Effect of adding phosphate to drinking water on bacterial growth in slightly and highly corroded pipes

The effect of phosphate addition in drinking water was tested under static conditions as batch tests and under dynamic conditions using continuously f ed reactors. Phosphate supplements in batch rests from 0.1 to 2 mgP-PO4 L-1 did not show any relationship between bacterial growth and phosphate conce ntration. Dynamic tests in slightly corroded reactor (stainless steel) trea ted at 1 mg P-PO4L-1 showed only a moderate improvement in the growth of mi croorganisms. On the contrary, phosphate treatment applied to the highly co rroded reactor (unlined cast iron) led to an immediate, drastic drop in iro n oxide release and bacterial production. Phosphate uptake by the reactor w all was less than 14% with the stainless-steel reactor and 70-90% with the corroded cast iron reactor. Moreover, about 5% of the phosphate associated to corroded iron pipe wens was released for 20 days after the end of treatm ent. (C) 2001 Elsevier Science Ltd. All rights reserved.