NR 110.18(2)(c)2.2. Sludge hoppers shall have a minimum side wall slope of 1.7 vertical to one horizontal. Hopper wall surfaces should be made smooth with rounded corners to aid in sludge removal. The department will not approve increasing the depth of sludge hoppers for the purpose of sludge thickening in settling tanks.
NR 110.18(2)(c)3.3. Each sludge hopper shall have an individually valved sludge withdrawal line at least 15 centimeters (6 inches) in diameter. Head available for withdrawal of sludge shall be at least 76 centimeters (30 inches), or greater as necessary, to maintain a velocity of 91 centimeters per second (3 feet per second) in the withdrawal pipe.
NR 110.18(2)(c)4.4. A sludge well or other appropriate equipment shall be provided for viewing and sampling sludge.
NR 110.18(2)(c)5.5. Provisions for cleaning sludge piping shall be made.
NR 110.18(2)(c)6.6. The department may approve the use of glass lined pipe for sludge. Glass lined pipe may not be less than 10 centimeters (4 inches) in diameter.
NR 110.18(2)(c)7.7. Suitable mechanical sludge and scum collection equipment shall be provided in all settling tanks. Provisions for separate scum washing shall be made for treatment facilities which do not have primary settling facilities.
NR 110.18(2)(d)(d) Design parameters.
NR 110.18(2)(d)1.1. Operating design parameters for settling facilities may not exceed the values given in Table 3. The surface settling rate for primary settling tanks shall be calculated with all flows received at the settling tank. The surface settling rate for final settling tanks shall be based on influent flow. The maximum hour solids loading shall be computed based on the maximum day design flow plus the maximum design return sludge rate requirement and the design mixed liquor suspended solids (MLSS) under aeration.
Table 3
- See PDF for table PDF
NR 110.18(2)(d)2.2. For treatment plants with an average design flow greater than 3,785 cubic meters per day (one million gallons per day), the department may approve an overflow rate of 188 cubic meters per meter per day (15,000 gallons per foot per day).
NR 110.18(2)(d)3.3. The design parameters shown in Table 3 may be waived by the department if the settling tank design is based on settling tests of wastes currently received at the existing treatment facility, or if the effluent from the sewage treatment facility is to be disposed on land.
NR 110.18 HistoryHistory: 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. (2) (d) Register July 2010 No. 655, eff. 8-1-10.
NR 110.19NR 110.19Trickling filters.
NR 110.19(1)(1)Applicability.
NR 110.19(1)(a)(a) Surface water discharge. New trickling filters shall be used in conjunction with other treatment units which, in combination, will produce an acceptable level of treatment as defined in s. NR 110.15 (2) (a). Existing trickling filters may be used as a treatment unit in plant expansion if the effluent quality requirements of s. NR 110.15 (2) (a) are met.
NR 110.19(1)(b)(b) Land disposal. Trickling filter treatment systems are an acceptable means of treatment prior to land disposal of effluent.
NR 110.19(2)(2)Design report. A design report must be submitted in accordance with s. NR 110.15 (1). The report shall show the empirical equations and the assumptions used for designing the trickling filter and the additional treatment units.
NR 110.19(3)(3)Design requirements.
NR 110.19(3)(a)(a) Recirculation. Recirculation shall be provided for intermediate and high-rate filters to increase treatment efficiency and to provide wetting of the biological growth. The recirculation rate shall be variable. The recirculation rate to average influent flow ratio should not exceed 4:1.
NR 110.19(3)(b)(b) Dosing cycle. The interval between dosing cycles may not exceed one hour.
NR 110.19(3)(c)(c) Flooding. Filter structures should be designed to allow flooding of the filter.
NR 110.19(3)(d)(d) Primary treatment. Trickling filters shall be preceded by primary treatment facilities.
NR 110.19(4)(4)Design loading. Hydraulic and organic loadings to trickling filters may not exceed the values given in Table 4. Higher loadings may be approved if justified by pilot studies or if manufactured media is used. Higher loadings may also be used if the trickling filter is intended to act only as a roughing or polishing treatment unit.
Table 4
- See PDF for table PDF
NR 110.19(5)(5)Hydraulic features.
NR 110.19(5)(a)(a) Dosing equipment.
NR 110.19(5)(a)1.1. Sewage shall be distributed over the filter by rotary distributors or other suitable devices which will permit uniform distribution to the filter surface area.