effects of antibiotics on specific methanogenic activity of anaerobic biomass

background: the antibiotics are excreted after their effect on the host body and together with other waste disposal are entered the treatment plant processes. antibiotics prevent the biological sewage treatment in the plant which consequently causes hazards to the environmental and human health. the purpose of this study was to investigate the effect of some popular antibiotics used by human and livestock on the anaerobic wastewater treatment process. methods: to evaluate the inhibitory effect of the antibiotics on biomass activity, particularly methane production (specific methanogenic activity; sma) using anaerobic biomass batch, the 90ml vials were filled by 15 percent volume and 70 mg biomass l substrate including volatile fatty acids, mainly acetic acid, or glucose and then various concentrations of antibiotics were added including amoxicillin, tetracycline and tylosin.  to provide the optimum temperature of 35 ° c in vials the hot water bath was used, and to mix the contents of the vial fully, the magnetic mixer was used. the methane gas produced was measured through its replacement with koh 2 n solution as co2 absorber and bromine thymol blue as indicator. each batch lasted for 10 days. cod tests were carried out before and after each test on the samples. findings: based on the findings of each batch, oxy tetracycline, amoxicillin and tylosin in 8000, 9000 and 9000 mg/ l concentrations, respectively, had a complete inhibitory effect on the specific methanogenic activity of anaerobic biomass. conclusion: the results of this study indicated that by increasing the antibiotics concentrations, the produced biogas volume as per biomass weight per unit is decreased. on the other hand, cod removal was 42% to 82%  due to long retention time and the groups adsorption.