Impacts of pipe materials on densities of fixed bacterial biomass in a drinking water distribution system

Densities of fixed bacterial biomass were measured on different pipe materials (PVC, PE, cemented steel, asbestos-cement, cemented cast iron, tarred steel and grey iron) incubated in drinking waters from different sources (ground waters and a surface water) which had different characteristics (temperature, concentration of residual oxidant and content of biodegradable organic matter). Results showed that the densities of bacterial biomass fixed on plastic-based materials (PE and PVC) were the lowest. Densities of bacterial biomass fixed on gray iron were from 10 to 45 times higher than those measured on plastic-based materials. Cement-based materials had intermediate values. Pairs of cement and PVC coupons were incubated at 15 different locations in a distribution system, and there was a strong correlation between the amount of fixed bacterial biomass on these coupons, with the cement containing 2.6 times more biomass.