The Effect And Biochemistry Mechanism Of Biogas Slurry Treatment By Two-stage A/O Processes Improvement

Animal husbandry develops rapidly in China, result in pollution increasingly. In recent years, the covered lagoon become more and more popular for pig wastewater treatment. But it still face a lot of problem including higher ammonia nitrogen concentration, C/N disorder, and low biodegradability and so on. This paper introduce a two-stage A/O process by adding the raw water and adjustment of hydraulic retention time(HRT) to improve the effect of biogas slurry treatment in coated digester, and explains its mechanism by using physical chemistry and microbiology analysis techneque.This study include three parts: first is the effect of different HRT on removal COD, NH4+-N and the TN during two-stage A/O process in summer; second is the effect of different season original water added proportion on two-stage A/O process; three is validation the biogas slurry treatment efficiency by the above improved method in actual production scale. The main results are as follows:(1) When the C/N values over 1.5, A/O system can significant increase the removal rate of COD, NH4+-N and TN by extension of HRT. HRT in 3d, 4.5d, 6d, the COD, NH4+-N and TN removal efficiencies are best with lowest effluent concentrations. When the C/N value is low, the effect of HRT on COD removal in two-stage A/O process decreased.(2) Add original water can significantly improve COD removal efficiency of biogas liquid, COD removal rate was 82.8% with the effluent concentration 258.75mg/L when adding 30% raw water. When HRT is longer than 4.5d, added original water can significantly increase the concentration of NH4+-N and removal rate of TN(P<0.05);When the HRT was 3d, removing effect by adding original water on the above index declined significantly.(3) Season(summer and winter) can significantly affect COD removal efficiency of biogas liquid. The effluent concentration in the summer was significant lower than that in winter. Effects of seasons on NH4+-N removal was not significant in two-stage A/O(P>0.05) and the effluent concentrations was lower in winter than that in summer. The effluent meet the GB18596-2001 criteria in both season; different season significantly affected the TN removal rate in two-stage A/O system(P<0.01).(4) The main bacteria in waste water treatment process was Proteobacteria?Firmicutes?Bacteroidetes ? Chloroflexi and Actinobacteria. Adding original water can promote the proteobacteria reproduction and growth and the relative content of Panthera Leo Dan Baoke was 18.5%. When the original water adding ratio increased from 0% to 30%, the Comamonadaceae increased from 13.6% to 27.1%, 9.5% to 13.2%, 4.9% to 39.8%, and 2.6% to 10.5% in the anoxic basin water, sludge, aerobic pool water and sludge, respectively. It had been reported that Comamonadaceae?Nitrosomonadaceae play an important role in the nitrogen removal process.Field verification study showed that extend A/O system's HRT can improve the COD, NH4+-N and TN removal rate, adding original water also can improve COD, NH4+-N and TN removal rate in A/O systems. When HRT was 6d, the orginal water ratio was 30%, two-stage A/O system had high efficiency on removing the COD, NH4+-N and TN, and meet the effluent with GB18596-2001 standards. Adding original water can improve the microbial reproduction and growth, especially proteobacteria and tuft aeromonas organisms, they play an important role in the nitrogen removal process.