Disinfection

PURPOSE: This rule specifies the minimum standards for the design of disinfection processes that are part of wastewater collection and treatment systems. This rule is to be used with rules 10 CSR 20-8.110 through 10 CSR 20-8.210. It does not address all aspects of design, and the design engineer may refer to other appropriate reference materials so long as these minimum standards set forth in this rule are met. (1) Applicability. Wastewater systems that utilize disinfection shall be designed based on criteria contained in this rule, published standards, applicable federal and state requirements, standard textbooks, current technical literature, and applicable safety standards. In the event of any conflict between the above criteria, the requirement in this rule shall prevail. (A) This rule shall not apply to treatment units covered in 10 CSR 20-8.300. (B) This rule shall not apply to treatment units covered in 10 CSR 20-8.500. (2) General. (A) Emergency Power. Disinfection and dechlorination processes, when used, shall be provided during all power outages. For additional emergency power requirements, refer to the provisions listed in 10 CSR 20-8.140(7). (B) Secondary containment. Secondary containment shall comply with the provisions listed in 10 CSR 20-8.140(9)(A)2. (3) Chlorine Disinfection. (A) Contact period. A minimum contact period of fifteen (15) minutes at design peak hourly flow or maximum rate of pumpage shall be provided after thorough mixing. (B) Gaseous Chlorine Housing. 1. Feed and storage rooms shall— A. Have chlorine gas feed and storage rooms constructed of fire and corrosion resistant material; B. Provide a gas-tight room to separate equipment from any other portion of the building if gas chlorination equipment or chlorine cylinders are to be in a building used for other purposes; C. Have smooth floor surfaces that are chemical resistant, impervious, and slip resistant. Floor drains are discouraged. Design floor drains, where provided, with the ability to be plugged and sealed; D. Have doors to this room that only open to the outside of the building, and are equipped with panic hardware. Provide door locks to prevent unauthorized access, but do not need a key to exit the locked room using the panic hardware; E. Be well-lit with lights that are sealed so that they will continue working during a chlorine leak. Comply with 10 CSR 20-8.140(7)(B), requirements for Class I, Division 2, Group D locations when selecting lighting and electrical equipment; F. Be at ground level and permit easy access to all equipment; G. Separate storage areas for one- (1-) ton cylinders from the feed area; and H. Have designated areas for “full” and “empty” cylinder storage. 2. Heating and cooling. A. Rooms containing disinfection equipment shall be provided with a means of heating and cooling so that a temperature of at least sixty degrees Fahrenheit (60° F) and no more than eighty-six degrees Fahrenheit (86°F) can be maintained. B. Heating or air conditioning equipment provided for the chlorinator room shall be separate from central heating and air conditioning systems to prevent chlorine gas from entering the central system and central heating or cooling ducts are not allowed to terminate or pass through a chlorinator room. 3. Ventilation shall conform to the following: A. Install forced mechanical ventilation to provide one (1) complete fresh air change per minute when the chlorinator room is occupied. Construct fans of chemical resistant materials and have chemical proof motors. Squirrel cage type fans located outside the chlorinator room may be approved if the fan housings and ducting are airtight and made of chlorine and corrosion resistant material; B. Locate the entrance to the air exhaust duct from the room no more than twelve inches (12") off the floor. Locate the point of discharge as not to contaminate the air inlet to any buildings or present a hazard at the access to the chlorinator room or other inhabited areas. Utilize louvers for air exhaust to facilitate airtight closure; C. Locate air inlets as to provide cross ventilation. Place the outside air inlet at least three feet (3') above grade. Utilize louvers for air inlets to facilitate airtight closure; and D. Position the vent hose from the chlorinator to the outside atmosphere above grade. Provide passive vent screens. 4. Electrical controls. Switches for fans and lights shall be outside of the chlorinator room at the entrance. 