Application Study Of Depth Denitriifcation In Food Wastewater By A-A-O-MBR Combined Process

With the eutrophication issues becomes increasingly serious, nitrogen andphosphorus removal of sewage treatment becomes an important research subject inthis field. In this paper, food wastewater of high ammonia-nitrogen concentrationfrom Suzhou food waste treatment plant is studied as the research object, andA-A-O-MBR technology has been used to wastewater treatment. The mainconclusions are obtained as follows:A-A-O-MBR technology has a good effect on treatment of food wastewater. Theresults indicate that in a140d operation, the average effluent COD, NH4+-N and TNare277,2.16and271mg/L, respectively, and the average removing rates reach95.68%,99.78%and79.43%, respectively. The average effluent COD, NH4+-N andTN are275,2.10and71mg/L, and the average removing rates reach95.35%,99.77%and95.01%,respectively, when the nitrification liquid return ratio is300%andCH3OH is added to the reactor influent as carbon source. When the massconcentration of sludge keeps at9-13g/L, the speed of membrane fouling could beslowed down, and the increase of TMP is slower.When in depth analysis of the denitrification reactor, the results show that: themechanism of nitrogen removal for denitrification reactor is denitrification. Denit-rifying bacteria use the nitrate in returned sludge and carbon sources in influent toproduce nitrogen gas. In a90d study of the denitrification reactor,the results indicatethat: The average removing rates of NH4+-N， NO3--N， TN are2.49%,53.55%and16.34%,respectively. In order to improve the nitrogen removing rate, CH3OH isadded as carbon source. A dosage of500mg/L、1000mg/L、1500mg/LCH3OH(calculated in COD) are added to the influent, respectively, and obtainednitrate removing rates are33.63%、61.99%、79.96%，respectively.Due to the insufficient of carbon source, the feasibility of raw wastewater ascarbon source is studied in this paper. The results show that: In a30d study，differentratio（2.5%、5%） of raw wastewater are added to influent, the average COD ofeffluent and MBR supernatant are250,1472mg/L,respectively.The nitrate removalefficiency is improved when the raw wastewater addition ratio increases from2.5%to5%.The TN of effluent decreases from278mg/L to188mg/L.The nitrogen removingrate of De-reactor are21.93%,33.31%,respectively. The acidizing raw wastewater ismore preferable as carbon source because of high concentration of VFAs.