SOLIDIFICATION AND NATURAL TREATMENT OF ARSENIC SLUDGE PRODUCED FROM

通过对孟加拉安装的4个砂石滤池4年来的除砷性能的考察，建立了砂石滤池除砷装置的设计图。这些GSFF是以社区为基础的单位，这些年来为村民提供了不含砷的水。GSF由砾石槽和砂槽组成。地下水中的砷通过与铁共沉淀的方法沉淀在砾石罐的砾石空隙中，铁在浓度较高的地下水中自然存在，地下水中的铁和砷首先在GSF的进水池被氧化。曝气量、铁和砷的接触以及竞争离子作为磷酸盐的浓度是影响GSF性能的关键因素。本研究提出了这些智能交通工具的设计方法。在地下水中Fe/As比值为10的情况下，GSF的性能一般可以接受。对于含磷酸盐…浓度较高的地下水，Fe/As比值应大于30在GSF的设计图中，当GSF必须安装在磷酸盐浓度较高的地下水比小于30的城市时，在GSF的进水池中设置装满大量废铁钉的箱体。GSF产生的含砷污泥通过排水沉降到GSF城市安装的污泥池中。污泥池的上清液流入人工池塘，在那里进行砷的自然处理试验。污泥池的沉降量由水泥固化。在没有水泥的情况下，定居点中90%的砷被拒之门外，但浸出试验的砷浓度为0.05~0.65 mg/L，超过孟加拉国0.05 mg/L的标准。2%水泥混合料的淋溶试验结果为0.05~0.11 mg/L，低于日本土地污染二级标准0.30 mg/L，pH值为10.5~10.9。这里的处理方法是将污泥沉降与2%水泥混合，不接触水沉淀，直到孟加拉国建立废物处理管理。我们估计了人工池塘底部的砷积累量，并在底部土壤中寻找能将无机砷转化为有机砷的微生物。在污泥池和人工池塘中均能检出部分单甲基砷(MMA)和二甲基砷(DMA)。确定了一株能在含砷浓度为1000 mg/L以下的条件下存活的抗砷微生物。

We have established the design chart of the arsenic removal unit, Gravel Sand Filter (GSF), by examining the arsenic removal performance of 4 GSFs installed in Bangladesh these 4 years. These GSFs are community-based units and have supplied arsenic-safe water to villagers in these years. GSF is composed of gravel tanks and sand tank. The arsenic in groundwater is to be settled in the gravel voids of gravel tanks by co-precipitation with iron, which exits naturally in groundwater with higher concentration.The iron and arsenic in groundwater are first to be oxidized at the inlet tank of GSF. The aeration, contact between iron and arsenic, and the concentration of competition ions as phosphate are key points for the performance of GSF. The design methods for these poi its are proposed in this research. The performance of GSF is usually O.K with 10 value of ratio, Fe/As, in groundwater. The ratio of Fe/As should be, however, bigger 30 for the groundwater with high concentration of phosphat … More e. The box filled with large amount of used iron nails is to be set in the inlet tank in the design chart of GSF, when GSF has to be installed at the cite where the groundwater has less ratio of 30 under the higher concentration of phosphate.Arsenic sludge from GSF is to be settled in the sludge tank installed in the GSF cite through draining. The supernatant of the sludge tank is flowed to the artificial pond where the natural treatment of arsenic is examined. The settlement of the sludge tank is solidified by cement. The 90% of arsenic in the settlement is shut out without cement but the arsenic concentration of the leaching test was 0.05〜0.65mg/L, showing beyond values of standards 0.05mg/L in Bangladesh. The leaching tests for the 2% mixing of cement show 0.05〜0.11mg/L, which is less than the second standard for land contamination in Japan, 0.30mg/L..The pH of the tests shows 10.5-10.9.The treatment method, here, is to mix the sludge settlement with 2% cement and deposit without contact to water until the establishment of waste treatment management in Bangladesh.We have estimated the accumulation of arsenic at the bottom of the artificial pond and looked for the micro-organism in the bottom soil which can change the inorganic arsenic to organic one. We can detect some of Monomethylarsine(MMA) andDimethylarsine(DMA) in both of sludge tank and artificial pond. And, the micro-organism strong to arsenic was confirmed, which can live under the condition of arsenic concentration of 1000mg/L. Less