| Ammonia(NH3)is the main alkaline gas in the atmosphere and plays an important role in atmospheric chemistry,transportation and sedimentation.Ammonia emissions have an important impact on the ecological environment and human health,which are mainly from agricultural sources.Among agricultural sources,livestock and poultry breeding is one of the most important sources of agricultural ammonia emission,and biogas slurry is the main link of ammonia emission in livestock and poultry breeding.Biogas slurry belongs to high-concentration organic wastewater,and there are two main treatment methods.One is standard treatment,and the other is returning to farmland.However,these two methods will cause the waste and loss of nitrogen-containing substances in biogas slurry.To this end,based on the investigation of the characteristics of large-scale piggery wastewater,the basic treatment process and the nitrogen characteristics of the inlet and outlet water of the anaerobic tank in different seasons,aiming at the problem of high ammoniation rate in the effluent of the anaerobic tank,this paper designed and developed a set of ammonium nitrogen nitrification device using biological trickling filter with microtrickling filter,evaluated the ammonium nitrogen nitrification conversion effect under different inlet flow rates,inlet concentration,and filler height,obtained and optimized the optimal operation parameters of the nitrification device,and evaluated the ammonia emission reduction effect of the breeding shed by using the simulation test of nitrification liquid backwashing shed.The main conclusions are:1.The investigation of nitrogen characteristic level of typical large-scale piggery wastewater and influent and effluent of anaerobic tank showed that the concentration of ammonia nitrogen and the proportion of ammonium nitrogen in biogas slurry were high,and the concentration of ammonia nitrogen and TN in each season were close,and there was no significant difference.The average concentrations of ammonia nitrogen and TN in the influent of the anaerobic tank were 675±43 mg·L-1 and 1398±116 mg·L-1,respectively.After anaerobic fermentation,the average concentrations of effluent were 870±37 mg·L-1 and 1121±33 mg·L-1,respectively.The NH4+/TN ratio also increased from 0.48 in the influent to 0.78 in the effluent,indicating that the anaerobic fermentation process had an important contribution to the transformation of ammonium nitrogen.2.Aiming at the problem of high ammoniation rate in the effluent of anaerobic tank,a set of biological trickling ammonium nitrogen nitrification device using micro foam filler was designed and developed to evaluate the effect of ammonium nitrogen nitrification under different influent flow,influent concentration and filler height.(1)The flow rate test showed that when the packing height was 50 cm,the influent ammonia nitrogen concentration was 80-100 mg·L-1,the residence time was 50 h,and the circulation flow rate was 0.4-3.6 L·min-1,the ammonium nitrogen nitrification conversion rate of the nitrification device was 60.0-87.1%.When the circulation flow rate was 2.0 L·min-1,the system had the best conversion effect of ammonia nitrogen,the nitrification conversion rate reached 87.1%,and the TN loss rate was 14.3%.Increasing or decreasing the circulation flow rate would reduce the conversion effect of ammonia nitrogen.Therefore,it is preliminarily concluded that the circulation flow is 2.0 L·min-1.(2)The study of packing height showed that when the influent ammonia nitrogen concentration was 80-100 mg·L-1,the residence time was 24 h,the circulating flow rate was 2.0 L·min-1,and the packing height was 30-110 cm,the ammonium nitrogen nitrification conversion rate of nitrification device was 58.3-80.6%.When the packing height was 90 cm,the system had the best ammonia nitrogen conversion effect,with the nitrification conversion rate reaching 80.6%and the TN loss rate reaching 6.5%.Increasing or reducing the packing height would reduce the ammonia nitrogen conversion effect.Thus,the best filler height is 90 cm.(3)The experimental results of parameter optimization under the optimum packing height show that when the influent ammonia nitrogen concentration is 80-100 mg·L-1,the residence time is 24 h,the packing height is 90 cm,and the circulating flow rate is 2.0-4.0 L·min-1,the ammonium nitrogen nitrification conversion rate of the nitrification device is 79.1-86.6%.When the circulation flow rate was 2.5 L·min-1,the system had the best conversion effect of ammonia nitrogen,the nitrification conversion rate reached 86.6%,and the TN loss rate was 10.0%.It is concluded that the optimum circulating flow rate is 2.5 L·min-1 when the optimum filler height is 90 cm.