This document has been superceded by the 2003 version, but is still referenced by 5-1.22 of the sanitary code.
"TEN STATE STANDARDS" aka BULLETIN 42
Copyright (c) 1997 by the Great Lakes - Upper Mississippi River Board of State and Provincial Public Health and Environmental Managers
This book, or portions thereof, may be reproduced without permission from the author if proper credit is given.
This book, or portions thereof, may be reproduced without permission from the author if proper credit is given.
TABLE OF CONTENTS from PRINTED VERSION (for cross-referencing)
The Great Lakes-Upper Mississippi River Board of Public Health and Environmental Managers in 1950 created a Water Supply Committee consisting of one associate from each state represented on the Board. A representative from the Province of Ontario was added in 1978. The Committee was assigned the responsibility for reviewing existing water works practices, policies and procedures, and reporting its findings to the Board. The report of the Water Supply Committee was first published in 1953, and subsequently has been revised and published in 1962, 1968, 1976, 1982, 1987, 1992 and 1997.
This document includes the following:
1. Policy Statements - Preceding the standards are policy statements of the Board concerning water works design, practice, or resource protection. Those policy statements recommending an approach to the investigation of innovative treatment processes have not been included as part of the standards because sufficient confirmation has not yet been documented to allow the establishment of specific limitations or design parameters.
2. Interim Standards - Following the policy statements are interim standards. The interim standards give design criteria which are currently being used for new treatment processes, but the use of the criteria is limited and insufficient for recognition as a recommended standard.
3. Recommended Standards - the Standards, consisting of proven technology, are intended to serve as a guide in the design and preparation of plans and specifications for public water supply systems, to suggest limiting values for Items upon which an evaluation of such plans and specifications may be made by the reviewing authority, and to establish, as far as practicable. uniformity of practice. Because statutory requirements and legal authority pertaining to public water supplies are not uniform among the states, and since conditions and administrative procedures and policies also differ, the use of these standards must be adjusted to these variations.
The terms shall and must are used where practice is sufficiently standardized to permit specific delineation of requirements or where safeguarding of the public health justifies such definite action. Other terms, such as should, recommended, and preferred, indicate desirable procedures or methods, with deviations subject to individual consideration.
It is not possible to cover recently developed processes and equipment in a publication of this type. However, the policy is to encourage, rather than obstruct, the development of new processes and equipment. Recent developments may be acceptable to individual states if they meet at least one of the following conditions: 1) have been thoroughly tested in full scale comparable installations under competent supervision, 2) have been thoroughly tested as a pilot plant operated for a sufficient time to indicate satisfactory performance, or 3) a performance bond or other acceptable arrangement has been made so the owners or official custodians are adequately protected financially or otherwise in case of failure of the process or equipment.
The Board recognizes that many states, other than those of the Great Lakes-Upper Mississippi River Board of State Public Health and Environmental Managers, utilize this publication as part of their design requirements for water works facilities. The Board welcomes this practice as long as credit is given to the Board and to this publication as a source for the standards adopted. Suggestions from non-member states are welcome and will be considered.
Pre-engineered water treatment plants are increasingly being considered for production of potable water at public water systems. Many applications being proposed are for small systems having relatively clean surface water sources which are now being required to provide filtration under the federal Save Drinking Water Act.
Pre-engineered water treatment plants are normally modular process units which are pre-designed for specific process applications and flow rates and purchased as a package. Multiple units may be installed in parallel to accommodate larger flows.
Pre-engineered treatment plants have numerous applications but are especially applicable at small systems where conventional treatment may not be cost effective. As with any design the proposed treatment must fit the situation and assure a continuous supply of safe drinking water for water consumers. The reviewing authority may accept proposals for pre-engineered water treatment plants on a case by case basis where they have been demonstrated to be effective in treating the source water being used.
Factors to be considered include:
1. Raw water quality characteristics under normal and worst case conditions. Seasonal fluctuations must be evaluated and considered in the design.
2. Demonstration of treatment effectiveness under all raw water conditions and system flow demands. This demonstration may be on-site pilot or full scale testing or testing off-site where the source water is of similar quality. On-site testing is required at sites having questionable water quality or applicability of the treatment process. The proposed demonstration project must be approved by the reviewing authority prior to starting.
3. Sophistication of equipment. The reliability and experience record of the proposed treatment equipment and controls must be evaluated.
4. Unit process flexibility which allows for optimization of treatment.
5. Operational oversight that is necessary. At surface water sources full-time operators are necessary except where the reviewing authority has approved an automation plan. See Policy Statement on Automated/Unattended Operation of Surface Water Treatment Plants.
6. Third party certification or approvals such as National Sanitation Foundation (NSF) for a) treatment equipment and b) materials that will be in contact with the water.
7. Suitable pretreatment based on raw water quality and the pilot study or other demonstration of treatment effectiveness.
8. Factory testing of controls and process equipment prior to shipment.
9. Automated troubleshooting capability built into the control system.
10. Start-up and follow-up training and troubleshooting to be provided by the manufacturer or contractor.
11. Operation and maintenance manual. This manual must provide a description of the treatment, control and pumping equipment, necessary maintenance and schedule, and a troubleshooting guide for typical problems.
12. On-site and contractual laboratory capability. The on-site testing must include all required continuous and daily testing as specified by the reviewing authority. Contract testing may be considered for other parameters.
13. Manufacturers warranty and replacement guarantee. Appropriate safeguards for the water supplier must be included in contract documents. The reviewing authority may consider interim or conditional project approvals for innovative technology where there is sufficient demonstration of treatment effectiveness and contract provisions to protect the water supplier should the treatment not perform as claimed.
14. Water supplier revenue and budget for continuing operations, maintenance and equipment replacement in the future.
Additional information on this topic is given in the State Alternative Technology Approval Protocol dated June, 1996 which was developed by the Association of State Drinking Water Administrators, U.S. Environmental Protection Agency and various industry groups.
Adopted April, 1997
Although standards and advisories for organics are being developed, there have been numerous cases of organic contamination of public water supply sources. In all cases, public exposure to organic contamination must be minimized. There is insufficient experience to establish design standards which would apply to all situations. Controlling organic contamination is an area of design that requires pilot studies and early consultation with the reviewing authority. Where treatment is proposed, best available technology shall be provided to reduce organic contaminants to the lowest practical levels. Operations and monitoring must also be considered in selecting the best alternative. The following alternatives may be applicable:
1. Alternate Source Development
2. Existing Treatment Modifications
3. Air Stripping For Volatile Organics (See 4.5.4 Packed Tower Aeration)
4. Granular Activated Carbon Consideration should be given to:
a. using contact units rather than replacing portion of existing filter media;
b. series and parallel flow piping configurations to minimize the effect of breakthrough without reliance on continuous monitoring;
c. providing at least two units. Where only two units are provided, each shall be capable of meeting the plant design capacity (normally the projected maximum daily demand) at the approved rate. Where more than two units are provided, the contactors shall be capable of meeting the design capacity at the approved rate with one or more (as determined in conjunction with the reviewing authority) units removed from service;
d. using virgin carbon; this is the preferred media. Although reactivated carbon may eventually present an economic advantage at large water treatment plants, such an alternative may be pursued only with the preliminary endorsement of the reviewing authority. Regenerated carbon using only carbon previously used for potable water treatment can be used for this purpose. Transportation and regeneration facilities must not have been used for carbon put to any other use;
e. acceptable means of spent carbon disposal
Except for temporary, emergency treatment conditions, particular attention should be given to developing an engineering report which, in addition to the normal determinations, includes the following:
1. For organic contaminants found in surface water sources:
a. type of organic chemicals, sources, concentration, frequency of occurrence, water pollution abatement schedule, etc.,
b. possible existing treatment plant modifications to lower organic chemical levels. Results of bench, pilot or full scale testing demonstrating treatment alternatives, effectiveness and costs,
c. a determination of the quality and/or operational parameters which serve as the best measurement of treatment performance, and a corresponding monitoring and process control program.
2. For organic contamination found in groundwater sources:
a. types of organic chemicals, sources, concentration, estimate of residence time within the aquifer, flow characteristics, water pollution abatement schedule, etc.,
b. results of bench or pilot studies demonstrating treatment alternatives, effectiveness, and costs,
c. a determination of the quality and/or operational parameters which serve as the best measure of treatment performance, and a corresponding monitoring and process control program.
d. development and implementation of a wellhead protection plan.
