NR 811.49(2)(a)
(a) Quality of raw water. Slow rate gravity filtration shall be limited to waters having maximum turbidities of 50 nephelometric turbidity units (NTUs) and maximum color of 30 units; turbidity may not be attributable to colloidal clay. Raw water quality data shall include examinations for algae.
NR 811.49(2)(b)
(b) Structural details and hydraulics. Slow rate gravity filters shall be designed to provide:
NR 811.49(2)(b)1.
1. Not less than 2 filter units. If only 2 units are provided, each shall be capable of meeting the plant design capacity, normally the projected maximum daily demand, at the approved filtration rate. If more than 2 filter units are provided, the filters shall be capable of meeting the plant design capacity at the approved filtration rate with one filter removed from service.
NR 811.49(2)(b)3.
3. Headroom to permit normal movement by operating personnel for scraping and sand removal operations.
NR 811.49(2)(b)5.
5. Filtration to waste and overflow at the maximum filter water level.
NR 811.49(2)(c)
(c) Rates of filtration. The permissible rates of filtration shall be based on the quality of the raw water as determined from experimental data. Proposed rates shall be submitted to the department for approval. The design rate shall be 45 to 150 gallons per day per square foot of sand area. However, the department may approve design rates of 150 to 230 gallons per day per square foot if effectiveness is demonstrated to the satisfaction of the department.
NR 811.49(2)(d)
(d) Underdrains. Each filter unit shall be equipped with a main drain and an adequate number of lateral underdrains to collect the filtered water. The underdrains shall be so spaced that the maximum velocity of the water flow in the lateral underdrain will not exceed 0.75 feet per second. The maximum spacing of the laterals may not exceed 3 feet if pipe laterals are used.
NR 811.49(2)(e)
(e) Filtering material. A minimum depth of 30 inches of filter sand, clean and free of foreign matter, shall be placed on graded gravel layers. The effective size shall be between 0.30 and 0.45 mm, and the uniformity coefficient may not exceed 2.5.
NR 811.49(2)(f)
(f) Filter gravel. The supporting gravel shall conform to the size and depth distribution requirements in sub.
(1) provided for rapid rate gravity filters.
NR 811.49(2)(g)
(g) Depth of water on filter beds. The design shall provide a depth of at least 3 feet of water over the sand. Influent water shall be distributed in a manner which will not scour the sand surfaces.
NR 811.49(2)(h)
(h)
Control appurtenances. Each filter shall be equipped with:
NR 811.49(2)(h)2.
2. An orifice, Venturi meter or other suitable metering device installed on each filter to enable measurement of the rate of filtration.
NR 811.49(2)(h)3.
3. An effluent pipe located at an elevation which will maintain the water level in the filter above the top of the sand.
NR 811.49 History
History: CR 09-073: cr.
Register November 2010 No. 659, eff. 12-1-10; renumbering of (1) (e) made under s.
13.92 (4) (b) 1., Stats.,
Register November 2010 No. 659;
CR 22-074: am. (1) (b), (c), (f) 6. b., (j) 1., cr. (1) (k) 9. Register January 2024 No. 817, eff. 2-1-24. NR 811.495
NR 811.495 Filtration — pressure. A pressure filter may not be used in the filtration of surface water, polluted waters, or following lime-soda softening as provided under s.
NR 811.57. A pressure filter shall meet all of the following requirements:
NR 811.495(1)
(1)
Number. At least 2 filter units or cells shall be provided. Provisions shall be made to meet the plant design capacity at the approved filtration rate with one filter out of service. If only 2 units or cells are provided, each shall be capable of meeting the plant design capacity, normally the projected maximum daily demand.
NR 811.495(2)
(2)
Rate of filtration. The rate of filtration shall not exceed 4 gallons per minute per square foot of filter area except when pilot testing under s.
NR 811.44 or full-scale testing as approved by the department has demonstrated adequate contaminant removal rates at the higher filtration rates, as determined by the department.
NR 811.495(4)
(4)
Design details. A filter shall be designed to provide for all of the following:
NR 811.495(4)(a)
(a) Loss of head gauges on the inlet and outlet pipes of each filter.
NR 811.495(4)(b)
(b) An easily readable meter of flow indicator on each battery of filters.
NR 811.495 Note
Note: A flow indicator is recommended for each filtering unit.
