Aerobic biological treatment of grease from urban installations

Abstract

In France, biological grease treatment is a rapidly expanding process, with some sixty plants recorded in 1998. Several sites have been studied and selected for their representativity. They are designed at a volumetric loading of 2.5 kg COD/m3 of reactor per day. Prior to detailed monitoring over a long period, pre-visits with summary measurements provided a certain amount of information on the operation of these reactors, the majority of which are not optimised (low yields) but have limited operational constraints given their low load. This study enabled an evaluation of the quantity actually creamed from the surface of the aerated grease separator in relation to the lipids collected within raw sewage, and an appreciation of the precautions to be taken with respect to sampling and analysis, before any interpretation. The recommendations prior to our measurements and the optimisation of the reactors made it possible to appreciate the considerable value of this process for the reduction of lipids and to highlight the main operational parameters in order to obtain high performance in combination with low operating constraints.