The collection of this type of data is often complicated and lengthy. Permanent engineering solutions will take significant time to develop. The cost of organic analyses and the availability of acceptable laboratories may further complicate both pilot work and actual operation.
Alternative source development or purchase of water from nearby unaffected systems may be a more expedient solution for contaminated groundwater sources.
Adopted April, 1987
Revised April, 1991
Revised April, 1997
Internal and external corrosion of a public water supply distribution system is a recognized problem that cannot be completely eliminated but can be effectively controlled. Aside from the cost of labor and materials for pipe replacement, the possible adverse health effects of corrosion products must be considered. A major corrosion failure in the distribution system mains or service connections could lead to the gross contamination of the water being delivered to the public, as well as service interruption and operation.
Control of corrosion is a function of the design, maintenance, and operation of a public water supply. These functions must be considered simultaneously in order for the corrosion control program to function properly. Corrosion problems must be solved on an individual basis depending on the materials used in the distribution system, and soil and water characteristics. Some specific information can be obtained from Section 4.8 (Stabilization) and from publications of technical societies such as the American Water Works Association, the National Association of Corrosion Engineers, and the American Society for Testing Materials. Broad areas of consideration for a corrosion control program follow.
1. Provide for a system of records by which the nature and frequency of corrosion problems are recorded. On a plat map of the distribution system, show the location of each problem so that follow-up investigations and improvements can be made when a cluster of problems is identified.
2 . When complaints are received from a customer, follow up with an inspection by experienced personnel or consultant experienced in corrosion control. Where advisable, obtain samples of water for chemical and microbiological analyses and piping and plumbing material samples. Analyses should be made to determine the type and, if possible, the cause of the corrosion.
3 . Establish a program whereby a determination of the stability of the water in representative parts of the distribution system can be made. Analysis for alkalinity, pH, and corrosion products (such as lead, cadmium, copper, and iron) should be performed on water samples collected at the treatment plant or wellhead and at representative points on the distribution system. In comparing the analyses of the source water with the distribution system water, significant changes in alkalinity, pH, or corrosion products would indicate that corrosion is taking place and thereby indicate that corrective steps need to be taken.
4. Where possible, especially when corrosion has been detected in the determination of water stability, provide a program that will measure both the physical and chemical aspects of the corrosion phenomena. Physical measurement of the rate of corrosion can be made by the use of coupons, easily removed sections of pipe, connected flow-through pipe test sections or other piping arrangements. At the same site, measure the relative degree of corrosivity on a routine basis by using corrosion indices such as the Langelier Index, Ryznar Index, or Aggressiveness Index (AWWA C-400). Correlation of the data from the physical measurement with the data from the selected corrosion index will provide information to determine the type of corrective treatment needed and may allow for the subsequent use of the corrosion index alone to determine the degree of corrosivity in select areas of the distribution system.
5. If corrosion is found to exist throughout the distribution system, corrective measures at the treatment plant, pump station or well head should be initiated. A chemical feed can be made to provide a stable to slightly depositing water. In calculating the stability index and the corresponding chemical feed adjustments, consideration must be given to items such as the water temperature, if it varies with the season and within various parts of the distribution system; the velocity of flow within various parts of the distribution system; the degree of stability needed by the individual customer; and the dissolved oxygen content of distributed water, especially in waters having low hardness and alkalinity. Threshold treatment involving the feeding of a polyphosphate or a silicate to control corrosion may be considered for both ground and surface water supplies.
6. Additional control of corrosion problems can be obtained by a regulation or ordinance for the materials used in or connected to a distribution system. Careful selection of materials compatible with the physical system or the water being delivered can aid in reduction of corrosion product production.
Note: Adjustment of pH for corrosion control must not interfere with other pH dependent processes (e.g., color removal by alum coagulation).
1. Provide for a system of records by which the nature and frequency of corrosion problems are recorded. On a plat map of the distribution system, show the location of each problem so that follow-up investigations and improvements can be made when a cluster of problems is identified.
2. If needed, perform a survey to determine the existence of facilities or installations that would provide the potential for stray, direct electric currents. Also, determine whether problems are caused by the use of water pipes as grounds for the electrical system.
3. In previously unexplored areas where aggressive soil conditions are suspect, or in areas where there are known aggressive soil conditions, perform analyses to determine the actual aggressiveness of the soil.
4. If soils are found to be aggressive, take necessary action to protect the water main, such as by encasement of the water main in polyethylene, provision of cathodic protection (in very severe instances), rerouting of water main through non-aggressive soil areas, or use of alternate, corrosion resistant water main materials.
Adopted April, 1982
Trihalomethanes (THMS) are formed when free chlorine reacts with organic substances, most of which occur naturally. These organic substances (called "precursors"), are a complex and variable mixture of compounds. Formation of THMs is dependent on such factors as amount and type of chlorine used, temperature, concentration of precursors, pH, and contact time. Approaches for controlling THMs include:
1. Control of precursors at the source.
a. Selective withdrawal from reservoirs -- varying depths may contain lower concentrations of precursors at different times of the year.
b. Plankton Control -- Algae and their by-products have been shown to act as THM precursors.
c. Alternative sources of water may be considered, where available.
2. Removal of THM precursors and control of THM formation.
a. Moving the point of chlorination to minimize THM formation.
b. Removal of precursors prior to chlorination by optimizing:
(1) Coagulation/flocculation -- sedimentation -- filtration
(2) Precipitative softening/filtration
(3) Direct filtration
c. Adding oxidizing agents such as potassium permangante, ozone or chlorine dioxide to reduce or control THM formation potential.
d. Adsorption by powdered activated carbon (PAC).
e. Lowering the pH to inhibit the reaction rate of chlorine with precursor materials. Corrosion control may be necessary.
3. Removal of THM.
a. Aeration -- by air stripping towers.
b. Adsorption by:
(1) Granular Activated Carbon (GAC)
(2) Synthetic Resins
4. Use of Alternative Disinfectants -- Disinfectants that react less with THM precursors may be used as long as bacteriological quality of the finished water is maintained. Alternative disinfectants may be less effective than free chlorine, particularly with viruses and parasites. Alternative disinfectants, when used, must be capable of providing an adequate distribution system residual. Possible health effects of by-products that may be produced by using alternative disinfectants must be taken into consideration. The following alternative disinfectants may be used:
a. Chlorine Dioxide
Using various combinations of THM controls and removal techniques may be more effective than a single control or a treatment method.
Any modifications to existing treatment process must be approved by the reviewing authority. Pilot plant studies are desirable.
Adopted April, 1987
Revised April, 1997
Reverse osmosis is a physical process in which a suitably pretreated water is delivered at high pressure against a semipermeable membrane. The membrane rejects most solute ions and molecules, while allowing water of very low mineral content to pass through. The process produces a reject concentrate waste stream in addition to the clear permeate product. Reverse osmosis systems have been successfully applied to saline groundwaters, brackish waters, and seawater.
The following items should be considered in evaluating the applicability for reverse osmosis:
1. Membrane Selection: Two types of membranes are typically used. These are Cellulose Acetate and Polyamide/Composite. Membrane configurations include tubular, spiral wound and hollow fine fiber. Operational conditions and useful life vary depending on type of membrane selected.
2. Useful Life of the Membrane: The membrane represents a major cost component in the overall water system. Membrane replacement frequency can significantly affect the overall cost of operating the treatment facility.
3. Pretreatment Requirements: Acceptable feedwater characteristics are dependent on the type of membrane and operational parameters of the system. Without pretreatment, the membrane may become severely fouled and severely shorten its useful life. Pretreatment may be needed for turbidity reduction, iron or manganese removal, stabilization of the water to prevent scale formation, microbial control, chlorine removal, dissolved solids reduction, pH adjustment or hardness reduction.
4. Treatment Efficiency: Reverse osmosis is highly efficient in removing metallic salts and ions from the raw water. Efficiencies, however, do vary depending on the ion being removed and the membrane utilized. For most commonly encountered ions, removal efficiencies will range from 85% to over 99%. Organics removal is dependent on the molecular weight, the shape of the organic molecule and the pore size of the membrane utilized. Removal efficiencies may range from as high as 99% to less than 30%.
