Resumen
The excessive H2S presence in water and wastewater can lead to corrosion, toxicity, and biological processes inhibition?i.e., anaerobic digestion. Production of H2S can occur in psychrophilic conditions. Biological removal of HS- by addition of NO3- as an electron acceptor under psychrophilic (10 °C) conditions in a continuous flow experiment is evaluated here. Four different N/S molar ratios?0.35, 0.40, 0.60, and 1.30?were tested in an expanded granular sludge bed (EGSB) reactor. Samples were analyzed daily by ion chromatography. Efficient psychrophilic HS- removal with sulfur products oxidation control by NO3- supply is documented. The highest HS- removal was obtained at N/S = 0.35 and 1.30 (89.1 ± 2.2 and 89.6 ± 2.9%). Removal of HS- was less at mid-N/S with the lowest value (76.9 ± 2.6%) at N/S = 0.60. NO3- removal remained high for all N/S ratios. N/S molar ratio influenced the sulfur products distribution with less S0 and increase in SO42- effluent concentration with increasing N/S ratio. Oxidation of HS- and accumulated S0 occurred simultaneously at N/S ratios >0.35. The observations are explained by culture flexibility in utilizing available resources for energy gain.