Study On Removal Of Ammonia Nitrogen From Source Water By Strengthening BAC Based On Functional Regulation Of Biofilm

The drinking water quality is polluted by different extent in China,among which the main pollution is ammonia nitrogen.Biological activated carbon（BAC）has become the core of drinking water advanced treatment process due to its economic,efficient,prevention of disinfection by-products and other characteristics.However,the catholic BAC crafts exist some weak point in ammonia nitrogen removal.For example,autotrophic nitrifying bacteria grow slowly and they are susceptible to the ambience which they live in.Mature and stable biofilms appear on granular activated carbon（GAC）need to be taken a long while.The autotrophic nitrification is unstable,which leads to a long while to switch on of BAC crafts.In addition,the physical function of GAC on ammonia nitrogen is weak,and the migration of ammonia nitrogen from water to the biofilm on the BAC is a key step that affects the efficiency of ammonia nitrogen removal.Due to the scant elimination of ammonia nitrogen caused by the above shortcomings,and combining with the particularity of ammonia nitrogen,this topic proposes a strategy of nMnO₂ coupled with carbon source interface regulation to strengthen the BAC to cast aside ammonia nitrogen from source water.The organic carbon sources are used to quicken the becoming of BAC biofilms,promote the natural enrichment of heterotrophic nitrifying bacteria,and strengthen the functionality and stability of biofilms.Meanwhile,nMnO₂ is used to control the interface of activated carbon to reinforce the migration ability of ammonia nitrogen at the liquid-solid interface,so as to comply sharp and stable clear away of ammonia nitrogen by BAC.The type of carbon source,the loading of carbon source,and the loading of nMnO₂as the single influencing factor to obtain the preliminary parameter range.Then the respond surface method was used to optimize the control mode of nMnO₂ coupling carbon source interface.The mathematical fitting equations of parameters of interface regulation（sucrose concentration,nMnO₂ concentration,load ratio）and response value（ammonia nitrogen removal and TOC removal）were simultaneously found to consequence.The two models both had a good correlation.Taking the optimal of two respond value as the goal,the finest suggestion for the interface control mode were obtained:100.00 mg-C·L^-1sucrose solution,25.00 mg-nMnO₂·L^-1 nMnO₂ solution,and 65%loading ratio(That is,preloaded with 1 mg-C·g^-1 dry weight of GAC sucrose,0.25 mg-nMnO₂·g^-1 dry weight of GAC nMnO₂ and 65%loading ratio).When the above scheme was adopted,the removal of ammonia nitrogen and TOC were（38.1±1.3）%and（68.9±2.7）%,respectively.Under the regulation of nMnO₂ coupled carbon source interface,the functionality and identity of microbe,including initial biomass,initial microbial community particularity,initial extracellular polymeric substances（EPS）and initial biofilm apparent properties on the erasure of pollutants by BAC were explored.The upshot manifested that preloading carbon source and nMnO₂ could hasten the profile of safe and ripe biofilm.Some microorganisms with nitrification and denitrification effects were found on the BAC biofilm,such as Bacillus,Aquabacterium and Hydrogenophaga,among which Bacillus was the dominant heterotrophic bacteria,accounting for 50.8%-67.2%of the four regulated BAC microbial communities.It could be scrutinized that the number of EPS in BAC biofilms with interface regulation was large and the distribution was scattered.Furthermore,rod-shaped microbial communities with filamentous viscous secretion were observed,which indicated that nMnO₂ coupled with carbon source interface regulation could enhance the functionality of BAC biofilms.BET analysis and FTIR analysis were conducted to study the change of the exterior and chemical particularity of BAC controlled by interface.The upshot manifested that the exterior pore and functional groups of GAC and BAC supports did not significantly diversify under the interface control mode.The research on the conversion products of ammonia attested that there was no congestion of nitrate and nitrite after the reaction,and the biodegradation of heterotrophic nitrifying bacteria might occur.The mechanism of strengthening BAC by interface regulation was explored.The upshot manifested that GAC adsorption,biofilm adsorption and microbial degradation acted synergistically in pollutants,accounting for（5.3±0.3）%,（38.7±2.1）%and（56.0±2.5）%respectively.Among them,microbiota degradation and biofilm adsorption pivotally involved in the removal of ammonia nitrogen.