Impact of Iron Salt Dosage to Sewers on Downstream Anaerobic Sludge Digesters: Sulfide Control and Methane Production

Abstract

The addition of iron salts to sewers for sulfide control has a significant impact on downstream wastewater-treatment performance, in which iron ions can be resolubilized from iron sulfide precipitates in aeration tanks to precipitate phosphate, thus enhancing phosphorus removal from the wastewater. In this study, the impact of iron salt dosage to sewers on the performance of anaerobic sludge digesters was investigated at bench scale. Anaerobic digesters were fed with mixed primary sludge, activated sludge, and sludge that contained ferric phosphate precipitates, formed by aerating iron sulfide- and phosphate-containing wastewater with activated sludge. In anaerobic conditions, ferric ions were released from ferric phosphate precipitates and utilized for a third time to precipitate sulfide that formed during sludge digestion, which ultimately resulted in complete control of