Effect of Iron Ion on Activated Sludge, 2000 Environmental Conference Proceedings

- Y. Zhang, P. Hynninen -- This study was conducted in order to determine the effect that introduced iron has on the treatment efficiency of activated sludge systems, and also to establish the upper limit of Fe concentration detrimental to micro-organisms. Fe ion concentrations of 0.0, 5, 10, 20, 30, 50, and 80 mg/l were introduced individually to 7 laboratory activated sludge systems. The settleability of sludge, dissolved and total COD, MLSS, ash content, SVI, surface charge, and the dissolved oxygen contents were measured. The study shows that introduced Fe improves the settleability of activated sludge; reduces sludge bulking problems; improves the treatment efficiency in concentrations up to 30 mg Fe/l, while overdosing decreases COD removal; causes the surface charge of the activated sludge particles to be slightly less negative, while increasing amounts of Fe produces sludge with poorer dewaterability; and also increases the rate of metabolism of activated sludge.