Effect Of Conditioner On Degradation Of Tetracycline Antibiotics In Deer Manure Composting

Nowadays,the problem of antibiotic pollution is becoming more and more serious,which attracts people’s attention.On the other hand,the unscientific disposal of agricultural solid waste brings more antibiotics and other pollutants into the environment.Composting,as an environmentally friendly solid waste disposal method,can be used as a green way to degrade antibiotics.Conditioner can adjust the microbial abundance,temperature,p H and other physical and chemical indicators.The effects of biochar,zeolite and their mixture on the degradation of tetracycline antibiotics during composting were studied.Deer manure and straw were used as raw materials for composting.Four groups of composts were set up,which were no conditioner(CK),biochar(B),zeolite(Z)and zeolite and biochar(BZ),respectively.The initial C / N ratio of 30 and moisture content of 60% were adjusted to start composting.Composting was carried out in a composting reactor for 36 days.The degradation of tetracycline antibiotics(TCs)including tetracycline(TC),chlortetracycline(CTC)and oxytetracycline(OTC)in compost was detected by monitoring the basic physical and chemical indexes such as temperature,moisture content,p H and EC.The compost with the highest degradation rate was selected to screen the degrading bacteria.Through high-throughput sequencing,the changes of microbial structure before and after composting were detected,and the degrading bacteria were identified.The mechanism of TCs removal during composting was explained from the effect of conditioner on physicochemical indexes and microbial community structure.The results showed that composting was an effective way to remove more than85.45% TCs from deer manure.Conditioning agent can significantly improve the removal efficiency and rate of TCs in compost.The degradation rates of TCs in zeolite group were the highest,which were TC-91.39%,CTC-97.18% and OTC-95.68%.Among the three antibiotics,TC was lower than CTC and OTC,and the lowest degradation rate was 85.45% in CK group.The degradation of the three TCs in the four composts was in accordance with the model and kinetic model.The first-order kinetic model showed that the degradation rate of TC and CTC was the highest in biochar zeolite mixed conditioner compost(B),and that of OTC was the highest in zeolite conditioner compost(Z).The sensitivity of TCs to conditioner was calculated by artificial neural network model.The final results were CK 14.86% < Z 25.60% < B 28.26% < BZ 31.28%.Redundancy analysis showed that the removal of tetracycline in compost was significantly correlated with physicochemical properties and microbial species.Conditioner can affect the removal of TCs in composting process by affecting the changes of physical and chemical properties and microbial community structure.The addition of biochar did not affect the initial fungal community structure in compost,but the three conditioners biochar,zeolite and the mixture of biochar and zeolite had a greater impact on the bacterial community structure,and affected the change of microbial community in high temperature period and the construction of microbial community in cooling period.According to Shannon index,the addition of biochar or zeolite alone did not affect the abundance of fungi in the pile,but the addition of conditioner significantly reduced the decrease of bacterial abundance in high temperature period and improved the uniformity.The phytotoxicity of deer manure compost was significantly reduced by adding conditioner.After composting,GI value increased and TCs concentration in Pakchoi leaves decreased by 100%.BZ composting reduced the migration of TCs to soil to the greatest extent.Grey correlation analysis showed that adding biochar zeolite mixed conditioner had the highest maturity and the correlation coefficient was 0.8346.Therefore,in general,adding biochar zeolite mixed conditioner is the best choice to improve the removal of TCs in compost,reduce the toxicity of compost plants,reduce the transfer of TCs from deer manure to soil and plants,and promote compost maturity.The acclimated mixed microbial agents,including Acinetobacter pittii,Stenotrophomonas maltophilia,Lactobacillus reuteri,Pseudomonas putida and Trichosporon dohaense,which could promote the removal of TC,CTC and OTC in compost,were identified by high-throughput sequencing.The acclimated mixed microbial agents were maintained at room temperature in Changchun,Jilin Province TC,CTC and OTC in deer manure compost could be completely removed.