title: Degradation of tetracycline and sulfadiazine during continuous thermophilic composting of pig manure and sawdust.
abstract: During composting, the thermophilic phase resulted in high degradation of antibiotics in the composting mass; thus temperature is considered as the major factor for degradation of antibiotics. Therefore, to achieve complete removal of antibiotics, the effect of continuous thermophilic composting on the degradation of antibiotics and their effect on antibiotic resistant bacteria in the pig manure were evaluated. Pig manure was mixed with sawdust, spiked with tetracycline (10 and 100 mg/kg) and sulfadiazine (2 and 20mg/kg) on dry weight (DW) basis and composted at 55 degrees C for six weeks. Based on the organic decomposition, the antibiotics did not affect the composting process significantly, but negatively influenced the bacterial population. Tetracycline clearly exhibited a negative but marginal influence on carbon decomposition at 100 mg/kg level. The bacterial population initially decreased steeply approximately 2 logs and slowly increased thereafter. Sulfadiazine and tetracycline resistant bacterial populations were stable/marginally increased after an initial decrease of about 2 or 3-5 logs, respectively. Sulfadiazine was not detectable after three days; whereas, approximately 8% of tetracycline was detected after 42 days of composting with a t(1/2) of approximately 11 days, irrespective of the initial concentration. The presence of tetracycline in the compost after 42 days of thermophilic composting indicates the involvement of a mesophilic microbial-mediated degradation; however, further studies are required to confirm the direct microbial involvement in the degradation of antibiotics.
authors.affiliation: Sino-Forest Applied Research Centre for Pearl River Delta Environment and Department of Biology, Hong Kong Baptist University, Kowloon, Hong Kong SAR.
authors.forename: Ammaiyappan
authors.initials: A
authors.lastname: Selvam
authors.affiliation: Sino-Forest Applied Research Centre for Pearl River Delta Environment and Department of Biology, Hong Kong Baptist University, Kowloon, Hong Kong SAR.
authors.forename: Zhenyong
authors.initials: Z
authors.lastname: Zhao
authors.affiliation: Sino-Forest Applied Research Centre for Pearl River Delta Environment and Department of Biology, Hong Kong Baptist University, Kowloon, Hong Kong SAR.
authors.forename: Yunchun
authors.initials: Y
authors.lastname: Li
authors.affiliation: Department of Chemistry, Hong Kong Baptist University, Kowloon, Hong Kong SAR.
authors.forename: Yumei
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Department of Chemistry, Hong Kong Baptist University, Kowloon, Hong Kong SAR.
authors.forename: Kelvin S-Y
authors.initials: KS
authors.lastname: Leung
authors.affiliation: Sino-Forest Applied Research Centre for Pearl River Delta Environment and Department of Biology, Hong Kong Baptist University, Kowloon, Hong Kong SAR.
authors.forename: Jonathan W-C
authors.initials: JW
authors.lastname: Wong
mesh_terms: D000818:Animals; D001673:Biodegradation, Environmental; D002244:Carbon / Q000378:metabolism; D002245:Carbon Dioxide / Q000378:metabolism; D024881:Drug Resistance, Bacterial; D006863:Hydrogen-Ion Concentration; D008372:Manure; D009584:Nitrogen / Q000378:metabolism; D012987:Soil / Q000737:chemistry*; D013411:Sulfadiazine / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D013552:Swine; D013752:Tetracycline / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D014934:Wood / Q000737:chemistry*
chemical_list: D008372:Manure; D012987:Soil; D013411:Sulfadiazine; D002245:Carbon Dioxide; D002244:Carbon; D013752:Tetracycline; D009584:Nitrogen