Appendix B: Acceptable Processes for Additional Pathogen Reduction

Additional processes which will further reduce pathogens are listed below. The processes listed in 310 CMR 32.81(5), (6), and (7) are in addition to processes listed or described in 310 CMR 32.80. (1) High Temperature Composting: A composting process using either the windrow, within-vessel, or static-aerated pile method; provided that whenever the windrow method is used, a composting temperature of not less than 55°C shall be continuously maintained for at least 15 days during the composting period, and that the windrow shall be turned at least five times during this 15-day period; and provided that whenever the static-aerated pile method or the within-vessel method is used, a composting temperature of not less than 55°C shall be continuously maintained for at least three consecutive days. (2) Heat Drying: A process in which a dewatered sludge cake is dried by direct or indirect contact with hot gases, and the moisture content is reduced to 10% or lower. Sludge particles shall reach temperatures well in excess of 80°C, or the wet bulb temperature of the gas stream in contact with the sludge at the point where it leaves the dryer shall be in excess of 80°C. (3) Heat Treatment: A process in which liquid sludge or septage is maintained at temperature of at least 180°C for at least 30 consecutive minutes. (4) Thermophilic Aerobic Digestion: The process by which liquid sludge or septage is agitated with air or oxygen to maintain aerobic conditions at a residence time of ten days at 55°C through 60°C, and has a volatile solids reduction of at least 38%. (5) Electron Radiation: A process in which sludge or septage is irradiated with electrons from an accelerator at dosages of at least 1.0 megarad at room temperature, i.e., approximately 20°C. (6) Gamma Ray Irradiation: A process in which sludge or septage is irradiated with gamma rays from certain isotopes, such as Cobalt-60 or Cesium-137, at dosages of a least 1.0 megarad at room temperature, i.e., approximately 20°C. (7) Pasteurization: A process in which sludge or septage is maintained for at least 30 continuous minutes at a temperature of not less than 70°C. (8) Other Methods: Other methods or operating conditions may be deemed acceptable by the Department if the owner or operator can provide data showing that the pathogen and vector attraction of the volatile solids are reduced to an extent equivalent to the reductions achieved by any of the other methods listed in 310 CMR 32.81. Written approval of equivalency by the Department shall be required.