable for the screening type of evaluations that were the intent of these chlorine dioxide tests. Initial testing was performed to assess capability to maintain a chlorine dioxide residual in treated TUW raw water derived from previously described bench -scale lime softening simulations. Results from this testing are shown in Table 5-5. In order to minimize possible effects of chlorine dioxide degradation in the feed solutions, all chlorine dioxide feed solutions were dosed within a few minutes after being collected from a sample tap at the Hillsborough Water Treatment Plant chlorine dioxide Because the pH7 titration does not distinguish chlorine dioxide afrrom a chlorine residual that may occur due to the presence chlorine as contaminant in the feed stream, data shown in Table 5-5 indicate adjusted chlorine dioxide residuals that are computed based on the maximum potential effects of background chlorine contamination. This basis for estimating chlorine dioxide residuals tends to understate the actual residual since it assumes that all of the chlorine will remain in solution. Even with this correction, these data indicate that significant levels of chlorine dioxide can be maintained as a residual in solution for periods of contact up to one hour. The present criterion for total oxidant residuals is 1.0 mg/l. Based on the results shown in Table 5-5, this criterion could be met at a chlorine dioxide dose of approximately 2 mg/l while maintaining a significant chlorine dioxide residual. However, if lower total oxidant levels are be required by future standards, it may not be Possible to maintain stable disinfecting residuals under such a limitation and chlorine dioxide could be eliminated as a viable approach. For this study, a chlorin subsequent experiments to using chlorine dioxide as TUW raw water was performed lime softening at the TUW in Table 5-6. R202/4340/122088 Hwd:1007-i/01-17-89 e dioxide dosage of 2 mg/l was selected for evaluate formation of TTHMs and TOX when an alternative disinfectant. Testing on using bench -scale methods for simulating water treatment plant. Results are shown 5-12 I K k k C C 0% Ln A O x "O CD p O F O .X r v � Ln r K k K m c N V 5 C r rl r c. 0 C 4 � k R k K d NY I!'1 N O •it P r r O x r Lj Q m R C _ N •L •7K N � Q � � O . n r G r �' � U A G R O G a N CD N N N N N N N m c •L •r O M G p Cf G r .w N !•'1 rt V r 5-13 m O r F u C u u o � C V � A A C � L P� L d m O L M L � L O V � A u N N .6.) A m N m d a L 4 d w m O .mi rrc o Y o V m C C r .4 O O r O r r •c V � V b Cc O A L 6 �.r C C d y u C o u U d r V X M- L O O r• d L •� m O N � c A M N L 7 O V y V A c Afo N L t iL A O O N a 0 r. � A •r d r A Y 00 o d i N A m G m d •r r O A ` u s k k K R k « R k C� 0 c�1 I C� 0 I � o u M Ln 1 N N O O O O CI H O %0 1 O O m N O Cl N pp p� Ln O 1•7 O F+ Id �� ^ - OI 1 10 © O ►n .0 FBI 1 O O O 0 o O « B « ko « N n n n « Z N in r 'O.. o, v b c./ N w N P IA'1 1► f► O CD O ' N � �G W p � O C �0 IA g J C N 10 ++ u O YI C N1 N N N E vaNi CO Qr 6 C +r x � W O 4 I co lw I W L O rt N N >1 CA c •� axi I I coam `o Y 1`ro ro J A d co 4 ++ O �v alro O TC; IL _ S m 41 J i in « g+ o M I-e Ioo 1`s v 1«I a ac 012� n n 11 m oe o�c 5-14 Two chloramination approaches were used in conjunction witn chlorine dioxide. These were compared with a control test that simulated the existing practice of using free chlorine to react with background ammonia in raw water in order to form chloramines. Jar No. 1 represents this control test using sodium hypochlorite to provide 4 mg/l of free chlorine prior to the addition of lime and 4 mg/l of free chlorine after lime addition. The sequence is represented schematically in Figure 4-1 for the full scale plant. In Jar No. 2, sodium hypochlorite is added to provide 4 mg/l of free chlorine prior to lime addition. Chlorine dioxide is added following the settling portion of this test along with 4 mg/l of a pre -formed chloramine solution. This solution replaces free chlorine in the second chlorination step as shown schematically in Figure 5-8 for a full scale process sequence. The solution was produced by prior reaction of sodium hypochlorite with ammonium sulfate: 2NaOC1 + (NH4)2SO4=2NH2C1+2NaOH+H2SO4. The chemical additions in jar No. 3, shown schematically in Figure 5-9 for a full scale process sequence, simulates the addition of pre -formed chloramine in place of free chlorine at both chlorination locations in conjunction with the addition of chlorine dioxide. This method of chloramination eliminates the opportunity for a period of contact between free chlorine and the process stream. Results for THM and TOX analyses from these experiments are shown in Table 5-6.Two sets of samples were obtained for these analyses: 1) samples taken immediately after the bench -scale testing, and 2) samples taken following a period of 5 days of incubation in the dark at the ambient laboratory temperature of 200C. The 5-day samples differ from analyses of formation potential in that no excess chlorine is added. Instead they are intended to indicate the levels to which THM and TOX will occur in the presence of typical chloramine concentrations added during the treatment process. These results indicate that while significant reductions in TTHM levels can be achieved by using free chlorine in combination with Pre -formed chloramines as simulated in Jar No. 2, TOX levels are not as significantly reduced. Results for Jar No. 3 indicate that the use of pre -formed chloramines at both chlorine addition points results in a greater reduction in TOX. Overall, th6-results from the chlorine dioxide evaluations indicate