Corrosion inhibition of iron pipes in drinking water distribution systems by a nitrate-reducing bacterium with varied nitrate concentrations

Iron pipe corrosion is the main reason of secondary pollution of drinking water, and nitrate -reducing bacteria (NRB) are considered as corrosion-related bacteria. However, the corrosion inhibition effects of NRB are not well publicized, and the inhibition mechanisms have not been well-understood. In this study, the corrosion inhibition of NRB (Pseudomonas monteilii CS01, a common nitrate-reducing bacterium) under drinking water conditions was investigated with varied nitrate supplements. Bench-scale reactors were employed to study the iron and nitrate transformation induced by NRB CS01. Four experimental groups were designed under differ-ent conditions. The characteristics of corrosion products and corrosion process were determined by physico-chemical analysis and weight loss method, respectively. The iron corrosion/release inhibition induced by CS01 was enhanced with the increase of initial nitrate levels. With NRB CS01 and 20.00 mg/L NO3--N, the corrosion rate and concentrations of total iron and Fe2+ were the lowest, with values of 0.036 +/- 0.003 mm/y (at 170 d), 2.30 +/- 1.25 mg/L and 0.19 +/- 0.15 mg/L, respectively. Moreover, the consumption of nitrate and the production of nitrite and ammonium were the highest under this condition. This study may be beneficial for developing the potential strategies for improving drinking water quality and water supply safety.