ABSTRACT
Many regulatory agencies are beginning to impose more stringent treatment requirements on municipal wastewater treatment plants. Primary treatment plants must upgrade to secondary treatment, and many secondary treatment plants must upgrade to higher flow capacities and higher levels of treatment. Primary treatment plants consisting of primary clarifiers, Imhoff tanks, or septic tanks can be upgraded to secondary treatment standards. Raw wastewater receives pretreatment either in an adjacent settling tank or by fine screening. The pretreated wastewater then enters what was previously the effluent end of the tank and passes through the stages of rotating contactor treatment. Lagoons which are not meeting treatment requirements due to overloading or a change in treatment requirements can be upgraded by the addition of rotating contactor process equipment. Primary treatment of the wastewater is required before rotating contactor treatment. Pretreatment should consist of a conventional primary clarifier or at least grit removal and fine screening.
