The Anaerobic Membrane Bioreactor (ANMBR) Process and the First Year of Full-Scale ANMBR Operation Treating Salad Dressing Wastewater

An existing anaerobic process, upgraded to an anaerobic membrane bioreactor (AnMBR) system, was commissioned in July 2008 to treat wastewater produced from salad dressings and barbeque sauce. Upgrading to an AnMBR provided additional capacity for flow and organic load beyond the original anaerobic system design parameters. Lack of space and superior economics made the conversion to an AnMBR an attractive option.The first year of AnMBR operation has shown that the system is very suitable for treating this high-strength industrial wastewater; it provides COD, BOD, and TSS removals in excess of 99.5 percent. Throughout the first year of operation, the AnMBR effluent BOD and TSS concentrations were consistently less than 25 mg/l and 2 mg/l, respectively, while influent BOD and TSS concentrations averaged 18,000 and 11,500 mg/l, respectively. The AnMBR system provides superior performance and a very low rate of membrane fouling, with the aid of biogas scour across the membrane surface. The change in transmembrane pressure was negligible over the first twelve months of operation (actually, there has been no transmembrane pressure change at the time of writing - 20 months after start-up) and has required no citric acid cleaning events while operating at a membrane flux rate ranging from 0.05 to 0.10 m3/m2-d (design flux of 0.10 m3/m2-d) and a MLSS concentration up to 45,000 mg/l.Upgrading the existing anaerobic treatment process to an AnMBR was considered the best choice. It has reduced operating and maintenance costs, provides stable operation, produces excellent quality anaerobic effluent, and removes the strain on the existing aerobic process. Biogas produced in the anaerobic system is used to heat the anaerobic system, as well as heat for the wastewater treatment facility.