Changes In Arsenic And Copper Bioavailability,Oxytetracycline Degradation And Microbial Community During The Composting Process

This research focuses on the effects of the composting process on oxytetracycline antibiotic degradation and the bioavailability of arsenic and copper.A compost experiment was conducted using cow and pig manure contaminated with oxytetracycline,and copper and arsenic salts.The changes in physicochemical properties,oxytetracycline concentration,and the germination index were measured.Copper and arsenic were estimated by sequential chemical extraction.The experiment was also conducted to assess the microbial community dynamics during the composting process(35 days).Relationships between environmental factors and microbial community compositions were evaluated by redundancy analysis.The results showed that the thermophilic phase during the composting process generates metabolic heat.We observed a rapid rise in temperature exceeding 50 °C during the first two weeks.Low-temperature values were found in the Cow-OTC+As&Cu and Pig-OTC+As&Cu treatments.The decrease in the bioavailable Cu extracts was more significant than that of the bioavailable As extracts while the total concentration of Cu and As increased during the composting process.The Cu bioavailable fraction decreased during composting.In pig manure,the percentage of low bioavailability As was smaller than that in cow manure,and its values increased over time.The antibiotic degradation rate on the first day in pig manure was lower than that in cow manure.The GI values in cow treatments gradually increased over time to register values higher than 95% by the end of the composting process and it was greater than 65% in the pig manure treatments.Linear regression results showed that the compost properties had the most significant impact on the germination index in the cow and pig manure treatments.The bacterial community varied significantly during the composting process.The dominant phyla included Actinobacteria,Bacteroidetes,Firmicutes,and Proteobacteria.The most common microbes present in cow manure were Firmicutes,followed by Actinobacteria,while Proteobacteria and Actinobacteria were in pig manure.All treatments during the experiment period especially during the thermal phase were different compared to the first day in cow manure and pig manure.The microbial diversity relative abundance transformation was equivalent to composting time.Redundancy analysis results indicated that environmental parameters are the most influence on bacterial communities.In conclusion,the composting process is one of the most valuable and sustainable technologies to reduce heavy metal(loid)s effects and antibiotic contamination.The variations in manure physicochemical properties had a significant effect on the microbial community however,the temperature change was the influential factor during the composting process.