Effect of iron hydroxide on the phosphate elimination during anaerobic digestion of active sludge

Addition of iron (III) hydroxide during methanogenic digestion of active sludge by anaerobic sludge displaying an iron-reducing activity resulted in a microbial reduction of iron (III) with formation of iron (II), capable of precipitating phosphates. Feasibility of eliminating 66.6 to 99.6% of dissolved phosphate at initial concentrations of 1000 to 3500 mg PO4(3-)/l by adding 6420 mg/l iron (III) hydroxide into a reactor for anaerobic fermentation of active sludge. The optimal ratio of iron (III) added to dissolved phosphate eliminated (mg) providing a 95% elimination amounted to 2:1. These results may be used in a new technology for anaerobic wastewater treatment with phosphate elimination.