NR 204.07 NoteNote: Copies of this section are available for inspection in the offices of the department of natural resources, secretary of state, and the legislative reference bureau, Madison, Wisconsin, or may be purchased from the superintendent of documents, U.S. government printing office, Washington DC 20402.

NR 204.07(6)(a)2.b.b. Compost the sludge using either within-vessel or static aerated pile composting methods and maintain the temperature of the sludge at 55° C or higher for 3 days, or compost the sludge using windrow composting methods and maintain the temperature of the sewage sludge at 55° C or higher for 15 days or longer. During this period, a minimum of 5 windrow turnings are required; or

NR 204.07(6)(a)2.c.c. Dry the sludge by direct or indirect contact with hot gases to reduce the moisture content of the sludge to 10% or lower. Either the temperature of the sewage sludge particles shall exceed 80° C or the wet bulb temperature of the gas in contact with the sludge as the sludge leaves the dryer shall exceed 80° C; or

NR 204.07(6)(a)2.e.e. Agitate liquid sludge with air or oxygen to maintain aerobic conditions. The mean cell residence time for the sludge shall be 10 days at 55° to 60° Celsius; or

NR 204.07(6)(a)2.f.f. Irradiate the sludge with beta rays from an accelerator at dosages of at least 1.0 megarad at room temperature; or

NR 204.07(6)(a)2.g.g. Sludge is irradiated with gamma rays from certain isotopes, such as Cobalt 60 and Cesium 137, at dosages of at least 1.0 megarad at room temperature; or

NR 204.07(6)(a)2.i.i. Treat the sludge in a process that is equivalent to a process to further reduce pathogens, as approved by the department.

NR 204.07(6)(b)(b) Either subd. 1. or one of the requirements in subd. 2. shall be met for the sludge to be classified as Class B. The Class B requirements are summarized in Table 6:

NR 204.07(6)(b)1.1. ‘Fecal coliform density.’ The sludge shall have a fecal coliform density of less than or equal to 2,000,000 most probable number (MPN) or colony forming units (CFU) per gram of total solids on a dry weight basis. Compliance with this requirement shall be demonstrated by calculating the geometric mean of at least 7 separate samples; or

NR 204.07(6)(b)2.a.a. Agitate the sludge with air or oxygen to maintain aerobic conditions for a mean cell residence time and temperature between 40 days at 20° C and 60 days at 15° C; or

NR 204.07(6)(b)2.b.b. Dry the sludge on sand beds or on paved or unpaved basins for a minimum of 3 months. During 2 of the 3 months, the ambient average daily temperature shall be above 0° C; or

NR 204.07(6)(b)2.c.c. Treat the sludge in the absence of air for a specific mean cell residence time at a specific temperature. Values for the mean cell residence time and temperature shall be between 15 days at 35° to 55° C and 60 days at 20° C; or

NR 204.07(6)(b)2.d.d. Compost the sludge using either the within-vessel, static aerated pile, or windrow composting methods and raise the temperature of the sludge to 40° C or higher for 5 days. For 4 hours during the 5 days, the temperature in the compost pile shall exceed 55° C; or

NR 204.07(6)(b)2.f.f. Treat the sludge in a process that is equivalent to a process to significantly reduce pathogens, as approved by the department.

NR 204.07(7)(7) Vector attraction reduction. Sludge may not be land applied unless one of the 11 vector attraction reduction options in pars. (a) to (k) is satisfied. Paragraphs (a) to (i) are processes which treat the sludge to reduce its attraction to vectors. Bagged sludge and exceptional quality sludge shall satisfy one of the requirements in pars. (a) to (i). The options are summarized in Table 7.

NR 204.07(7)(a)(a) The mass of volatile solids in the sludge shall be reduced by a minimum of 38% between the time the sludge enters the digestion process and the time it either exits the digester or a storage facility; or

NR 204.07(7)(b)(b) The specific oxygen uptake rate SOUR for aerobic sludge shall be equal to or less than 1.5 milligrams of oxygen per hour per gram of total solids on a dry weight basis, corrected to 20° Celsius; or

NR 204.07(7)(c)(c) Demonstrate through additional digestion, in a bench-scale test, that additional volatile solids reduction for anaerobically digested sludge is less than 17%. This shall be demonstrated by digesting a portion of the previously digested sludge anaerobically in the laboratory in a bench-scale unit for 40 additional days at a temperature between 30° and 37° Celsius. This requirement is satisfied when, at the end of the test, volatile solids have been reduced by less than 17%, as measured from the beginning to the end of the test; or

NR 204.07(7)(d)(d) Demonstrate through additional digestion, in a bench scale test, that additional volatile solids reduction for aerobically digested sludge is less than 15%. This shall be demonstrated by digesting a portion of the previously digested sludge, at a concentration of 2% solids or less, aerobically in the laboratory in a bench-scale unit for 30 additional days at a temperature of 20° Celsius. Sludge with higher percent solids shall be diluted with effluent down to 2% at the start of the test. This requirement is satisfied when, at the end of the test, volatile solids have been reduced by less than 15%, as measured from the beginning to the end of the test; or

NR 204.07(7)(e)(e) Sludge shall be treated in an aerobic process for 14 days or longer. During that time, the temperature of the sludge shall be higher than 40° Celsius and the average temperature of the sludge shall be higher than 45° Celsius; or

NR 204.07(7)(f)(f) The pH of the sewage sludge shall be raised to 12 or higher by alkali addition and, without the addition of more alkali, shall remain at 12 or higher for 2 hours and then at 11.5 or higher for an additional 22 hours; or

NR 204.07(7)(g)(g) Dry the sludge to 75% total solids when the sludge contains no unstabilized solids from primary treatment; or

NR 204.07(7)(h)(h) Dry the sludge to 90% total solids when the sludge contains unstabilized solids from primary treatment; or

NR 204.07(7)(i)(i) Treat the sludge in a process which is equivalent to one of the vector attraction reduction requirements specified in pars. (a) to (h), as approved by the department.