Effects Of Fe₃O₄NPs On Anaerobic Digestion And Antibiotic Content In The Mesophilic And Thermophilic Digestion

The current research on anaerobic digestion of manure mainly focuses on the direction of methane production,but the research on the efficiency and harm lessness of the whole process is relatively small,especially on the degradation of antibiotics in livestock and poultry manure in large and medium-sized farms.less.In this study,cow manure and chicken manure were used as digestion substrates,respectively,and different doses?0 mg,10 mg,20 mg,50 mg,100 mg?of nano-iron tetroxide?Fe₃O₄ nanoparticles,Fe₃O₄NPs?were added at 35?and 55?,respectively.Constant temperature anaerobic digestion,and on methane production,p H,total solids content?TS?,volatile fatty acids?VFA?,ammonia nitrogen?AN?,alkalinity,dehydrogenase?DHA?,acetic acid Kinase?ACK?and coenzyme F420 and the dynamic monitoring of the content of four tetracycline antibiotics in the digestion process to explore the effects of temperature and nanoparticles addition on the anaerobic digestion characteristics and antibiotic degradation of different raw materials.under the conditions,the optimal temperature of anaerobic digestion and the process of adding nanoparticles optimize the anaerobic digestion conditions of antibiotic-containing feces,which provides a certain experimental basis for improving the digestion gas production rate and the removal of antibiotics.conclusion as below:1. Fe₃O₄NPs can increase the degree of anaerobic digestion substrate hydrolysis and enhance the stability of the digestion system;at the same time,it can increase the gas production and enzyme activity during the digestion process.The addition of 50 mg Fe₃O₄NPs can increase the gas production of chicken manure at a medium temperature of 35?and a high temperature of 55?by up to 16%and 16.4%;adding 20 mg and 50 mg Fe₃O₄NPs,respectively,can maximize the increase of dehydrogenase and acetate kinase during the digestion of chicken manure at 35?.The activity of F420 and F420 increased the total content of dehydrogenase by 53.9%and35.6%,and at the same time,the content of acetate kinase and F420 could be optimized.During the digestion process of cow dung at a medium temperature of 35?and a high temperature of 55?,the addition of 10 mg Fe₃O₄NPs can maximize the digestion efficiency and increase the gas production by 10%and 14%,respectively.Fe₃O₄NPs had less effect on the enzymatic activity of cow dung digestion than chicken manure,and did not promote each enzyme during cow dung digestion at 35?,but inhibited it slightly;while adding 50 mg Fe₃O₄NPs to dehydrogenate cow dung during digestion at 55?The total enzyme content was increased by 44.8%,and the addition of 10 mg Fe₃O₄NPs can make acetate kinase and F420 enzymes the most active.2. The addition of Fe₃O₄NPs can increase the degradation rate of tetracycline antibiotics in the digestion process to different degrees,but the optimal amount of different types of antibiotics is different.During the digestion process of chicken manure at 35?,the dosage of Fe₃O₄NPs with the highest degradation rate of four tetracycline antibiotics:oxytetracycline?OTC?,tetracycline?TC?,chlortetracycline?CTC?,and doxycycline?DC?:100 mg and 10 mg,respectively,0 mg,and 100 mg;during the digestion process of chicken manure at a high temperature of 55?,the optimal dosages are:100 mg,100 mg,10 mg and 0 mg.The addition amount of Fe₃O₄NPs with the highest degradation rate of OTC,TC,CTC and DC during the 35?digestion of cow dung was 10 mg,100 mg,20 mg and 10 mg,respectively.100 mg,20 mg and 0 mg.Oxytetracycline and tetracycline had the highest degradation rate and the shortest half-life when 100 mg Fe₃O₄NPs were added.Fe₃O₄NPs had a greater effect on the half-life of oxytetracycline and tetracycline than chlortetracycline and doxycycline.3. Tetracycline antibiotics have different effects under different digestion conditions.The chicken manure digestion process is generally suppressed,while the effect on the cow manure digestion process changes with temperature.The inhibition rates of tetracycline antibiotics on the total gas production of chicken manure at 35?and 55?digestion reached 4%and 15.98%,respectively;the tetracycline antibiotics inhibited the enzyme content of chicken manure at 35?in the early stage of digestion,but in the late stage It was released,and the inhibition rate of the total dehydrogenase content in the digestion process reached 36.29%.During the digestion process of chicken manure at 55?,the tetracycline antibiotics showed an inhibitory effect on the content of dehydrogenase,acetate kinase and coenzyme F420 thro?ghout the digestion stage,and the inhibition rate of dehydrogenase content reached 40.9%.For the whole stage of cow dung digestion at 35?,the tetracycline antibiotics showed inhibitory effect,the total gas production decreased by 10.15%,the content of dehydrogenase,acetate kinase and coenzyme F420 were suppressed,and the inhibition rate of the total content of dehydrogenase reached 9.8%.However,the 55?digestion process is promoted,which shortens the start-up time of the digestion system by 12 days and increases the gas production by 14.04%.At the same time,the addition of tetracycline antibiotics can slightly promote the dehydrogenase,acetate kinase and coenzyme F420 during the 55?digestion of cow dung.The total content of dehydrogenase increased by 9.6%.4. High temperature is more obvious than anaerobic digestion characteristics and antibiotic degradation.Relative to the middle temperature of 35?,the high temperature of 55?can improve the anaerobic digestion characteristics of chicken manure and cow manure,and increase gas production.At the same time,the temperature increase is conducive to the degradation of tetracycline antibiotics and can also shorten the degradation half-life.under high temperature,the degradation rate of tetracycline antibiotics can be increased by about5%.Among them,chlortetracycline has the most promoting effect on degradation of chlortetracycline.under moderate temperature conditions,chlortetracycline cannot be completely degraded;under high temperature,chlortetracycline can be completely degraded on the 7th day of digestion.