Anaerobic biotrickling filter for the removal of volatile inorganic and organic compounds

Effluents from pulp and paper making industries are major contributors of methanol (CH3OH) and thiosulfate (S2O32-) contamination in waste streams which pose environmental challenges. CH3OH and S2O32-are biodegraded anaerobically by a consortia of microorganisms such as methanogenic archaea, homoacetogens and sulphur reducing bacteria (SRB), into CH4, volatile fatty acids (VFA), SO42-and H2S. This consortia of microorganisms, use CH3OH as both carbon source and electron donor, while S2O32-and SO42-are used as electron acceptors - in their metabolic reactions. A study was carried out to assess the biodegradation of CH3OH in the presence of S2O32-in a continuous anaerobic biotrickling filter (BTF). Two sets of batch experiments were conducted at COD/S2O32-and COD/SO42-ratio of 0.8, and COD/S2O32-and COD/SO42-ratio of 1.5 using S2O32-and SO42-individually as electron acceptors. CH4, VFA, SO42-and H2S produced in the BTF and batch experiments were monitored. The BTF was operated for 59 days in three phases determined by a stepwise increased inlet gas CH3OH concentration. Inlet CH3OH concentration in phase 1, 2 and 3 were 0.3 ± 0.07 g/m3, 0.6 ± 0.05 g/m3 and 0.9 ± 0.05 g/m3, respectively. Each phase consisted of cycles determined by a fresh dose of 1000 mg/L of S2O32-. At inlet CH3OH concentration of 0.3 ± 0.07 g/m3 and 0.6 ± 0.05 g/m3, the BTF achieved 100% removal efficiency of CH3OH, while 70% removal efficiency was attained at 0.9 ± 0.05 g/m3 inlet CH3OH concentration. An average of 1200 ± 360 mg/L acetic acid was produced throughout the three phases. Production of isovaleric and valeric acids was constant at 84 ± 7 mg/L and 37 ± 5 mg/L, respectively throughout the BTF operational time. CH4 production was not recorded in BTF. S2O32-was completely biodegraded in 4 days. CH3OH was 100% removed in batch experiment with COD/S2O32-and COD/SO42-ratio of 0.8 in 16 and 14 days respectively. For COD/S2O32-and COD/SO42-ratio of 1.5, 100% biodegradation of CH3OH was achieved in 28 days for both treatments with S2O32-and ...