Consider also the 2012 Edition.
Policies for the Review and Approval
of Plans and Specifications for Public Water Supplies
A Report of the Water Supply Committee of the
Great Lakes--Upper Mississippi River Board
of State and Provincial Public Health and Environmental
Managers
MEMBER STATES AND PROVINCE
Illinois Indiana Iowa Michigan Minnesota Missouri
New York Ohio Ontario Pennsylvania Wisconsin
Published by: Health Research Inc., Health
Education Services Division,
P.O. Box 7126, Albany, NY 12224
(518)439-7286 www.hes.org
Copyright © 2007 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.
The Great Lakes-Upper Mississippi River Board of State and Provincial 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. Throughout this document the term state shall mean a representative state or the Province of Ontario. 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, 1997, 2003 and 2007.
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. Some policy statements recommend an approach to the investigation of innovative treatment processes which 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. Other policy statements recommend approaches, alternatives or considerations in addressing a specific water supply issue and may not develop into standards.
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.
Most quantified items in this document are cited in US customary units and are rounded off at two significant figures. Metric equivalent quantities, also rounded off at two significant figures, follow in brackets where compound units are involved. The metric unit symbols follow International System conventions. In the event of a conflict between quantities in US units and the metric equivalent the quantity in US units shall take precedence.
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 and Provincial 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.
Adopted April, 1997
Revised April, 2007
Pre-engineered water treatment plants are becoming available and being used 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 Safe 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), International Underwriters Laboratory (UL) or other acceptable ANSI accredited third parties 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. Pretreatment may be included as an integral process in the pre-engineered module.
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. In addition to any automation, full manual override capabilities must be provided.
13. Cross-connection control including, but not limited to the avoidance of single wall separations between treated and partially or untreated surface water.
14. 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.
15. 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.
16. Water supplier revenue and budget for continuing operations, maintenance and equipment replacement in the future.
17. Life expectancy and long-term performance of the units based on the corrosivity of the raw and treated water and the treatment chemicals used.
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
Revised April, 2006
Recent advances in computer technology, equipment controls and Supervisory Control and Data Acquisition (SCADA) Systems have brought automated and 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 an 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 and loss of communications or power.
An engineering report shall be developed as 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 and treatment facilities that will be electronically monitored, have alarms and can be operated automatically or off-site via the control system. Include a description of automatic plant shut-down controls with alarms and conditions which would trigger shut-downs. Dual or secondary alarms may be necessary for certain critical functions.
2. Automated monitoring of all critical functions with major and 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 the 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 adjust and 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 of 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 and training planned or completed in both process control and the automation system.
9. Operations manual which gives operators step by step procedures for understanding and 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 6 month or more demonstration period 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 and alarms that occurred during the demonstration period. Challenge testing of each critical component of the overall system must be included as part of the demonstration project.
11. Schedule for maintenance of equipment and critical parts replacement.
12. Sufficient finished water storage shall be provided to meet system demands and CT requirements whenever normal treatment production is interrupted as the result of automation system failure or plant shutdown.
13. Sufficient staffing must be provided to carry out 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 and 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 of the treatment facilities at 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 some time 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 have accepted bag and cartridge technology as an alternate technology for compliance with the filtration requirements of the Surface Water Treatment Rule and the Long Term 1 Enhanced Surface Water Treatment Rule. In addition, bag and cartridge filters are included in the microbial toolbox options for meeting the Cryptosporidium treatment requirements of the Long Term 2 Enhanced Surface Water Treatment Rule.
The particulate loading capacity of 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 Cryptosporidium oocyst removal.
With this type of treatment there is no alteration of water chemistry. So, once the technology has demonstrated the required removal efficiency, no further pilot demonstration may be 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 a surface water should include source water protection, filtration, and disinfection.
The following items should be considered in evaluating the applicability of bag or cartridge filtration.