(4)The parameter optimization experiments under low DO inflow and optimal packing height showed that when the influent ammonia nitrogen concentration was 80-100 mg·L-1,the packing height was 90 cm,the residence time was 24 h,and the circulating flow rate was 2.0-4.0 L·min-1,the ammonium nitrogen nitrification conversion rate of the nitrification device was 69.0-80.7%under low DO inflow.When the circulation flow rate was 2.5 L·min-1,the system had the best conversion effect of ammonia nitrogen,with nitrification conversion rate of 80.7%and TN loss rate of 14.3%.Under this optimized research condition,continuous aeration with aeration rate of 2.0 L·min-1 was added,and it was found that the conversion effect of ammonia nitrogen in the system was decreased.When the circulating flow rate was 2.5 L·min-1,the highest ammonia nitrogen nitrification conversion rate was only 76.0%,and the operation cost was increased.Therefore,the parameters were optimized as follows:the optimal circulation flow rate was 2.5 L·min-1,the optimal packing height was 90 cm,and the residence time was 24 h without aeration.(5)The system shock loading test showed that when the circulation flow rate was 2.5 L·min-1,the packing height was 90 cm,the residence time was 24 h,and the influent ammonia nitrogen concentration was 100-200 mg·L-1,the ammonium nitrogen nitrification conversion rate of the nitrification device was 30.7-81.1%.When the influent ammonia nitrogen concentration was about 100 mg·L-1,the system had the best conversion effect of ammonia nitrogen,and the nitrification conversion rate was 8 1.1%.When the influent ammonia nitrogen concentration was about 150 mg·L-1,the nitrification conversion rate of ammonia nitrogen was 58.4%.When the influent ammonia nitrogen concentration was about 200 mg·L-1,the system still had a certain conversion effect of ammonia nitrogen,and the nitrification conversion rate was 30.7%.The results showed that the system had good impact load resistance,but in order to ensure that the nitrification conversion efficiency was not less than 60%,the influent ammonia nitrogen concentration should not be higher than 150 mg·L-1.3.Through the analysis of microbial communities under different influent ammonia concentrations,it was found that different influent ammonia concentrations had significant effects on species diversity and species abundance in biofilm.According to OTU cluster analysis and Alpha diversity analysis,when the influent ammonia nitrogen concentration was 100-200 mg·L-1,the species abundance and species diversity in biofilm increased first and then decreased with the increase of ammonia nitrogen concentration.From the classification level of bacterial phylum and genus,with the increase of influent ammonia nitrogen concentration and reaction,the dominant phylum in biofilm remained unchanged,with the first dominant phylum being Proteobateria(>85%)and the second dominant phylum being Bacteroidota(1.1-8.5%).The abundance of the first dominant genus Comamonas increased gradually with the increase of reaction time(0-24 h)(3 1.3-80.1%to 59.3-91.1%),and decreased with the increase of influent ammonia nitrogen concentration(100-200 mg·L-1)(89.5%to 67.5%).The abundance of the second dominant genus Rhodanobacter was the highest(5.0%)when the ammonia nitrogen concentration was 150 mg·L-1.Reducing or increasing the ammonia nitrogen concentration would reduce the relative abundance of Rhodanobacter.4.The effect of ammonia emission reduction in aquaculture sheds was evaluated by simulation test of nitrification liquid back flushing sheds.The results showed that the concentrations of NH4+-N and NO3--N decreased with the increase of mixing time after mixing pig manure with nitrification solution.The removal efficiency of ammonia nitrogen and nitrate nitrogen could be increased by increasing the mixing ratio of nitrification liquid and pig manure.After mixing for 17 h,the removal rate of nitrate nitrogen could reach about 90%.Compared with tap water shed,using the ratio of 1:1 to 3:1(nitrification liquid:manure)for nitrification liquid shed can increase the removal of ammonia nitrogen by 1.65-10.55%.The ammonia emission reduction efficiency of 14.4-26.3%can be estimated,which can effectively improve the air quality of sheds.The comprehensive benefit analysis shows that the economic benefit of farmland utilization of nitrification liquid in this ammonia nitrogen nitrification device can reach RMB 2.08 yuan·m-3,which is conducive to the sustainable and healthy development of livestock and poultry farms and has a positive impact on the living environment and income level of local residents.It also indirectly reduces the cost of air pollution control. |
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