Proceedings

Every year in the UK around 150,000 tonnes of grit and screenings are produced during the treatment of wastewater. The organic content of this material is high and up to 90% by volume, however it is not practical to pass it forward to the sludge handling system due to the grit and plastics that would cause mechanical handling problems. Consequently, it is currently disposed of to landfill and so represents a lost source of energy to the Water Companies. This paper will present the findings of preliminary experiments have been undertaken to recover this energy by high rate, semi-batch anaerobic digestion to produce a liquid effluent high in soluble COD and volatile fatty Acids. This liquid stream can then be passed forward to the digesters to permit energy recovery as biogas. The digestate resulting from the high rate digestion process will be investigated for its potential to generate a saleable end-product, e.g. struvite.