Upgrading effluent quality for lagoon-based systems

To establish Best Available Technology Economically Achievable (BATEA) in non-urban communities which presently use conventional lagoon technology, an investigation was undertaken to evaluate alternatives which can be used to improve lagoon effluent and establish costs. Evaluated were the “Sutton” and the intermittent sand filtration or “New Hamburg” processes. The Sutton concept consists of a nitrifying extended-aeration plant followed by polishing lagoons, with waste sludge discharged into the lagoons. The New Hamburg concept consists of aerated or facultative lagoons, with the lagoon effluent sprayed intermittently over sand filters.

The Sutton plants produce an improved effluent quality relative to conventional facultative lagoons in terms of BOD₅ and TSS concentrations. Increases in ammonia concentration across the polishing pond occur after 5-7 years of plant operation, suggesting a need to implement a regular program of sludge removal from the lagoon. The New Hamburg process results in a significant improvement in effluent quality in terms of BOD₅, TSS, TP, TKN, NH₃-N and H₂S concentrations. Approximate capital costs for upgrading the existing conventional lagoons in Ontario to Sutton and New Hamburg process facilities are estimated at US $221 million and US $93 million, respectively.