To supply safe water to the arsenic affected community, an arsenic removal unit, gravel sand filter (GSF), was developed by modifying the pond sand filter (PSF) so that it can be used to overcome the dry season low flow problem of it. Performance data of that arsenic removal unit shows that it can be the most suitable option to solve that problem of the PSF. GSF uses the naturally occurring iron to remove arsenic by coprecipitation. In this process it produces arsenic rich iron sludge. Disposal of this sludge to the nature may pose a risk of secondary contamination to the stratum. Leaching tests of the arsenic rich iron sludge and the solidified sludge with cement indicates that arsenic leaching ratio of sludge ranges between 3 and 13 % and that of cement stabilized sludge is between 1 and 6 %. This means that the arsenic has a strong bond with the iron sludge and its treatment may not be difficult.