Study On The Characteristics And Reduction Of NH₃ And Greenhouse Gas Emissions From Raw Water Of Cattle Farm Wastewater

With the country’s strong support for modern animal husbandry in recent years,the proportion of medium and large-scale beef cattle and dairy farms has increased,and it has also brought serious environmental pollution pressure.At present,there are many domestic studies on NH₃ and greenhouse gas emissions from solid manure produced by livestock and poultry,and they are relatively mature.However,there are few studies on liquid manure NH₃ and greenhouse gases,and most of the studies are conducted on raw water and biogas slurry from pig farms,and relatively few studies on cattle farm sewage.The liquid manure of the cattle farm has the characteristics of large daily sewage discharge,large storage capacity,and the main composition of sewage is urine.The physical and chemical indicators of cattle farm wastewater are different from those of other livestock and poultry farms,so the systematic detection of NH₃ and greenhouse gases in cattle farm wastewater has certain research significance.In this paper,the raw wastewater of dairy farms is the research object,and the dynamic box method is used to explore the emission characteristics of NH₃,CO₂,CH₄,N₂O and other greenhouse gases and emission reduction technologies during storage:1.Seasonal monitoring of ammonia and greenhouse gas emissions in raw sewage water.After35 days of monitoring in each season,it is concluded that the cumulative emissions of ammonia in summer,autumn and winter are 140.08,78.34 and 47.01 g·m^-2,respectively;cumulative CO₂emissions The emissions are 2259.03,1347.97 and 293.79 g·m^-2 respectively;the cumulative emissions of CH₄ are 147.87,147.78,1.84 g·m^-2,respectively;the cumulative emissions of N₂O in summer are 810.10 mg·m^-2,and the cumulative emissions in autumn are 704.24 mg·m^-2.The cumulative emissions in winter are almost zero.Compared with emissions such as CO₂,the overall emissions of N₂O are low,and the winter can be basically ignored.2.The raw water was acidified with citric acid,and the acidification pH was 6.5 and 4.5.The results showed that the acidification treatment can significantly reduce the emission of NH₃ and N₂O（P<0.01）.Compared with the control group,the acidification pH6.5 treatment group and pH4.5 treatment group reduced the cumulative emissions of NH₃ by 69.76%and 84.44%（P<0.01）,and at the same time reduced the cumulative emissions of N₂O by 62.92%and 85.01%（P<0.01）;however,the acidification treatment increased CO₂.The cumulative emissions reached 56.05%（pH6.5）and 203.14%（pH4.5）;the effects of different acidification pH on the cumulative emissions of CH₄ were inconsistent.When the pH was 4.5,the cumulative emissions of CH₄ were reduced by 96.25%（P<0.01）,while the cumulative emissions increased by 226.83%at pH 6.5（P<0.01）.3.The raw water was covered with coconut shell activated carbon and straw used for feeding,and the covering thickness was 5 cm.The results showed that both straw mulching and activated carbon mulching could reduce the cumulative emissions of NH₃ and CO₂（NH₃ compared to the control group reduced by 16.91%⁷6.67%,CO₂ reduced emissions by 9.49%²8.75%）,while the straw and activated carbon covering treatment significantly increased the cumulative emissions of CH₄（P<0.05）.Compared with the control group,the straw group and activated carbon group increased 34.60%and 32.00%;Different covering materials have different effects on N₂O emissions.Compared with the control group,the activated carbon group can reduce the cumulative N₂O emissions by 8.08%,while the straw group increases the N₂O emissions by10.73%.4.After acidification with citric acid,the mulching treatment was carried out with coconut shell activated carbon and rice straw.The acidification pH was 6.5 and 4.5,and the cover thickness was 5 cm.The results showed that both acidification and mulching treatments can significantly reduce the cumulative emission of NH₃ in raw water（P<0.01）,the pH6.5+straw,pH6.5+activated carbon,pH4.5+straw,and pH4.5+activated carbon groups reduced emissions by75.22%⁹4.83%compared with the control group.Among them,the two acidification groups covered with straw have reduced emissions It is better than the activated carbon group,and the pH6.5+straw group has the best effect.The effects of acidification+covering treatment on greenhouse gas emissions are inconsistent:among the effects on CO₂ emissions,only the pH4.5+activated carbon group reduced the cumulative CO₂ emissions of sewage raw water by 10.58%（P>0.05）;the remaining three groups increased CO₂ compared to the control group Emissions are38.73%¹75.58%;in the impact on CH₄ emissions,the pH4.5+straw and pH4.5+activated carbon groups reduce the cumulative emissions of CH₄ by 97.80%and 97.35%respectively（P<0.01）,but pH6.5+straw and pH6.5+activated carbon group increased the cumulative CH₄ emissions by174.25%and 76.30%respectively（P<0.01）;in the impact on N₂O emissions,the acidification pH6.5+straw and pH6.5+activated carbon treatment groups increased by 63.42%respectively.And60.53%of cumulative N₂O emissions（P<0.05）,while the two groups of pH4.5+straw and pH4.5+activated carbon treatments reduced emissions by 9.59%and 49.06%of cumulative N₂O emissions,pH4.5+activated carbon The group was significant（P<0.05）.5.In terms of CO₂ equivalent,the comprehensive greenhouse gas analysis of each treatment group in the emission reduction study found that CH₄ is still the main contributor of greenhouse gases compared with the control group after the coverage treatment,while the pH6.5 group after the acidification treatment is CH₄,The pH4.5 group is CO₂.Similarly,the main contributors of greenhouse gases in the two test groups with pH4.5 after acidification+covering treatment also become CO₂.From the comprehensive greenhouse effect analysis,only the pH4.5 group and the two groups with pH4.5 in acidification+covering had a smaller greenhouse effect than the control group,and the pH4.5+activated carbon group had the best effect in reducing greenhouse effect.