1. The filter housing and bag/cartridge filter must demonstrate a filter efficiency of at least 2-log reduction in particles size 2 micron and above. Demonstration of higher log removals may be required by the reviewing authority depending on raw water quality and other treatment steps to be employed. The reviewing authority will decide whether or not a pilot demonstration is necessary for each installation. This filtration efficiency demonstration may be accomplished by:
a. Microscopic particulate analysis, including particle counting, sizing and identification, which determines occurrence and removals of micro-organisms and other particle across a filter or system under ambient raw water source condition, or when artificially challenged.
b. Cryptosporidium particle removal evaluation in accordance with procedures specified in NSF Standard 53 or equivalent. These evaluations must be conducted by NSF or by another third-party whose certification would be acceptable to the reviewing authority.
c. "Protocol for Equipment Verification Testing for Physical Removal of Microbiological and Particulate Contaminants" procedure specified by the EPA/NSF Environmental Technology Verification Program.
d. Challenge testing procedure for bag and cartridge filters presented in Chapter 8 of the Long Term 2 Enhanced Surface Water Treatment Rule Toolbox Guidance Manual.
e. "Nonconsensus" live Cryptosporidium challenge studies that have been designed and carried out by a third-party agent recognized and accepted by the reviewing authority for interim evaluations. At the present time uniform protocol procedures for live Cryptosporidium challenge studies have not been established.
f. 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 less than 3 NTU.
4. The flow rate through the treatment process shall be monitored with a flow valve and meter. The flow rate through the bag/cartridge filter must not exceed the maximum flow rate verified by filtration efficiency testing.
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 filter and to extend bag and cartridge life. 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. Filter to waste shall be provided for the final filter(s) and a set amount of water shall be discharged to waste after changing the filters.
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 gages 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 filter 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 bag or cartridge filter to as low as possible to lengthen 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 treatment 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 available to run the treatment plant.
17. A plan of action should be in place should the water quality parameters fail to meet EPA or the local reviewing authorities 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 or the reviewing authority 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 manufacturers recommendations.
4. Sterile rubber gloves and a disposable face mask covering the nose and mouth should be worn when replacing or cleaning the cartridge or bag filters.
5. The filter system shall be properly disinfected and water shall be ran to waste each time the cartridge or bag filter vessels are opened for maintenance.
6. The following parameters should be monitored:
Flow rate, instantaneous
Flow rate, total
Operating pressure
Pressure differential
Turbidity
Adopted April, 1997
Revised April, 2003
Revised April, 2007
The United States Environmental Protection Agency (EPA) has promulgated the Long Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR) to further reduce microbial contamination of drinking water. The rule requires additional treatment for some public water supplies based on their source water Cryptosporidium concentrations and current treatment practices. Ultraviolet Light (UV) disinfection is one option public water supplies have to comply with the additional treatment requirements. The EPA has released a document entitled ULTRAVIOLET DISINFECTION GUIDANCE MANUAL FOR THE FINAL LONG TERM 2 ENHANCED SURFACE WATER TREATMENT RULE. This guidance manual will be used as the basis for the validation, design, and operation of all UV systems used for public water systems and for the development of the recommended standards for those systems. UV disinfection may also be considered as primary disinfection for public water systems with microbiologically safe ground water and must meet the same requirements as UV systems used to meet LT2ESWTR. The reviewing authority shall be contacted regarding use of UV treatment.
Supplemental disinfection for additional virus inactivation or to provide a residual in the water distribution system may be required by the reviewing authority. When UV light treatment devices are used for non-health related purposes the UV device may provide doses less than indicated in the following criteria.
A. CRITERIA FOR UV WATER TREATMENT DEVICES
1. UV water treatment devices must be validated by a third-party entity in accordance with the USEPA Ultraviolet Light Disinfection Guidance Manual (USEPA UVDGM), the German Association for Gas and Water (UVGW), the Austrian Standards Institute (ONORM), the National Water Research Institute/ American Water Works Association Research Foundation (NWRI/AwwaRF), the Class A criteria under ANSI/NSF Standard 55 - Ultraviolet Microbiological Water Treatment Systems; or other standards acceptable to the reviewing authority. The validation must demonstrate that the unit is capable of providing a UV light dose of 40 millijoules per square centimeter (mJ/cm2). In addition to the requirements cited in the USEPA UVDGM each UV water treatment device shall meet the following:
a. The UV assemblies shall be accessible for visual observation, cleaning and replacement of the lamp, lamp jackets and sensor window/lens. A wiper assembly or chemical cleaning-in-place system may be installed to allow in-situ cleaning of lamp jackets. Adequate controls shall be in place to prevent contamination of the potable water with cleaning chemicals;
b. An automatic shutdown valve shall be installed in the water supply line ahead of the UV treatment system that will be activated whenever the water treatment system loses power or is tripped by a monitoring device when the dosage is below the validated operating design dose. When power is not being supplied to the UV unit the valve shall be in a closed (fail-safe) position.
