Characteristics of phosphorus removal from wastewater by biofilm sequencing batch reactor (SBR)

Sequencing batch reactor (SBR) of biofilm formed on fibrous carriers was effective for phosphorus removal from wastewater when conditions included a 30% packing ratio for the carriers and 9 h hydraulic retention time (3 h for the anaerobic reaction phase and 6 h for the aerobic reaction phase). After 6 months of operation at chemical oxygen demand (COD) loading of 1.00 kg COD/m(3) per day, the biomass concentration in the biofilm reached a high level of 8855 mg/l in terms of MLSS and 5532 mg/l in terms of MLVSS, while as the suspended biomass concentration in the liquid phase of the reactor, it was almost 60 mg/l in terms of MLSS. In every cycle, phosphorus removal was achieved by removing the biomass detached from the biofilm (excess sludge) after 20 min sedimentation. When the influent COD loading rate increased from 0.27 to 1.32 kg COD/m(3) per day, the phosphorus removal efficiency surpassed 90%, and this process showed a strong tolerance for the increase of COD loading. The dominant bacterial species were found to be Pseudomonas, Aeromonas and Bacillus. The excess sludge detached from the biofilm had a high phosphorus content of 5.67% (w/w) in dry biomass and good settling performance with an SVI of 99.5-103.8 ml/g. (C) 2003 Published by Elsevier Science B.V.