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.