Study On The Removal Effect Of Contaminants In Black Water And Gray Water During MBR Process

Traditional centralized sewage treatment system often aims at the safe discharge of sewage,these system often have the disadvantages of complex water quality conditions,high energy consumption and low utilization of resources.Sewage is regarded as a renewable resource in source separation treatment system,these system can select more targeted and cost-effective treatment process according to the different characteristics of the pollutants contained in different kinds of sewages,often has the advantages of low energy consumption and high utilization of resources,which can indirectly alleviate the shortage of water resources.At present,experts and scholars mostly focus on the study of nitrogen and phosphorus removal performance of source separation sewage treatment system,while there is no practical data for the study of other organic and inorganic pollutants,however,if these part of pollutants(such as Cl^-,SO₄^2-,DOM,etc.)are not effectively removed,they will also affect the quality of reclaimed water adversely.Therefore,a source separation sewage treatment project in Qingdao was selected as the research object in this paper,treatment efficiency of inorganic pollutants,organic pollutants and biological toxicity in black water and gray water during MBR treatment was studied,meanwhile,migration and variation of pollutants in MBR process was investigated.The main results are as follows:（1）The removal effect of conventional pollutants in black water and gray water during MBR process showed that,black water treatment process can effectively reduce the contents of COD,NH₃-N,TP and total iron in raw black water,the removal rates of each pollutant was 97.28%,96.44%,98.37%and 88.37%.However,the removal capacity of TN,total manganese,total hardness,TDS,Cl^-,SO₄^2-were limited.Gray water treatment process can effectively reduce the contents of COD,TN,NH₃-N and total iron in raw gray water,the removal rates of each pollutant was 95.32%,79.5%,97.61%and 86.11%.However,the removal capacity of TP,total manganese,total hardness,TDS,Cl^-,SO₄^2-was limited.After treatment,the concentration of COD,TN,NH₃-N,TDS,Cl^-and Larsen index in black water effluent were much higher than those in gray water effluent.The concentration of total iron,total manganese,total hardness and SO₄^2-in black water effluent were similar to that in gray water effluent,while the concentration of TP and total alkalinity in black water effluent were lower than those in gray water effluent.Compared with black water,gray water can obtain better quality of effluent while using simpler treatment process,so it was more suitable for reuse.（2）Change of ultraviolet and fluorescence spectra of DOM in black water and gray water during MBR process showed that,the UV₂₅₄54 and E₄/E₆ of raw black water were higher than those of raw gray water,while the SUVA of raw black water was lower than that of raw gray water.During MBR process,the UV₂₅₄54 of black water and gray water gradually decreased,while the SUVA and E₄/E₆ increased gradually.After treatment,the UV₂₅₄,SUVA and E₄/E₆ of the effluent of black water were higher than those of gray water effluent.There were two distinct fluorescence peaks in the fluorescence spectra of raw black water and raw gray water,which were tryptophan peak and humic acid peak.During MBR process,the tryptophan peaks of black water and gray water disappeared,and the fluorescence intensity of humic acid peaks decreased 38.4%and 37.83%,respectively.After treatment,the fluorescence intensity of humic acid peak in the effluent of black water is higher than that in gray water effluent.（3）Change of molecular weight distribution and hydrophilicity-hydrophobicity distribution of DOM in black water and gray water during MBR process showed that,DOM in black water and gray water mainly contained the substances with molecular weights<1kDa and>100kDa.MBR system had good removal effect on DOM with molecular weight>100kDa,but the removal of small molecule DOM was poor.After treatment,DOM in the effluent of black water and gray water mainly contain the organic matter with molecular weight<3kDa.DOM in black water mainly contained N-HPI and HPO,while DOM in gray water mainly contained HPO.MBR system can effectively remove N-HPI in black water.After treatment,DOM in the effluent of black water and gray water mainly contained hydrophobic substances,and the concentration of hydrophobic substances in the effluent of black water is more than that in gray water effluent.（4）Change biotoxicity of black water and gray water during MBR process showed that,MBR process can reduce the genotoxicity of black water and gray water.During MBR treatment,MCN and PI of black water and gray water gradually decreased,while MI increased gradually.After treatment,genotoxicity of the effluent of black water was much higher than that of gray water.Raw black water inhibited the germination of wheat and soybean seeds,raw gray water inhibited the germination of wheat seeds,but can promote the germination of soybean seeds.After MBR treatment,the effluent of gray water inhibited the germination of wheat and soybean seeds,the effluent of black water inhibited the germination of soybean seeds,but promoted the germination of wheat seeds.