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.
