A method of treating wastewater sludge includes pumping, continuously, raw sludge
into a first digester and treating the raw sludge at a specific temperature of
between about 51 C. to 60 C.; transferring the treated wastewater sludge
to a batch tank; treating the wastewater sludge in the batch tank, anaerobically,
at a thermophilic temperature which is not more than 2 C. warmer than the
specific temperature in the first digester; and disposing of the treated wastewater
sludge as a Class A biosolid. A wastewater sludge treatment system includes a first
thermophilic digester for treating raw wastewater sludge at a specific temperature
in a range of between about 51 C. to 60 C., and discharging a treated
wastewater sludge; a batch tank for receiving the treated wastewater sludge discharged
from the first digester and for thermophilically treating sludge at a temperature
in a range of between about 51 C. to 60 C. and not more than 2
C. warmer than the specific temperature in the first digester, for between about
0.5 hours and 5 hours; and a disposal mechanism for disposing of the treated wastewater
sludge as a Class A biosolid.
