Full-scale Test And Study On Biological Phosphorus Removal Of UNITANK Process Treating Urban Sewage

Based on summing up actual EBPR technology of home and overseas, full-scale test and study was made considering UNITANK reactor of Dongpo sewage treatment plant in Foshan as research objective. The results show that: 1. UNITANK process has unique merits such as tight structure, high integration, reducing floor area, less equipment, convenient for maintenance and flexible operation. Operation results of Dongpo sewage plant show that UNITANK process have high efficiency to remove organic substance, NH3-N, TN, but efficiency of phosphorus removal waits for improvement. 2. In order to find the reason why efficiency of removal total phosphorus is not perfect, the principle of denitrification and dephosphorization in aerobic-anaerobic-aerobic phase in side tank and middle tank was analyzed. The prime reasons to effect phosphorus removal are large dilution of dissolved BOD from inlet, high concentration of nitrate in anaerobic phase and deficiency of anaerobic time. Anaerobic phase is set up in side tank, anaerobic procedure is firstly set up in main body, optimum anaerobic time is determined, thus are control points to enhanced biologic dephosphorization in UNITANK process. While sludge concentration is control factor to effect sludge sedimentation. 3. Considering the management of WWTP, the appropriate anaerobic time is 60 min and a better operation matrix based on EBPR technology is obtained. In operation, MLSS concentration of middle tank should be controlled at about 2000mg/L. 4. Terminal of anaerobic procedure of side tank in operation matrix of EBPR process is not in good working order, which causes mainly by infinite reflux of sludge and water and NO3-N concentration in anaerobic procedure is too high. 5. Lab-scale test which simulates work condition of anaerobic procedure in main body in side tank when operation matrix of EBPR process is used show that time expand of anaerobic phase in now process does not conduce to the change of ORP and the release and intake of phosphorus. 6. Lab-scale test which simulates work condition of preposition anaerobic phase shows that it is necessary to set up preposition anaerobic phase. In some extent, if HRT of preposition anaerobic phase is prolonged and anaerobic condition is more sufficient, phosphorus-intake dynamic force of POAs will be stronger. Therefore, in process design, HRT of preposition anaerobic phase should be around 60 minutes, should not be less 30 minutes.