Neutralization of acidified water by use of Rhizopus delemar immobilized with a cellulose membrane

To solve serious environmental problems caused by the acidification of pond and lake water by acid rain, remediation methods must be used to keep water pH values neutral. In this study, a microbial method to neutralize acidified water was developed. The neutralization activities of 30 strains of bacteria, yeasts and fungi were measured with a medium adjusted to pH 3.0. Because fungi showed high neutralization properties, the Rhizopus delemar fungus was used to study the characteristics of acidified water neutralization. When R. delemar cells were cultured in a media acidified with nitric, sulfuric and hydrochloric acids, the cells neutralized acids by secreting basic compounds including ammonia. The cells also assimilated nitric acid. R. delemar was used to neutralize pond water adjusted to pH 4.0 with nitric acid. R. delemar cells increased the pH value of pond water from 4.0 to around 7.0 within 2 days, although indigenous microorganisms had not been able to neutralize the same pond water. In this study, R. delemar immobilized in a cellulose tube neutralized acidified water repeatedly by the draw-fill method.