SOLIDIFICATION AND NATURAL TREATMENT OF ARSENIC SLUDGE PRODUCED FROM

通过对4年来在孟加拉国安装的4台砂砾过滤器（GSF）的除砷性能进行研究，建立了砂砾过滤器（GSF）除砷装置的设计图。这些gsf是基于社区的单位，这些年来一直向村民提供砷安全的水。GSF由砾石罐和砂石罐组成。地下水中的砷通过与铁的共沉淀沉淀在砾石罐的砾石空隙中，铁在地下水中自然存在，浓度较高。地下水中的铁和砷首先在地下水进水口被氧化。曝气、铁与砷的接触、竞争离子作为磷酸盐的浓度是影响GSF性能的关键因素。本研究提出了这些点的设计方法。地下水中铁砷比为10时，矿粉的性能一般为ok。Fe /的比例应该,然而,大30与高浓度的phosphat地下水 ... e。盒子里充满了大量的使用铁钉进气槽中设置在确定的设计图表,当确定要安装在引用地下水少比30下磷酸的浓度就越高。GSF产生的砷污泥通过排水沉降到GSF城市内的污泥池中。污泥池的上清液流入人工池塘，进行砷的自然处理试验。污泥池的沉降是用水泥固化的。沉降物中90%的砷在未加水泥的情况下被挡出，但浸出试验砷浓度为0.05 ~ 0.65mg/L，超出了孟加拉国0.05mg/L的标准值。2%水泥掺量的浸出试验结果为0.05 ~ 0.11mg/L，低于日本土地污染第二标准0.30mg/L。试验pH值为10.5-10.9。这里的处理方法是将污泥沉降物与2%的水泥和不与水接触的沉积物混合，直到孟加拉国建立废物处理管理。对人工池塘底部的砷积累量进行了估算，并在池底土壤中寻找能使无机砷转化为有机砷的微生物。在污泥池和人工池塘中均检测到一定量的一甲基larsin （MMA）和二甲基larsin （DMA）。同时，证实了对砷有较强抵抗力的微生物，能在砷浓度为1000mg/L的条件下生存。少

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