Preparation Of Aerobic Denitrifying Bacteria Agent With Corncob As Carrier And Its Performance On Rural Domestic Sewage

Nitrogen pollution of rural domestic sewage is a common problem,especially in Taihu Lake Basin areas where has a dense population.Dramatic increases in nutrients loading,particularly nitrogen and phosphorus loading,have increased the risk of algae outbreak,which results from the lack of effective collection and treatment for rural domestic sewage.In order to improve the rural water environment and alleviate the eutrophication of Taihu Lake,it is urgent to seek efficient and economical ways of nitrogen removal.Aerobic denitrifying bacteria can complete the nitrification and denitrification processes simultaneously.Additionally,as a kind of microbial immobilization carrier,agricultural waste can provide a suitable attachment place and carbon source for microorganisms.Therefore,the treatment technology combined aerobic denitrifying bacteria and agricultural waste has the advantages of simple,economical and efficient.Generally,the combining technology is suitable for the decentralized treatment mode of rural domestic sewage and can effectively increase the carbon concentration in the system.It provides a new way for the denitrification of rural domestic sewage.Based on the previous research,the immobilized bacteria agent was prepared using agricultural wastes as carrier that attached the bacteria microflora LHJ-2 with the function of heterotrophic nitrification and aerobic denitrification.The carrier comparisons and the optimization of preparation processes were carried out in the process of bacterial agent preparation.Finally,the immobilized bacterial agent was applied to the simulated denitrification of rural domestic sewage.The main conclusions are as follows:（1）Among corncob,rice husk,cotton husk and bagasse,the corncob had the highest moisture content（12.37%）,and the aqueous p H of corncob extract was alkaline with the value of 7.89.The corncob also had the best performance of adsorption and organic carbon release,and the adsorption capacity for bacterial microflora LHJ-2 was4.56×10⁹ cfu/g.The removal efficiency of TN and NH₄⁺-N by immobilized bacteria microflora LHJ-2 with corncob was 86.49%and 93.75%,which was 6.75%and 6.52%higher than those by free bacteria microflora,respectively.After physical broken,the adsorption capacity of bacteria of corncob increased to 5.19×10⁹cfu/g,and the denitrification efficiency reached 91.73%.The results of electron microscopy and infrared spectroscopy showed that the corncob has the characteristic of rough,porous,lamellar structure and abundant hydroxyl groups.Moreover,scanning electron microscope pictures showed there were many bacterial cells on the corncob surface,indicating that the bacteria have been immobilized well.（2）The immobilized aerobic denitrifying bacteria microflora agent was prepared by the adsorption.The adsorption capacity of the bacteria microflora agent reached11.72×10⁹ cfu/g under the optimal conditions（solid-liquid ratio of 4g:100m L,90 r/min,90 min）.Using sodium alginate as the protectant,when the drying temperature was60℃,the survival rate of the bacteria was 70.07%.Meanwhile,the drying time was10h.The immobilization process had little effect on the community composition of LHJ-2,and the total relative abundance was slightly increased in the dominant species.The denitrification efficiency of the bacteria agent reached 96.93±1.21%with the cellulase（1:20）and iron addihve.After 6 months of storage at room temperature,the survival rate of the bacteria was 71.53%and the denitrification efficiency of bacteria agent remained over 90%.（3）The aerobic denitrification reactor adding LHJ-2-Corncob bacteria agent had stable and efficient nitrogen removal ability for simulated rural domestic sewage and can adapt to the reduction of influent carbon concentration.In the stable stage,the removal efficiency of COD,TN and NH₄⁺-N of the reactor ranged from 87.77～90.78%,84.09～87.63%and 93.69～95.72%,respectively.The effluent water quality also reached grade I-A as the HRT was shortened to 8 h or the influent COD was reduced to 220mg/L.Besides,aerobic denitrifying microflora LHJ-2 was the dominant community in the microbial community composition of the reactor.Other evaluation results showed that the bacteria agent can better adapt to the change of temperature and p H value than the free bacteria meanwhile it maintain good denitrification activity after reusing for several times.