5. Bypass Water: Reverse osmosis permeate will be virtually demineralized. The design should provide for a portion of the raw water to bypass the unit to maintain a stable water within the distribution system.
6. Post Treatment: Post treatment typically include degasification for carbon dioxide and hydrogen sulfide removal (if present), pH adjustment for corrosion control and chlorination.
7. Reject Water: Reject water may range from 25% to 50% of the raw water pumped to the reverse osmosis unit. This may present a problem both from the source availability and from the waste treatment capabilities. The amount of reject water from a unit may be reduced to a limited extent by increasing the feed pressure to the unit; however, this may result in a shorter membrane life. Acceptable methods of waste disposal include discharge to the municipal sewer system or to an evaporation pond.
8. Cleaning the Membrane: The osmosis membrane must be replaced or periodically cleaned with acid. Method of cleaning and chemicals used must be approved by the state reviewing agency. Care must be taken in the acid cleaning process to prevent contamination of both the raw and finished water system.
9. Pilot Plant Study: Prior to initiating the design of a reverse osmosis treatment facility, the state reviewing agency should be contacted to determine if a pilot plant study will be required. In most cases, a pilot plant study will be required to determine the best membrane to use, the type of pretreatment, type of post treatment, the bypass ratio, the amount of reject water, process efficiency and other design criteria.
10. Operator training and startup: The ability to obtain qualified operators must be evaluated in selection of the treatment process. The necessary operator training shall be provided prior to plant startup.
Adopted April, 1991
Recent advances in computer technology, equipment controls and Supervisory Control and Data Acquisition (SCADA) systems have brought automated an off-site operation of surface water treatment plants into the realm of feasibility. Coincidentally, this comes at a time when renewed concern for microbiological contamination is driving optimization of surface water treatment plant facilities and operations and finished water treatment goals are being lowered to levels of <0.1 NTU turbidity and <20 total particle counts per milliliter.
Review authorities encourage any measures, including automation, which assist operators in improving plant operations and surveillance functions.
Automation of surface water treatment facilities to allow unattended operation and off-site control presents a number of management and technological challenges which must be overcome before and approval can be considered. Each facet of the plant facilities and operations must be fully evaluated to determine what on-line monitoring is appropriate, what alarm capabilities must be incorporated into the design and what staffing is necessary. Consideration must be given to the consequences and operational response to treatment challenges, equipment failure in loss of communications or power.
In engineering report shall be developed of the first step in the process leading to design of the automation system. The engineering report to be submitted to review authorities must cover all aspects of the treatment plant and automation system including the following information/criteria:
1. Identify all critical features in the pumping in treatment facilities that will be electronically monitored, have alarms and can be operated automatically or off-site by the control system. Included description of automatic plant shut-down controls with alarms and conditions which would trigger shutdowns. Tool or secondary alarms may be necessary for certain critical functions.
2. Automated monitoring of all critical functions with major minor alarm features must be provided. Automated plant shutdown is required on all major alarms. Automated startup of the plant is prohibited after shutdown due to a major alarm. The control system must have response and adjustment capability on all minor alarms. Built-in control system challenge test capability must be provided to verify operational status of major and minor alarms.
3. The plant control system must have the capability for manual operation of all treatment plant equipment and process functions.
4. A plant flow diagram which shows location of all critical features, alarms and automated controls to be provided.
5. Description of off-site control station(s) that allow observation of plant operations, receiving alarms and having the ability to adjusting control operation of equipment and the treatment process.
6. A certified operator must be on "standby duty" status at all times with remote operational capability and located within a reasonable response time in the treatment plant.
7. A certified operator must do an on-site check at least once per day to verify proper operation and plant security.
8. Description of operator staffing in training plans are completed in both process control any automation system.
9. Operations manual which gives operators step-by-step procedures for understanding in using the automated control system under all water quality conditions. Emergency operations during power or communications failures or other emergencies must be included.
10. A plan for a six-month or more demonstration. To prove the reliability of procedures, equipment and surveillance system. A certified operator must be on-duty during the demonstration period. The final plan must identify and address any problems of alarms that occurred during the demonstration period. Challenge testing of each critical component of the overall system must be included as part of demonstration project.
11. Schedule for maintenance of equipment critical parts replacement.
12. Sufficient finished water storage shall be provided to meet system demands and CP requirements whenever normal treatment production is interrupted as the result of an automation system failure or plant shutdown.
13. Sufficient staffing must be provided to carry a daily on-site evaluations, operational functions and needed maintenance and calibration of all critical treatment components and monitoring equipment to ensure reliability of operations.
14. Plant staff must perform as a minimum weekly checks on the communication control system to ensure reliability of operations. Challenge testing of such equipment should be part of normal maintenance routines.
15. Provisions must be made to ensure security the treatment facilities all times. Incorporation of appropriate intrusion alarms must be provided which are effectively communicated to the operator in charge.
Adopted April, 1997
Bag and cartridge technology has been used for sometime in the food, pharmaceutical and industrial applications. This technology is increasingly being used by small public water supplies for treatment of drinking water. A number of states of accepted bag and cartridge technology as an alternate technology for compliance with filtration requirements of The Surface Water Treatment Rule.
The particular loading capacity these filters is low, and once expended the bag or cartridge filter must be discarded. This technology is designed to meet the low flow requirement needs of small systems. The operational and maintenance cost of bag and cartridge replacement must be considered when designing a system. These filters can effectively remove particles from water in the size range of Giardia cysts (5-10 microns) and Cryptosporidium (2-5 microns).
At the present time, filtration evaluation is based on Giardia cyst removal. However, consideration should be given to the bag or cartridge filter's ability to remove particles in the size range of Cryptosporidium since this is a current public health concern.
With this type of treatment there is no alteration of water chemistry. So, once the technology has demonstrated the 2-log removal efficiency, no further pilot demonstration is necessary. The demonstration of filtration is specific to a specific housing and a specific bag or cartridge filter. Any other combinations of different bags, cartridges, or housings will require additional demonstration of filter efficiency.
Treatment of the surface water should include source water protection, filtration, and disinfection.
The following items should be considered in evaluating applicability of bag or cartridge filtration.
1. The filter housing and bag/cartridge filter must demonstrate a filter efficiency of 2-log reduction in particle size 2 microns and above. The review and authority will decide whether or not a pilot demonstration is necessary for each installation. This filtration efficiency may be accomplished by:
a. Microscopic particulate analysis, including particle counting, sizing and identification, which determines occurrence and removals of micro-organisms and other particles across a filter or system under ambient raw water source condition, or when artificially challenged.
b. Giardia/Cryptosporidiom surrogate particle removal valuation in accordance with procedures specified in NSF Standard 53 or equivalent. These evaluations can be conducted by NSF or by another third-party whose certification would be acceptable to the reviewing authority.
c. "Particle Size Analysis Demonstration for Giardia Cyst Removal Credit" procedure presented an Appendix M of the EPA Surface Water Treatment Rule guidance manual.
d. "Nonconsensus" live Giardia challenge studies that have been designated and carried out by a third-party agent recognized accepted by the reviewing authority for interim devaluations. At the present time uniform particle procedures for live Giardia challenge studies have not been established. If a live Giardia challenge study is performed on-site there must be proper cross-connection control equipment in place in the test portion must be operated to waste.
e. Methods other than these that are approved by the reviewing authority.
2. System components such as housing, bags, cartridges, membranes, gaskets, and O-rings should be evaluated under NSF Standard 61 or equivalent, for leaching of contaminants. Additional testing may be required by the reviewing authority.
3. The source water or pre-treated water should have a turbidity of less than 5 NTU.
4. It is recommended that the flow rate through the treatment process be monitored. The flow rate through the bag/cartridge filter must not exceed 20 gpm, unless documentation at higher flow rates demonstrates that it will meet the requirements for removal of particles.
5. Pretreatment is strongly recommended (if not required by the reviewing authority). This is to provide a more constant water quality to the bag/cartridge fileter. Examples of pretreatment include media filters, larger opening bag/cartridge filters, infiltration galleries, and beach wells. Location of the water intake should be considered in the pretreatment evaluation.
