Upgrading of a biological-chemical treatment plant for cheese factory wastewater

A biological-chemical treatment plant for cheese factory wastewater was upgraded to handle increased loads and achieve higher removal efficiencies with respect to organic matter and phosphorus. An existing aeration basin was converted to an aerated equalization tank and two existing trickling filters were replaced by two moving bed biofilm reactors (MBBRs). In the MBBRs biomass is attached to small plastic elements that move freely along with the water in the reactors. A new final settling tank was added after an existing intermediate settling tank and existing flocculation chambers. At loads that were highly variable and often above the design values, the upgraded plant achieved average removal efficiencies of 98% with respect to both total COD and total P. An average effluent concentration of 0.36 mg total P/l was obtained with an average coagulant dose of 2.0 mol Al3+/mol P.