Effectiveness Research On Advanced Treatment Of Dyeing Wastewater By Zero-valent Iron Biological Aerated Filter

Because of the dyeing wastewater of urban sewage treatment plant is featured by complex composition,great fluctuation in quality and quantity,difficult biodegradation and poor biodegradability,the effluent water quality are generally not able to meet the first class criteria of Discharge Standard of Pollutants for Municipal Wastewater?GB18918-2002?by conventional biological treatment.Many urban sewage treatment plants are facing the problem of upgrading and reconstruction,therefore,the development of depth treatment process is a common method for the transformation of the sewage treatment plant.In this study,zero-valent iron?Fe⁰?respectively with ceramsite,activated carbon combined into the integration of BAF,with Ceramsite BAF as the reference,the biochemical effluent of dyeing wastewater as the processing object,optimizing the process parameters by single factor experiment and determining the optimum condition.The purpose of this study was to study the effects of Fe⁰ and filler properties on the removal of organic matter,nitrogen and phosphorus from BAFs;investigate the effect of Fe⁰ and filler characteristics on the degradation process of pollutants in BAFs by comparing the variation regularity of the concentration of contaminants along the filtration layer in each reactor;microbial community structure in three reactors by using molecular biology techniques,to elucidate the microbial mechanism of Fe⁰ and filler characteristics affect nitrogen immigration,to explain the correlation between BAFs removal efficiency with microbial properties.The main conclusions are as follows:?1?The method of natural inoculation combine with domestication can be used to successfully start-up BAFs in a month,and after start-up completes,the COD and NH₃-N concentrations of BAFs were respectively lower than 18 mg/L,2 mg/L,and the removal rate respectively reached 67.3% and 87.5%,Fe⁰+activated carbon BAF has the best effect and Fe⁰+ceramsite BAF is followed.By observing the biological phase of the filler surface,theCeramsite BAF are mainly cocci,Bacillus and filamentous bacteria,and the filamentous bacteria as the supporting structure of biofilm structure.There are many cocci and bacillus on the Fe⁰-BAF,only a few filamentous bacteria are distributed around the biofilm.?2?The optimized p H,gas-water ratio,COD/TN,HRT of BAFs were 7,5:1,8.5 and 8 h respectively.Under the optimal condition,maximum removal efficiency of COD,SOP,and TN were 76%,62.7%,and 29.7%,respectively for the ceramsite BAF;81.6%,97%,and 57.4%,respectively for the Fe⁰+ceramsite BAF,84.5%,97%,and 68.7%,respectively for the Fe⁰+activated carbon BAF.Effluent COD,SOP and TN concentrations all meet the first class A emission standard in GB18918-2002,and the Fe⁰+activated carbon BAF has the best effect and Fe⁰+ceramsite BAF is followed.That shows that the Fe⁰ and activated carbon fillers can effectively improve the treatment efficiency of BAF.?3?In the Ceramsite BAF,COD,NH₃-N,SOP,TN were removed within the media layer height of 0⁴0 cm,0⁴0 cm,0⁸0 cm,0¹00 cm respectively,biomass showed a downward trend with height,the main organic compounds in the effluent are tetrahydrofuran.And in the Fe⁰-BAF,COD,NH₃-N,SOP were removed within the media layer height of 0⁶0 cm,0⁵0cm,0⁴0 cm respectively,and removal of TN mainly in 0⁵0 cm and 70¹00 cm,biomass increased with height,decreased first,then increased,and finally decreased,the effluent organic matter decreased with tetrahydrofuran content.The dissolution of Fe⁰-BAF mainly exists in the form of Fe3+,and the content in the water is less,most of the biofilm adsorption filter in central,interception,total Fe content in solution is about 1.8 mg/L,total content of Fe on biological membrane can reach above 30 mg/g.And the Fe⁰-BAF need 9h to recovery efficiency after the back washing,while ceramsite BAF need 24 h above.?4?The iron-containing BAF can decreased abundance and diversity of microbial community,but the dominant bacteria in the system were strengthened and the relative abundance of miscellaneous bacteria decreased.In the Fe⁰-BAF,the relative abundance of Proteobacteria and Nitrospirae improved 7.4% more than the ceramsite BAF,and the iron ions can also enhance the relative abundance of Pseudomonas,Hyphomonas and Rhodobacter,these bacterias are closely related to denitrification.The relative abundance of Bacteroidetes in Fe⁰+activated charcoal BAF is much larger than other BAFs,which showed that Fe⁰+activated charcoal BAF had better nitrogen removal performance.