6. Particle count analysis can be used to determine what level of pretreatment should be provided. It should be noted that particulate counting is a 'snap shot' in time and that there can be seasonal variations such as algae blooms, lake turnover, spring runoff, and heavy rainfall events that will give varied water quality.
7. It is recommended that chlorine or another disinfectant be added at the head of the treatment process to reduce/eliminate the growth of algae, bacteria, etc., on the filters. The impact on disinfection-by-product formation should be considered.
8. A filter to waste component is strongly recommended (if not required by the reviewing authority), for any pretreatment pressure sand filters. At the beginning of each filter cycle and/or after every backwash of the prefilters a set amount of water should be discharged to waste before water flows into the bag/cartridge filter.
9. If pressure media filters are used for pretreatment they must be designed according to Section 4.2.2.
10. A sampling tap shall be provided ahead of any treatment so a source water sample can be collected.
11. Pressure gauges and sampling taps shall be installed before and after the media filter and before and after the bag/cartridge filter.
12. An automatic air release valve shall be installed on top of the filter housing.
13. Frequent start and stop operation of the bag or cartridge fitler should be avoided. To avoid this frequent start and stop cycle the following options are recommended:
a. a slow opening and closing valve ahead of the filter to reduce flow surges.
b. reduce the flow through the bag or cartridge filter to as low as possible to lengthen the filter run times.
c. install a recirculating pump that pumps treated water back to a point ahead of the bag or cartridge filter. Care must be taken to make sure there is no cross connection between the finished water and raw water.
14. A minimum of two bag or cartridge filter housings should be provided for water systems that must provide water continuously.
15. A pressure relief valve should be incorporated into the bag or cartridge filter housing.
16. Complete automation of the treatment system is not required. Automation of the treament plant should be incorporated into the ability of the water system to monitor the finished water quality. It is important that a qualified water operator is availibale to run the treament plant.
17. A plan of action should be in place should the water quality parameters fail to meet EPA or the local reviewing authority standards.
1. The filtration and backwash rates shall be monitored so that the prefilters are being optimally used.
2. The bag and cartridge filters must be replaced when a pressure difference of 30 psi or other pressure difference recommended by the manufacturer is observed. It should be noted that bag filters do not load linearly. Additional observation of the filter performance is required near the end of the filter run.
3. Maintenance (o-ring replacement) shall be performed in accordance with the manufacturer's recommendations.
4. The following parameters should be monitored:
Flow rate, instantaneous
Flow rate, total
Adopted April, 1997
Ammonia can be used for conversion of chlorine in drinking water into the longer lasting but less powerful disinfectant chloramine. Possible advantages and disadvantages of the use of chloramine rather than free chlorine include:
Use of chlorine may reduce total trihalomethane concentrations reaching consumers. This is because chlorine does not form trihalomethanes on contact with natural organic matter in the water, although it may form other by-products.
Use of chlorine may reduce the need for high disinfectant concentrations to be added that the plant and/or at booster stations. This can be an advantage during the warmer seasons of the year for protection of the water and mains system from bacterial overgrowth. The lowered disinfectant requirements also can avoid complaints due to some unacceptable chlorine taste/odor problems from consumers located close to water plants, although they may contribute to other problems.
The use of chlorine may provide less protection from contamination in the distribution system through cross connections, water main breaks and other causes.
Unlike most substances added to water for treatment purposes, chloramine cannot be preprepared at high concentrations. It can only be made by addition of ammonia to lightly chlorinated water or of chlorine to water containing low concentrations of ammonia. Contact between high concentrations of chlorine and ammonia or ammonium salts must be avoided because the sensitive and violently explosive substance, nitrogen trichloride, may be formed.
Operating authorities who wish to modify disinfectant practices by using chloramine may must show the State Reviewing Authority clear evidence that bacteriological and chemical protection of consumers will not be compromised in any way and that aspects of chloramination mentioned below are considered in any permit application.
1. Chloramine, which is less powerful than free chlorine, may be suitable for disinfection of some groundwater supplies but it is inadequate strength for primary disinfection of surface waters. 2. Chloramine can be suitable for protecting possible water and distribution systems against bacterial contamination. The chloramine tends to remain active for longer periods at greater distances from the plant than free chlorine. Chloramine concentrations should be maintained higher than for chlorine to avoid nitrifying bacteria activity. A range of 1 - 2 milligrams per liter, measured as combined chlorine, on entry to the distribution system and greater than 1 mg/L at the system extremities is recommended. Chloramine can be less odorous than chlorine so these concentrations may be tolerated well by consumers.
3. Suitable commercial sources of ammonia for chloramine production are either ammonia gas or water solutions of ammonia or ammonium sulfate. Ammonia gas is supplied as compressed liquid in cylinders which must be stored in separate facilities designed as for chlorine gas. Ammonia solutions must be stored in containment with adequate cooling to prevent gas release of storage and gas release must be handled with pressure relief systems. Absorption/neutralization systems for ammonia gas leak/spills must be designed specially for ammonia. Ammonium sulfate is available as free-flowing powdered solid which must be stored in cool dry conditions and dissolved in water for use.
4. Thorough and reasonably rapid mixing of chlorine and ammonia in the main plant stream shall be arranged so is to avoid formation of odorous dichloramine. Sufficient ammonia must be added to provide at least a small excess (more than one part of ammonia to 4 parts chlorine) over that required to convert all the free chlorine present to chlorine.
5. Addition of ammonia gas or ammonia solutions will increase the pH of the water and addition of ammonium sulfate depresses the pH. The actual pH shift may be small in well buffered water but the effects on disinfectant power and corrosiveness of the water may require consideration. Ammonia gas forms alkaline solutions which may cause local plugging by lime deposition. Where hard water is to be treated, a sidestream of pre-softened water may be needed for ammonia dilutions so as to reduce plugging problems.
6. The use of chloramine in distribution systems which are not well maintained by flushing, swabbing and other regular routine maintenance activities can lead to local loss of disinfectant residual, nitrifying bacterial activity and, possibly over a period of time, to persistent high coliform bacterial counts which may not respond to reversion to the use of free chlorine. Early detection and of nitrifying bacteria activity may be made by checking for reduced dissolved oxygen and elevated nitrate levels.
7. Chloramine in water is considerably more toxic to fish and other aquatic organisms than free chlorine. Consideration must therefore be given to the potential for leaks to contaminate and damage natural water course eco-systems. Kidney dialysis treatment can be upset by the use of chloraminated water. Medical authorities, hospitals and other commercial and domestic aquarium keepers should be notified so they can arrange for precautions to be taken.
Adopted April, 1997
The zebra mussel (Dreissena polymorpha) is a freshwater bivalve that was believed to have been accidentally introduced into the Great Lakes ecosystem around 1986. The zebra mussel has the potential to biofoul public water supply intake facilities and cause loss of intake capacity as well as contribute to taste and odor problems. The zebra mussel has spread rapidly throughout the Great Lakes and Mississippi River Basins and could potentially affect surface water supplies throughout the country.
The zebra mussel breeds prolifically and waters with temperatures between 45-52 degrees Fahrenheit with the larval, or veliger, stage being highly mobile in water currents. The post veligers settle out and attach themselves to a hard substrate (such as an intake structure) where they become adults; reaching sizes up to two inches. Many common construction materials can serve as substrates on which the mussels can build onto themselves and form deep layers within a few seasons.
Water suppliers should periodically assess the condition of their intakes to determine if zebra mussel veligers or adults are or potentially may be present and implement the system of control. Physical controls typically include removal of adults by mechanical scraping (pigging) and hydroblasting; whereas chemical treatment has proven to be most effective for short and long term control and elimination.
The most accepted and currently recommended forms of chemical treatment for public water supplies are the use of oxidants such as chlorine, chlorine dioxide, potassium permanganate and ozone. Various approved molluscicides have also been used. Chemical dosage is a typically applied at the intake through solution piping and a diffusor to prevent the formation of zebra mussel colonies within the intake and piping. The type of chemical selected in frequency of application will depend on the type of existing chemical treatment facilities, zebra mussel breeding season, potential for THM formation, other pre-treatment objectives such as taste and over control, safety and economy.
