Performances et limites du procede de dephosphatation biologique par biofilm sur lit mobile en mode concentrat.

摘要

An original bioprocess has been developed to reduce phosphate concentration of fish farms in partially closed circuit (PCC). The process is using a stock tank to alternate anaerobic and aerobic conditions and to avoid the presence of nitrate during the anaerobic phase. During the aerobic phase, phosphate of the affluent is stocked as polyphosphate by Polyphosphate Accumulating Organisms (PAO) and nitrate is consumed. During the anaerobic phase, carbon substrate contained in the water of the stock tank is consumed while phosphate is released. Through multiple cycles, phosphate is repeatedly released in the water of the stock tank where it accumulates. The objective of this study is to grow PAO on a biofilm to test the limits of this process and enhance its overall performance.;Two submerged moving bed biofilm reactors were operated at pilot scale during 257 days. The presence of acetate and propionate as carbon substrate as well as aeration and trace elements allowed the removal of 4,4 mg o-PO 4-P/L of an affluent containing 14.5 mg o-PO4-P/L. However, after introducing colonized carriers from the Laboratoire regional des sciences aquatiques de l'Universite Laval, 10.8 mg o-PO4-P/L of an affluent containing 14.9 mg o-PO4-P/L was removed. After inoculating a second reactor with the same biomass, 7.2 mg o-PO4O-P/L of an affluent containing 14.6 mg o-PO4-P/L was removed.;Overall system performance varied according to carbon substrate concentrations, to anaerobic phase length, to biofilm thickness and to the number of cycles the stock tank water was submitted. Therefore, it is believed that diffusion processes, phase length, biomass removal and phosphorus precipitation must be optimised in order to enhance biological phosphorus removal of biofilms.