Appendix II to Part 257
40:27.0.1.4.38.4.36.37.20 : Appendix II
Appendix II to Part 257 A. Processes To Significantly Reduce
Pathogens
Aerobic digestion: The process is conducted by agitating
sludge with air or oxygen to maintain aerobic conditions at
residence times ranging from 60 days at 15 °C to 40 days at 20 °C,
with a volatile solids reduction of at least 38 percent.
Air Drying: Liquid sludge is allowed to drain and/or dry
on under-drained sand beds, or paved or unpaved basins in which the
sludge is at a depth of nine inches. A minimum of three months is
needed, two months of which temperatures average on a daily basis
above 0 °C.
Anaerobic digestion: The process is conducted in the
absence of air at residence times ranging from 60 days at 20 °C to
15 days at 35 to 55 °C, with a volatile solids reduction of at
least 38 percent.
Composting: Using the within-vessel, static aerated pile
or windrow composting methods, the solid waste is maintained at
minimum operating conditions of 40 °C for 5 days. For four hours
during this period the temperature exceeds 55 °C.
Lime Stabilization: Sufficient lime is added to produce a
pH of 12 after 2 hours of contact.
Other methods: Other methods or operating conditions may
be acceptable if pathogens and vector attraction of the waste
(volatile solids) are reduced to an extent equivalent to the
reduction achieved by any of the above methods.
B. Processes To Further Reduce Pathogens
Composting: Using the within-vessel composting method,
the solid waste is maintained at operating conditions of 55 °C or
greater for three days. Using the static aerated pile composting
method, the solid waste is maintained at operating conditions of 55
°C or greater for three days. Using the windrow composting method,
the solid waste attains a temperature of 55 °C or greater for at
least 15 days during the composting period. Also, during the high
temperature period, there will be a minimum of five turnings of the
windrow.
Heat drying: Dewatered sludge cake is dried by direct or
indirect contact with hot gases, and moisture content is reduced to
10 percent or lower. Sludge particles 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 is
in excess of 80 °C.
Heat treatment: Liquid sludge is heated to temperatures
of 180 °C for 30 minutes.
Thermophilic Aerobic Digestion: Liquid sludge is agitated
with air or oxygen to maintain aerobic conditions at residence
times of 10 days at 55-60 °C, with a volatile solids reduction of
at least 38 percent.
Other methods: Other methods or operating conditions may
be acceptable if pathogens and vector attraction of the waste
(volatile solids) are reduced to an extent equivalent to the
reduction achieved by any of the above methods.
Any of the processes listed below, if added to the processes
described in Section A above, further reduce pathogens. Because the
processes listed below, on their own, do not reduce the attraction
of disease vectors, they are only add-on in nature.
Beta ray irradiation: Sludge is irradiated with beta rays
from an accelerator at dosages of at least 1.0 megarad at room
temperature (ca. 20 °C).
Gamma ray irradiation: Sludge is irradiated with gamma
rays from certain isotopes, such as 60 Cobalt and 137 Cesium, at
dosages of at least 1.0 megarad at room temperature (ca. 20
°C).
Pasteurization: Sludge is maintained for at least 30
minutes at a minimum temperature of 70 °C.
Other methods: Other methods or operating conditions may
be acceptable if pathogens are reduced to an extent equivalent to
the reduction achieved by any of the above add-on methods.