that chlorine dioxide could be applicable as a disinfectant for achieving concentration and time requirements for primary disinfection. Additionally, when used in conjunction with pre -formed chloramines, this approach can yield very low levels of TTHM and TOX that would be capable of complying with standards requiring low levels of disinfection byproducts. However, before detailed testing of this alternative is undertaken, final standards that establish allowable residuals for chlorine dioxide and its degradation products should be known. These standards are presently being developed. • R202/4340/122088 Hwd:1007T/01-24-89 5-15 17� N 0 Z -1 00 Q Q = Z -j C) a QQ I- n� ` W LL p o Z 0Q WW Z� d c c w U . W U. z zwo V© 2 U C9 Z wZ cr W J O a Z- w o J � W a LXOK* Z 00 (yQq Q Q W c LL o z N 0 . Z U Q =� R_4r7_1?7 . Evaluations of OzQnC as aa_Alternativei in n Unlike the other disinfecting chemicals evaluated in this study, ozone does not contain chlorine, thereby reducing the potential for formation of chlorinated byproducts. Although some concern exists for some of its byproducts that are listed Table 2-1, they are presently -of less concern than those of chlorine. Ozone is typically produced by passing air or oxygen through an electric discharge, with ozone formation occurring as described by the following idealized reaction sequence: 302 + electric discharge - 203 Because ozone is not stable for extensive periods of time, generation equipment is normally provided at the site of application. For this reason it was necessary to use a pilot scale ozone generator, which was supplied by Griffin Technics. This generator had a capacity range of 0.1 to 1.0 pounds of ozone per day. Evaluations of ozone were performed at two application points within the process train: 1) in the raw water prior to the addition of lime and 2) in the Accelator effluent following lime softening. The advantage of application at the first location derives from the fact that ozone is more stable in the near neutral pH range (approximately pH7) found at this point in the process train than in the more alkaline pH range found in Accelator effluent • (approximately pH9). if the goal of ozonation is to achieve a measurable ozone residual to meet disinfection criteria for concentration and time, this aspect of ozone chemistry suggests that PH adjustment to a more neutral range might be required for an application point at the Accelator effluent, thereby increasing process complexity. A schematic of the pilot facilities is shown in Figure 5-10. These facilities consisted of two columns in series. Flow was introduced at the top of each column and was discharged from the bottom. The first column had the capability for introduction of carbon dioxide from a liquid carbon dioxide cylinder. This allowed for pH ,adjustment during selected experiments. Ozone from the generator was introduced into the second column through a fine bubble diffuser, loSated at a depth of submergence of 15 feet. This is typical of the submergence depths provided in full scale ozone facilities and was intended to give a representation of results that could be achieved at full scale for a given applied ozone dose. The method of contacting is referred to as a counter —current method in that liquid flow is in the downward direction counter to the gas bubbles rising from the bottom. • R202/4340/122088 Hwd :1007T/01-24-89 5-16 0 a o C?I a U I W I J r- F t M t a w _ w aQ 3 En �;z z o cn in w D .2 a� z F. 06 a� U D I � wo ac a p oK1 • R-89'97 Figure 5-11 shows ozone residual results for application of ozone in the raw water. Although the pH of raw water entering column was near neutral, the pH of the ozonated water was increased to a level 7.8 - 8.0. This is most likely to have been caused by stripping of carbon dioxide from raw water through the introduction of the ozone laden airstream from the ozone generator. The ozone contactor was operated at a flow rate of 5.5 gpm, achieving a contact time of approximately 4 minutes from the top of the contactor to the point of ozone introduction. Samples were withdrawn at a level 2 feet below the ozone diffuser, this resulted in a total theoretical time of contact of 0.5 minutes between the point of ozone introduction and the point of sample collection. Therefore, a time of contact with ozone residual resulted from these experiments indicating capability for achieving contact with a measurable ozone residual. This capability was also confirmed by sampling at locations immediately downstream of the ozone contactor. Figure 5-12 shows color levels achieved at different applied ozone dosages. In all cases, color was significantly reduced below the level of 25 color units in the raw water, indicating significant reaction with ozone at all of the applied dosages. As would be expected, color levels were progressively reduced as applied ozone doses was increased. Bench scale softening simulations were performed using raw water that had been ozonated at an applied dose of 9 mg/l. These were compared with a control test that simulated the existing method of chlorination. THM and TOX results from these evaluations are shown in Table 5-7. As in the case of the chlorine dioxide experiments, the 5-day samples were incubated without addition of excess free chlorine and are intended to represent THM and TOX levels to be expected in the presence of the normal chlorine and chloramine dosages. Jar No. 1 is the control which simulates the existing lime softening process in un-ozonated raw water, using present methods of chlorination. Sodium hypochlorite was