Study Of Novel Membrane Bioreactor For Low-Concentration Wastewater Treatment

Water pollution is an important challenge to humanity.In recent years,China's economic level has been growing year by year,and people's quality of life has been significantly improved.However,as a result,more and more low-concentration wastewater is discharged,and the composition becomes more and more complex,which brings huge challenges to urban sewage treatment plants.How to deal with low-concentration wastewater effectively is one of the important research contents of Chinese and foreign scholars.In general,domestic sewage with COD concentration less than 1 000 mg/L and diluted industrial wastewater can be defined as low-concentration wastewater.Membrane bioreactor?MBR?is a new wastewater treatment technology,which can not only ensure efficient sludge-water separation,but also increase the sludge concentration in the reactor and improve the treatment efficiency.Based on MBR technology,a new anaerobic membrane bioreactor?AnMBR?and an aerobic membrane bioreactor?AeMBR?with cheap stainless steel wire mesh as membrane material were constructed in the laboratory.The removal capacity of COD and micro-pollutants in these two reactor technologies were explored.The results are showed as follows:AnMBR can effectively remove COD in low-concentration wastewater.The artificial simulated wastewater is used as the influent.When the influent COD concentration was 500 mg/L,the effluent COD concentration was kept below 40mg/L,and the COD removal rate was over 93%.Only acetate could be detected in the effluent with average concentration less than 10 mg/L.The system has high methane yield with 0.28 L/g-COD,averagely.The reactor has strong resistance to temperature fluctuation from 35°C to 25°C.In addition,during 66 days operation,the transmembrane pressure?TMP?slowly increased from 0 to 20 kPa and the highest membrane resistance was 4×10¹22 m^-1.Through the acclimation of activated sludge,AeMBR can effectively remove tetracycline hydrochloride,COD and ammonia nitrogen in wastewater.When COD concentration in the reactor was 300 mg/L,the removal rates of tetracycline hydrochloride with initial concentration of 200,400 and 600 g/L were 76%,90%and95%,respectively,and the removal rates of COD and ammonia nitrogen were 95%and 98%,respectively.The increase of influent tetracycline hydrochloride did not significantly inhibit COD and ammonia nitrogen removal.As the concentration of tetracycline hydrochloride in the influent increases,the growth rate of TMP in the reactor increases,which aggravated the membrane pollution.In addition,the relative abundance of tetA and sulII resistance genes in effluent and sludge also increased with the increase of tetracycline hydrochloride concentration.