Section NR 811.50 - Filtration - membrane Membrane technologies have a wide range of applications from the use of lower pressure membranes for removal of surface water contaminants such as Giardia Lamblia and Cryptosporidium to the use of reverse osmosis for desalination, inorganic compound removal, and radionuclide removal. The following specific requirements shall be met:
(1) TREATMENT OBJECTIVES. The selection of the specific membrane process shall be matched to the desired treatment objectives. The department shall be contacted to determine inactivation/removal credits for the specific membrane and treatment objective membranes to be used in treatment of surface water or groundwater under the direct influence of surface water.(2) WATER QUALITY CONSIDERATIONS. A review of historical source raw water quality data, including turbidity or particle counts or both, seasonal changes, organic loading, microbial activity, and temperature differentials as well as other inorganic and physical parameters shall be conducted. The data shall be used to determine feasibility and cost of the system and the degree of pre-treatment. Design considerations and membrane selection at this phase shall 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 shall be considered when establishing the design flux of the membrane under consideration and the number of treatment units to be installed. Seasonal variation of design flow rates may be based on documented lower demand during colder weather.(3) PILOT TESTING. Prior to initiating the design of a membrane treatment facility, pilot testing under s. NR 811.44 shall be conducted. The pilot plant study shall be designed to identify the best membrane to use, need for pre- treatment, type of post- treatment, cold and warm water flux, backwash optimization, chemical cleaning optimization, fouling potential, operating and transmembrane pressure, integrity testing procedures, bypass ratio, amount of reject water, system recovery, process efficiency, particulate or organism removal efficiencies, and other design and monitoring considerations, each when applicable. The duration of the pilot testing shall be 9 to 12 months for microfiltration and ultrafiltration and 2 to 7 months for reverse osmosis and nanofiltration. The pilot testing shall be operated for a minimum of 3 clean in-place cycles unless an alternate operation schedule is approved by the department. The general protocol and sampling schedule shall follow the U.S. Environmental Protection Agency Membrane Filtration Guidance Manual, EPA 815-R-06-009, November 2005 Table 6.2, which is incorporated by reference, unless the department approves an alternative sampling schedule. Note: U.S. Environmental Protection Agency Membrane Filtration Guidance Manual, EPA 815-R-06-009 is the U.S. Environmental Protection Agency guidance for membrane filtration published on November 5, 2005. A copy of the U.S. Environmental Protection Agency standard is available for inspection at the Legislative Reference Bureau and may be obtained from the U.S. Environmental Protection Agency, https://www.epa.gov.
(4) CHALLENGE TESTING. Membranes treating surface waters or groundwater under the direct influence of a surface water shall be challenge tested to establish a product specific maximum Cryptosporidium and Giardia Lamblia log removal credit. Challenge testing shall meet the requirements of s. NR 810.45 (2).(5) PRETREATMENT. Pretreatment shall be as follows:(a)Microfiltration and ultrafiltration. Pretreatment shall be designed to remove suspended solids and large particulate matter. The pretreatment may consist of a screen or strainer with a 200 to 500 micron rating. Chemicals used for pretreatment shall be certified for compliance with ANSI/NSF Standard 60.(b)Reverse osmosis and nanofiltration. Pretreatment shall be provided where appropriate 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. At a minimum, cartridge filters shall be provided for the protection of the reverse osmosis or nanofiltration membranes against particulate matter.(6) MEMBRANE MATERIALS. Two types of membranes may be used for reverse osmosis and nanofiltration. These are cellulose acetate based and polyamide composites. Microfiltration and ultrafiltration membranes may be organic polymers such as: cellulose acetate, polysulfones, polyamides, polypropylene, polycarbonates or polyvinylidene. The physical configurations may include: hollow fiber, spiral wound or tubular. Membrane materials shall be compatible with any pre-oxidants.(7) USEFUL LIFE OF MEMBRANES. The life expectancy of a particular membrane under consideration shall be evaluated during the pilot study or from other relevant available data.(8) BACKWASHING. Automated periodic backwashing shall be provided for microfiltration and ultrafiltration on a timed basis or once a target transmembrane pressure differential or a high resistance have been reached. Back flushing volumes may range from 5% to 15% of the permeate flow depending upon the frequency of flushing or cleaning and the degree of fouling. The back flushing volumes shall be considered in the treatment system sizing and the capacity of the raw water source. For systems using pressurized air, the compressors shall utilize food grade oil and filters shall be provided to prevent oil from reaching the membranes. Chemically enhanced backwash systems shall be protected from cross connections and shall be followed by a regular backwash. Backwash wastes shall be disposed of in accordance with subch. XII.