added to achieve a total free chlorine dosage of 8 mg/l, with 4 mg/l added prior to lime addition and 4 mg/l after lime addition. In Jar No. 2, lime softening of ozonated effluent was simulated in conjunction with a combined free chlorine/chloramination approach as represented schematically in Figure 5-13: Sodium hypochlorite was added to the first chlorine addition point prior to lime addition. Preformed chloramines are added at the second chlorine addition point in place of free chlorine, thereby reducing contact with free chlorine as compared with the existing method of chlorination. The third jar also simulates lime softening of ozonated effluent, however, pre -formed chloramines are added at both chlorination points as represented schematically in Figure 5-14 for a full scale plant. R202/4340/122088 Hwd:1007T/01-24-89 5-17 E 1�1 0 No Text p p p ro �. Comm ^� �I o 0 O p p ►+ �I M p J J m m O M M it r P�7 101f INA t M My �•'� F* � rr�� IA Pp. IN► FI N 6� 8 ro IA IA �O H N N N C W •r og b N N a G r n lD 1� u r ro <) CV)M :F� iy �;y r C 1-4 1A O O J ` H Z C W • CA M 1.2 C I « Ln ^ N p W N ^ r- a OaD 11D O •.r Go OA N N O N S d d u N 1 N � J L • LO N ' O a N m Z r = z0 $.. L. r: 1, n 5-18 C • 0 ro LO -jQ aZ U w 2� W J =a U � W Z Z W N N © W L ozxo t t cc J � as U_Z mJ vQ w~ Z Z Ow N O W ,' 4 U • • 11 ZXOK* R-- o"l -- 97' Chlorine dosages for the ozonated samples were decreased in order to adjust for the effects of ozone on chlorine demand as illustrated in comparative "breakpoint chlorination" curves shown in Figure 5-15. Although these curves indicate a slight reduction in chlorine demand at the breakpoint, significantly greater levels of chlorine residual can be maintained in ozonated water at chlorine dosages less than the breakpoint. Therefore, chlorination can be reduced in ozonated effluent when operating in this dosage range. These adjustments were made in the bench scale tests of ozonated water so that the final residual chlorine levels would be comparable to those in tests on raw, un—ozonated water. Results in Table 5-7 indicate that significant reductions in TTHM can be achieved when using ozone in combination with pre —formed chloramines. It should be noted that the method presently used in the full scale plant is still basically a chloramination approach that uses background ammonia in raw water to react with the free chlorine. Even this approach achieves a degree of TTHM reduction as compared with use of free chlorine at dosages that exceed the break—point. This approach may still be applicable in conjunction with ozone if new regulations do not require that trihalomethanes be reduced to extremely low levels. The remaining ozonation studies evaluated the second point of ozone application at the Accelator effluent. Figure 5-16 shows results for ozone residual that were obtained for this point of ozonation. For these experiments, operational changes were made within the full scale TUW Water Treatment Plant to move the point of chlorination to downstream locations. This eliminated chlorine from the Accelator effluent that served as the feed stream for these experiments. Two ozone residual curves are shown in Figure 5-16, one for a recarbonated stream that had the pH adjusted to a range of 6.8 to 7.2 by recarbonation and the other for Accelator effluent with no pH adjustment. The pH range for the second feed stream was 9.0 to 9.2. These results demonstrate the effect of pH on capability for maintaining ozone residual and it is clear that pH adjustment would be required if provision of an ozone residual was a process goal. Figure 5-17 shows the effect of applied ozone dose on color levels. These are reduced from an initial color level of 12.5 color units in the Accelator effluent. Effective color removal is maintained at all applied -dosages indicating that effective ozone transfer is occurring at -the full range of applied dosages. Bench scale studies were performed to assess the effectiveness of using pre —formed chloramine. Process sequence for these experiments is represented schematically in Figure 5-18. Both recarbonated and non—recarbonated Accelator effluent feeds were evaluated. Results for these tests, shown in Table 5-8, indicate that TTHM formation R202/4340/122088 Hwd:1007T/01-24-89 5-19 0 r �J [6a 0.1 [a] w _ z 4 6 8 10 12 14 APPLIED OZONE DOSE (mg/1) CITY OF TAMARAC S.D.W.A. EVALUATION OZONE RESIDUAL IN LIME SOFTENED WATER HAZEN AND SAWYER. P.C. FIG. 5_16 Engineara R_89 -97 25 20 z 15 O J O 0 10 O J O V 5 0 10 12 14 16 APPLIED 03 DOSE (mg/1) RECARBONATED pH RANGE 6.8-7.2 NON-RECARBONATED pH RANGE 9.0-9.2 ACCELATOR COLOR=25 F TAMARAC EVALUATION ppNF CC0 $NEENE ATERWYER, P.C. FIG. 5--�17 Engin, 11 NON--RECARBONATED RECARBONATED 0 2 4 6 8 11 0. v x Q Q -� a aZ S2w w-i =a U W ~ Z Z W Z N F OW r„ W m 9 C 30 W xD �N z 00 =F a m a �U WW cy- LL W" Z = a �a aZ W 7L W W H X OV 2 Z • SXOIKr m LO OF W ..I On H � 1 I d o w m as _ 1 1 � ro �I o 0 1 1 4 p m pp N r� C b 0 1 I C+ eh e p� J c r r O O O OD O J �.. Cf 4 N i p41 eh " 11 O C7 C C? 1 X « O L ! r Ln O 1lf 1!9 N N { C I O ' A ^ i Fa ► F� . y 7 I M A I � it, A � e •r I � N � �^ F r r ^ 0 d C Q L O N CL L L J O •� V V w d y m u C w N N L p L O O O CAC V ^ i� A C tw.i C O C y m G 7 CC 7 e w 1. N r- I ^ Id ^ J p CwC C! W Z w pC L" m 5-20 E 9 can be minimized by this approach. However, higher levels of TOX are encountered than in previous pre -formed chloramine experiments with chlorine dioxide (Table 5-6) and ozonated raw water (Table 5-7). This may have resulted either from background contamination in testing equipment or from some differences