c. The UV housing shall be stainless steel 304 or 316L;
2. A flow or time delay mechanism wired in series with the well or service pump shall be provided to permit a sufficient time for lamp warm-up per manufacturer recommendations before water flows from the unit upon startup. Where there are extended no-flow periods and fixtures are located a short distance downstream of the UV unit, consideration should be given to UV unit shutdown between operating cycles to prevent heat build-up in the water due to the UV lamp;
3. A sufficient number (required number plus one) of parallel UV treatment systems shall be provided to assure a continuous water supply when one unit is out of service unless other satisfactory disinfection can be provided when the unit is out of service;
4. No bypasses shall be installed;
5. All water from the well shall be treated. The well owner may request a variance to treat only that portion of the water supply that is used for potable purposes provided that the daily average and peak water use is determined and signs are posted at all non-potable water supply outlets.
6. The well or booster pump(s) shall have adequate pressure capability to maintain minimum water system pressure after the water treatment devices;
B. PRETREATMENT
The reviewing authority will determine pre and post treatment on a specific case basis depending on raw water quality. See Section G for raw water quality limitations. If coliform bacteria or other microbiological organisms are present in the untreated water appropriate filtration shall be provided as minimum pretreatment. A 5 um sediment filter or equivalent is recommended for all UV installations.
C. ONLINE MONITORING, REPLACEMENT PARTS
UV light intensity of each installed unit shall be monitored continuously. Treatment units and the water system shall automatically shutdown if the UV dosage falls below the validated operating and approved design dose. Water systems that have source water exceeding 5 NTU turbidity may be required to install additional pretreatment and/or an online turbidimeter ahead of the UV water treatment device. An automatic shutdown valve shall be installed and operated in conjunction with the turbidimeter. Each owner shall have available on site at least one replacement lamp, a 5 micron replacement filter and, where applicable, a replacement cyst reduction filter and any other components necessary to keep the treatment system in service.
D. SEASONAL OPERATIONS
UV water treatment devices that are operated on a seasonal basis shall be inspected and cleaned prior to use at the start of each operating season. The UV water treatment system including the filters shall be disinfected prior to placing the water treatment system back into operation. A procedure for shutting down and starting up the UV treatment system shall be developed for or by each owner based upon manufacturer recommendations and submitted in writing to the review authority.
E. RECORD KEEPING AND ACCESS
A record shall be kept of the water quality test data, dates of lamp replacement and cleaning, a record of when the device was shutdown and the reason for shutdown, and the dates of prefilter replacement.
The reviewing authority shall have access to the UV water treatment system and records.
Water system owners will be required to submit operating reports and required sample results on a monthly or quarterly basis as required by the reviewing authority.
F. RAW WATER QUALITY CHARACTERISTICS
The water supply shall be analyzed for the following water quality parameters and the results shall be included in the UV application. Pretreatment is required for UV installations if the water quality exceeds any of the following maximum limits. When an initial sample exceeds a maximum limit, a check sample shall be taken and analyzed.
| Parameter | Maximum* |
|---|---|
| UV 254nm Absorption | 0.155 cm-1 |
| Dissolved Iron | 0.3 mg/L |
| Dissolved Manganese | 0.05 mg/L |
| Hardness | 120 mg/L |
| Hydrogen sulfide (if odor is present) | Non-Detectable |
| Iron Bacteria | None |
| pH | 6.5 to 9.5 |
| Suspended Solids | 10 mg/L |
| Turbidity | 1.0 NTU |
| Total Coliform | 1,000/100 ML |
| E. Coli | ** |
| Cryptosporidium | ** |
| Giardia | ** |
* Higher values may be acceptable to the reviewing authority if experience with similar water quality and reactors shows that adequate treatment is provided and there are no treatment problems or excessive maintenance required, or if the reactor was validated for parameters higher than these maximums.
