Microbial sulfate reduction at low (8 degrees C) temperature using waste sludge as a carbon and seed source

Biological treatment of sulfate and metal-containing wastewater (such as acid mine drainage) is a viable option due to lower cost and better sludge quality compared to conventional chemical treatment. Although several substrates can be used as carbon source, a low-cost substrate is required for large scale applications. This study was conducted to investigate the suitability of waste sludge as a carbon and seed source for sulfate reduction at 8 degrees C in batch bioassays. Around 7 mmol of sulfate was reduced when the waste sludge mixture (WS) (6700 mg SS l(-1)) from primary and secondary settling tank was supplemented as a carbon and seed source. However, only 1.6 mmol of sulfate was reduced with anaerobic digester effluent (ADS) (5300 mg 55 l(-1)). The produced H(2)S from 1 g VSS l(-1) WS and ADS oxidation can theoretically precipitate around 90 and 35 mg Fe(2+), respectively. Both WS and ADS oxidized ethanol to acetate at similar rates. It appears that WS is a good candidate for carbon and start-up seed source of sulfate reduction at 8 degrees C, whereas sulfidogenic acetate oxidation was the limiting step. Denaturing gradient gel electrophoresis (DGGE) analysis of 16S rRNA genes showed that both sludge sources contain Desulfomicrobium apsheronum strain. (C) 2008 Elsevier Ltd. All rights reserved.