Using Lime Treated Acid Mine Water for Irrigation

The disposal of acid sulphate mine water poses a universal problem. Although water quality is much improved when neutralised by lime treatment high salt loads nevertheless make release to better quality surface streams undesirable. The feasibility of using such water for irrigation was evaluated using a steady state chemical equilibrium model to predict the composition of water draining from successive soil segments under a range of leaching fractions. Large amounts of gypsum are expected to precipitate in the soil profile resulting in a greater reduction in salinity than would occur if the water contained chloride instead of sulphate. A comparatively smaller reduction in crop yields can thus be expected and a greater variety of the marginally salt sensitive crops can be grown. The precipitation of gypsum however results in an increased sodium hazard to soil physical properties. This does not appear serious when evaluated against published data on soil hydraulic conductivity as affected by sodium and electrolyte concentration. A drastic reduction in the salt load in drainage from irrigated land compared to that in the applied water is predicted. Irrigation with lime treated acid mine water does not only seem feasible but also advantageous for the protection of water resources from mineral pollution.