Anaerobic degradation of organic pollutants in high saline wastewater with the aid of halophilic methanogens

This research was designed to investigate the potential use of halophilic methanogens from a saline environment. Three groups of bacteria, halophilic methanogens, digester sludge and mixed cultures of halophilic methanogens and digester sludge in the ratio of 1:2 were used in this study. The effects of various sodium chloride concentrations including trace metals and betaine on the cultures were tested in batch experiments. The impact of sodium chloride was determined by using lag period and specific methanogenic activity.; At 35°C, halophilic methanogens had the ability to function in a broad range of sodium concentrations. The highest initial and maximum specific methanogenic activity (SMA) was found in salt concentrations of 30–35 and 20 g/L, respectively. Lower or higher salt concentrations than these caused reduced SMA. The shortest lag period of halophilic methanogens was also found in these salt concentrations. There was no significant difference of initial SMA of the mixed culture at any of the salt concentrations used in this research.; Betaine was found to be an excellent compatible solute in this research. The initial and maximum SMA was increased for all three bacterial cultures (halophilic, mixed, and digester sludge) and the lag period was decreased for digester sludge and mixed culture, when 5 to 10 mMol betaine was added to the system.; Experimental results were used to estimate Monod parameters (both the maximum substrate utilization rate, k, and the half velocity coefficient, Ks). The effect of sodium inhibition on the cultures was determined by a linear inhibition model. The toxicity of salt in halophilic methanogens and mixed cultures was classified as noncompetitive inhibition. The kinetic values of digester sludge did not fit into any of the linear inhibition models.; The feasibility of using anaerobic filter reactors containing halophilic methanogens and mixed culture to treat organic pollutants in high salinity was examined at 35°C. Both halophilic and mixed culture anaerobic filter reactors were able to operate at the high salt concentration of 35 g/L for organic loading rates of 6.2 and 5 kg COD/m3·d, respectively. Chemical oxygen demand (COD) removal efficiency was as high as 80% and the systems were able to maintain a low volatile fatty acids (VFA) concentration of 500 mg/L. Higher salt or higher organic loading rates caused system imbalance. Increasing the salt concentration to 37 g/L at an organic loading rate of 3 kg/m3·d caused system failure. (Abstract shortened by UMI.)...