Experimental Study On Domestic Sewage Treatment With Moving Bed Sequencing Batch Biofilm Reactor

Based on the latest researches on the biological nitrogen and phosphorus removal, a moving bed sequencing batch biofilm reactor (MBSBBR) system was explored in this paper. The sludge training process and the start-up of MBSBBR were explored. Analyzing influence factors on the nitrogen and phosphorus removal and optimizing operating parameters were studied. Detailed study of the system on the removal of pollutants was carried out. The mechanisms of simultaneous nitrification and denitrification and simultaneous nitrogen and phosphorus removal in MBSBBR system were also studied.The experimental results show that the PAOs and denitrifying PAOs in hybrid sludge are formed and accumulated rapidly when the transfer of organic substrates is improved by increasing the COD loading and augmenting the shear force in the MBSBBR system operated in the periods of anaetobic/aerobic/anoxic. At the end of the cultivating, 100% of NH4+-N is almostly removed, and the average removal of TP and COD is over 90% and 85%, respectively; the suspended activated sludge in the MBSBBR system shows good settling ability (the Sludge Volumetric Index (SVI) and the Mixed Liquid Suspended Solid (MLSS) are 60.0 mg/g and 3000-4200 mg/L, respectively). The attached biofilm in MBSBBR system exist at a very dense and irregular structure, and its color is brown yellow. Coccus, bacillus, as well as protozoan, metazoan were observed in the attached biofilm by microscope, and they all show good activity.By adjusting COD loading and period of the different duration, the optimum operation conditions were determined as anaerobic reaction 150 min (DO<0.2 mg/L), aerobic reaction 210 min (DO 1.5-2.0 mg/L), anoxic reaction 90min (DO<0.5 mg/L), settling 30min, temperature 20-25℃, pH 6.5-8. Results of continuous stable 6-month operation show that the MBSBBR system has high removal efficiency for TN, TP and COD. With NH4+-N 25-50 mg/L, TN 26.7-54.9 mg/L, TP 8-15 mg/L and COD 200-400 mg/L in the influent, the removal rates of NH4+-N, TN, TP and COD are nearly reach 99.8%, 90.7%, 95.8%, 95%, respectively.Appropriate commissioning and sludge training way is a precondition for the successful operation of MBSBBR. As a result of the sequencing batch operation and the existence of transfer gradient of oxygen and organic carbon substrate, different microorganism varienties were enriched in the system. The microorganism varieties of suspended activated sludge and attached biofilm in the system form a more stable eco-system, which could rapidly accommodate to environment. The denitrifying PAOs were accumulated and enriched in the hybrid sludge, coexisting with nitrifiers under appropriate operational conditions. What is more important, the denitrifying PAOs take up and store phosphate using nitrate as electron acceptor, then the organic carbon substrate is used simultaneously for both phosphorus and nitrogen removal. This is very important for saving organic carbon and oxygen. Sludge production also reduces in the reactor. The decontamination effect of MBSBBR process is high and stable. In line with requirements of China's national conditions, the market prospects of MBSBBR are very broad.