** These organisms may indicate that the source is either a surface water or ground water under the direct influence of surface water and may require additional filtration pretreatment. Consult the reviewing authority for guidance.
Raw water quality shall be evaluated and pretreatment equipment shall be designed to handle water quality changes. Variable turbidity caused by rainfall events is of special concern.
Adopted April, 2003
Revised April, 2007
Review of public water system security infrastructure and practices has shown an industry-wide vulnerability to intentional acts of vandalism, sabotage and terrorism. Protection from these types of threats must be integrated into all design considerations. Many public drinking water systems have implemented effective security and operational changes to help address this vulnerability, but additional efforts are needed.
Security measures are needed to help ensure that public water suppliers attain an effective level of security. Design considerations need to address physical infrastructure security, and facilitate security related operational practices and institutional controls. Because drinking water systems cannot be made immune to all possible attacks, the design needs to address issues of critical asset redundancy, monitoring, response and recovery. All public water supplies need to identify and address security needs in design and construction for new projects and for retrofits of existing drinking water systems.
The following concepts and items should be considered in the design and construction of new water system facilities and improvements to existing water systems:
1. Security shall be an integral part of drinking water system design. Facility layout shall consider critical system assets and the physical needs of security for these assets. Requirements for submitting, identifying and disclosing security features of the design, and the confidentiality of the submission and regulatory review should be discussed with the reviewing authority.
2. The design should identify and evaluate single points of failure that could render a system unable to meet its design basis. Redundancy and enhanced security features should be incorporated into the design to eliminate single points of failure when possible, or to protect them when they cannot reasonably be eliminated.
3. Consideration should be made to ensure effective response and timely replacement of critical components that are damaged or destroyed. Critical components that comprise single points of failure (e.g., high volume pumps) that cannot be eliminated should be identified during design and given special consideration. Design considerations should include component standardization, availability of replacements and key parts, re-procurement lead times, and identification of suppliers and secure retention of component specifications and fabrication drawings. Readily replaceable components should be used whenever possible and provisions should be made for maintaining an inventory of critical parts.
4. Human access should be through controlled locations only. Intrusion deterrence measures (e.g., physical barriers such as fences, window grates and security doors; traffic flow and check-in points; effective lighting; lines of sight; etc.) should be incorporated into the facility design to protect critical assets and security sensitive areas. Effective intrusion detection should be included in the system design and operation to protect critical assets and security sensitive areas. All cameras and alarms installed for security purposes should include monitors at manned locations.
5. Vehicle access should be through controlled locations only. Physical barriers such as moveable barriers or ramps should be included in designs to keep vehicles away from critical assets and security sensitive areas. It should be impossible for any vehicle to be driven either intentionally or accidentally into or adjacent to finished water storage or critical components without facility involvement. Designated vehicle areas such as parking lots and drives should be separated from critical assets with adequate standoff distances to eliminate impacts to these assets from possible explosions of material in vehicles.
6. Sturdy, weatherproof, locking hardware must be included in the design of access for all tanks, vaults, wells, well houses, pump houses, buildings, power stations, transformers, chemical storage, delivery areas, chemical fill pipes, and similar facilities. Vents and overflows should be hardened through use of baffles or other means to prevent their use for the introduction of contaminants.
7. Computer based control technologies such as SCADA must be secured from unauthorized physical access and potential cyber attacks. Wireless and network based communications should be encrypted as deterrence to hijacking by unauthorized personnel. Vigorous computer access and virus protection protocols should be built into computer control systems. Effective data recovery hardware and operating protocols should be employed and exercised on a regular basis. All automated control systems shall be equipped with manual overrides to provide the option to operate manually. The procedures for manual operation including a regular schedule for exercising and insuring operator's competence with the manual override systems shall be included in facility operation plans.
8. Real time water quality monitoring with continuous recording and alarms should be considered at key locations to provide early warning of possible intentional contamination events.
9. Facilities and procedures for delivery, handling and storage of chemicals should be designed to ensure that chemicals delivered to and used at the facility cannot be intentionally released, introduced or otherwise used to debilitate a water system, its personnel, or the public. Particular attention should be given to potentially harmful chemicals used in treatment processes (e.g., strong acids and bases, toxic gases and incompatible chemicals) and on maintenance chemicals that may be stored on-site (e.g., fuels, herbicides, paints, solvents).