that might be controlled with more attention to ozone dosage or conditions of reaction. It is also possible for a degree of formation of halogenated organics to occur as a result of ozonation. This has been observed in other studies as reported in 1 n i i (AWWA Research Foundation, 1986). However, these reported increases have been slight and would not explain the results in Table 5-8. Although resolution of this question was not considered important to the existing study because of uncertainties of regulation for specific contaminants that comprise TOX, opportunities for further reducing halogenated byproduct formation should be considered in future evaluations. Results in Tables 5-6 and 5-7 indicate that relatively low levels can be attained under proper conditions. It should be noted that although ozonation was applied to Accelator effluent for these studies, actual application of ozone might be downstream of the filters. With the exception of some additional removal of solids, water quality characteristics of the Accelator effluent test location are similar to those of filter effluent. Therefore, no major differences in response to ozone would occur between these two locations. However, application at the filter effluent may be necessary under some possible disinfection criteria. Under these criteria, disinfection for certain pathogen categories may only be allowed in application to low turbidity process streams such as those that receive prior filtration. As an example, in the aEaf t Qui danCe.n 1 F r m li w h h F i r i n n Di i n i R m n 1i W �►si ng�i,irrf , ce_il tars (US EPA,at m 1987), it was recommended that disinfection credit be allowed for virus inactivation only where the disinfectant is being added to water where the turbidity is less than 1NTU. CDNCLUSIONS The significant findings of this testing program can be summarized as follows: - o Chlorine dioxide and ozone can be applied to achieve measurable residuals to meet future criteria for primary disinfection. Because of possible regulations to limit allowable residual levels of chlorine dioxide and its degradation products, ozone was selected as the basis for economic evaluations of potential costs for meeting future disinfection requirements. Although less concern presently R202/4340/122088 Hwd:1007T/01-24-89 5-21 exists for ozone byproducts, possible regulations are under consideration as indicated in Table 2-5. The implications of these regulations will need to be resolved before a final decision for ozone can be made. o If ozone is applied to lime softened water, pH adjustment to a more. neutral range may be necessary to maximize ozone concentrations. o The existing method of chlorination can meet current TTHM standards for Maximum Contaminant Level at 0.100 mg/l. This practice involves the use of background ammonia in the raw water for reacting with chlorine to form chloramines. o Supplemental addition of ammonia to pre -form chloramines was found to limit TTHM and TOX formation. This approach would be capable of meeting a wide range of possible standards for disinfection byproducts that might be applied in the future. Additional evaluations of possible byproducts and the effects of any future limitation on chloramine residual may be required once regulations for disinfection byproducts have been established. Also, partial nitrification has been observed to result in undersirable nitrite levels in some systems where chloramines have been used. This phenomenom is not fully understood and could limit available chloramination approaches under some circumstances. Chlorine to ammonia ratios may need to be tightly controlled to minimize the potential for free ammonia to occur at significant levels downstream of the water treatment plant. This may require that a portion of the total chlorine dose be provided with free chlorine to react with background ammonia in raw water. Pre -formed chloramines would then be added to meet the remainder of the chlorine dose requirement. While this approach is less effective for reducing TTHM's and TOX, than sole use of pre -formed chloramines, results in this study indicate that significant reductions can still be achieved. o The existing method of chlorination is not necessary for control of color, iron, manganese; and tastes and odors. Therefore, these functions, which chlorine performs in many water treatment plants, are not a significant factor in selecting modified disinfection approaches. o Under "the iS�ja - based regulations for ozone that are proposed in the Surface Water Treatment Rule, a CxT of 1 mg/1-minute has been recommended for the water temperature of 250C that is typical for the TUW Water Treatment Plant. Proposed regulations also allow credit for non -disinfection GJArdia removal by coagulation, sedimentation and filtration processes. By applying these removal credits the CxT would be reduced to 0.3 mg/1-minute. R202/4340/122088 Hwd:1007T/01-24-89 5-22 i --�9- 9 7 For the purpose of economic evaluations developed for this study, an applied ozone dosage of 9 mg/l was used. This dosage achieved an ozone residual of 0.2 mg/l in recarbonated Accelator effluent as shown in Figure 5-16 n capableg and should be of providing a modest residual for the short time period that would be required to achieve CxT of 0.3 mg/1—minute. Design of full scale ozone contacting facilities may allow reductions in dosage through use of multi —stage contacting configurations that are intended to optimize ozone utilization. Additionally, future groundwater regulations, which will actually establish disinfection requirements