Study On The Degradation Of Food Waste Biogas Slurry Ammonia Nitrogen And Its Mechanism By Gamma Irradiation

Food waste biogas slurry refers to organic matter such as food waste in a sealed biogas tank,and various microorganisms participate in anaerobic fermentation to produce liquid residue after biogas production.The composition of the biogas slurry is complex,and the concentration of organic and ammonia nitrogen is at a high level.The biogas slurry is difficult to be degraded due to the severe imbalance of the carbon—Nitrogen ratio and the microbial inhibition caused by the high concentration of ammonia nitrogen.The untreated biogas slurry may cause serious pollution to the environment.In this study,the food waste biogas slurry is selected as the research object to study the effect of the different factors on gamma radiation degradation of the biodegradability and ammonia nitrogen of biogas slurry and its radiation degradation mechanism.In this paper,the main content of the complete and the main results are as follows:?1?A series of experiments on the degradation of food waste biogas slurry were performed by ⁶⁰Co?-ray irradiation.The effects of different dilution factors of biogas slurry,initial pH value and different absorbed doses on the radiation degradation of biogas slurry and ammonia nitrogen in biogas slurry were studied by analyzing ammonia nitrogen removal rate,chemical oxygen demand COD_cr),five-day biochemical oxygen demand?BOD₅?and biodegradability(BOD₅/COD_cr).The results indicated when the biogas slurry is diluted 10 times,the ammonia nitrogen irradiation removal rate is up to about 55%;when the dilution factor is 40,the COD_cr removal rate of biogas slurry is up to about 33%;in the same dilution multiple and the absorbed dose of radiation,the concentration of ammonia nitrogen,COD_cr,BOD₅ and biodegradability indicators with the similar changes,both increased first and then decreased.When the dilution factor is 10 and the absorbed dose is 10.35 kGy,the maximum ammonia nitrogen degradation rate is 11.4%;when the dilution factor is 40 and the absorbed dose is 3.45 kGy,the maximum value of BOD₅/COD_cr is 0.47.The biogas slurry with the same dilution factor and irradiation absorbed dose?10.35 kGy?has a maximum ammonia nitrogen concentration degradation of 213.48 mg·L^-1 at pH=9.07,and COD_cr The removal rate of COD_cr is up to 26.45%at pH=2.08.?2?Ammonia nitrogen in biogas slurry was treated by gamma irradiation associated with the methods of titanium dioxide?TiO₂?and titanium dioxide-photocatalytic oxidation.The results show that this method is beneficial to promote the effect of?-radiation degradation of ammonia nitrogen in biogas slurry.When the absorbed dose of 10.35 kGy and pH=11.05,the maximum degradation of ammonia nitrogen changed from 137.69 mg·L^-1 to 501.46 mg·L^-1,and the maximum degradation of COD_crr was from 1169.76 mg·L^-1 to 3656.16 mg·L^-1.?3?The radiation degradation mechanism of ammonia nitrogen in biogas slurry was studied by?-rays.The results indicated that the ionic nitrogen in the biogas system was balanced,that is,no gaseous nitrogen?such as nitrogen?was formed in the process of radiation degradation and only the ionic nitrogen was converted into each other after oxidation and reduction.The maximum amount of ammonia nitrogen degradation decreased from 315.17 mg·L^-1 to 236.72 mg·L^-1 by adding free-radical scavenger tert-butanol and the results also show that the oxidation of hydroxyl radicals was stronger than that of hydrogen radicals and hydrated electrons.Due to the complexity of the biogas slurry system,the possible ways and mechanisms of ammonia nitrogen degradation in biogas slurry were derived by analyzing the changes of nitrogen in the process of radiation degradation in a simple nitrogenous solution system.