Disposal of the arsenic-contaminated coagulation sludge from the Coagulation/Filtration and Lime Softening technologies may be a concern. For large treatment plants, a large body of water would likely be needed to discharge the contaminated brine stream from the Reverse Osmosis/Nano-Filtration technologies. Inland treatment plants would possibly need either some pretreatment prior to discharge or would need to discharge to the sanitary sewer due to the increase in salinity. Discharge to sanitary sewers may require pretreatment to remove high arsenic levels. The waste stream produced by Ion Exchange (IE)/Activated Alumina (AA) technologies is a highly concentrated brine with high Total Dissolved Solid. These brine streams may required some pretreatment prior to discharge to either a receiving body of water or the sanitary sewer.
Low Cost Tech:
Regeneration of AA columns results in a toxic waste containing very high concentration of soluble arsenic. The effluent of acid rinses is mixed with the caustic rinses and this mixed arsenic waste can then be disposed on a prepared bed of cowdung in a shallow hole dug in earth. The micro-organisms in cowdung transform the arsenic to gaseous arsine and arsenic is thus released into the surrounding air.