at TUW, may have less stringent CxT requirements for ozone because of reduced concerns for GiarAia. For example, enteric viruses, which represent a pathogen category of possible concern in some groundwater supplies have less stringent CxT criteria for ozones. The US EPA Comp1 1jance -with Pubof it m 1 indicates an ozone CxT of 0.2 mg/1 minute for achieving desired disinfection levels for enteric viruses. If credit is allowed for virus removal by coagulation, sedimentation and filtration, the CxT level could be reduced to 0.15 mg/1—minute. o Use of ozone in combination with pre —formed chloramines would allow flexibility for the existing lime softening process to meet a wide range of possible standards for primary and secondary disinfection as well as for disinfection byproducts. Therefore, the existing softening system has a good likelihood for meeting future standards with future modifications to disinfection and should not be considered obsolete at this time. More specific evaluations may be tA appropriate when definitive regulations have been developed. R202/4340/122088 Hwd:1007T/01-24-89 5-23 CHAPTER 6 EVALUATION OF SOFTENING WITH LOW PRESSURE REVERSE OSMOSIS Softening -.with low pressure reverse osmosis (RO) systems is being considered in a number of Florida locations as an alternative to conventional lime softening systems. Membranes used for this technology are more permeable to many ionic constituents found in water than are other RO membranes. However, they are capable of reducing water hardness by removing larger ions, such as calcium and magnesium. Capability for removal of these ions, while of the smaller ions, reduces the osmotic nt acrosof many the membrane, allowing for operation at muchrelower totals pressurres than those required for other membranes. A significant benefit from the use of low pressure RO membranes can derive from removal of organic constituents that are responsible for background TTHM and TOX formation potential in a raw water. Depending on the severity of future standards for disinfection byproducts, this reduction in formation potential disinfection byproduct standards to be met while usinglda afree chlorine residual for achieving primary disinfection criteria. If future disinfection standards for groundwater require a stronger disinfectant than chloramines for meeting . criteria, this capability would avoid the need for r using disinfection dioxide or ozone to meet these criteria. On the other hand, this benefit would be diminished if future standards allow continued use of chloramines for meeting criteria for disinfection and disinfection byproducts. Therefore, a key factor in evaluating RO as a potential replacement for existing lime softening be the extent to which a stronger disinfecting capability willibe required to meet future standards for disinfection of groundwater. This question will not be resolved until these standards, as well as standards for chloramine byproducts, are established. Evaluations for RO were performed in 'conjunction with Rostek Services, Incorporated, a specialty firm with broad knowledge of the application of membrane processes to Florida water. The level of assessment provides a preliminary economic evaluation of the potential for RO at the TUN water treatment plant. If RO is selected for- further evaluation, specific on —site testing would be required to" confirm its operational applicability and specific capability for meeting goals for TTHM and other disinfection byproducts. Estimates of RO performance were based on typical raw water quality for TUW. as summarized in Table 6-1. No data were available for strontium, potassium or silica. However, while these constituents can have significant effects on other membranes, silica should not be significant considerations forplow Potasand sium • membranes. Strontium can be a concern because of potential for R205/4340/122088 Hwd:1008T/01-17-89 6-1 R-89-97 TABLE 6-1 CITY OF TAMARAC TYPICAL RAW WATER CHARACTERISTICS FOR REVERSEOSMOSIS EVALUATION Calcium (as Ca) Magnesium (as Mg) Sodium Barium Iron Bicarbonate (as HCO3) Sulfate Chloride Total Dissolved Solids pH Color Total Organic Carbon (TOC) R205/4340/122088 Hwd:1008T/01-24-89 100 mg/l 4 mg/l 33 mg/1 0.058 mg/l 0.5 mg/l 280 mg/l 37 mg/l 62 mg/1 376 mg/l 7.2 30 color units 15 mg/l 0 C� • R-89-97 n LJ membrane scaling from precipitation of strontium sulfate. However, experience with shallow groundwater in the eastern coastal region of Florida indicates that this is not likely to be a problem. From the standpoint of the data compiled in Table 6-1, the major concern from a scaling. -standpoint would be for precipitation of barium sulfate. However, this is likely to be controllable by pretreatment with scale inhibitor prior to RO. Estimates for the RO system are based on recovery of 85 percent of the feed stream as a permeate or product water, with the remaining 15 percent rejected as a concentrated brine stream that must be disposed. A process schematic for the proposed RO system is shown in Figure 6-1. The basic process train includes: 1. Pretreatment that consists of cartridge filters to remove solids, addition of scale inhibitors, and addition of sulfuric acid to adjust pH to an optimal range for RO effectiveness. 2. Feed pumps designed for a RO feed pressure of 130 psi. 3. Low pressure RO system, including provision for periodic addition of cleaning chemicals and sodium bisulfite, which is often added for control of biological growth. 4- Degassers for stripping hydrogen sulfide and carbon dioixde. 5. Chlorination for disinfection. 