The following items should be addressed in the design:
1. Chemical treatment design shall be in accordance with applicable sections of Recommended Standards For Water Works and shall be acceptable to the reviewing authority.
2. Plant safety items, including but not limited to ventilation, operator protective equipment, eye washes/showers, cross connection control, etc., shall be provided.
3. Solution piping and diffusers shall be positively anchored. Piping shall have appropriate valving and shall be preferably installed within the intake pipe or in a suitable carrier pipe. Provisions shall be made to prevent dispersal of chemical into the water environment outside the intake. Diffusers shall be located and designed to protect all intake structure components.
4. Consideration shall be given to providing a spare solution line to provide redundancy and facilitate the use of alternate chemicals.
5. Chemical feeders shall be interlocked with the plant system controls to shut down automatically when raw water flows stop.
6. Provisions for obtaining raw water samples not influenced by chemical treatment.
7. When alternative control methods are proposed, for example, sonic energy, non-adhering surfaces or infiltration galleries, appropriate piloting or demonstration studies, satisfactory to the reviewing authority, shall be considered.
All designs of zebra mussel control systems shall be submitted to and receive the approval of the reviewing authority prior to installation.
Adopted April 1997
Characteristics: MF and UF membranes are most commonly made from organic polymers (for example, cellulose acetate, polysulfones, polyamides, polypropylene or polycarbonates). The physical configurations includes hollow-fiber, spiral wound and tubular. MF membranes are capable of removing particles with sizes down to 0.1-0.2 microns. UF processes have a probable lower cutoff rating of .005-.01 microns.
Typical flux (rate of finished water permeate per unit membrane surface area) at 20 degrees C for MF ranges between 50-100 gallons/square foot/day (gsfd) whereas the typical U.S. flux range is 10-50 gsfd. Required operating pressures ranges from 5-10 psi for MF and 15-70 psi for UF.
Since both processes have relatively small membrane pore diameters, membrane fouling, caused by organic and inorganic as well as physical contaminants, is expected. Periodic flushing and cleaning is employed once the targeted transmembrane pressure differential has been reached. Typical cleaning agents include acids, bases, surfactants, enzymes and certain oxidants, depending upon membrane material and foulants encountered.
Overall treatment requirements and disinfection credits must be discussed with and approved by the reviewing authority. Disinfection is required with membrane filtration.
Selection design considerations:
1. A review of historical source raw water quality data, including turbidity and slashed or particle counts, organic loading, temperature differentials as well as other organic and physical parameters, can indicate whether either process is feasible. The degree of pre-treatment, if any, may be ascertained. Design considerations and membrane selection at this phase must also address the issue of target removal efficiencies versus acceptable transmembrane pressure differentials.
2. The useful life expectancy of particular membrane under consideration should be evaluated. A membrane replacement frequency is a significant factor in operation and maintenance cost comparisons of the selection of a process.
3. Many membrane materials are incompatible with certain oxidants. If the system must rely on pre-treatment oxidants for other purposes, for example, zebra muscle control, taste and over control, the selection of the membrane material becomes a significant design consideration.
4. The source water temperature can significantly impact the flocks of the membrane under consideration. At low water temperatures of flux can be reduced appreciably, possibly impacting processes ability or the number of membrane units required for full-scale facility.
5. Flushing volumes can range form 5-25 percent of the permeate flow, depending upon the frequency of flushing/cleaning and the degree of fouling and is an important factor in specifying the number of treatment units required.
6. An appropriate level of finished water monitoring should be provided to routinely evaluate membrane and housing integrity and overall filtration performance. Monitoring options may include particle counters, manual and/or automated pressure testing or air diffusion testing.
7. Cross connection considerations are necessary, particularly with regard to chemical feeds used for membrane cleaning.
8. Redundancy of critical control components must be considered in the final design.
9. Other post-membrane treatment requirements must be evaluated in the final design to address other contaminants of concern such as color and disinfection by-product precursors.
10. Prior to initiating the design of a membrane treatment facility, the state reviewing authority should be contacted to determine if a pilot plant study will be required. In most cases, a pilot plant study will be necessary to determine the best membrane to use, particulate/organism removal efficiencies, cold and warm water flux, the need for pre-treatment, fouling potential, operating and transmembrane pressure and other design considerations. Any virus removal credit must also be documented through an appropriate piloting process. The state reviewing authority should be contacted prior to conducting the pilot study to establish the protocol to be followed.
Adopted April 1997
Ozonation systems are generally used for the purpose of disinfection, oxidation and microflocculation. When applied, all of these reactions may occur but typically only one is the primary purpose for its use. The other reactions would become secondary benefits of the installation.
Effective disinfection occurs as demonstrated by the fact that the "CT" values for ozone, for inactivation of viruses and Giardia cysts, are considerably lower than the "CT" values for other disinfectants. In addition, recent research indicates that ozone can be an effective disinfectant for the maturation of cryptosporidium. Microflocculation and enhanced filterability has been demonstrated for many water supplies but has not occurred in all waters. Oxidation of organic compounds such as color, taste and odor, and detergents and inorganic compounds such as iron, manganese, heavy metals and hydrogen sulfide has been documented. The chemical ineraction of ozone with organic components, however, may result in an undesirable increase in the level of assimilable organic carbon (AOC) and THM precursors and, therefore, should be an initial process selection consideration. The effectiveness of oxidation has been varied, depending on pH and alkalinity of the water. These parameters affect the formation of highly reactive hydroxyl radicals, or, conversely the scavenging of this oxidant. High levels of hydroxyl radicals cause lower levels of residual ozone. Depending on the desired oxidation reaction, it may be necessary to maximize ozone residual or maximize hydroxyl radical formation. For disinfection, residual ozone is necessary for development of "CT".
As a minimum, bench scale studies shall be conducted to determine minimum and maximum ozone dosages for disinfection "CT" compliance and oxidation reactions. More involved pilot studies shall be conducted when necessary to document benefits and THM pre-cursor removal effectiveness. Consideration shall be given to multiple points of ozone addition. Pilot studies shall be conducted for all surface waters. Extreme care must be taken during bench and pilot scale studies to ensure accurate results. Particularly sensitive measurements include gas flow rate, water flow rate, and ozone concentration.
Following the use of ozone, the application of a disinfectant which maintains a measurable residual will be required in order to ensure a bacteriologically safe water is carried throughout the distribution system.
Furthermore, because of the more sophisticated nature of the ozone process a higher degree of operator maintenance skills and training is required. The ability to obtain qualified operators must be evaluated in selection of the treatment process. The necessary operator training shall be provided prior to plant startup.
The following items shall be addressed in the design:
1. Feed Gas Preparation
Feed gas can be air., high purity oxygen, or oxygen enriched air. Air handling equipment on conventional low pressure air feed systems shall consist of an air compressor, water/air separator, refrigerant dryer, heat reactivated desiccant dryer, and particulate filters. Some "package" ozonation systems for small plants may work effectively operating at high pressure without the refrigerant dryer and with a "heat-less" desiccant dryer. In all cases the design engineer must ensure that the maximum dew point of -60 °C (-76 °F) will not be exceeded at any time. For oxygen-feed systems, dryers typically are not required.
b. Air Compression
(1) Air compressors shall be of the liquid-ring or rotary lobe, oil-less, positive displacement type for smaller systems or dry rotary screw compressors for larger systems.
(2) The air compressors shall have the capacity to simultaneously provide for maximum ozone demand, provide the air flow required for purging the desiccant dryers (where required) and allow for standby capacity.
(3) Air feed for the compressor shall be drawn from a point protected from rain, condensation, mist, fog and contaminated air sources to minimize moisture and hydrocarbon content of the air supply.
(4) A compressed air after-cooler and/or entrainment separator with automatic drain shall be provided prior to the dryers to reduce the water vapor.
(5) A back-up air compressor must be provided so that ozone generation is not interrupted in the event of a break-down.
c. Air Drying
(1) Dry, dust-free and oil-free feed gas must be provided to the ozone generator. Dry gas is essential to prevent formation of nitric acid, to increase the efficiency of ozone generation and to prevent damage to the generator dielectrics. Sufficient drying to a maximum dew point of minus 60 °C (-76 °F) must be provided at the end of the drying cycle.
