The effect of the chlortetracycline addition method on methane production from the anaerobic digestion of swine wastewater
Wu Yin-Bao
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Received December 28, 2013,Revised April 29, 2014, Accepted April 30, 2014, Available online 2014-06-05
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The effects of antibiotic residues on methane production in anaerobic digestion are commonly studied by using the following two antibiotic addition methods: (i) adding manure from animals that consume a diet containing antibiotics, (ii) adding antibiotic-free animal manure spiked with antibiotics. No publications have been found that simultaneously compare different antibiotic addition methods in anaerobic digestion. This study used chlortetracycline (CTC) as a model antibiotic to examine the effects of the antibiotic addition method on methane production in anaerobic digestion under two different swine wastewater concentrations (0.55 and 0.22 mg CTC/g dry manure). The results showed that the CTC degradation rate in which manure was directly added at 0.55 mg CTC/g (HSPIKE treatment) was lower than the control values and the rest of the treatment groups. Methane production from the HSPIKE treatment was reduced (P<0.05) by approximately 12% during the whole experimental period and approximately 15% during the first 7 days. The treatments had no significant effect on the pH and chemical oxygen demand value of the digesters, and the total nitrogen of the 0.55 mg CTC/kg manure collected from mediated swine (HMED) was significantly higher than the other values. Therefore, the different methane production under different antibiotic addition methods might be explained by the microbial activity and the concentrations of antibiotic intermediate products and metabolites. Because the primary entry route of veterinary antibiotics into an anaerobic digester is by contaminated animal manure, the most appropriate method for studying antibiotic residue effects on methane production may be by using manure from animals that are given a particular antibiotic, rather than by adding the antibiotic directly to the anaerobic digester.