5. Protective and respiratory gear. Where chlorine gas is present the applicant shall comply with 10 CSR 20-8.140(9)(D)1. (C) Alarm System. The applicant shall conform to 10 CSR 208.140(7)(C) and be responsible for specifying what the alarm requirements are necessary to assure consistent disinfection in compliance with the applicable bacteria limits and the disinfection residual limit in the effluent. (D) Sampling Equipment. Sampling equipment shall be consistent with the requirements in 10 CSR 20-8.140(7)(F). (4) Dechlorination. (A) Containers. Dilution tanks and mixing tanks are required when using dry compounds and may be necessary when using liquid compounds to deliver the proper dosage. (B) Mixing and Contact Requirements. 1. Mixing requirements. Solid dechlorination systems shall not be located in the chlorine contact tank. 2. Contact time. A minimum of thirty (30) seconds for mixing and contact time shall be provided at the design peak hourly flow or maximum rate of pumpage. (C) Housing Requirements. 1. Feed and storage rooms. The requirements for housing sulfite gas equipment shall follow the same guidelines as for chlorine gas. For specific details follow the provisions listed in subsection (3)(B). 2. Protective and respiratory gear. See paragraph (3)(B)5. of this rule. (D) Alarm System. See subsection (3)(C) of this rule. (E) Sampling Equipment. Sampling equipment shall be consistent with the requirements in 10 CSR 20-8.140(7)(F). (5) Ultraviolet Disinfection. (A) Dosage and System Sizing. 1. General. The UV dosage shall be based on the design peak hourly flow, maximum rate of pumpage, or peak batch flow. 2. Batch discharges. If no flow equalization is provided for a batch discharger, the dosage shall be based on the peak batch flow. 3. Bioassay. The UV system shall deliver the target dosage based on equipment derating factors and, if needed, have the UV equipment manufacturer verify that the scale up or scale down factor utilized in the design is appropriate for the specific application under consideration. 4. The design delivered UV dosage for a wastewater treatment facility shall be a minimum of thirty thousand microwatt seconds per centimeters squared (30,000 μW • s/cm2) based on MS-2 phage inactivation. (B) Design. 1. Open channel systems. The combination of the total number of banks shall be capable of treating the design peak hourly flow, maximum rate of pumpage, or peak batch flow. 2. Closed vessel systems. The combination of the total number of closed vessels shall be capable of treating the design peak hourly flow, maximum rate of pumpage, or peak batch flow. 3. Cleaning. Closed vessel systems utilizing medium-pressure lamps shall be provided with an automatic cleaning system in order to prevent algae growth. (C) Monitoring and Alarms. 1. The UV system must continuously monitor and display at the UV system control panel the following minimum conditions: A. The relative intensity of each bank or closed vessel system; B. The operational status and condition of each bank or closed vessel system; C. The ON/OFF status of each lamp in the system; and D. The total number of operating hours of each bank or each closed vessel system. 2. The UV system shall include an alarm system. Alarm systems shall comply with 10 CSR 20-8.140(7)(C). (D) Electrical Controls. For electrical controls, follow the provisions listed in 10 CSR 20-8.140(7)(B) for electrical controls requirements. (E) Sampling Equipment. Sampling equipment shall be consistent with the requirements in 10 CSR 20-8.140(7)(F). AUTHORITY: section 644.026, RSMo 2016.* Original rule filed Aug. 10, 1978, effective March 11, 1979. Amended: Filed June 15, 2018, effective Feb. 28, 2019. *Original authority: 644.026, RSMo 1972, amended 1973, 1987, 1993. 10 CSR 20-8.200 Wastewater Treatment Lagoons, Wastewater Irrigation Alternatives, and Earthen Basins PURPOSE: This rule specifies the minimum standards for the design of lagoons and wastewater irrigation alternatives that are part of wastewater collection and treatment systems. This rule is to be used with rules 10 CSR 20-8.110 through 10 CSR 20-8.210. It does not address all aspects of design, and the design engineer may refer to other appropriate reference materials so long as these minimum standards set forth in this rule are met. PUBLISHER’S NOTE: The secretary of state has determined that publication of the entire text of the material that is incorporated by reference as a portion of this rule would be unduly cumbersome or expensive. This material as incorporated by reference in this rule shall be maintained by the agency at its headquarters and shall be made available to the public for inspection and copying at no more than the actual cost of reproduction. This note applies only to the reference material. The entire text of the rule is printed here. (1) Applicability. Wastewater systems that utilize lagoons, earthen basins, and wastewater irrigation alternatives shall be designed based on criteria contained in this rule, published standards, applicable federal and state