Effects Qf Solids Residence Time on Phosphorus Removal with Oxygen or Nitrate

Abstract

Two sets of experiments were conducted by sequencing batch reactors (SBRs) to study the effects of solids residence time (SRTI and type of electron acceptor on the removal of phosphorus Nitrate was applied in one set while oxygen in the other and each set was conducted in parallel by varying SRT operations that were 5 days, 10 days and 15 days and maintaining cycle time at 8 hours. When tested with synthetic waste water having acetate as sole carbon source with COD 400 mg/l and phosphorus of 20 mgA, the effluent COD concentrations in all runs were in the same level and slightly higher oxidation were obtained at anaerobic-aerobic SBRs (98% -97.9%) than those at anaerobic-an oxic SBRs (92.4% - 98%). However varying SRTs results insignificant difference on phosphorus removal. At the SRT of 5 days, 10 days and 15 days, the phosphorus removal efficiencies were 47.5%, 84%. and 75% respectively, in the anaerobic aerobic process and 28.5%, 76.6% and 67.5%. respectively, in the anaerobic anoxic one. Cycle measurement showed that low SRT operating gave high remaining COD in external electron acceptor phase and therefore can reduce the capability on phosphorus uptake.