(2) Drying for high pressure systems may be accomplished using heatless desiccant dryers only. For low pressure systems, a refrigeration air dryer in series with heat-reactivated desiccant dryers shall be used.
(3) A refrigeration dryer capable of reducing inlet air temperature to 4 °C (40 °F) shall be provided for low pressure air preparation systems. The dryer can be of the compressed refrigerant type or chilled water type.
(4) For heat-reactivated desiccant dryers, the unit shall contain two desiccant filled towers complete with pressure relief valves, two four-way valves and a heater. In addition, external type dryers shall have a cooler unit and blowers. The size of the unit shall be such that the specified dew point will be achieved during a minimum adsorption cycle time of 16 hours while operating at the maximum expected moisture loading conditions.
(5) Multiple air dryers shall be provided so that the ozone generation is not interrupted in the event of dryer breakdown.
(6) Each dryer shall be capable of venting "dry" gas to the atmosphere, prior to the ozone generator, to allow start-up when other dryers are "on-line".
d. Air Filters
(1) Air filters shall be provided on the suction side of the air compressors, between the air compressors and the dryers and between the dryers and the ozone generators.
(2) The filter before the desiccant dryers shall be of the coalescing type and be capable of removing aerosol and particulates larger than 0.3 microns in diameter. The filter after the desiccant dryer shall be of the particulate type and be capable of removing all particulates greater than 0.1 microns in diameter, or smaller if specified by the generator manufacturer.
e. Air Preparation Piping
Piping in the air preparation system can be common grade steel, seamless copper, stainless steel or galvanized steel. The piping must be designed to withstand the maximum pressures in the air preparation system.
2. Ozone Generator
(1) The production rating of the ozone generators shall be stated in pounds per day and kW-h per pound at a maximum cooling water temperature and maximum ozone concentration.
(2) The design shall ensure that the minimum concentration of ozone in the generator exit gas will not be less than I percent (by weight).
(3) Generators shall be sized to have sufficient reserve capacity so that the system does not operate at peak capacity for extended periods of time. This can result in premature breakdown of the dielectrics.
(4) The production rate of ozone generators will decrease as the temperature of the coolant increases. If there is to be a variation in the supply temperature of the coolant throughout the year, then curves or other data shall be used to determine production changes due to the temperature change of the supplied coolant. The design shall ensure that the generators can produce the required ozone at maximum coolant temperature.
(5) Appropriate ozone generator backup equipment must be provided.
The generators can be low, medium or high frequency type.
Specifications shall require that the transformers, electronic circuitry and other electrical hardware be proven, high quality components designed for ozone service.
The required water flow to an ozone generator varies with the ozone production. Normally unit design provides a maximum cooling water temperature rise of 2.8 °C (5 °F). The cooling water must be properly treated to minimize corrosion, scaling and microbiological fouling of the water side of the tubes. A closed loop cooling water system is often used to insure proper water conditions are maintained. Where cooling water is treated cross connection control shall be provided to prevent contamination of the potable water supply in accordance with Section 8.8.2.
To prevent corrosion, the ozone generator shell and tubes shall be constructed of Type 316L stainless steel.
3. Ozone Contactors
The selection or design of the contractor and method of ozone application depends on the purpose for which the ozone is being used.
a. Bubble Diffusers
(1) Where disinfection is the primary application a minimum of two contact chambers each equipped with baffles to prevent shortcircuiting and induce countercurrent flow shall be provided. Ozone shall be applied using porous-tube or dome diffusers.
(2) The minimum contact time shall be 10 minutes. A shorter contact time may be approved by the reviewing authority if justified by appropriate design and "CT" considerations.
(3) For ozone applications in which precipitates are formed, such as with iron and manganese removal, porous diffusers should be used with caution.
(4) Where taste and odor control is of concern, multiple application points and contactors shall be considered.
(5) Contactors should be separate closed vessels that have no common walls with adjacent rooms. The contactor must be kept under negative pressure and sufficient ozone monitors shall be provided to protect worker safety. Placement of the contactor where the entire roof is exposed to the open atmosphere is recommended. In no case shall the contactor roof be a common wall with a separate room above the contactor.
(6) Large contact vessels should be made of reinforced concrete. All reinforcement bars shall be covered with a minimum of 1.5 inches of concrete. Smaller contact vessels can be made of stainless steel, fiberglass or other material which will be stable in the presence of residual ozone and ozone in the gas phase above the water level.
(7) Where necessary a system shall be provided between the contactor and the off-gas destruct unit to remove froth from the air and return the other to the contactor or other location acceptable to the reviewing authority. If foaming is expected to be excessive, then a potable water spray system shall be placed in the contactor head space.
(8) All openings into the contactor for pipe connections, hatchways, etc. shall be properly sealed using welds or ozone resistant gaskets such as Teflon or Hypalon.
(9) Multiple sampling ports shall be provided to enable sampling of each compartment's effluent water and to confirm CT calculations.
(10) A pressure/vacuum relief valve shall be provided in the contactor and piped to a location where there will be no damage to the destruction unit.
(11) The diffusion system should work on a countercurrent basis such that the ozone is fed at the bottom of the vessel and water is fed at the top of the vessel.
(12) The depth of water in bubble diffuser contactors should be a minimum of 18 feet. The contactor should also have a minimum of 3 feet of freeboard to allow for foaming.
(13) All contactors shall have provisions for cleaning, maintenance and drainage of the contactor. Each contactor compartment shall also be equipped with an access hatchway.
(14) Aeration diffusers shall be fully serviceable by either cleaning or replacement.
b. Other contactors
Other contactors, such as the venturi or aspirating turbine mixer contactor, may be approved by the reviewing authority provided adequate ozone transfer is achieved and the required contact times and residuals can be met and verified.
4. Ozone Destruction Unit
a. A system for treating the final off-gas from each contactor must be provided in order to meet safety and air quality standards. Acceptable systems include thermal destruction and thermal/catalytic destruction units.
b. In order to reduce the risk of fires, the use of units that operate at lower temperatures is encouraged, especially where high purity oxygen is the feed gas.
c. The maximum allowable ozone concentration in the discharge is 0.1 ppm (by volume).
d. At least two units shall be provided which are each capable of handling the entire gas flow.
e, Exhaust blowers shall be provided in order to draw off-gas from the contactor into the destruct unit.
f. Catalysts must be protected from froth, moisture and other impurities which may harm the catalyst.
g. The catalyst and heating elements shall be located where they can easily be reached for maintenance.
5. Piping Materials
Only low carbon 304L and 316L stainless steels shall be used for ozone service with 316L the preferred.
6. Joints and Connections
a. Connections on piping used for ozone service are to be welded where possible.
b. Connections with meters, valves or other equipment are to be made with flanged joints with ozone resistant gaskets, such as Teflon of Hypalon. Screwed fittings shall not be used because of their tendency to leak.
c. A positive closing plug or butterfly valve plus a leak-proof check valve shall be provided in the piping between the generator and the contactor to prevent moisture reaching the generator.
a. Pressure gauges shall be provided at the discharge from the air compressor, at the inlet to the refrigeration dryers, at the inlet and outlet of the desiccant dryers, at the inlet to the ozone generators and contactors and at the inlet to the ozone destruction unit.
b. Electric power meters should be provided for measuring the electric power supplied to the ozone generators. Each generator shall have a trip which shuts down the generator when the wattage exceeds a certain preset level.
c. Dew point monitors shall be provided for measuring the moisture of the feed gas from the desiccant dryers. Because it is critical to maintain the specified dew point, it is recommended that continuous recording charts be used for dew point monitoring which will allow for proper adjustment of the dryer cycle. Where there is potential for moisture entering the ozone generator from downstream of the unit or where moisture accumulation can occur in the generator during shutdown, post-generator dew point monitors shall be used.
d. Air flow meters shall be provided for measuring air flow from the desiccant dryers to each of other ozone generators, air flow to each contactor and purge air flow to the desiccant dryers.
e. Temperature gauges shall be provided for the inlet and outlet of the ozone cooling water and the inlet and outlet of the ozone generator feed gas, and, if necessary, for the inlet and outlet of the ozone power supply cooling water.
f. Water flow meters shall be installed to monitor the flow of cooling water to the ozone generators and, if necessary, to the ozone power supply.
g. Ozone monitors shall be installed to measure zone concentration in both the feed-gas and off-gas from the contactor and in the off-gas from the destruct unit. For disinfection systems, monitors shall also be provided for monitoring ozone residuals in the water. The number and location of ozone residual monitors shall be such that the amount of time that the water is in contact with the ozone residual can be determined.
h. A minimum of one ambient ozone monitor shall be installed in the vicinity of the contactor and a minimum of one shall be installed in the vicinity of the generator. Ozone monitors shall also be installed in any areas where ozone gas may accumulate.