requirements, standard textbooks, current technical literature, and applicable safety standards. In the event of any conflict between the above criteria, the requirement in this rule shall prevail. (A) This rule shall not apply to treatment units covered in 10 CSR 20-8.300. (B) This rule shall not apply to treatment units covered in 10 CSR 20-8.500. (C) This rule shall not apply to lagoons or earthen basins built to contain or control the release of stormwater only that does not come in contact with process waste or process wastewater. (D) This rule shall not apply to any earthen basin constructed to retain and settle nontoxic, nonmetallic earthen materials such as soil, silt, and rock. (2) Alternative Design. The department may approve an alternative design, after public participation in accordance with 10 CSR 20-6.020, when it determines that the proposed alternative design is as effective or more effective than the requirements of this chapter and when compliance with the design requirements of this chapter would be unfeasible or impractical. The owner of a project proposing an alternative design must provide engineering justification to the department. The justification must— (A) Be requested in writing; (B) Be signed, sealed, and dated by a professional engineer licensed in Missouri; (C) Include an explanation of how compliance with a design requirement of this chapter is unfeasible or impractical; and (D) Include all pertinent facts, data, reports, and studies certifying the proposed alternative design will result in equivalent or improved effectiveness compared to the minimum design requirement in this chapter. (3) Supplementary Field Data for the Facility Plan. The facility plan shall contain pertinent information on location, geology, soil conditions, area for expansion, and any other factors that will affect the feasibility and acceptability of the proposed project, including the information required per 10 CSR 20-8.110. The following information must be submitted: (A) Lagoons and spray irrigation fields shall be located where stormwater runoff from the watershed is minimized; (B) Geohydrologic Evaluation. A geohydrologic evaluation shall be requested from the department’s Missouri Geological Survey on all new lagoons, lagoon major modifications, earthen basins, earthen basin major modifications, new wastewater irrigation sites, and subsurface absorption fields. Supplemental information may be submitted for consideration by the department. 1. Severe collapse potential. Lagoons and earthen basins shall not be located in areas with a severe collapse potential rating unless additional information supports an alternative determination by the department for the proposed location; (C) Soils Investigation. Detailed soils investigations and reports shall be submitted for facilities surface irrigating more than twenty-four inches per year (24"/yr) and for all subsurface absorption fields. Soils reports shall comply with 10 CSR 208.110(7); (D) Where geosynthetic liners are used in storage or treatment basins for wastewaters of an industrial nature, the application shall— 1. Document that the liner or storage structure material is capable of containing the wastewater for at least twenty (20) years; 2. Specify repair or replacement procedures in the event of leakage or damage to the seal; and 3. Include an evaluation of secondary containment or leakage detection and collection devices for corrosive or reactive wastewaters and for toxic materials. (4) Basis of Design. (A) Area and Loadings for Discharging Lagoons. 1. Lagoon design for BOD5 loadings shall not exceed thirtyfour pounds per day per acre (34 lbs/day/acre) at the three-foot (3') operating depth in the primary cells. 2. Aerated lagoons. Aeration equipment shall be capable of— A. Maintaining the design level of dissolved oxygen within a particular cell with one (1) unit in the cell out of service; B. Maintaining a minimum dissolved oxygen level of two milligrams per liter (2 mg/L) in the lagoon at all times; C. Delivering one and four-tenths pounds of oxygen per pound of biochemical oxygen demand removed (1.4 lbs O2/1 lb BOD); and D. Delivering an additional four and sixth-tenths pounds of oxygen per pound of ammonia nitrogen removal (4.6 lbs O2/1 lb NH3). (B) Area and Loadings for Wastewater Irrigation Storage Basins. Treatment prior to surface irrigation shall provide performance equivalent to that obtained from a primary wastewater lagoon cell designed and constructed in accordance with section (5) of this rule, except that the lagoon depth may be increased to include wastewater storage in addition to the primary volume. (5) Lagoon and Earthen Basin Construction Details. (A) Embankments and Berms. 