6. Addition of caustic for final pH adjustment. A building with approximate dimensions of 90 feet by 140 feet would be required to house the membrane facilities, RO feed pumps, cartridge filters and chemical feed systems. Additional treatment may also be required to provide corrosion control in order to meet forthcoming standards for lead and copper, both corrosion byproducts found in distribution piping and home plumbing. Because of greater operating complexity associated with RO units that are taken on -and off-line for short periods of time, the RO system is sized for modular expansion to a maximum seasonal flow of 12 mgd instead of the peak daily demand of 14.6 mgd (see Table 3-2). Storage would be required to meet peak daily requirements, while the RO system is seasonally operated on a nearly continuous basis. For the purpose of this study, it is assumed that an additional storage volume of 10 million gallons will be added to meet this need. This will provide approximately 4 days of storage at the incremental flow difference of 2.6 mgd between the production capacity of RO and the peak daily demand. R205/4340/122088 Hwd:1008T/01-17-89 6-3 W 0- 0- 2 oD ,a W J � a� I U I I I I Z O Q �Q o UL i `° C i `v r > W _ W o O = VV'l M in in3a W a F-_ • Uq a 4 Ll stixoKt 7Z] 11 U 1 0 9 7 Capital costs for the RO system and RO operating costs are summarized in Appendix A. A modular expansion of the system is assumed over the planning period with an initial construction of four 2-mgd modules to provide a capacity of 8 m d. additional modules can be added to bring the ultimate capacity tto ,12 mgd towards the end of the planning period. Costs for the initial construction include the addition of the 10 million of storage to meet peak demands. Also, because the TUW plantllons is at an inland location that is remote from suitable saltwater disposal sites for brine disposal, it is assumed that subsurface injection will be required for disposal of the reject brine stream. Based on estimates for similar systems in the area, million (injection well and monitoring well)caistaus d costBased this0 estimate. Although not included in cost estimates provided in Appendix A. additional costs may be incurred for replacement of existing well pumps with new pumps to meet new the RO system. Stainless steel submersible the needs for to produce fewer problems in this application umps have been observed R205/4340/122088 Hwd:1008T/01-17-89 6-4 CHAPTER 7 ASSESSMENT OF ALTERNATIVES AND RECOMMENDED IMPLEMENTATION PLAN TREATMENT NEEDS If the existing lime softening system is to be retained, a near term need has been identified for standby and expanded treatment capacity for the Accelators. A new 8 mgd Accelator unit has been recommended in past planning documents. Alternatively, a low pressure RO process could be installed in place of a new Accelator in order to achieve such capacity and redundancy. Two sets of future regulations for disinfection have a significant effect on the ultimate merits of these alternatives: 1) standards for disinfection under the groundwater treatment regulations and 2) standards for disinfection byproducts. Final regulations in both areas are anticipated in 1991. Required implementation in response to these standards is possible as early as 1992. The present approach to disinfection involves the addition of free chlorine at dosages that will result in reactions with a background ammonia in the raw water to form chloramines. A critical factor for continued use of this existing chloramination approach is the extent to which this approach will be acceptable for meeting primary disinfection criteria under the forthcoming groundwater treatment regulations. Restrictive regulations in this area may prohibit the use of chloramine for achieving these criteria. Assuming that free chlorine will not be acceptable within the existing lime softening system due to concern for formation of TTHMs and other halogenated byproducts, ozone and chlorine dioxide would represent the most likely alternative disinfectants for meeting such restrictive primary disinfection criteria. Uncertainties due to present health —related concerns for chlorine dioxide residual make ozone the more logical choice for planning at this time. However, knowledge of disinfection byproducts for alternative disinfectants is evolving and changes in this knowledge may occur. If groundwater regulations do not require a strong disinfectant for meeting primary disinfection criteria, chloramines may be capable of providing the required capabilities. A critical factor in making this -regulatory determination will be the extent to which groundwaters are considered to be at risk due to enteric viruses, a class of pathogens not considered to be effectively disinfected with chloramines. If this is not a problem, the need for adding ozone or chlorine dioxide can be eliminated and chloramination will suffice. This will not significantly differ from the existing method of disinfection. The only modification may result from partial or full use of pre —formed chloramines if very low levels of disinfection byproducts are required. This would require the addition ammonia feed facilities. R206/4340/122088 1009T/01-24-89 7-1 R-Y?