The function of sulfate-reducing bacteria in corrosion of potable water mains

Growing awareness of the detrimental effect of corrosion in conjunction with bacterial activity in potable drinking water systems has led to an increase in research sponsored by water companies. In particular, sulfate-reducing bacteria (SRB), found in anaerobic conditions underneath the main corrosion shell, are noted for their effects in promoting localized corrosion. This study investigates the presence of sulfate-reducing bacteria in sampled water mains, in a region that would otherwise be expected to be stable, both by direct sampling, by using coupons in a Robbins device installed in the distribution network, and by sampling from laboratory tanks. Samples of pipes of various materials show a high frequency of SRB. Cast iron coupons from the Robbins device gave positive results for SRB after only 1 month in the distribution system, though negative for total viable count and coliforms. Corrosion rates of the coupons in the Robbins device increased in the presence of sulfate-reducing bacteria, indicating microbially induced corrosion. Laboratory coupon tests indicated no sulfate-reducing bacteria present.