The Two-Stage Moving-Bed/Activated-Sludge Process: An Effective Solution for High-Strength Wastes

The paper describes a moving-bed bioreactor which was used as the first stage of a two-stage process to provide an effective and simple means of reducing the biochemical oxygen demand of a wastewater prior to further treatment in a conventional second-stage activated-sludge plant.
At Corby, a scheme was required to (a) meet the requirements of a more stringent effluent consent and (b) provide capacity for further anticipated growth in industrial effluent loads. The original works comprised conventional primary sedimentation tanks, biological filters and humus tanks, followed by an activated-sludge oxidation ditch and further settlement tanks. A pilot plant has been in operation at Corby for two years, and the results were used to design a moving-bed bioreactor to replace the existing filters.
At Pyewipe, a new coastal treatment plant was required and, following the change in status from a 'high natural dispersion area &, a 'normal' programme was initiated to achieve the required completion date. A value-management workshop was held which identified the two-stage moving-bed bioreactor/activated-sludge process, and a pilot plant was operated for eighteen months. A full-scale plant is now under construction and incorporates a number of innovative features.