1. Berms shall be constructed of relatively impervious material and compacted to at least ninety-five percent (95%) maximum dry density test method to form a stable structure. 2. The minimum berm width shall be eight feet (8') to permit access of maintenance vehicles. 3. Minimum freeboard shall be two feet (2'). 4. An emergency spillway shall be provided that— A. Prevents the overtopping and cutting of berms; B. Is compacted and vegetated or otherwise constructed to prevent erosion; and C. Has the ability for a representative sample to be collected, if discharging. (B) Lagoon and Earthen Basin Bottom. Soil shall be compacted with the moisture content between two percent (2%) below and four percent (4%) above the optimum water content and compacted to at least ninety-five percent (95%) maximum dry density test method. (C) Lagoon and Earthen Basin Seal. 1. The lagoon or earthen basin shall be sealed to ensure that seepage loss is as low as possible and has a design permeability not exceeding 1.0 x 10-7 cm/sec. 2. Soil seals. The minimum thickness of the compacted clay liner must be twelve inches (12"). For permeability coefficients greater than 1.0 × 10-7 cm/sec or for design average operating depths over five feet (5'), such as an aerated lagoon system, the following formula shall be used to determine minimum seal thickness, Equation 200-1: Equation 200-1 H × K t = ______________________ 5.4 × 10-7 cm/sec where: K = the permeability coefficient of the soil in question; H = the design average operating depth of water in the lagoon or earthen basin, excluding the inner berm depth; and t = the thickness of the soil seal. 3. Synthetic liners. Synthetic seals thickness may vary due to liner material, but the liner thickness shall be no less than two-hundredths inch (.02") or twenty (20) mil and be the appropriate material to perform under existing conditions. 4. Seep collars shall be provided on drainpipes where they pass through the lagoon or earthen basin seal. (D) Influent Lines. 1. Unlined corrugated metal pipe shall not be used due to corrosion problems. 2. A manhole shall be installed with its invert at least six inches (6") above the maximum operating level of the lagoon or earthen basin, prior to the entrance into the primary cell, to provide sufficient hydraulic head without surcharging the manhole. For manhole installation, follow the provisions listed in 10 CSR 20-8.120(4). 3. The influent line(s) shall be located along the bottom of the lagoon or earthen basin so that the top of the pipe is just below the average elevation of the lagoon or earthen basin seal; however, there shall be an adequate seal below the pipe. (6) Covers for Lagoon Retrofits. (A) Lagoon covers shall be constructed with a minimum thickness of two-thousandths inch (.002"), two (2) mil, or meet the manufacturer’s recommendations, and be ultraviolet- and weather-resistant. (B) Trial seams shall be used to verify acceptable installation techniques. (C) The cover shall include a stormwater removal system that conveys collected precipitation to sumps or includes drainage areas in the membrane within the acceptable leakage rate to allow stormwater to drain into the lagoon. (7) Surface Irrigation of Wastewater. (A) Site Considerations. For site considerations, follow the provision in section (3) of this rule. (B) Wetted Application Area. The wetted application area is the land area that is normally wetted by wastewater application. The wetted application area must be— 1. Located outside of flood-prone areas having a flood frequency greater than once every ten (10) years; 2. Established— A. At least one hundred fifty feet (150') from existing dwellings or public use areas, excluding roads or highways; B. At least fifty feet (50') inside the property line; C. At least three hundred feet (300') from any sinkhole, losing stream, or other structure or physiographic feature that may provide direct connection between the ground water table and the surface; D. At least three hundred feet (300') from any existing potable water supply well not located on the property. Adequate protection shall be provided for wells located on the application site; E. One hundred feet (100') to wetlands, ponds, and gaining streams (classified or unclassified; perennial or intermittent); and F. If an established vegetated buffer or the wastewater is disinfected, the setbacks established in subsections (A)–(E) of this section may be decreased if the applicant demonstrates the risk is mitigated; and 3. Fenced, or if not fenced, provide in the construction permit application or the facility plan, the— A. Method of disinfection being utilized; B. Suitable barriers in place; or C. Details on how public access is limited and not expected to be present. (C) Preapplication Treatment. At a minimum, treatment prior to irrigation shall provide performance equivalent to that obtained from a primary wastewater lagoon cell designed and constructed in accordance with sections (4) and (5) of this rule, except that the lagoon depth may be increased to include wastewater storage in addition to the primary volume. 