| The application prospect of the physicochemical system technology based on membrane separation in wastewater treatment field is very bright.But in practice the membrane fouling and the disposal of the concentrate still need to be resolved;there is no uniform reference standard when choosing the membrane combination form according to local conditions;the membrane combination process for secondary effluent has been relatively mature,however,further engineering research is still needed in the process of chemical system of raw water with membrane separation as the main technology.According to the problems above,this topic selection three grit chamber in wastewater treatment plant effluent for raw water samples,design by coagulation sedimentation/level 3 microfiltration/nanofiltration process for the combination of physical and chemical systems,monitoring and regular data for each level of the water,at the same time,combined with high performance liquid chromatography(HPLC)method and three-dimensional fluorescence spectrometry for the analysis of membrane separation characteristics of various pollution factor.The conclusions are as follows:(1)By coagulation sedimentation/level 3 microfiltration/nanofiltration process for the combination of physical and chemical system for the average COD removal rate was 79.33%,the average removal rate of TN was 33.01%,the average of NH4 +-n removal rate was 34.05%,the removal efficiency of TP depends on what dosage in the process of coagulation,in practice according to the specific removal and recovery of the target to determine the dosage.The removal efficiency of SS by coagulation precipitation unit was excellent,with a removal rate of 95.65%.After microfiltration,SS was completely removed.The change in pH throughout this process is less than1.With the fluctuation of water quantity and water quality,the final effluent of urban sewage treated by coagulation sedimentation/tertiary microfiltration/nanofiltration combined physicochemical system is a low carbon nitrogen ratio wastewater.(2)The relative molecular weight of DOM in the raw water of urban sewage is widely distributed,but mainly concentrates around 16,000,accounting for 84.48% on average.The smaller the variety of incoming water,the higher the microbial activity of raw water,the higher the content of small molecular substances,but the proportion is limited,and the DOM with a relative molecular weight less than 8000 takes up about10% at most;aromatic protein substances account for the largest proportion in urbansewage,about 50%.In summer,due to the washing of heavy rain,humic acid in soil would accumulate in sewage pipe network in large amounts,leading to a high content of humic acid in urban sewage in summer,up to 62.12%.The average proportion of humic acid in summer was 25.87%,higher than the perennial average of24.89%.Garbage leachate for aromatic protein biggest contribution rate of urban sewage,especially aromatic ? protein substances.The contribution rate of industrial wastewater to various substances in urban sewage should change with the change of wastewater type.(3)Coagulation filtration mainly enriched the non-dissolved organic matter and aromatic protein materials with molecular weight greater than 30,000 Da in sewage.And the degree of the enrichment of aromatic protein materials is 60.93%,especially of tyrosine and tryptophanoids;Acetate microfiltration membrane can enrich all the DOM with molecular weight greater than 30000 Da,but it is not selective for the enrichment of organic matters.The nanofiltration membrane mainly enrich the fulvic acids and humic acids in sewage.The degree of enrichment of the matters mentioned above are 52.01% and 53.57%.The degree of the total enrichment of DOM is about 42%.There is little correlation between the characteristics of the enrichment of organic matters and the molecular weight of organic matters. |
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