Development for Arsenic Removal using Iron Reducing Bacteria in Ground Water

IRB法除铁、除锰、除砷、除氨的试验于2006年在京都牧古市的净水厂和兵库县川西市的防洪土方工地开始。目古市和川西市两个地点的砷浓度分别为19.3 mg/L和218 mg/林。在慕科市进行了不同渗流速度(150m/d~600m/d)的试验，结果表明，铁、锰、砷的去除效果约为72%~98%。在川西市进行了以500m/d的渗流速度进行的试验，结果除铁75%，除砷59%，但除锰不稳定。根据Spring-8的XAFS分析，As(III)和As(III)被氧化为As(V)后，首先在IRB附近被吸附，然后被吸附的As(III)逐渐被氧化为As(V)。这意味着这一结果推翻了公认的砷被氧化后被吸附的观念。2007年慕科市的实验继续分为第一阶段和第二阶段。两个阶段的除铁效果均在90%以上且稳定。第二阶段的除砷效果优于第一阶段，达到60%左右。在这两个阶段，锰都没有被去除。第二阶段氨氮硝化效果好于第一阶段。滤料的不同和反冲洗频率的不同似乎有一定的影响。第二阶段进行小柱试验，50d后除锰、硝化氨氮。XAFS分析发现，活体IRB聚集是As(V)的最高吸附。活体IRB对As(III)的吸附及其聚集速度优于冻干IRB对As(V)的吸附及其聚集速度。

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.