Growth Characteristics and Control of Iron Bacteria on Cast Iron in Drinking Water Distribution Systems

This study investigated the growth characteristics of iron bacteria on cast iron and relationship between suspended and attached iron bacteria.The steady-state growth of iron bacteria would need 12 d and iron bacteria level in effluents increased 1 lg.Hydraulics influence on iron bacteria level and detachment rate of steady-state attached iron bacteria was not significant.But it could affect the time of attached iron bacteria on cast-iron coupons reaching to steady state.When the chlorine residual was 0.3(mg/L),the iron bacteria growth could be controlled effectively and suspended and attached iron bacteria levels both decreased 1 lg.When the chlorine residual was more than 1.0(mg/L),it could not inactivate the iron bacteria of internal corrosion scale yet.There was little effect on inhibiting the iron bacteria growth that the chlorine residual was 0.05(mg/L) in drinking water quality standard of China.The iron bacteria on coupons reached to steady state without disinfectant and then increased the chlorine residual to 1.25(mg/L),the attached iron bacteria level could decrease 2 lg to 3 lg.Under steady-state,the suspended iron bacteria levels were linearly dependent on the attached iron bacteria.The control of iron bacteria in drinking water distribution systems was advanced: maintaining the chlorine residual(0.3(mg/L)),flushing the pipeline with high dosage disinfectant,adopting corrosion-resistant pipe materials and renovating the old pipe loop.