Abstract: A wastewater pretreatment tank assembly reduces the amount of solid matter on sludge in household sewage before the wastewater is introduced into a municipal sewage treatment system. Bacteria and enzymes are added to the wastewater in a first chamber where the sludge is digested. Then the wastewater spills over a weir into another chamber where ammonia is stripped. The wastewater is aerated and optionally chlorinated. The pretreatment of household sewage reduces the burden on the municipal sewage treatment facility, and reduces the risk of exceeding the capacity of the facility.