Adopted April, 2003
Revised April, 2007
Arsenic in groundwater is an issue that many water systems must deal with following the maximum contaminant level revision from 50 parts per billion (ppb) to 10 ppb on January 22, 2006. Several technologies are available to remove arsenic, from fairly simple to more complex. In much of the Upper Midwest, arsenic typically exists as As (III) in groundwater, and as As (V) in surface waters. Arsenic in the form of As (V) is easier to remove due to its insolubility and negative charge. Arsenic As (III) can be changed to As (V) by a simple oxidation process.
With the different removal technologies comes a wide range of monetary investment. In addition, the issue of discharging concentrated waste water and/or disposal of solid wastes must be resolved. The safe and proper disposal of all related treatment wastes must comply with all local, state, federal and provincial requirements. When the maximum contaminant limit (MCL) for arsenic is exceeded, it is recommended that the treatment is capable of reducing arsenic levels in the water to one-half the MCL (currently 5 ppb) or less. The following list provides information on different types of typical arsenic treatment technologies and options for optimization:
Adsorptive Media - Uses metal oxide coatings, usually iron, titanium or aluminum, on the filter media to remove arsenic. Pre- and post-adjustment of pH will enhance removal rates and reduce corrosivity. This method needs chemical oxidation of arsenic, iron and manganese (if present), a pre-filter to remove iron and manganese to prevent fouling of the adsorptive media (if iron levels are too high [near or above 1.0 ppm]), followed by the adsorptive filter media. Costs for implementing this technology may be low to moderate if a system currently has an iron and/or manganese filter. High levels of iron, sulfate, and dissolved solids may cause interference or reduce the treatment efficiency.
Oxidation/Filtration (Iron & Manganese removal) - This method uses chemical oxidation of arsenic, iron and manganese with free chlorine, potassium permanganate (KMnO4), ozone or manganese dioxide with a manganese greensand, anthracite, pyrolusite, or other proprietary filter media. The water is allowed detention time and filtration after chemical oxidation. Water with low iron (less than a 20 to 1 ratio of iron to arsenic) may need additional iron in the form of ferric chloride or ferric sulfate to increase arsenic removal efficiencies.
Coagulation/Filtration - Typically chemical oxidation of arsenic, iron and manganese, pre- and post-adjustment of pH (to enhance coagulation; reduce corrosivity), the use of ferric chloride, ferric sulfate, or alum as a coagulant, use a polymer (filter aid or enhanced coagulation), and settling time (sedimentation) to remove arsenic. Other contaminants may be removed in this process. Sulfate may cause interference or reduce treatment efficiency.
Anion Exchange - Chloride (strong-base) sulfate-selective or nitrate-selective resins, are used to remove contaminants. This process may also require the chemical oxidation of arsenic, iron and manganese (if present), and pre-filters to maximize contaminant removal, and to prevent fouling of the exchange resin. Post-treatment adjustment of pH is required to reduce corrosivity. Treatment columns may be in parallel or series (avoid sulfate, nitrate and arsenic breakthrough, and avoid lowered pH breakthrough immediately after regeneration). Treatment may use anion exchange after cation exchange to remove hardness (mixed beds not recommended - anion resins are lighter and column becomes service intensive). Other contaminants that can be removed include sulfate (sulfate-selective resins); nitrate (nitrate-selective resins); and hardness (mixed cation/anion beds). Iron, sulfate, and dissolved solids may cause interference or reduce treatment efficiency.
Electrodialysis/Electrodialysis Reversal - Uses an electrical charge of a reverse osmosis (R.O.) membrane to remove arsenic. Chemical oxidation of arsenic, iron and manganese with filtration is used to remove oxidized iron and manganese to prevent fouling of the R.O. membrane. Pre- and post-adjustment of pH may be needed to prevent scaling, to enhance filtration, and to reduce corrosivity. Other contaminants that may be removed using this technology include hardness, dissolved solids, nitrates, and sulfates. If iron and manganese are too high, this may cause interference with the arsenic removal process.