1. The size of storage basins shall be based on the design wastewater flows and net rainfall minus evaporation expected for a one (1) in ten (10) year frequency for the storage period selected and shall meet the minimum storage days listed below. A. Seventy-five (75) days for facilities located in Barry, Barton, Bollinger, Butler, Cape Girardeau, Carter, Christian, Dade, Dent, Douglas, Dunklin, Greene, Howell, Iron, Jasper, Lawrence, Madison, McDonald, Mississippi, New Madrid, Newton, Oregon, Ozark, Pemiscot, Perry, Reynolds, Ripley, Scott, Shannon, Stoddard, Stone, Taney, Texas, Wayne, Webster, and Wright counties. B. Ninety (90) days for facilities located in Bates, Benton, Camden, Cedar, Cole, Crawford, Dallas, Franklin, Gasconade, Henry, Hickory, Jefferson, Laclede, Maries, Miller, Moniteau, Morgan, Osage, Phelps, Polk, Pulaski, St. Charles, St. Clair, St. Francois, St. Louis, St. Louis City, Ste. Genevieve, Vernon, and Washington counties. C. One hundred five (105) days for facilities located in Audrain, Boone, Callaway, Carroll, Cass, Chariton, Clay, Cooper, Howard, Jackson, Johnson, Lafayette, Lincoln, Monroe, Montgomery, Pettis, Pike, Platte, Ralls, Randolph, Ray, Saline, and Warren counties. D. One hundred twenty (120) days for facilities located in Adair, Andrew, Atchison, Buchanan, Caldwell, Clark, Clinton, Daviess, DeKalb, Gentry, Grundy, Harrison, Holt, Knox, Lewis, Linn, Livingston, Macon, Marion, Mercer, Nodaway, Putnam, Schuyler, Scotland, Shelby, Sullivan, and Worth counties. E. Seasonal facilities. For facilities that operate and generate flows only from April through October season, a minimum storage capacity of forty-five (45) days shall be provided. For facilities that operate or generate flows only from November through March, the minimum storage listed in subsections (A)–(D) of this section is required. (D) Application Rates and Soils Information. The application rates for each individual site shall be based on topography, soils, geology, hydrology, weather, agricultural practice, adjacent land use, and application method. Application of wastewater shall not be allowed during periods of ground frost, frozen soil, saturated conditions, or precipitation events. In design of the application rates, the following shall apply: 1. Do not exceed the hourly application rate at the design sustained permeability rate except for short periods when initial soil moisture is significantly below field capacity. Do not exceed an hourly rate of one-half (1⁄2) the design sustained permeability for slopes exceeding ten percent (10%); 2. Base the daily and weekly application rates on soil moisture holding capacity, antecedent rainfall, and depth to the most restrictive soil permeability. A. For facilities applying at twenty-four inches per year (24"/yr), the application rate cannot exceed one inch (1") per day and three inches (3") per week. B. For facilities applying above twenty-four inches per year (24"/yr), the application rate cannot exceed the values determined in the soils report and loading design. Follow the provisions in 10 CSR 20-8.110(7), Soils Reports, for additional information; and 3. Design the maximum annual application rate not to exceed ten percent (10%) of the design sustained soil permeability rate for the number of days per year when soils are not frozen. (E) The applicant shall defer the grazing of animals or harvesting of forage crops, as listed below, following wastewater irrigation, depending upon ambient air temperature and sunlight conditions: 1. Fourteen (14) days from grazing or forage harvesting during the period from May 1 to October 31 of each year; and 2. Thirty (30) days from grazing or forage harvesting during the period from November 1 to April 30 of each year. (F) Public Access Areas. Wastewater shall be disinfected prior to irrigation (not storage) in accordance with 10 CSR 20-8.190. 1. The wastewater shall contain as few of the indicator organisms as possible and in no case contain more than one hundred twenty-six (126) Escherichia coliform colony forming units per one hundred milliliters (126 cfu/100 ml); 2. The public shall not be allowed into an area when irrigation is being conducted. 3. For golf courses utilizing wastewater, all piping and sprinklers associated with the distribution or transmission of wastewater shall be color-coded and labeled or tagged to warn against the consumptive use of contents. (G) Alarm System. An automatic notification alarm system shall be installed on the pressure monitoring system, on each pivot and pump system, and be capable of notifying an on-call operator when a fault occurs in the system. (8) Subsurface Absorption Systems. (A) Site Restrictions. 