Development for Arsenic Removal using Iron Reducing Bacteria in Ground Water

IRB法去除铁、锰、砷和氨的实验于2006年在京都木子市净水厂和兵库县川西市防洪土工现场开始。两个地点的砷浓度分别为木子市19.3 mg/L和林川西市218 mg/L。在木谷市以150m/d ~ 600m /d不同的渗流速度进行试验，结果表明铁、锰、砷的去除率在72% ~ 98%左右。在川西市以500m/d的渗滤速度进行试验，铁去除率达75%，砷去除率达59%，但锰去除率不稳定。根据Spring-8的XAFS分析，As（III）和被氧化为As(V)的As（III）首先在IRB附近被吸附，吸附的As（III）逐渐被氧化为As(V)。这意味着这一结果推翻了人们所接受的砷在氧化后被吸附的观点。2007年在木子市继续进行了第一阶段和第二阶段的试验。两个阶段的铁去除率均在90%以上且稳定。第二阶段的砷去除率约为60%，优于第一阶段。锰在两个阶段都没有被去除。第二阶段的氨硝化效果优于第一阶段。过滤介质和反洗频率的差异。第二阶段进行的小柱试验在50天后获得了锰的去除和氨的硝化效果。XAFS分析发现，活性IRB聚集体对As(V)的吸收率最高。活性IRB吸附As（III）及其聚集速度优于冻干IRB吸附As(V)及其聚集速度。

Experiments for IRB method to remove iron, manganese, arsenic and ammonia started at the water purification plant in Muko city, Kyoto and earth work site for flood control in Kawanishi city, Hyogo in 2006. Arsenic concentrations of both site are 19.3 mg/L in Muko city and 218 mg/Lin Kawanishi city. The experiment in Muko city was implemented with different percolation velocities as 150m/day to 600 m/day, and the result was around 72 to 98% removals of iron, manganese and arsenic. The experiment in Kawanishi city was implemented with 500m/day percolation velocity, and the result was 75% removal of iron, 59% removal of arsenic, however manganese removal was not stable. According to XAFS analysis at the Spring-8, As(III) and As(III) which was oxidized as As(V) was sorbed near IRB at first, and sorbed As(III) was gradually oxidized to As(V). It means that this result disproves accepted notion (arsenic was sorbed after oxidation.).The experiment in Muko city was continued as first stage and second stage in 2007. Iron removals of both stage were more than 90% and stable. Arsenic removal was around 60% in second stage better than first stage. Manganese was not removed in both stages. Ammonia nitrification in second stage was better than first stage. It seems that differences of filter media and back-washing frequency. Small column tests implemented in second stage got a result removal of manganese and nitrification of ammonia after 50 days. XAFS analysis found living IRB aggregation was the highest sorption of As(V). And As(III) sorption and its velocity of living IRB aggregation was better than As(V) sorption and its velocity of freeze-dried IRB aggregation.