Microbiological Characteristics Of Nitrification And Solid-phase Denitrification System For Low-carbon Sewage

According to the traditional theory of biological nitrogen removal, adequate organic carbon source is a necessary for nitrogen removal. The low-carbon urban sewage is becoming more and more obvious, especially in the south of China. For low-carbon sewage, the TN has been the main target to meet the standard of discharging. Based on the comprehensive analysis of existing low-carbon sewage treatment technology and low-carbon sewage biological treatment characteristics, this research constructed the enhanced biological nitrification and solid-phase denitrification sewage treatment technology, and developed the Sequencing Batch Biofilm Reactor-Solid Carbon Denitrification Biofilter(SBBR-SCDNBF). Microorganism is the core of the bioreactor, and its quantity and activity directly affects wastewater treatment efficiency.In this research, molecular biological technique such as DGGE and high-throughput sequencing combining with water quality analysis results were used.the microbial community characteristics and contribution to low-carbon sewage nitrification of suspended sludge and biofilm in the biofilm reactor was researched. For revealing the internal reasons that the high molecular solid carbon source can be used as electron donor for denitrification from the microorganis, the microbial community changes of solid carbon denitrification biofilter along the heights and its start-up were also studied. Research results showed that:(1)Under the operating conditions of aeration rate 15m3/(h·m3), cycle time 3h, the sequencing batch biofilm reactor treated the low-carbon sewage(COD 93~140mg/L,TN 38.4~42.8mg/L). The effluent ammonia concentration was lower than 1.64mg/L, the average removal rate was 96.6%, the nitrate nitrogen was 15.9~24.5mg/L. The average removal rate of TN was 38.2%. The contribution of suspended sludge and biofilm to nitrification was 45% and 55%, respectively.(2) In the sequencing batch biofilm reactor(SBBR), the abundance of Proteobacteria is highest.Then ?-Proteobacteria and ?-Proteobacteria is respectively most abundant in the biofilm and activated sludge. Microbial diversity of the biofilm was lower than that of the suspended sludge. The main ammonia oxidizing bacteria in the suspended sludge are Nitrosomonas and Nitrosomonas uncultured,while in the biofilm is Nitrosomonas.The main nitrification bacteria in SBBR is Nitrospira.And Nitrospira was enriched in the biofilm.(3) For solid carbon denitrification biofilter(SCDNBF), the effluent TN was 1.1~3.5mg/L,the ammonia concentration was below 2mg/L,the average removal rate was more than 90.5%,COD concentration was 50mg/L when the influent TN was 32.0~37.7mg/L,the ammonia was below 1mg/L,COD was 11~43mg/L at the hydraulic retention time of 1.5h. The removal of TN mainly happened at the height below 40 cm in the filter. The biomass and denitrification rate decreased gradually with the increase of the filter height,and had a negative linear correlation with the filter height(y=-0.471x+38.77,R2=0.976). The denitrification rate was between 0.08~0.22mg·(g·h)-1.(4)In solid carbon denitrification biofilter(SCDNBF), The solid carbon source biological film was mainly cocci and bacilli. Denitrification bacteria Dechloromonas?Comamonas and Rubrivivax were the dominant bacteriain in the SCDNBF. The microbial diversity is lowest at the bottom of the filter,and most abundant in the middle part. Comamonas, Dechloromonas, Rubrivivax and so on were common along the height,while Desulfobacter postgatei only existed in the top of the filter. The same kind of microorganism had different number along the way for the difference environmen.(5)In solid carbon denitrification biofilter(SCDNBF), there was PCL degrading bacteria such as Comamonas ? Acidovorax; acidification bacterium such as Desulfovibrio ? Flavobacterium, and multiple denitrification bacteria(Thauera ?Dechloromonas?Hydrogenophaga?Simplicispira and so on.The abundant microbial community structure could support the successful denitrification using solid carbon source.This paper provided theoretical basis for the further research and application of the solid carbon source denitrification technology.