An investigation of inhibition effect of metronidazole before and after using advanced oxidation process (UV254/H2O2) on specific methanogenic activity of anaerobic biomass

Disposal of pharmaceutical compounds to environment as an emerging pollutants cause concerns significantly and it is necessary to use new methods of sewage treatment for removal of these compounds. The aim of this study was to investigate the inhibition effects of metronidazole before and after using UV254/H2O2 process on specific methanogenic activity of.anaerobic biomass. Fourteen anaerobic digestion tests were carried out at batch scale before and after using UV254/H2O2 process in 500 ml reactors with 30% anaerobic biomass and 70% substrate. The liquid displacement method was used. Duration of each test was in the range of 10-17 days. Cumulative Biomethane production in concentrations of 1, 5, 10, 25, 50, and 100 mg/l metronidazole was 34.04, 95.12, 100.86, 3.28, 27.88, and 6.97 ml respectively. This production was 800.73, 243.54, and 10.66 ml in concentrations of 25, 50, and 80 mg/l respectively using UV254/H2O2 process as pretreatment at 60 min retention time. Biomethane production in concentrations of 80,120, and 150 mg/l was 377.2, 380.48, and 63.14 ml respectively at 90 min retention time. Different concentrations of metronidazole had an inhibition effect on anaerobic digestions and therefore the efficient pretreatment method is needed to reduce this inhibition effect. The UV254/H2O2 process is an effective method for degradation and conversion of metronidazole to more biodegradable compounds for anaerobic bacteria consumption and, in turn, to increase biogasproduction in anaerobic digestions.