Treating Industrial Discharges by Thermophilic Sulfate Reduction Process with Molasses as Electron Donor

Abstract

Thermophilic sulfate reduction process with molasses as an electron donor was investigated for the removal of zinc from rayon industry wastewater. Sulfide rich effluent from the process was used to remove zinc as zinc sulfide precipitate. The investigations with sulfate reduction process were conducted with synthetic (Stage I) as well as real wastewater from Rayon industry (Stage II) as feed. The effect of feed COD: sulfate ratio, which is the key factor for operating the sulfate reduction process, was focused on in this study. The experimental results showed that the process could achieve a high sulfate conversion rate of about 7.22 ± 1.91 g SO₄ l⁻¹.d⁻¹ at COD: sulfate ratio of 1.5:1 and 7.20 ± 2.27 g SO₄ l⁻¹.d⁻¹ at COD: sulfate ratio of 3:1 during stage I and stage II, respectively. At the end of the operation of stage II, a maximum sulfide production of 496.2 mg S l⁻¹ was achieved at COD: sulfate ratio of 3:1. Furthermore, sulfide rich effluent from sulfate reduction process was used for zinc sulfide precipitation. The results showed that more than 95% of zinc was removed from a high sulfate-containing wastewater.

Keywords:

• SULFATE REDUCTION
• SULFIDE PRODUCTION
• MOLASSES
• RAYON INDUSTRY