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.