-97 0 At this time, uncertainty still exists for the status of regulations for disinfection byproducts. In this regard, there is a strong possibility that TTHM standards will be lower than the existing level of 0.10 mg/l. Although a number of alternatives have been discussed, no specific standards have been proposed. Other halogenated byproducts may also be regulated. Many of these can be reduced by using chloramines with little modification to the existing method of disinfection. However, uncertainties still exist and there is some possibility that chloramination may not control all byproducts of concern within acceptable limits. In the case of chlorine dioxide and ozone, some concern also exists for byproducts. These are presently being evaluated by the U.S. EPA and no final conclusions have been drawn relative to future regulations. Testing performed under this study indicates that significant flexibility exists for using ozone and chlorine dioxide in combination with chloramines to reduce TTHMs and halogenated organics as measured by TOX. Therefore, use of alternative disinfectants has a good potential for allowing the existing lime softening system to be adapted to meet these future standards. However, given the uncertain status of future regulations at this time, no final commitment to an alternative is appropriate until these issues are further resolved by the U.S. EPA. Use of low pressure softening membranes is an alternative to • continued use of the existing lime softening system. This approach can result in removal of much of the organic content that is responsible for the formation of TTHMs and TOX. Removal of organic content by RO would allow free chlorine to be used for primary disinfection at much lower levels of formation of TTHMs and TOX than would occur in the existing lime softening system. This would be a viable approach unless TTHMs or other byproducts must be controlled to very low levels. In such a circumstance, avoidance strategies using alternative disinfectants such as ozone or chlorine dioxide might also be required as in the case of the lime softening system. While RO has shown capability for removal of TOX, this parameter is only a general indicator of effectiveness for control of halogenated byproducts. The U.S. EPA is just beginning evaluations of the capab4lities of low pressure RO for more specific control of disinfection- byproducts that will actually be regulated. Therefore, a degree of uncertainty will exist for RO processes until the complete list of byproducts to be regulated is known and specific capability for limiting the formation potential of each byproduct has been established. A degree of uncertainty also results from the fact that RO can produce a more corrosive end —product, resulting in increased concern for capability to meet forthcoming regulations for lead and copper, both byproducts of pipe corrosion. R206/4340/122088 1009T/01-24-89 7-2 13-X?- 77 0 EVALUATION OF ALTERNATIVE TREATMENT PLANS Economic evaluations were performed over a planning period from 1988 to 2008 using demand projections shown in Table 3-2. Three basic alternatives for treatment to meet future regulations were evaluated-:. 1. n w 8 . mad 6ccelator in 1982 and mgdify disinfection r i wi hin h lime -softning system in 1992 as _required r new rUulations. A range of outcomes are possible under this alternative. If new standards are not highly restrictive in terms of disinfection and disinfection byproduct requirements, little change in plant processes may be necessary and present disinfection methods may be applicable with slight modification. In the extreme, ozone may be required in conjunction with pre -formed chloramines to meet stringent requirements for primary disinfection, while achieving low levels of disinfection byproducts. Costs are presented for this extreme case. Two possible locations for ozone application were evaluated experimentally under this study: 1) ozonation of raw water and 2) ozonation of lime softened water. Because of the added requirement for pH adjustment to maintain an ozone residual , the second approach provides a more conservative • cost estimate. As such, it is used for the planning assessments presented in this chapter. For these evaluations, it is assumed that pH adjustment to the neutral range would be achieved in a recarbonation contact zone in the first -stage of the ozone contactor. Ozone would then be applied in downstream contacting stages. Subsequent pH adjustment using lime to achieve corrosion control was assumed following ozonation. An average applied ozone dose of 9 mg/l was used for computing ozone operating costs and a peak ozone production capacity for a 12 mg/1 dose was used for estimating capital costs of ozone generation equipment. An allowance was made for equipment redundancy requirements anticipated under future disinfection regulations. Cost for addition of ammonia to provide for generation of pre -formed chloramines was also included. 2. Eliminate addition---Q—ftherep1 aCe existina lime n i i wit v m R n 1289. A phased approach is assumed involving initial installation of four 2 mgd RO trains and appurtenant facilities in order to provide an initial RO capacity of 8 mgd. Subsequently, 2 mgd trains are assumed to be added in 1996 and 2007, bringing the overall capacity to 12 mgd by the end of the planning period. As discussed in Chapter 6, this R206/4340/122088 1009T/01-24-89 7-3 P-99-77 is less than the projected maximum daily demand of 14.6 mgd, reflecting the desirability for avoiding extreme variations in RO operating conditions. This requires that additional storage be provided to meet excess flow requirements under extreme demand conditions. For the purpose of this cost evaluation, it was assumed that 10 million gallons of additional storage would be provided to meet this need. This corresponds to approximately 4 days of operation at an incremental flow difference of 2.6 mgd between the 12 mgd production capacity and the 14.6 mgd peak daily demand. As discussed in Chapter 6, disposal of the waste brine from R0 was assumed to require deep well injection. 