Membrane Filtration (Micro, Ultra, Nanofiltration, and Reverse Osmosis) - Membrane removal utilizes chemical pre-oxidation (except when using polypropylene membranes), a pre-filter to remove oxidized iron and manganese to prevent fouling of the membranes), pre- and post-adjust pH (prevent scaling, enhance filtration; reduce corrosivity). The treatment can also use ferric chloride or ferric sulfate as a coagulant. Iron, manganese, and other dissolved solids may cause interference or reduce treatment efficiency. Reverse osmosis membranes will also remove hardness in the water.
Lime Softening - This technology is based on the optimization of Mg(OH)2 precipitation. High iron concentrations are desired for optimal arsenic removal. Waters with low dissolved iron may require the addition of ferric chloride or ferric sulfate. Hardness may also be removed in this process. Other issues include the disposal of lime sludge, and the high labor intensity of handling lime.
Adopted April, 2007
Four treatment processes are generally considered acceptable for Nitrate/Nitrite removal. These are anion exchange, reverse osmosis, nanofiltration and electrodialysis. Although these treatment processes, when properly designed and operated will reduce the nitrate/nitrite concentration of the water to acceptable levels, primary consideration shall be given to reducing the nitrate/nitrite levels of the raw water through either obtaining water from an alternate water source or through watershed management. Reverse osmosis nanofiltration or electrodialysis should be investigated when the water has high levels of sulfate or when the chloride content or dissolved solids concentration is of concern.
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 exhaustion, the resin will continue to remove sulfate from the water by exchanging the sulfate for previously removed nitrates 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 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 exceeds 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 regulating valves must be provided on the bypass line.
Anion exchange media will remove both nitrates and sulfate from the water being treated. The design capacity for nitrate and sulfate removal expressed as CaCO3 should not exceed 16,000 grains per cubic foot (37 g/l) when the resin is regenerated with 10 pounds of salt per cubic foot (160 g/l) of resin when operating at 2 to 3 gallons per minute per cubic foot (0.27 to 0.4 L/min per litre). However, if high levels of chlorides exist in the raw water, the exchange capacity of 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/minute down flow rate). The back wash flow rate should be 2 to 3 gallons per minute per square foot of bed area (8 to 12 cm/minute rise rate) with a fast rinse approximately equal to the service flow rate.
Adequate freeboard must be provided to accommodate the backwash flow rate of the unit.
The system shall be designed to include an adequate under drain and supporting gravel system, brine distribution equipment, and cross connection control.
When ever possible, the treated water nitrate/nitrite 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 and 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 to regeneration of the unit.
Generally, waste from the anion exchange unit should be disposed in accordance with Section 9.2 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
Revised April, 2007
Chloramination is an application of ammonia and chlorine, with ammonia addition usually downstream of the application of chlorine at a proper mass ratio of chlorine to ammonia to produce a combined chlorine residual predominantly in form of monochloramine. Proper chlorine to ammonia ratio must be maintained to prevent the formation of dichloramine and trichloramine which create taste and odor in drinking water.
Monochloramine is rarely suitable for use as a primary disinfectant because it requires very long contact time to achieve adequate disinfection at the normally used concentration. Because of its high persistence characteristics, monochloramine is more commonly used to maintain a chlorine residual in the water distribution system as a secondary disinfectant.
Chloramine residual is more stable and longer lasting than free chlorine, and it provides better protection against bacterial re-growth in water distribution systems including large storage tanks, lower flow demand and dead-end water mains. As a result, it is more effective in controlling biofilm growth in the water distribution system. Chloramine is not as reactive as chlorine with organic material in water, thereby producing substantially less disinfection by-products such as trihalomethanes in the water distribution system. However, chloramine may provide less protection from contamination of the distribution system through cross connections, water main breaks and other causes.
Unlike most substances added to water for treatment purposes, chloramine cannot be prepared at high concentrations. It can only be made by addition of ammonia to pre-chlorinated water or by adding chlorine to water containing low concentrations of ammonia. Contact of high concentrations of chlorine with ammonia or ammonium salts must be avoided to prevent the formation of nitrogen trichloride which is a sensitive and violently explosive substance.
Operating authorities who wish to modify disinfectant practices by using chloramine must show the 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 ground water supplies but it is inadequate in strength for primary disinfection of surface waters.
