A method for managing multivalent metal ion concentrations in low-yield
wastewater treatment processes. The method includes combining wastewater
containing BOD with bacteria-laden sludge in a mainstream reactor to form
a mixed liquor, separating the mixed liquor into a clear effluent and an
activated sludge stream, returning a first portion of the activated
sludge stream to the mainstream reactor, processing a second portion of
the activated sludge stream in a sidestream bioreactor, returning at
least a portion of the activated sludge stream in the sidestream
bioreactor to the mainstream reactor, and adding multivalent metal ions
to at least one of the wastewater, the mixed liquor, the activated sludge
stream and combinations thereof to reduce the generation of waste
activated sludge.