The following alarm/shutdown systems should be considered at each installation:
a. Dew point shutdown/alarm - This system should shut down the generator in the event the system dew point exceeds - 60 °C (-76 °F).
b. Ozone generator cooling water flow shutdown/alarm - This system should shut down the generator in the event that cooling water flows decrease to the point that generator damage could occur.
c. Ozone power supply cooling water flow shutdown/alarm - This system should shut down the power supply in the event that cooling water flow decreases to the point that damage could occur to the power supply.
d. Ozone generator cooling water temperature shutdown/alarm - This system should shutdown the generator if either the inlet or outlet cooling water exceeds a certain preset temperature.
e. Ozone power supply cooling water temperature shutdown/alarm - This system should shutdown the power supply if either the inlet or outlet cooling water exceeds a certain preset temperature.
f. Ozone generator inlet feed-gas temperature shutdown/alarm - This system should shutdown the generator if the feed-gas temperature is above a preset value.
g. Ambient ozone concentration shutdown/alarm - The alarm should sound when the ozone level in the ambient air exceeds 0.1 ppm or a lower value chosen by the water supplier. Ozone generator shutdown should occur when ambient ozone levels exceed 0.3 ppm (or a lower value) in either the vicinity of the ozone generator or the contactor.
h. Ozone destruct temperature alarm - The alarm should sound when temperature exceeds a preset value.
a. The maximum allowable ozone concentration in the air to which workers may be exposed must not exceed 0.1 ppm (by volume).
b. Noise levels resulting from the operating equipment of the ozonation system shall be controlled to within acceptable limits by special room construction and equipment isolation.
c. High voltage and high frequency electrical equipment must meet current electrical and fire codes.
d. Emergency exhaust fans must be provided in the rooms containing the ozone generators to remove ozone gas if leakage occurs.
e. A portable purge air blower that will remove residual ozone in the contactor prior to entry for repair or maintenance should be provided.
10. Construction Considerations
a. Prior to connecting the piping from the desiccant dryers to the ozone generators the air compressors should be used to blow the dust out of the desiccant.
b. The contactor should be tested for leakage after sealing the exterior. This can be done by pressurizing the contactor and checking for pressure losses.
c. Connections on the ozone service line should be tested for leakage using the soap-test method.
Adopted August, 1991
Revised April, 1997
Most anion exchange resins used for nitrate removal are sulfate selective resins. Although nitrate selective resins are available, these resins typically have a lower total exchange capacity.
If a sulfate selective anion exchange resin is used beyond bed xhaustion, the resin will continue to remove sulfate from the water by exchanging the sulfate for previously removed nitrate resulting in treated water nitrate levels being much higher than raw water levels. Therefore it is extremely important that the system not be operated beyond the design limitations.
An evaluation shall be made to determine if pretreatment of the water is required if the combination of iron, manganese, and heavy metals exceed 0.1 milligrams per liter.
Anion exchange units are typically of the pressure type, down flow design. Although a pH spike can typically be observed shortly before bed exhaustion, automatic regeneration based on volume of water treated should be used unless justification for alternate regeneration is submitted to and approved by the reviewing authority. A manual override shall be provided on all automatic controls. A minimum of two units must be provided. The total treatment capacity must be capable of producing the maximum day water demand at a level below the nitrate/nitrite MCL. If a portion of the water is bypassed around the unit and blended with the treated water, the maximum blend ratio allowable must be determined based on the highest anticipated raw water nitrate level. If a bypass is provided, a totaling meter and a proportioning or regulating device or flow regulation valves must be provided on the bypass line.
Anion exchange media will remove both nitrate and sulfate from the water being treated. The design capacity for nitrate ansulfate removal expressed as calcium carbonate (CaCO3) should not exceed 16,000 grains per cubic foot (37 grams per liter) when the resin is regenerated with 10 pounds of salt per cubic foot (160 grams per liter) of resin when operating at 2 to 3 gallons per minute per cubic foot (0.27 to 0.4 liters per minute per liter). However, if high levels of chlorides exist in the raw water, the exchange capacity the resin should be reduced to account for the chlorides.
The treatment flow rate should not exceed 7 to 8 gallons per minute per square foot of bed area (29 to 32 cm per minute down flow rate). The backwash flow rate should be two to three gallons per minute per square foot of bed area (8 to 12 cm per minute rise rate) with a fast rinse approximately equal to the service flow rate.
Adequate free board must be provided to accommodate the backwash flow rate of the unit.
The system shall be designed to include an adequate underdrain and supporting gravel system, brine distribution equipment, and cross connection control.
Whenever possible, the treated water nitrate/nitrate level should be monitored using continuous monitoring and recording equipment. The continuous monitoring equipment should be equipped with a high nitrate level alarm. If continuous monitoring recording equipment is not provided, the finished water nitrate/nitrite levels must be determined (using a test kit) no less than daily, preferably just prior regeneration the unit.
Generally, waste from the anion exchange unit should be disposed in accordance with Section 4.11.2 of these standards. However, prior to any discharge, the reviewing authority must be contacted for wastewater discharge limitations or NPDES requirements.
Certain types of anion exchange resins can tolerate no more than 0.05 mg/L free chlorine. When the applied water will contain a chlorine residual, the anion exchange resin must be a type that is not damaged by residual chlorine.
