Anaerobic Degradation of Sulfate Laden Organics Employing Different Reactor System Configurations

Anaerobic degradation of sulfate laden organics has been investigated employing bench-scale models of an upflow anaerobic sludge blanket (UASB) reactor, anaerobic baffled reactor (ABR), and hybrid ABR (HABR). Results indicated chemical oxygen demand (COD) removal over 65% in all three systems at a COD/SO(2-)4 ratio of 8.57-8.59. However, the performance deteriorated at a low COD/SO(2-)4 ratio of 6.92-7.05 with a reduction in COD removal to 41-55%. Supplementation of limiting nutrients improved COD removal (~~94.5%) in an UASB system and indicated nutrient deficiency as a primary cause of poor performance. However, poor COD removal (45.92-56.12%) in ABR and HABR indicated a severe inhibition of microbial consortia by sulfide. This study revealed that system configuration aggravated the problem of sulfide toxicity due to sequential phase separation in ABR and HABR systems at low dissolved sulfide concentration relative to the UASB reactor, a single-phase system. Sulfate removal was over 88% in all three systems.