Effects of using arsenic-iron sludge in brick making

Abstract

Arsenic-iron treatment plants generate huge amount of sludge. The aeeumulation of these materials is not only burden to the treatment plant but also affects the environment adversely. Therefore, development of new teehnologies to reeycle and convert waste into reusable materials is critically important for protection of environment and sustainable development of society. There is a strong demand for environmentally safe reuse and effective disposal methods of iron and arsenic contaminated sludgc out of water treatment plant duc to thc increasing amount of sludge generated by the water treatment plants in Bangladesh. A possible long-term solution appears to be recycling of the sludge and using it for beneficial purposes. Thc study work has been performed to study and analyse the effects of using arsenic-iron sludge in making of bricks. Leaching of arsenic li'om brick manufactured out of arscnic-iron sludge was investigated with a view to assessing its environment quality. TCLI' tcst of sludge indicated that leaching of arsenic from sludge is more than that of burnt bricks. Increasing the firing temperature resulted in decrease in leaching of arscnic. Howcver. leachate concentrations of bricks manufactured at varying temperature indicate it to be independent of temperature and mix proportion. As leachate from arsenic laden sludge out of Column Leaching method reflects values higher than 5 mg/L; as such indicates it to be toxic waste. The results of compressive strength tests on the bricks indicate that the strength is greatly dependent on the amount of sludge in the brick and the firing temperature. The optimum amount of sludge that could be mixed with clay to produce good bonding of bricks was 15% by weight firing at IOOO°C. The recommended proportion of sludge in brick making is 15% to 25% by weight and fired at IOOOoCto l0500C to produce a good quality brick. It was revealed that addition of sludge up to 25% by weight retain the original characteristics of normal clay bricks. further, leaching of arsenic is largely reduced when sludge mix is burnt at high temperature in the brick making process.