R 323.2418 Pathogen treatment processes.

Rule 2418. (1) The process to significantly reduce pathogens (PSRP) is as follows: (a) Biosolids are agitated with air or oxygen to maintain aerobic conditions for a specific mean cell residence time at a specific temperature. Values for the mean cell residence time and temperature shall be between 40 days at 20 degrees Celsius and 60 days at 15 degrees Celsius. (b) Biosolids are dried on sand beds or on paved or unpaved basins. The biosolids dry for a minimum of 3 months. During 2 of the 3 months, the ambient average daily temperature is above 0 degrees Celsius. (c) Biosolids are treated 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 degrees Celsius and 60 days at 20 degrees Celsius. (d) Using the within-vessel, static aerated pile, or windrow composting method, the temperature of the biosolids is raised to 40 degrees Celsius or higher and remains at 40 degrees Celsius or higher for 5 days. For 4 hours during the 5 days, the temperature in the compost pile exceeds 55 degrees Celsius. (e) Sufficient lime is added to the biosolids to raise the pH of the biosolids to 12 after 2 hours of contact. (2) The processes to further reduce pathogens (PFRP) are as follows: (a) Using either the within-vessel composting method or the static aerated pile composting method, the temperature of the biosolids is maintained at 55 degrees Celsius or higher for 3 days. Using the windrow composting method, the temperature of the biosolids is maintained at 55 degrees or higher for 15 days or longer. During the period when the compost is maintained at 55 degrees or higher, there shall be a minimum of 5 turnings of the windrow. (b) Biosolids are dried by direct or indirect contact with hot gases to reduce the moisture content of the biosolids to 10% or lower. Either the temperature of the biosolids particles is more than 80 degrees Celsius or the wet bulb temperature of the gas in contact with the biosolids as the biosolids leaves the dryer is more than 80 degrees Celsius. (c) Liquid biosolids are heated to a temperature of 180 degrees Celsius or higher for 30 minutes. (d) Liquid biosolids are agitated with air or oxygen to maintain aerobic conditions and the mean cell residence time of the biosolids is 10 days at 55 to 60 degrees Celsius. (e) Biosolids are irradiated with beta rays from an accelerator at dosages of at least 1.0 megarad at room temperature (approximately 20 degrees Celsius). (f) Biosolids are irradiated with gamma rays from certain isotopes, such as 60Cobalt and 137Cesium, at dosages of at least 1.0 megarad at room temperature (approximately 20 degrees Celsius). (g) The temperature of the biosolids is maintained at 70 degrees Celsius or higher for 30 minutes or longer.