NR 110.21(7)(a)(a) Return sludge rate. The rate of sludge return expressed as a percentage of the average design flow of sewage shall lie within the limits shown in Table 6:
NR 110.21(7)(b)1.1. If motor driven return sludge pumps are used, the maximum return sludge capacity shall be met with the largest pump out of service. A positive head shall be provided on pump suctions. Pumps shall also have at least 7.6 centimeter (3-inch) suction and discharge openings.
NR 110.21(7)(b)2.
2. If air lifts are used for returning sludge from each settling tank hopper, no standby unit will be required provided the design of the air lifts allows rapid and easy cleaning. Air lift pumps shall be designed to provide positive control of the return sludge rate.
NR 110.21(7)(c)
(c) Return sludge piping. Suction piping and discharge piping for returning activated sludge shall be at least 10 centimeters (4 inches) in diameter and must be designed to maintain a velocity of not less than 60 centimeters per second (2 feet per second) at normal return sludge rates. Suitable devices for observing, sampling and controlling return activated sludge flow from each settling tank shall be provided.
NR 110.21(7)(e)
(e) Waste sludge pumps. Variable speed or multiple constant speed waste sludge pumps shall be provided. The maximum sludge pumping rate shall be at least 200% of the anticipated volumetric sludge production rate. Devices for measuring waste activated sludge flow rates shall be provided.
NR 110.21 History
History: 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. (4) (b), (d) 5., (5) (b) 2., 3., (c) 2., (6) (a) 2., (b) 1. and Table 5 (title)
Register July 2010 No. 655, eff. 8-1-10.
NR 110.22
NR 110.22 Physical-chemical treatment. NR 110.22(1)(1)
Applicability. Physical-chemical treatment processes may be used where appropriate to achieve the required effluent limits.
NR 110.22(2)
(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.
NR 110.22(3)(a)(a) Chemical selection. Selection of chemicals used in chemical treatment shall be based on the characteristics of the wastewater and constituents to be removed.
NR 110.22(3)(b)1.1. Design of chemical treatment processes shall be based on laboratory testing, pilot plant studies or practical operating experience.
NR 110.22(3)(b)2.
2. Design of chemical treatment equipment, reactors, and appurtenances shall consider:
NR 110.22(3)(b)2.f.
f. The velocity of waste streams in flow conduits to minimize destruction of floc.
NR 110.22(3)(c)1.1. Addition of lime or the salts of aluminum or iron may be used for the chemical precipitation of soluble phosphorus.
NR 110.22(3)(c)2.
2. The addition of polyelectrolytes to aid in the settling of phosphate precipitates should be considered.
NR 110.22(3)(c)3.
3. Chemicals shall be mixed rapidly and thoroughly with the wastewater.
NR 110.22(4)(a)1.1. 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.
NR 110.22(4)(a)2.
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.
NR 110.22(4)(a)3.
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).
NR 110.22(4)(a)4.
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:
NR 110.22(4)(a)4.a.
a. Chemical worker's goggles or other suitable goggles (safety glasses are insufficient);
NR 110.22(4)(b)1.1. The materials used for storing of hazardous chemicals shall be selected based on the physical and chemical characteristics of each chemical used.
NR 110.22(4)(b)2.
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.
NR 110.22(4)(b)3.
3. Chemical storage and mixing areas shall be separate from other treatment plant functions.
NR 110.22(4)(c)1.1. 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.
NR 110.22(4)(c)2.
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.
NR 110.22(4)(c)3.
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.
NR 110.22(4)(c)4.
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.
NR 110.22(5)(a)(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.
NR 110.22(5)(b)1.1. 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.
NR 110.22(5)(b)3.
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.
NR 110.22(5)(b)4.
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.
NR 110.22(5)(b)7.
7. Backwash reservoirs shall be provided. Total backwash water storage provided shall equal or exceed the volume required for 2 complete backwash cycles.
NR 110.22(5)(b)8.
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.
NR 110.22(5)(c)2.
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.
NR 110.22(5)(c)3.
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).
NR 110.22(5)(c)4.
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.
NR 110.22(6)(a)(a) Applicability. Recirculating sand filters may be approved on a case-by-case basis.
NR 110.22(6)(b)
(b) Primary treatment. Recirculating sand filters shall be preceded by a minimum of primary treatment.
NR 110.22(6)(c)
(c) Recirculation tanks. Recirculation tanks shall be equipped with a highwater and pump failure alarm.
NR 110.22(6)(d)
(d) Maintenance. Recirculation tanks and sand filters shall be readily accessible for inspection and maintenance.
NR 110.22(7)(a)(a) Applicability. Intermittent sand filters may be approved on a case-by-case basis.
NR 110.22(7)(b)
(b) Primary treatment. Intermittent sand filters shall be preceded by a minimum of primary treatment.
NR 110.22(7)(c)1.1. 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.
NR 110.22(7)(c)2.
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.
NR 110.22(7)(d)3.
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.
NR 110.22(7)(e)1.1. 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.
NR 110.22(7)(e)2.
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.
NR 110.22(7)(f)1.1. 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.
NR 110.22(7)(f)3.
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.
