Microbiologically induced corrosion of copper pipes in low-pH water

The aim of this paper was to study the influence of microbial biofilms on the high copper levels measured in the drinking water of rural houses. Drinking water parameters and copper pipe surfaces were analysed in the copper plumbing systems of rural and urban houses. The water in rural houses had pH values of 6.2 and alkalinity values of 63 mg/L as CaCO₃, whereas in urban houses the pH values were 6.9 with alkalinity values of 98 mg/L as CaCO₃. The stagnant water of rural houses contained more than 5 mg/L of soluble copper in comparison with just 0.4 mg/L in urban houses. The inner surface of copper pipes in rural houses showed very porous deposit of malachite and cuprite along with extracellular polymeric substances, rod-shaped microorganisms, and pits. A bacterial strain identified as Variovorax sp. was isolated from bacterial biofilms. In contrast, the copper pipes of urban houses did not contain bacterial biofilms, the deposit of malachite and cuprite were homogenous and showed uniform attack. The existence of bacterial biofilms along with the aggressive water quality could contribute to the increase of the copper by-product release to water and to the formation of pits on copper pipe surfaces.