The Stratified Facultative Lagoon for the Treatment and Storage of High Strength Agricultural Wastewaters

A research and development programme at The University of New South Wales and a large intensive piggery located on the outskirts of Sydney, Australia, has culminated in the successful commissioning of an odour control process for the storage and treatment of wastewaters from the piggery. The stratified facultative lagoon utilises surface aeration of an otherwise anaerobic lagoon to provide a non-odorous cover for the anaerobic contents. The process has filled a need in the pig industry for a non-odorous cost effective alternative to conventional treatment systems, prior to wastewater re-use or disposal by land application. Critical design parameters include lagoon depth, specific energy input and aeration system design. Mean removal efficiencies of biochemical oxygen demand of 75 per cent have been achieved consistently. The development of the process was facilitated by the use of wastewater redox potential testing to indicate the likely presence of odorous compounds in the liquid on the surface of the lagoon and in the surrounding atmosphere. Surface redox potential readings (E_h) greater than −76 mV resulted in non-odorous operation of the process.