Disposal of industrial waste liquids by evaporation and capillary storage in waste dumps

In semi-arid and arid regions the atmosphere has a considerable capacity to evaporate liquid industrial wastes such as brines. The evaporation capacity may be as high as 2000 mm/year, which means that 20 megalitres of liquid can potentially be evaporated per year per hectare. In the past, lined evaporation ponds were used to evaporate waste liquids. Recently, the tendency has been to spray-irrigate waste liquids over the surface of deposits of solid waste, eg landfills, ash dumps and mine waste dumps. To be environmentally acceptable, the rate of irrigation must be related to the overall water balance of the waste body, so that all waste liquid that infiltrates the waste is either re-evaporated or permanently held within the pores of the waste by capillarity. No liquid can be allowed to escape from the usually unlined base of the waste body to become a potential source of groundwater pollution. The paper will describe how to establish acceptable rates of irrigation as well as irrigation cycles. Also, how to establish the quantity of water it is possible safely to absorb in the waste body so that nothing will leach into the ground water even under the most adverse weather conditions.