(9) MEMBRANE CLEANING. A means shall be provided to allow for periodically cleaning the membrane. Cleaning shall include a soak type cleaning and may also include more frequent maintenance cleans. The cleaning process shall protect the raw and finished water from contamination. Cleaning chemicals, frequency and procedure should follow membrane manufacturer's guidelines. Some cleaning solutions require heated water. Cleaning chemicals shall be NSF/ANSI Standard 60 certified. Membrane cleaning shall be initiated by the operator. Waste streams from chemical cleaning shall be discharged to the sanitary sewer. Adequate space shall be provided for different or additional chemicals which may be required to adequately clean the membranes in the future.(10) MEMBRANE INTEGRITY TESTING. A means shall be provided to conduct direct and indirect integrity testing to routinely evaluate membrane and housing integrity and overall filtration performance. Direct integrity testing may include pressure and vacuum decay tests for microfiltration and ultrafiltration and marker-based tests for nanofiltration and reverse osmosis. The direct testing method shall allow for conducting tests at least once per day and may be required 3 times per day. Indirect monitoring options may include particle counters or turbidity monitors or both and shall allow for testing continuously. The testing methodology shall be approved by the department during startup procedures.(11) MONITORING. Equipment shall be provided to monitor water quality, flow rates, and water pressure. (a)Water quality. Sampling taps shall be provided to allow monitoring of water quality from the source water, from the water after any pretreatment, from the filtrate of each membrane unit, from the combined filtrate of all membranes, from the backwash, and prior to the entry to any clearwell.(b)Flow monitoring. Water meters shall be provided to allow flow measurement from the source water, from the filtrate of each unit, from the combined filtrate of all units, from the backwash source, from any recirculation line, and from any waste line.(c)Pressure monitoring. Pressure gauges shall be provided prior to the membrane units, after each membrane unit, and on the combined effluent of all membrane units.(d)Additional monitoring. Additional monitoring points shall be provided as necessary to satisfy integrity testing requirements and operational reporting requirements of sub. (10) and s. NR 810.07.(12) CROSS CONNECTION CONTROL. Cross connection control considerations shall be incorporated into the system design, particularly with regard to chemical feeds and waste piping used for membrane cleaning, waste stream and concentrate. Protection may include block and bleed valves on the chemical cleaning lines and air gaps on the drain lines.(13) REDUNDANCY OF CRITICAL COMPONENTS. Redundancy of critical control components including but not limited to pumps, valves, air supply, chemical feed equipment and computers shall be provided.(14) POST TREATMENT. Post treatment of water treated using reverse osmosis or nanofiltration shall be provided. Post treatment may consist of 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.(15) BYPASS WATER. The design shall 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 shall be provided for bypassed surface water or groundwater under the direct influence of surface water.(16) REJECT WATER. Reject volumes shall 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. Waste disposal from reverse osmosis or nanofiltration reject water shall discharge to a municipal sewer system, to waste treatment facilities, or to an evaporation pond.(17) TREATMENT EFFICIENCY. The design treatment efficiency shall be determined by pilot testing.(18) POWER CONSUMPTION. The power consumption of a particular membrane under consideration shall be evaluated during the pilot study or from other relevant data.(19) CONTROL SYSTEMS. (a)Back-up systems. Automated monitoring and control systems shall be provided with back-up power and operational control systems consisting of the following: 1. Dual running programmable logic controllers (PLCs) with synchronized programs and memory, or spare PLCs loaded with the most current program.2. Spare input/output (I/O) cards of each type.3. A minimum of 2 human machine interfaces (HMI).4. Backup power supply including uninterruptible power supply (UPS).(b)Remote or unmanned operational control. Systems designed for remote or unmanned control shall be provided alarms, communication systems, and automatic shutdown processes. The department shall be contacted to determine the extent of operational control required. At a minimum the following alarms shall be provided: 1. High raw or filtrate turbidity.3. High pressure decay test.4. High transmembrane pressure.6. Membrane unit shutdown.7. Clearwell level high or low.9. High or low chlorine residual.13. Building low temperature.Wis. Admin. Code Department of Natural Resources NR 811.50
CR 09-073: cr. Register November 2010 No. 659, eff. 12-1-10.Amended by, CR 22-074: am. (3) Register January 2024 No. 817, eff. 2/1/2024