title: Treatment of high-strength synthetic sewage in a laboratory-scale upflow anaerobic sludge bed (UASB) with aerobic activated sludge (AS) post-treatment.
abstract: Performance of a combined system up-flow anaerobic sludge blanket (UASB) followed by aerobic treatment activated sludge (AS) for removal of carbonaceous and nitrogenous contaminants at an average temperature of 25°C was investigated. The combined system was fed with high strength synthetic sewage having chemical oxygen demand (COD) of 2500 mg L(-1). The organic loading rate (OLR) of the UASB reactor was increased gradually from 1.1 to 3.8 gCOD L(r) (-1) d(-1). At steady state condition, the UASB reactor achieved removal efficiency up to 83.5% of total COD (COD(tot)), 74.0% of volatile fatty acid (VFA) and 94.0% of protein. The combined system performed an excellent organic removal pushing the overall removal efficiency of COD(tot), VFA and protein to 91.0%, 99.9% and 98.2%, respectively. When the OLR of the UASB increased to 4.4 g COD L(r) (-1) d(-1), the UASB was overloaded and; thus, its effluent quality deteriorated. In respect to nitrogen removal, both partial nitrification and complete nitrification took place in aerobic post-treatment. When the dissolved oxygen (DO) concentration was >2.0 mg L(-1), complete nitrification (period B) occurred with an average nitrification efficiency of 96.2%. The partial nitrification occurred due to high OLR to AS during the overloading event (period A) and when DO concentration was <2.0 mg L(-1) (period C). The maximum accumulated nitrite concentration in periods A, B and C were 90.0, 0.9 and 75.8 mg NO(-) (2) -N L(-1), respectively. The nitrogen balance results of periods A and C indicated that there was a discrepancy between the amount of ammonium nitrogen removed and the amount of oxidized nitrogen formed. This suggests the occurrence of simultaneous nitrification/denitrification (SND) in aerobic post-treatment.
authors.affiliation: Department of Chemical and Environmental Engineering, University of Arizona, Tucson, Arizona, USA. q.banihani@ju.edu.jo
authors.forename: Qais H
authors.initials: QH
authors.lastname: Banihani
authors.forename: Jim A
authors.initials: JA
authors.lastname: Field
mesh_terms: D000332:Aerobiosis; D019149:Bioreactors; D002852:Chromatography, Ion Exchange; D003124:Colorimetry; D005410:Flame Ionization; D009566:Nitrates / Q000378:metabolism*; D058465:Nitrification; D017672:Nitrogen Compounds / Q000378:metabolism; D009930:Organic Chemicals / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D012722:Sewage / Q000382:microbiology*; D014865:Waste Disposal, Fluid / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000378:metabolism*
chemical_list: D009566:Nitrates; D017672:Nitrogen Compounds; D009930:Organic Chemicals; D012722:Sewage; D014874:Water Pollutants, Chemical; D010100:Oxygen