Effects of Iron Bacteria on Cast Iron Pipe Corrosion and Water Quality in Water Distribution Systems

The corrosion behavior of cast iron influenced by bacteria was studied in the presence of iron bacteria, with sterile water acting as a reference. The corrosion process and corrosion scales were characterized by electrochemical and surface analysis methods. The results indicated that iron bacteria favored the formation of corrosion products due to the microbial activity, hence inhibiting the corrosion process periodically. With the breaking off of corrosion products and biofilms, corrosion, cast iron surfaces become more susceptible to corrosion and show higher corrosion rate. In the sterile water, no significant changes in Ecorr were observed and the curve varied slightly whereas in the presence of iron bacteria, drastic changes of Ecorr occurred between -0.745V and -0.658V. The values of Rct under the abiotic condition were lower than those in the presence of iron bacteria due to the formation of a microcell with a small anode and a big cathode, indicating that iron bacteria play an important role in the corrosion process. Corrosion products formed with iron bacteria had a layered structure and heterogeneous distribution of floccules with different substances. Due to the metabolic activity, the growth and propagation of iron bacteria were closely related to the ferrous ion and dissolved oxygen concentration changes. Iron bacteria might lead to an increase of pH values and higher concentration of ferrous ion in bulk water.