Study On Denitrification Performance Of SC-MBBR Enhanced By Agricultural Wastes As Solid Carbon

In order to cope with the demand for upgrading the urban sewage treatment plant and solve the problem of poor TN removal caused by low water inflow C/N,the use of natural cellulose agricultural waste as an external solid carbon source is to strengthen the biological nitrogen removal effect.One of the effective technical means.However,the untreated natural cellulose-based solid carbon source contains components that are not easily decomposed,so it is necessary to pretreat the solid carbon source to improve its carbon release performance.In this study,the corn core was used as a carbon source and a biological carrier to construct a SC-MBBR biological nitrogen removal process using agricultural waste as a solid carbon source.The system of solid carbon source denitrification was systematically studied from the whole process of " pretreatment-operation-supplement ".which provided technical support and theoretical basis for the development and application of solid nitrification technology.The corncob was pretreated with 2%sulfuric acid and 1.5%sodium hydroxide respectively.The physicochemical properties,carbon release law and denitrification potential(DP)of corncob before and after pretreatment were studied.Acid treatment had obvious degradation effect on hemicellulose,and the content of hemicellulose decreased by 47.40%.Alkali treatment had a strong influence on the content of cellulose and lignin components,and the content of cellulose component increased by 48.83%.The content of lignin and lignin decreased by 51.26%.After carbon and alkali pretreatment,the carbon release capacity of corn cobs increased by 30.93%and 46.41%,respectively.Denitrification potential DP base(249.34 mgNO3-N/g)>DP acid(219.98 mgNO3-N/g)>DP original(121.93 mgNO3-N/g).Considering comprehensively,alkali pretreatment promotes the carbon release performance of corn cobs best.The corncore was treated with alkali as an external carbon source and a biofilm carrier to construct a SC-MBBR biological nitrogen removal system.The optimum carbon source dosage and initial sludge concentration(MLSS)were analyzed and compared.Under the optimal carbon source dosage of 150 g and initial MLSS 4 000 mg/L,the effluent COD,TN and ammonia nitrogen concentrations were respectively32.34 mg/L,2.72 mg/L,0.43 mg/L,TN,ammonia nitrogen removal rate was stable at 92%,98%.High-throughput sequencing technology was used to analyze the changes of microbial composition when the influent C/N was 3:1,5:1,and 8:1,respectively.The synergistic metabolic mechanism between microorganisms in the system was investigated.With the increase of influent C/N,the organic matter is relatively abundant,the demand for microbial external carbon source is reduced,and the pre-existing cellulose degrading Azoarcus,Flavobacterium,and Cellvibrio is gradually replaced by a genus such as Portibacter,Devosia,and Saccharibacteria_genera incertae_sedis,which have degraded organic matter and denitrification function.For long-running SC-MBBR systems,the way in which solid carbon sources are supplemented and replaced is examined.Comprehensive operation time,time required for stabilization,and TN removal of effluent,it is considered that 50 g(ie,1/3 carbon source dosage)is the best way to supplement the carbon source.After the system is stabilized,the effluent COD and TN are respectively At 30?35 mg/L,2?3.5 mg/L,the average TN removal rate is 90.21%;the spent carbon source can be replaced by clinker,and the SC-MBBR denitrification system can be quickly stabilized after replacement.