Biological FOG degradation: development of a standardised bioadditive protocol.

Abstract

FSE, wastewater, Gerber, COD:N, bioaddition, bioremediation, Fat, oil and grease (FOG) rich effluents from commercial food service establishments (FSEs) have been identified as major contributors to sewer blockages. Under UK Legislation, all FSE kitchens should be fitted with an ‘effective mean of grease removal’. Currently, microbial bioadditives, one of the preferred FOG management options, do not have an industry-agreed testing methodology to prove their ‘effectiveness’. The primary goal of this research was to generate the scientific knowledge underpinning a testing protocol for FOG- degrading bioadditives. Environmental conditions prevalent in FSE wastewater streams were identified in a characterisation of effluents from three catering outlets on Cranfield University campus and used as a basis for design of synthetic culture media for testing bacterial degradation. To address interferences caused by high levels of surfactants in FSE wastewater, a novel FOG quantification method, based on the Gerber method used in the milk industry, was developed for the protocol. This method is efficient at recovering emulsified FOG, and also allows emulsified and free fractions to be quantified separately. Microbial utilisation of different wastewater components was evaluated in batch degradation trials using a model bacterium, Bacillus licheniformis NCIMB 9375, and different synthetic wastewater compositions. The source of readily available carbon showed great influence on FOG-degradation response. FOG uptake was also influenced strongly by the carbon to nitrogen ratio in the media composition, with removal rate constants decreasing by over an order of magnitude from 0.0285 to 0.0026 h-1 when initial COD:N increased from 33:1 to 147:1. A cost-benefit analysis of the currently available FOG management solutions suggest that bioadditives, as a standalone solution, are the best option in terms of total cost and space requirements, followed by bioadditives used with grease separators. Combining physical and biological treatments can enhance the individual performance of both technologies and allow energy recovery from physically separated FOG.