Sequencing batch reactor and continuous flow system: A comparative biological phosphorus removal study

A laboratory bench-scale sequencing batch reactor (SBR) and a continuous flow activated sludge (CFAS) systems were compared for biological phosphorus removal (BPR) performance. Both systems followed the Anaerobic/Oxic configuration, were fed with the same synthetic wastewater, and inoculated with the same biological seed. In addition, both SBR and CFAS systems were operated under similar hydraulic retention time and solids retention time (SRT). The purpose of operating both systems under similar conditions was to compare their performance based on the following key criteria: (1) BPR capabilities of biomass produced in both systems. (2) Performance of both systems under different SRTs, and the applicability of the effective SRT in the SBR system. (3) BPR capabilities of both systems under varying substrate concentrations. (4) BPR performance of both systems after exchanging the biomass from one reactor into the other.; The results obtained under this investigation are: the average total phosphorus removal efficiency in the SBR system was nearly complete, while the average phosphorus removal efficiency of the CFAS system was 65 percent. Both systems however presented similar average carbon and nitrogen removal efficiencies of 92 and 55 percent respectively. The average total suspended solids concentration in the effluent from SBR and CFAS systems were 3 and 20 mg/L respectively. The operation of CFAS was constantly troublesome due to bulking of sludge. The average sludge volume index (SVI) value in the CFAS system was 273 mL/mg before using chlorination as a control strategy for bulking of sludge. During chlorination the average SVI was reduced to 172 mL/mg. Contrary, the settling characteristics of the sludge in the SBR system were excellent with an average SVI of 49 mL/mg.; Based on the results of this investigation it is concluded that the SBR system offers more stable and efficient BPR performance than the CFAS system.