1. Subsurface systems shall— A. Exclude unstabilized fill and soils that have been highly compacted and/or disturbed, such as old road beds, foundations, or similar things; B. Provide adequate surface drainage where slopes are less than two percent (2%); C. Provide surface and subsurface water diversion where necessary, such as a curtain or perimeter drain; and D. Have a ten-foot (10') buffer from the property line. 2. The vertical separation between the bottom of the drip lines and/or the trench and a limiting layer, including but not limited to bedrock, restrictive horizon, or seasonal high water table, shall be no less than— A. Twenty-four inches (24"); or B. Twelve inches (12") for systems dispersing secondary or higher quality effluent; or C. Forty-eight inches (48") where karst features are present. (B) Preliminary treatment. Subsurface systems shall be, at a minimum, preceded by preliminary treatment. For design of a secondary treatment system, follow the provisions in 10 CSR 20-8.180 or section (4) of this rule. (C) Loading rates shall not exceed the values assigned by the site and soil evaluation. (9) Low Pressure Pipe (LPP) Subsurface Systems. (A) Design. 1. The LPP system shall be sized in accordance with the following equations, Equation 200-2 and Equation 200-3: Equation 200-2 Q A = ______ LTAR and Equation 200-3 A L = ______ 5 ft where: A = Minimum LPP soil treatment area (square feet (sq.ft)) L = Minimum total length of LPP trench (ft) Q = Maximum daily wastewater flow (gallons per day (gpd)) LTAR = Long term acceptance rate (gpd/sq.ft). This is the lowest reported LPP soil loading rate between the soil surface and at least twelve inches (12") below the specified LPP trench bottom, or as approved by the Missouri Department of Natural Resources (department). 2. All network piping and low pressure distribution piping and fittings with polyvinyl chloride (PVC) shall meet ASTM Standard D 1785 Standard Specification for Poly(Vinyl Chloride) (PVC) Plastic Pipe, Schedules 40, 80, or 120 as approved and published August 1, 2015, or equivalent rated to meet or exceed ASTM D2466 Standard Specification for Poly(Vinyl Chloride) (PVC) Plastic Drain, Waste, and Vent Pipe and Fittings as approved and published August 1, 2017. These standards are incorporated by reference into this rule, as published by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. This rule does not incorporate any subsequent amendments or additions. 3. Manifold design shall address freeze protection while assuring uniform distribution and to minimize drain down of laterals into other laterals at a lower elevation between dosing events. (B) Dosage. The dosing frequency shall be based on the soils report and the dosing volume in zoned systems. (C) Orifices and Orifice Shielding. 1. The orifice number and spacing shall be designed to provide a distribution of no more than six (6) square feet per orifice with an orifice size of not less than one-eighth (1/8) inch. 2. The distal pressure shall be designed and maintained at the end of each lateral to be no less than two feet (2 ft) (0.87 psi) when using three-sixteenth inch (3/16") or larger diameter orifices, and no less than five feet (5 ft) (2.18 psi) when using orifices smaller than three-sixteenth inch (3/16"). (10) Drip Dispersal Subsurface Systems. (A) Design. 1. The location and size of the drains and buffers must be factored into the total area required for the drip dispersal system. 2. The drip dispersal system shall be sized with the minimum soil treatment area and total length, in accordance with the following equations, Equation 200-4 and Equation 200-5: Equation 200-4 Q A = ______ HLR Equation 200-5 A L = _____ 2 feet Where: A = Minimum soil treatment area (square feet (sq. ft)) Q = Maximum daily wastewater flow (gallons per day (gpd)) HLR = Maximum hydraulic loading rate determined in the soils report (gpd/sq.ft) L = Minimum total length of drip dispersal lines (ft) (B) Lines. 1. The drip dispersal lines shall be placed at a minimum depth of six inches (6") below the surface. 2. Emitters and drip dispersal lines shall be placed at a minimum on a two-foot (2') spacing to achieve even distribution of the wastewater and maximum utilization of the soil. AUTHORITY: section 644.026, RSMo 2016.* Original rule filed Aug. 10, 1978, effective March 11, 1979. Amended: Filed June 15, 2018, effective Feb. 28, 2019. Amended: Filed June 14, 2024, effective Jan. 30, 2025. *Original authority: 644.026, RSMo 1972, amended 1973, 1987, 1993, 1995, 2000, 2012, 2014.