Control of filamentous bulking and interactions among sulfur oxidation-reduction and iron oxidation-reduction in activated sludge using an iron coagulant

The effect of iron coagulant on control of filamentous bulking and phosphate removal was investigated using a laboratory scale activated sludge process. Sulfate reduction was correlated to activated sludge bulking. When FeCl2 was added to the aeration tank, most of the phosphate was removed. Sulfate reduction and filamentous bulking were also suppressed. The addition of FeCl2 was also effective in suppressing phosphate release and sulfide production from wasted sludge. Interactions among sulfur oxidation-reduction and iron oxidation-reduction were examined in the batch experiments. When FeCl2 was added, iron reducing bacteria outcompeted sulfate reducing bacteria and iron oxidizing bacteria grew predominantly.