2. Chloramine can be suitable for protecting potable water in distribution systems against bacterial contamination. The chloramine tends to remain active for longer periods and at greater distances from the plant than free chlorine. Chloramine concentrations should be maintained higher than for chlorine to avoid nitrifying bacterial activity. A range of 1-2 mg/L, 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 sulphate. 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 from storage and gas release must be handled with pressure relief systems. Absorption/neutralization systems for ammonia gas leaks/spills must be designed specially for ammonia. Ammonium sulphate 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 as to avoid formation of organic chloramines and of odorous dichloramine. Sufficient ammonia must be added to provide at least a small excess (more than one part of ammonia to between 3 and 5 parts of chlorine) over that required to convert all the free chlorine present to chloramine.
5. Addition of ammonia gas or ammonia solution will increase the pH of the water and addition of ammonium sulphate 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 side stream of pre-softened water may be needed for ammonia dilution 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, increased 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 of nitrifying bacteria activity may be made by checking for reduced dissolved oxygen, elevated free ammonia, elevated HPC, and elevated nitrite and 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 use of chloraminated water. Medical authorities, hospitals and commercial and domestic aquarium keepers should be notified so they can arrange for precautions to be taken.
Policy Statement Adopted April, 1997
Re-Adopted as Interim Standard April, 2003
Revised October, 2005
Membrane technologies have a wide range of applications from the use of reverse osmosis for desalination, inorganic compound removal, and radionuclide removal to the use of lower pressure membranes for removal of surface water contaminants such as giardia and cryptosporidium. Membrane technologies are typically separated into four categories based on membrane pore size: reverse osmosis, nanofiltration, ultrafiltration, and microfiltration. When using membranes for treatment of surface water or groundwater under the direct influence of surface water the reviewing agency should be contacted to determine inactivation/removal credits for the specific membrane and treatment objective.
The following items should be considered when evaluating the applicability of membrane processes.
1. Treatment objectives. The selection of the specific membrane process should be matched to the desired treatment objectives. Removal is generally related to pore size and as such the larger pore size membranes are not appropriate for applications such as inorganic compound or radionuclide removal.
2. Water quality considerations. A review of historical source raw water quality data, including turbidity and/or particle counts, seasonal changes, organic loading, microbial activity, and temperature differentials as well as other inorganic and physical parameters should be conducted. The data should be used to determine feasibility and cost of the system. The degree of pre-treatment may also be ascertained from the data. Design considerations and membrane selection at this phase must also address the issue of target removal efficiencies and system recovery versus acceptable transmembrane pressure differentials. On surface water supplies, pre-screening or cartridge filtration may be required. The source water temperature can significantly impact the flux of the membrane under consideration. At low water temperatures, the flux can be reduced appreciably (due to higher water viscosity and resistance of the membrane to permeate), possibly impacting process economics by the number of membrane units required for a full scale facility. Seasonal variation of design flow rates may be based on documented lower demand during colder weather.
3. Pilot study/preliminary investigations. Prior to initiating the design of a membrane treatment facility, the 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 need for pretreatment, type of post treatment, the bypass ratio, the amount of reject water, system recovery, process efficiency, particulate/organism removal efficiencies, cold and warm water flux, fouling potential, operating and transmembrane pressure and other design and monitoring considerations. Any virus removal credit must also be documented through an appropriate piloting process. The reviewing authority should be contacted prior to conducting the pilot study to establish the protocol to be followed.
4. Challenge Testing. Membranes treating surface waters or groundwater under the direct influence of a surface water must be challenge tested to establish a product specific maximum Cryptosporidium log removal credit.
5. Pretreatment. Acceptable feedwater characteristics are dependent on the type of membrane and operational parameters of the system. Without suitable pretreatment or acceptable feed water quality, the membrane may become fouled or scaled and consequently shorten its useful life. For reverse osmosis and nanofiltration processes pretreatment is usually needed for turbidity reduction, iron or manganese removal, stabilization of the water to prevent scale formation, microbial control, chlorine removal (for certain membrane types), and pH adjustment. Usually, at a minimum, cartridge filters should be provided for the protection of the reverse osmosis or nanofiltration membranes against particulate matter.
