The head space biogas composition
Sulfate presence in the environment can affect public water supplies and pose health threat to life forms (Speece, 1996). In the absence of dissolved oxygen and nitrate, sulfate acts as a source of oxygen or AUY922 acceptor and is converted to sulfide (H2S). This phenomenon creates odor and corrosion problems (Sawyer et al., 2003). The recommended upper concentration limit of sulfate in water intended for human consumption is 250 mg/L (Sawyer et al., 2003). Therefore, it is essential to treat sulfate rich wastewater prior to its discharge into the environment.
All chemicals and reagents used in this study were of analytical grade and were obtained from either Merck India Ltd. or Himedia India Ltd.
2.2. Collection of anaerobic sludge biomass from different sources
Anaerobic sludge biomass samples were collected from five different sources (Table 1). Among these five biomass samples, three were collected from large scale upflow anaerobic sludge blanket reactors treating domestic wastewater, whereas the other two biomass types were collected from a local wastewater treatment plant located in IIT Guwahati (IITG) and a lab scale packed bed anaerobic reactor treating sulfate rich wastewater, respectively. During the biomass sample collection, contact with air was avoided to ensure anaerobic condition. Following collection, the biomass samples were stored in a refrigerator at 4 °C until further use.