Adopted April, 1997
|POLICY STATEMENT ON|
PRE-ENGINEERED WATER TREATMENT PLANTS FOR PUBLIC WATER SUPPLIES
|POLICY STATEMENT ON|
CONTROL OF ORGANIC CONTAMINATION FOR PUBLIC WATER SUPPLIES
|POLICY STATEMENT ON|
CORROSION CONTROL FOR PUBLIC WATER SUPPLIES
|POLICY STATEMENT ON|
TRIHALOMETHANE REMOVAL AND CONTROL FOR PUBLIC WATER SUPPLIES
|POLICY STATEMENT ON|
REVERSE OSMOSIS (RO) FOR PUBLIC WATER SUPPLIES
|POLICY STATEMENT ON|
AUTOMATED/UNATTENDED OPERATION OF SURFACE WATER TREATMENT PLANTS
|POLICY STATEMENT ON|
BAG AND CARTRIDGE FILTERS FOR PUBLIC WATER SUPPLIES
|POLICY STATEMENT ON|
USE OF CHLORAMINE DISINFECTANT FOR PUBLIC WATER SUPPLIES
|POLICY STATEMENT ON|
CONTROL OF ZEBRA MUSSELS FOR PUBLIC WATER SUPPLIES
|POLICY STATEMENT ON|
MEMBRANE FILTRATION FOR TREATING SURFACE SOURCES
|INTERIM STANDARD - OZONATION||xxxi|
|INTERIM STANDARD - NITRATE REMOVAL USING SULFATE SELECTIVE ANION EXCHANGE RESIN||xxxviii|
|PART 1||SUBMISSION OF PLANS||1|
|1.1.1 General information||1|
|1.1.2 Extent of water works system||1|
|1.1.3 Alternate plans||2|
|1.1.4 Soil, ground water conditions, and foundation problems||2|
|1.1.5 Water use data||2|
|1.1.6 Fire flow requirements||2|
|1.1.7 Sewerage system available||2|
|1.1.8 Sources of water supply||3|
|1.1.9 Proposed treatment processes||4|
|1.1.10 Waste disposal||4|
|1.1.12 Project sites||4|
|1.1.14 Future extensions||4|
|1.2.1 General layout||5|
|1.2.2 Detailed plans||5|
|1.5||REVISIONS TO APPROVED PLANS||7|
|1.6||ADDITIONAL INFORMATION REQUIRED||7|
|PART 2||GENERAL DESIGN CONSIDERATIONS||8|
|2.4||LOCATION OF STRUCTURES||9|
|2.7||SHOP SPACE AND STORAGE||9|
|2.8.1 Testing Equipment||9|
|2.8.2 Physical Facilities||10|
|2.11||FACILITY WATER SUPPLY||11|
|2.14||PIPING COLOR CODE||11|
|2.16||OPERATION AND MAINTENANCE MANUAL||12|
|PART 3||SOURCE DEVELOPMENT||13|
|3.1.3 Minimum treatment||14|
|3.1.5 Impoundments and reservoirs||15|
|3.2.4 Testing and Records||17|
|3.2.5 General well construction||19|
|3.2.6 Aquifer types and construction methods -- Special conditions||23|
|3.2.7 Well pumps, discharge piping and appurtenances||25|
|4.1.2 Rapid mix||29|
|4.1.5 Solids contact unit||32|
|4.1.6 Tube or plate settlers||34|
|4.2.1 Rapid rate gravity filters||36|
|4.2.2 Rapid rate pressure filters||42|
|4.2.3 Diatomaceous earth filtration||43|
|4.2.4 Slow rate gravity filters||45|
|4.2.5 Direct filtration||47|
|4.2.6 Deep bed rapid rate gravity filters||49|
|4.2.7 Biolgically active filters||49|
|4.3.1 Chlorination equipment||51|
|4.3.2 Contact time and point of application||52|
|4.3.3 Residual chlorine||52|
|4.3.4 Testing equipment||52|
|4.3.5 Chlorinator piping||53|
|4.3.7 Other disinfecting agents||53|
|4.4.1 Lime or lime-soda process||54|
|4.4.2 Cation exchange process||55|
|4.4.3 Water quality test equipmetn||57|
|4.5.1 Natural draft aeration||58|
|4.5.2 Forced or induced draft aeration||58|
|4.5.3 Pressure aeration||59|
|4.5.4 Spray aeration||59|
|4.5.5 Packed Tower aeration||59|
|4.5.6 Other methods of aeration||62|
|4.5.7 Protection of aerators||62|
|4.5.10 Corrosion control||63|
|4.5.11 Quality control||63|
|4.6||IRON AND MANGANESE CONTROL||64|
|4.6.1 Removal by oxidation, detention and filtration||64|
|4.6.2 Removal by the lime-soda softening process||64|
|4.6.3 Removal by manganese greensand filtration||64|
|4.6.4 Removal by ion exchange||65|
|4.6.5 Sequestration by polyphosphates||65|
|4.6.6 Sequestration by sodium silicates||65|
|4.6.7 Sampling taps||66|
|4.6.8 Testing equipment shall be provided for all plants||66|
|4.7.1 Fluoride compound storage||67|
|4.7.2 Chemical feed equipment and methods||67|
|4.7.3 Secondary controls||68|
|4.7.4 Protective equipment||68|
|4.7.5 Dust control|
|4.7.6 Testing equipment||68|
|4.8.1 Carbon dioxide addition||69|
|4.8.2 Acid addition||69|
|4.8.4 "Split treatment"||70|
|4.8.5 Alkali feed||70|
|4.8.6 Carbon dioxide reduction by aeration||70|
|4.8.7 Other treatment||70|
|4.8.8 Water unstable due to biochemical action in distribution system||70|
|4.9||TASTE AND ODOR CONTROL||71|
|4.9.3 Chlorine dioxide||71|
|4.9.4 Powdered activated carbon||71|
|4.9.5 Granular activated carbon adsorption units||72|
|4.9.6 Copper sulfate and other copper compounds||72|
|4.9.8 Potassium permanganate||72|
|4.9.10 Other methods||72|
|4.11||WASTE HANDLING AND DISPOSAL||74|
|4.11.1 Sanitary wastes||74|
|4.11.2 Brine wastes||74|
|4.11.3 Lime softening sludge||74|
|4.11.4 Alum sludge||76|
|4.11.5 "Red water" waste||76|
|4.11.6 Waste filter wash water||77|
|PART 5||CHEMICAL APPLICATION||79|
|5.0.1 Plans and specifications||79|
|5.0.2 Chemical application||79|
|5.0.3 General equipment design||79|
|5.1.1 Number of feeders||80|
|5.1.3 Dry chemical feeders||81|
|5.1.4 Positive displacement solution pumps||81|
|5.1.5 Liquid chemical feeders - Siphon control||81|
|5.1.6 Cross-connection control||81|
|5.1.7 Chemical feed equipment location||82|
|5.1.8 In-plant water supply||82|
|5.1.9 Storage of chemicals||82|
|5.1.10 Solution tanks||83|
|5.1.11 Day tanks||83|
|5.1.12 Feed lines||84|
|5.2.1 Shipping containers||85|
|5.3.2 Respiratory protection equipment||85|
|5.3.3 Chlorine leak detection||85|
|5.3.4 Protective equipment||86|
|5.4.1 Chlorine gas||86|
|5.4.2 Acids and caustics||87|
|5.4.3 Sodium chlorite for chlorine dioxide generation||87|
|PART 6||PUMPING FACILITIES||89|
|6.1.1 Site protection||89|
|6.2.1 Suction well||89|
|6.2.2 Equipment servicing||90|
|6.2.3 Stairways and ladders||90|
|6.2.8 Sanitary and other conveniences||91|
|6.3.1 Suction lift||91|
|6.4.1 Duplicate pumps||92|
|6.4.3 Inline booster pumps||92|
|6.4.4 Individual home booster pumps||92|
|6.5||AUTOMATICAND REMOTE CONTROLLED STATIONS||92|
|6.6.3 Gauges and meters||93|
|6.6.4 Water seals||93|
|6.6.7 Water pre-lubrication||94|
|PART 7||FINISHED WATER STORAGE||95|
|7.0.2 Location of ground-level reservoirs||95|
|7.0.4 Protection from trespassers||95|
|7.0.10 Roof and sidewall||97|
|7.0.11 Drainage of roof||97|
|7.0.14 Internal catwalk||98|
|7.0.15 Silt stop||98|
|7.0.17 Painting and/or cathodic protection||98|
|7.0.19 Provisions for Sampling||99|
|7.1.1 Washwater tanks||99|
|7.1.3 Adjacent compartments||99|
|7.1.4 Basins and wet-wells||99|
|7.3.3 Level controls||100|
|PART 8||DISTRIBUTION SYSTEMS||101|
|8.0.1 Standards, materials selection||101|
|8.0.2 Permeation of system by organic compounds||101|
|8.0.3 Used materials||101|
|8.1||WATER MAIN DESIGN||101|
|8.1.3 Fire protection||102|
|8.1.4 Small mains||102|
|8.1.6 Dead ends||102|
|8.3.1 Location and spacing||102|
|8.3.2 Valves and nozzles||103|
|8.3.3 Hydrant leads||103|
|8.4||AIR RELIEF VALVES; VALVE, METER AND BLOW-OFF CHAMBERS||103|
|8.4.1 Air relief valves||103|
|8.4.2 Air relief valve piping||103|
|8.4.3 Chamber drainage||103|
|8.5||INSTALLATION OF MAINS||103|
|8.5.5 Pressure and leakage testing||104|
|8.6||SEPARATION OF WATER MAINS, SANITARY SEWERS AND STORM SEWERS||104|
|8.6.2 Parallel installation||105|
|8.6.5 Force mains||105|
|8.6.6 Sewer manholes||105|
|8.6.7 Separation of water mains from other sources of contamination||106|
|8.7||SURFACE WATER CROSSINGS||106|
|8.7.1 Above-water crossings||106|
|8.7.2 Underwater crossings||106|
|8.8||CROSS CONNECTIONS AND INTERCONNECTIONS||106|
|8.8.1 Cross connections||106|
|8.8.2 Cooling water||106|
|8.9||WATER SERVICES AND PLUMBING||107|
|8.9.2 Booster pumps||107|
|8.11||WATER LOADING STATIONS||107|
|FIGURE I||SUGGESTED FILLING DEVICE FOR WATER LOADING STATIONS||108|
|TABLE 1||STEEL PIPE||28|