Study On Treatment Of Recycled Fiber Wastewater By Sequencing Batch Biofilm Reactor

As the global largest producer and consumer of paper and cardboard,China is facing problems of water pollution and natural resource shortages.In recent years,the proportion of recycled fibers used in the pulp and paper(P&P)industry has increased year by year.Fiber recycling is an important way to solve the shortage of raw materials in the P & P industry and also an effective measure to protect the environment and reduce ecological damage.The recycled fiber wastewater has the characteristics of highly polluted,complex composition,and high content of recalcitrant organic matters in the wastewater.Based on the coagulation-sedimentation pretreatment of the recycled fiber pulp and paper wastewater,this paper used UASB(Up-flow Anaerobic Sludge Blanket),SBR(Sequencing Batch Reactor)and two SBBR reactors(Sequencing Batch Biofilm Reactor),to compose of three processes,named UASB-SBR,UASB-SBBR1 and SBBR2 process,respectively,and evaluated UASB-SBBR1 process in terms of COD(Chemical Oxygen Demand),BOD(Biological Oxygen Demand),color,and SS(Suspended Solids)and compared with the UASB-SBR process.Meanwhile the SBBR2 reactor was used to treat recycled fiber wastewater,and the potential of SBBR reactor was explored.The UASB-SBR,UASB-SBBR1 and SBBR2 processes were used to treat the pretreated recycled fiber wastewater.By testing the parameters such as COD,BOD,SS and color to compare the effluents of three processes,the results indicated that the highest color and SS removal efficiency were reached by SBBR2 process,the highest COD removal efficiency was obtained by UASB-SBBR1 process.The results showed that the SBBR reactor has a significant effect on the treatment of recycled fiber wastewaterA comparative analysis of the sludge particle size in the SBR,SBBR1 and SBBR2 reactors revealed that the average particle size of the sludge in the SBBR2 reactor was the largest,the particle size distribution of the sludge were between 0-2500?m,SBBR1 were 0?2000?m,and SBR was 0?500?m,and granular sludge.was found in SBBR1 and SBBR2.The effluent of the three processes and the effluent after coagulation were characterized by FTIR,UV and GCMS.The results showed that the three processes can effectively degrade and remove organic pollutants in wastewater,the types of pollutants in wastewater had been greatly reduced and the structure had changed a lot.The results showed that the effluent after coagulation contains 66 main kinds of pollutants and including a large amount of aromatic hydrocarbon compounds.The UASB-SBBR1,SBBR2 and UASB-SBR process effluent detected 14,20 and 23 main organic compounds,respectively.However,after treated,esters,phenols and various alkane long-chain compounds still remained in the effluent,which requireed further treatment of the wastewater.The effluent of UASB-SBBR system was contained 14 main kinds of organic compounds,with the least types of residual pollutants,followed by the SBBR and UASB-SBR processes,the effluents were detected 20 and 23 main kinds of organic compounds,respectively.After treatment of the recycled fiber wastewater,esters,phenols and various alkane long-chain compounds still remained in the effluents,and the further treated was needed.The high-throughput sequencing of the microbial populations in the SBR,SBBR1 and SBBR2 reactors revealed that the SBBR1 reactor had the highest microbial abundance,the SBBR2 reactor had the highest microbial diversity,and the SBBR2 reactor contained more unique OTUs,it may be related to the existence of biofilm.In addition,SBBR1 and SBBR2 reactors had a relatively high abundance of dominant bacteria with denitrification,dephosphorization and removal of recalcitrant organic matters,therefore,SBBR had obvious advantages in the treatment of recycled fiber wastewater.