3. Construct a- new 8 mad Accelator in 1 f r construe ion of av mystem to a futr compliance r regulation5 in 1992. Under this alternative, the new 8 mgd Accelator unit would initially be installed to meet immediate plant needs for redundancy in the existing lime softening system. Replacement of the lime softening system by RO would then be deferred until 1992. At that time, a phased implementation of RO would be initiated resulting in the construction of four 2 mgd trains in 1992, with subsequent 2 mgd additions in 1996 and 2007. Estimated capital, operation and maintenance and total present worth costs for these alternatives are presented in Table 7-1. For comparison purposes, all costs are expressed in terms of a common 1988 dollar base. An interest rate of 8 5/8% was used for computing present worth. These analyses indicate that continued use of lime softening, at least on an interim basis, is the most economical approach for TUW. Even if RO is ultimately selected as the treatment technology for meeting future needs, plant rehabilation and addition of an Accelator unit for interim use of lime softening is more economical than abandoning these facilities in favor of immediate plant modification to RO. Also, by deferring a potential conversion to RO, it is possible to take advantage of any improvements to this technology that might occur during the interim period. Maintaining the lime softening system for the interim period retains the option for use of lime softening in conjunction with alternative lisinfection methods if such an approach is determined to be capable of meeting future needs. Retaining this option is extremely valuable to TUW since the results in Table 7-1 indicate that a reduction in present worth costs can be achieved even for relatively conservative assumptions for alternate disinfection methods using ozone as compared with either RO alternative. Even greater savings are possible if future standards allow lower ozone doses or eliminate the need for ozone. It is also possible that ultraviolet radiation, a technology with uncertain application for R206/4340/122088 1009T/01-24-89 7--4 E L 11 R-57-- 97 TABLE 7-1 CITY OF TAMARAC ALTERNATIVE WATER TREATMENT SYSTEMS QT$UMMARY (Cost in $1,000) 1988 ACCELATOR PRESENT CONSTRUCTION �kL W/OZDNATION IN 1992 CAPITAL $ 4,747 0 & M 0; 7ar, TOTAL $11,042 REVERSE OSMOSIS IN $12,822 1� $27,251 INTERIM ACCELATOR AND CONSTRUCTION OF RO IN 1922 $10,977 11,785 $22,762 NOTE: Present worth calculated in 1988 dollars at 8 5/8 percent over 20 years. R206/4340/122088 100917/01-24-89 7-5 ■ i R-eFq-97 meeting needs under pia - based surface water disinfection • criteria may be applicable to pathogen categories of concern in groundwater. Therefore, greater flexibility in disinfection approaches may be available than with those evaluated in this study. A primary reason interim use of lime softening is favored in this case is because most of the facilities for this process already exist, thereby substantially reducing capital costs for this alternative. Additionally, raw water available to TUW is more readily treated by lime softening for removal of color and other constituents of concern than are many Florida groundwater sources. Therefore, added costs for modifications to further control these constituents are unnecessary. RECOMMENDED IMPLEMENTATION PLAN Given the possible outcomes under these alternatives, the most practical approach is to continue use of lime softening on an interim basis. Subsequently, a decision for replacement of lime softening with RO can be made based on regulatory requirements as they become established. Modifications to provide a standby Accelator and other necessary rehabilitation measures should proceed so that reliable operation can be maintained for the interim period. Information developed in this study provides a general overview of • treatment capabilities for alternative methods. This information base should be supplemented as required to assess definitive regulatory requirements as they are developed in the future. Critical regulations to be considered are those for disinfection byproducts and disinfection of groundwater. Both regulations are scheduled to reach final rules in 1991. Some evaluation prior to this time can be undertaken based on proposed rules for these regulations. However, changes have occurred from proposed rules to final rules in the past and no completed analysis is appropriate until the final rule has been published. When this occurs, a final selection should be made between continued use of the existing lime softening system or replacement of this system with a low pressure RO system. 0 R206/4340/122088 1009T/01-24-89 7-6 11 Cl • Hwd :1518R/01--09-89 APPENDIX A m m m 4 n T • n � � J1 ./1 T JI • O• .A 0• Jf .n �1 • O n O •n e0 d. ¢ A r' w' N T � � � N 4 • W � .� n r rr �. m .. w � rr N t•"i [+ � imp m ~� N� •Il '� r m •11 H'I r!1 • m n• rn � m n m ry w• � ' r .d N 4• .r N .A n w .n •n 4 m A O .n m b. 4 A w N ,y N � ti ti ry v � M "' '� ry .ti • • m .a v� A y r! � t� n m S •? a • n m .c o. ! o r• rr ,n dy ap � • ,n m rn • n ! .e m _ N N �• � n4b , � ✓? •a Kh rY .o ...n w r rt w .n 4 4 n o .� m e. • F w n m i W n N r1 .p ry T!!! • m n 4 v1 m O• 4 A T , ey N "� '• pyp ry .rv. ervr '_" ti N '"' • w m ^` n .n y m .. ! m • W •• 1 N � w n n .O • N m T 1? t"1 ti• at 4 n• .n m v 4 A! P rf ry .r� N n wmmnu'+ ! 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