Study On Anaerobic-Anoxic-Oxic Membrane Bioreactor (MBR) For Coke Plant Wastewater Treatment

In this study, the Anaerobic-Anoxic-Oxic membrane bioreactor (A1-A2-MBR) system was used for coke-plant wastewater treatment by continuous flow test. Treatment results of the system, variation of water quality, sludge characteristics and membrane fouling condition were investigated in order to supply instruction for practical projects. A comparative test between (A1-A2-MBR) system and Anaerobic-Anoxic-Conventional active sludge reactor (CASR) was undertaken in operational charactoristics.When the total hydraulic residence time (HRT) of system is 37.4h or 33.2h, and the recycle ratio of mixed liquor is 3, the removal rates of COD are between 80%~90%, ammonia removal rates are above 90%, and total nitrogen removal rates are above 50%. Removal rate of turbidity is effective and it contributes a lot to post treatment.COD and ammonia are mainly removed in anaerobic reactor. Total nitrogen is degradated in nitrification and denitrification processes and TN is mainly removed in anoxic reactor. Impact load and heterocyclic compounds can suppress nitrobacteria activity and lead to the accumulation of nitrate nitrogen.By a long-term running test, MBR is superior in total sludge activity to CASR. However, its unit mass sludge activity is inferior to CASR. Average particle size of sludge in MBR was smaller than that in CASR, which promotes the mass transfer process in MBR. Soluble microbial products (SMP) accumulated at first and then were gradually degradated. Mixed liquor viscosity also increased as the accumulation of SMP and MLSS.Rising of Trans-membrane pressure (TMP) can be divided into two steps, which were gentle rising phase and sharp rising phase. The former was caused by pore blockage and gel layer fouling, and the latter was caused by mud-cake layer fouling. After the comparative test, it was approval that chemical clean should use oxidant in priority and alkali if necessary.