Effects of Chemical Oxygen Demand, Nutrients and Salinity on Sulfate-Reducing Bacteria

“As a result of seawater intrusion in sewer systems or due to seawater toilet flushing, domestic wastewater may contain significant amounts of sulfate, which might lead to sulfate reducing bacteria (SRB) activity. Because of the low biomass sludge-yield of SRB, application of SRB is beneficial for reduction of sludge treatment costs. Moreover, the produced sulfide helps to remove heavy metals from treated water. In this study, short-term (6 h) effect on sulfate reduction rate of chemical oxygen demand (COD), N, P, SO42−, and salinity variations, far beyond (10-fold) the regular concentrations in municipal wastewater, was investigated. Increased propionate levels (>1,000 mg COD/L) have shown to reduce sulfate reduction rate, while acetate up to 4,000 mg COD/L did not. Nitrate became inhibitory at levels higher than 500 mg N/L, due to formation of nitrite (<10 mg N/L). Higher concentrations of ammonium and phosphate did not lead to a change in the sulfate reduction rate. Increased salinity decreased sulfate reduction rate by 41%. Batch tests with separate sulfate or NaCl elevation demonstrated that the inhibition of increased seawater portion of the sewage was mainly caused by increase of NaCl. The inhibitory effect of salinity on the sulfate reduction rate reduced after an adaptation period (months) of the biomass to higher salinity. Assuming the minor effect of COD (400 mg/L), N (100 mg/L), and P (10 mg/L) in ranges typical for domestic wastewater, and adaptation to higher salinities, SRB can be applied successfully for the treatment of saline wastewater." (Citaat: Brand, T.P.H. van den, Roest, K., et al. - Effects of chemical oxygen demand, nutrients and salinity on sulfate-reducing bacteria - Environmental Engineering Science 32(2015)10, p.858-864)