Section NR 110.22 - Physical-chemical treatment(1) APPLICABILITY. Physical-chemical treatment processes may be used where appropriate to achieve the required effluent limits.(2) DESIGN REPORT. A design report shall be submitted in accordance with s. NR 110.05(1). The report shall detail any lab testing, pilot plant studies or operating experience used to design the physical-chemical process.(3) CHEMICAL TREATMENT. (a)Chemical selection. Selection of chemicals used in chemical treatment shall be based on the characteristics of the wastewater and constituents to be removed.(b)Design basis.1. Design of chemical treatment processes shall be based on laboratory testing, pilot plant studies or practical operating experience.2. Design of chemical treatment equipment, reactors, and appurtenances shall consider: a. The chemical requirements and feed rates;b. The location of chemical injection into the waste stream;c. The need for rapid mixing and flocculation basins;d. The settling characteristics of the chemical sludge;e. The need for pH adjustment to optimize chemical reactions; andf. The velocity of waste streams in flow conduits to minimize destruction of floc.(c)Phosphorus removal.1. Addition of lime or the salts of aluminum or iron may be used for the chemical precipitation of soluble phosphorus.2. The addition of polyelectrolytes to aid in the settling of phosphate precipitates should be considered.3. Chemicals shall be mixed rapidly and thoroughly with the wastewater.(4) HAZARDOUS CHEMICAL HANDLING. (a)Safety.1. Eye-wash fountains and safety showers using potable water shall be provided in the laboratory and on each floor level or work location where hazardous chemicals are stored, mixed or slaked, pumped, metered or unloaded. These fountains and showers shall be less than 7.6 meters (25 feet) from points of exposure to hazardous chemicals and shall be fully usable during all weather conditions.2. Eye-wash fountains shall be supplied with water with a temperature not exceeding 38°C (100°F). This supply shall be separate from the hot water supply and be able to provide 15 to 30 minutes of continuous irrigation of the eyes.3. Safety showers shall be capable of discharging 1.9 to 3.2 liters per second (30 to 50 gallons per minute) of water with a temperature not exceeding 38°C (100°F) temperature, and at pressures of 1.41 to 3.52 kilograms force per square centimeter (20 to 50 pounds per square inch).4. The following protective clothing and equipment shall be available for use with all operations or procedures in which their use will minimize the risk of injury to personnel: a. Chemical worker's goggles or other suitable goggles (safety glasses are insufficient);b. Face masks or shields for use over goggles;d. Rubber aprons with leg straps;f. Safety harness and line.5. Warning signs shall be installed where appropriate.(b)Storage requirements.1. The materials used for storing of hazardous chemicals shall be selected based on the physical and chemical characteristics of each chemical used.2. Chemical storage areas shall be enclosed by dikes or curbs which will contain the stored volume in case of a spill until it can be either safely transferred to another storage area or released to the wastewater at a controlled rate which will not damage the treatment facilities, inhibit the treatment processes, or contribute to stream pollution. Liquid polymer shall be similarly contained.3. Chemical storage and mixing areas shall be separate from other treatment plant functions.4. Nonslip floor surfaces are desirable in polymer handling areas.(c)Pumping and piping requirements.1. The materials used for piping, valves, pumping, metering, splash guards and any other equipment used to convey hazardous chemicals shall be selected based on the physical and chemical characteristics of each chemical used.2. All piping containing or transporting hazardous chemicals shall be identified with labels every 3 meters (10 feet) and with at least 2 labels in each room, closet or pipe chase. Color coding may also be used but is not an adequate substitute for labeling.3. All pumps or feeders for hazardous or corrosive chemicals shall have splash guards which will effectively prevent spray of chemicals into space occupied by workers. The splash guards are in addition to guards to prevent injury from moving or rotating machinery parts. All connections except those adjacent to storage or feeder areas shall have guards which will direct any leakage away from space occupied by workers.4. Exposed pipes containing hazardous chemicals may not be located above shoulder level except where continuous drip collection trays and coupling guards will eliminate the spraying or dripping of these chemicals onto workers.(5) PHYSICAL TREATMENT. (a)Design. Physical treatment shall be evaluated on a case-by-case basis. The design shall be based on pilot plant studies or operating experience.