Aerobic Granular Sludge In SBR Combined With Membrane Bioreactor For Municipial Sewage Treatment

Nowadays,majority of municipal sewage treatment plants have to face the upgradation of the effluent quality to satisfy strict standards.Conventional activated sludge process has its own shortages,such as rather low resistance to the influent loading,instable nitrogen and phosphorus removal effectiveness,high effluent concentration,and complex process,which restrict the sewage treatment plant to enhance the capacity and efficiency.Therefore,a noval hybrid system comporised of aerobic granular sludge?AGS?and membrane bioreactor?MBR?was proposed in this study for municipal sewage treatment,and the operation parameters were optimized to make it more economical and low-energy-consumption.The stability of the system under the varied influent C/N ratio was also investigated,and the membrane fouling in the membrane bioreactor was studied.Technical analysis and the practical application value of the AGS-MBR process were discussed.The start-up of AGS-MBR process was completed by raising the organic loading rate step by step and shortening the settling time to accelerate granulation process under low organic loading rate.SBR adopted the periodic operation mode of water intake-aeration-static-drainage.The aeration in SBR rate is 5 L/min,HRT is 6 h,and HRT of MBR is 3 h.The start-up of AGS-MBR process was completed.After 40 days of continuous operation,SV₃₀/SV₅ was 0.95.Aerobic granular sludge with particle size of 2mm was formed in the SBR.The AGS was matured.The results showed that the effluent quality of SBR in the first stage fluctuated greatly.In the second stage,the removal rates of COD,NH₄⁺-N,TN and TP in the combined process increase to 93.39%,99.4%,70.89%and 87%respectively.Upon the start-up of AGS-MBR system,the operating parameters such as air velocity in SBR,the ratio of HRT to air-water and so on were optimized.On the 41st day,the settling time of SBR was shortened from 6 min to 5 min,and the granular sludge with poor settling performance was eliminated.The results showed that when the air velocity in the SBR was 2 cm/s,the HRT of MBR was 3 h,and the air-water ratio in MBR was25:1,a stable excellent effluent quality of MBR was obtained with the minimum membrane fouling rate.The average concentration of COD,ammonia nitrogen,TN and TP in MBR effluent was 21.2 mg/L?0.08 mg/L?7.8 mg/L?0.4 mg/L,which has reached the first level A in Chinese GB18918-2002.By exploring the adaptability and resistance of the process to the change of influentl loading rates,the results showed that the influent C/N ratio was less than 10,synchronous nitration denitrification lacked carbon source with high TN in effluent water.The concentration of NH₄⁺-N in effluent was also adapted to the high ammonia load after 2days.Hydraulic physical cleaning and chemical cleaning selected can be used to recovery membrane permeability to more than 99%.Finally,through technological analysis,it was concluded that the technology was being practical application value.