NR 811.495(4)(c)
(c) Piping that allows filtration and backwashing of each filter individually.
NR 811.495(4)(d)
(d) Minimum side wall shell height of 5 feet. A reduction in side wall height may be approved by the department when proprietary filter bottoms permit reduction of the gravel depth.
NR 811.495(4)(e)
(e) The top of the wash water collectors to be at least 18 inches above the surface of the media.
NR 811.495(4)(f)
(f) The underdrain system to efficiently collect the filtered water and to uniformly distribute the backwash water at a rate not less than 15 gallons per minute per square foot of filter area.
NR 811.495(4)(g)
(g) Backwash flow indicators and controls that are easily readable while operating the control valves.
NR 811.495(4)(h)
(h) An air release valve on the highest point of each filter cell. The discharge line from the relief valve shall be metal and terminate downward facing with a 24-mesh corrosion resistant screen, at least 24 inches above the floor.
NR 811.495(4)(i)
(i) An accessible manhole to facilitate inspection and repairs for each filter cell.
NR 811.495 History
History: CR 22-074: cr. Register January 2024 No. 817, eff. 2-1-24; correction in (2) made under s. 35.17, Stats., Register January 2024 No. 817. NR 811.50
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:
NR 811.50(1)
(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.
NR 811.50(2)
(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.
NR 811.50(3)
(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.
NR 811.50 Note
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.
NR 811.50(4)
(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).
NR 811.50(5)
(5)
Pretreatment. Pretreatment shall be as follows:
NR 811.50(5)(a)
(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.
NR 811.50(5)(b)
(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.
NR 811.50(6)
(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.
NR 811.50(7)
(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.
NR 811.50(8)
(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.
NR 811.50(9)
(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.
NR 811.50(10)
(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.
NR 811.50(11)
(11)
Monitoring. Equipment shall be provided to monitor water quality, flow rates, and water pressure.
NR 811.50(11)(a)
(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.
NR 811.50(11)(b)
(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.
NR 811.50(11)(c)
(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.
NR 811.50(11)(d)
(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.
NR 811.50(12)
(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.
NR 811.50(13)
(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.
NR 811.50(14)
(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.
NR 811.50(15)
(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.
NR 811.50(16)
(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.
NR 811.50(17)
(17)
Treatment efficiency. The design treatment efficiency shall be determined by pilot testing.
NR 811.50(18)
(18)
Power consumption. The power consumption of a particular membrane under consideration shall be evaluated during the pilot study or from other relevant data.
NR 811.50(19)(a)(a)
Back-up systems. Automated monitoring and control systems shall be provided with back-up power and operational control systems consisting of the following:
NR 811.50(19)(a)1.
1. Dual running programmable logic controllers (PLCs) with synchronized programs and memory, or spare PLCs loaded with the most current program.
NR 811.50(19)(b)
(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:
NR 811.51
NR 811.51 Fluoridation. Sodium fluoride, sodium fluorosilicate and fluorosilicic acid shall conform to the applicable NSF/ANSI Standard 60 and AWWA standards B701, B702, and B703 in effect at the time of use. Other fluoride compounds which may be available shall be approved by the department. The following specific requirements shall be met:
NR 811.51(1)
(1)
Fluoride chemical storage. Fluoride chemicals shall be stored in accordance with the following requirements:
NR 811.51(1)(a)
(a) Fluoride chemicals shall be isolated from other chemicals to prevent contamination.
NR 811.51(1)(b)
(b) Fluoride chemicals shall be stored in covered or unopened shipping containers and stored inside a building.
NR 811.51(1)(c)
(c) Unsealed storage units for fluorosilicic acid shall be vented to the atmosphere at a point outside the building. The vent piping shall terminate a minimum of 24 inches above grade with a down-turned U-bend. The vent pipe opening shall be covered with a 24-mesh corrosion resistant screen.
NR 811.51(2)
(2)
Fluoride Acid housing. Equipment for feeding fluoride in the acid form and unsealed acid storage containers shall be housed in accordance with the following requirements:
NR 811.51(2)(a)
(a) All chemical feed equipment, solution tanks, and acid containers shall be housed in a separate room within the pumphouse away from controls, electrical contacts, and other equipment subject to damage. Fluoride chemical feed installations shall be installed in a room separate from all other chemicals.