(b)Filtration.1. Selection of type, size, and depth of filter media shall depend on the filtration rate, the type of treatment provided prior to filtration, filter configuration, available hydraulic head, and the desired effluent quality.2. Multiple filters shall be provided.3. For high rate effluent filtration, the filtration rate at maximum hour design flow may not exceed 3.4 liters per second per square meter (5 gallons per minute per square foot). The filtration rate shall be calculated on the total available filter area with one filter unit out of service.4. Provisions shall be made for backwashing each filter. The backwash system shall be capable of providing a variable backwash rate with a maximum rate sufficient to fluidize the filtering material. A minimum backwash period of 10 minutes shall be provided.5. Air scour for aiding backwashing is recommended.6. Provision shall be made for chlorinating each filter.7. Backwash reservoirs shall be provided. Total backwash water storage provided shall equal or exceed the volume required for 2 complete backwash cycles.8. Spent backwash water shall be individually treated or returned to the head of the treatment facility. The return rate of backwash to the head of the treatment facility may not exceed 15% of the average design flow rate.(c)Microstraining.1. Multiple screening units shall be provided.2. The screening rate at maximum daily design flow may not exceed 3.4 liters per second per square meter (5 gallons per minute per square foot) based on submerged area with one screening unit out of service.3. Provisions shall be made for backwashing each unit. The backwash system shall be capable of delivering at least 1.7 liters per second per meter (8 gallons per minute per foot) of filter length. Backwash shall be delivered at 4.2 kilograms force per square centimeter (60 pounds per square inch).4. Spent backwash shall be individually treated or returned to the head of the treatment facility. The return rate of backwash to the head of the treatment facility may not exceed 15% of the average design flow rate.(6) RECIRCULATING SAND FILTERS. (a)Applicability. Recirculating sand filters may be approved on a case-by-case basis.(b)Primary treatment. Recirculating sand filters shall be preceded by a minimum of primary treatment.(c)Recirculation tanks. Recirculation tanks shall be equipped with a highwater and pump failure alarm.(d)Maintenance. Recirculation tanks and sand filters shall be readily accessible for inspection and maintenance.(7) INTERMITTENT SAND FILTERS. (a)Applicability. Intermittent sand filters may be approved on a case-by-case basis.(b)Primary treatment. Intermittent sand filters shall be preceded by a minimum of primary treatment.(c)Loading.1. The loading rate for installations which operate with significant rest periods may not exceed 41 liters per square meter (one gallon per square foot) per day, at the average design flow.2. The loading rate for filters which operate on a continuous basis may not exceed 20 liters per square meter (0.5 gallons per square foot) per day, at the average design flow, for total bed area.(d)General requirements.1. Duplicate filters shall be provided.2. Intermittent sand filters shall be sealed in compliance with the provisions of s. NR 110.24(4).3. Intermittent sand filters shall be underdrained. Underdrains may be constructed of open jointed or perforated clay, concrete or plastic pipe. Underdrain spacing may not exceed 3 meters (10 feet) on center.(e)Media.1. Clean graded gravel shall be placed around the underdrains. Depth of the gravel shall be at least 15 centimeters (6 inches) over of the top of the underdrains.2. At least 60 centimeters (2 feet) of clean sand shall be placed over the gravel. The effective size of the sand shall be 0.3 to 0.6 millimeter (0.01 to 0.02 inches) with a uniformity coefficient of 3.5.(f)Buried sand filters.1. Distribution piping shall have a minimum diameter of 10 centimeters (4 inches). Spacing of distribution pipes may not exceed 3 meters (10 feet). Distribution pipes may not be placed directly above underdrains.2. The distribution piping shall be vented to the atmosphere.3. Buried sand filters shall be dosed by pumps or siphons. The dosing volume shall be 90% of the volume of the distribution piping. The dosing system and distribution piping shall be sized to handle the average daily design flow.4. Buried sand filters shall be covered by a minimum of 91 centimeters (36 inches) of soil.(g)Exposed sand filters.1. Exposed filters may be used when the filter will be designed to operate during the summer months.2. Distribution troughs or piping shall be spaced not more than 6 meters (20 feet) on center.3. Splash pads shall be provided at each point of discharge.4. Exposed sand filters shall be dosed by pumps or siphons. The dosing volume shall be sufficient to cover the filter with 3 to 6 centimeters (2 to 4 inches) of effluent. The dosing system shall be sized to handle the average daily design flow.5. Exposed sand filters shall have a freeboard of at least 60 centimeters (2 feet).Wis. Admin. Code Department of Natural Resources NR 110.22
Cr. Register, November, 1974, No. 227, eff. 12-1-74; r. and recr. Register, February, 1983, No. 326, eff. 3-1-83; CR 09-123: am. (5) (b) 3., (c) 4., (6) (c) and (7) (c) Register July 2010 No. 655, eff. 8-1-10; CR 12-027: am. (5) (b) 2., (c) 1. Register July 2013 No. 691, eff. 8-1-13.