Combined biological and membrane treatment of food-processing wastewater to achieve dry-ditch criteria: pilot and full-scale performance.
This study tested the applicability of a submerged vacuum ultrafiltration membrane technology in combination with the biological treatment system to achieve dry-ditch criteria stipulated as follows: BOD5, TSS, NH3-N, and total phosphorous (TP) concentration not exceeding 10, 10, 1, and 0.5 mg/L respectively for the treatment of high strength food-processing wastewater. During the study, the biological system, operated at average hydraulic retention time of 5-6 days, achieved 95-96.5% BOD removal and 96-99% COD removal. The external membrane system ensured the achievability of the BOD and TSS criteria, with BOD and TSS concentrations in the permeate of 1-2 and 1-8 mg/L respectively. Nitrate, and nitrite concentrations increased during membrane filtration, while ammonia concentrations decreased. The most salient finding of this study is that, contrary to common belief, for industrial wastewaters, the filterability of the mixed liquor is influenced by the soluble organics, and may be low, thus necessitating operation of bioreactors at low mixed liquor solids. This study demonstrated that bioreactors operated at low SRTs and in combination with ultrafiltration can still achieve superior effluent quality that may meet reuse criteria at reasonable cost.
Nakhla
George
G
Department of Chemical and Biochemical Engineering, University of Western Ontario, London, ON, Canada N6A 5B9. gnakhla@eng.uwo.ca
Lugowski
Andrew
A
Patel
Javnika
J
Rivest
Victor
V
D000641:Ammonia / Q000032:analysis; D001673:Biodegradation, Environmental; D018533:Biomass; D019149:Bioreactors; D005525:Food-Processing Industry / Q000592:standards; D007220:Industrial Waste; D008567:Membranes, Artificial; D009584:Nitrogen / Q000032:analysis; D009930:Organic Chemicals / Q000032:analysis; D010101:Oxygen Consumption; D010758:Phosphorus / Q000032:analysis; D010865:Pilot Projects; D012722:Sewage / Q000737:chemistry / Q000382:microbiology; D014462:Ultrafiltration; D014618:Vacuum; D018508:Water Purification / Q000379:methods* / Q000592:standards
D007220:Industrial Waste; D008567:Membranes, Artificial; D009930:Organic Chemicals; D012722:Sewage; D010758:Phosphorus; D000641:Ammonia; D009584:Nitrogen