6. Membrane materials. Two types of membranes are typically used for reverse osmosis and nanofiltration. These are cellulose acetate based and polyamide composites. Membrane configurations typically include tubular, spiral wound and hollow fiber. Microfiltration (MF) and nanofiltration (NF) membranes are most commonly made from organic polymers such as: cellulose acetate, polysulfones, polyamides, polypropylene, polycarbonates, and polyvinylidene. The physical configurations include: hollow fiber, spiral wound, and tubular. Operational conditions and useful life vary depending on type of membrane selected, quality of feed water, and process operating parameters. Some membrane materials are incompatible with certain oxidants. If the system must rely on pre-treatment oxidants for other purposes, for example, zebra mussel control, taste and odor control, or iron and manganese oxidation, the selection of the membrane material becomes a significant design consideration.
7. Useful life of membranes. Membrane replacement represents a major component in the overall cost of water production The life expectancy of a particular membrane under consideration should be evaluated during the pilot study or from other relevant available data. Membrane life may also be reduced by operating at consistently high fluxes. Membrane replacement frequency is a significant factor in operation and maintenance cost comparisons in the selection of the process
8. Treatment efficiency. Reverse osmosis (RO) and nanofiltration (NF) are 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, shape and charge 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%, depending on the membrane type and organic being considered.
9. Power consumption. Power consumption may be a significant coast factor for reverse osmosis plants. The power consumption of a particular membrane under consideration should be evaluated during the pilot study or from other relevant data.
10. Bypass water. Reverse osmosis (RO) permeate will be virtually demineralized. Nanofiltration (NF) permeate may also contain less dissolved minerals than desirable. The design should provide for a portion of the raw water to bypass the unit to maintain stable water within the distribution system and to improve process economics as long as the raw water does not contain unacceptable contaminants. Alternative filtration is required for bypassed surface water or ground water under the direct influence of surface water.
11. Reject water. Reject water from reverse osmosis and nanofiltration membranes may range from 10% to 50% of the raw water pumped to the reverse osmosis unit. For most brackish waters and ionic contaminant removal applications, reject is in the 10-25% range while for seawater it could be as high as 50%. The reject volume should be evaluated in terms of the source availability and from the waste treatment availabilities. 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 typically include discharge to a municipal sewer system, to waste treatment facilities, or to an evaporation pond.
12. Backflushing or cross flow cleansing. Automated periodic backflushing and cleaning is employed on microfiltraion and ultrafiltration on a timed basis or once a target transmembrane pressure differential has been reached. Back flushing volumes can range from 5 -15 percent of the permeate flow depending upon the frequency of flushing/cleaning and the degree of fouling and this should be considered in the treatment system sizing and the capacity of the raw water source
13. Membrane cleaning. The membrane must be periodically cleaned with acid, detergents and possibly disinfection. Method of cleaning and chemicals used must be approved by the state reviewing agency. Care must be taken in the cleaning process to prevent contamination of both the raw and finished water system. Cleaning chemicals, frequency and procedure should follow membrane manufacturer's guidelines. Cleaning chemicals should be NSF/ANSI Standard 60 certified.
14. Membrane integrity and finished water monitoring. An appropriate level of direct and indirect integrity testing is required to routinely evaluate membrane and housing integrity and overall filtration performance. Direct integrity testing may include pressure and vacuum decay tests for MF& UF and marker-based tests for NF & RO. These are usually conducted at least once per day. Indirect monitoring options may include particle counters and/or turbidity monitors and should be done continuously. Consult the appropriate regulatory agency regarding specific process monitoring requirements.
15. Cross connection control. Cross connection control considerations must be incorporated into the system design, particularly with regard to chemical feeds and waste piping used for membrane cleaning, waste stream and concentrate. Typical protection includes block & bleed valves on the chemical cleaning lines and air gaps on the drain lines.
16. Redundancy of critical components. Redundancy of critical control components including but not limited to valves, air supply, and computers shall be required as per the reviewing authority.
17. Post treatment. Post treatment of water treated using reverse osmosis or nanofiltration typically includes degasification for carbon dioxide (if excessive) and hydrogen sulfide removal (if present), pH and hardness adjustment for corrosion control and disinfection as a secondary pathogen control and for distribution system protection.
18. Operator training. 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.
Interim Standard Adopted April, 2007