Treatment and Use of Distillery Wastewater for Irrigation Purposes

Abstract

Distillery digester overflow (DOF) from sugar industries is a dark and high-strength wastewater containing recalcitrant melanoidins, which prevent light from passing through and spoil soil quality. This study investigated the exclusive removal of DOF colour through hydrogen peroxide (H2O2) oxidation, subsequently sutilising the clarified effluent for irrigating wheat and cotton under controlled pot conditions. Treatment of melanoidin with H2O2, used at concentrations up to 12–15% v/v, provided a high degree of colour decolourisation, which is in agreement with the results from other reports that sdecolourised 64-97% at neutral to alkaline pH. The H2O2-treated effluent was then applied at a fixed dilution to Triticum aestivum (wheat) and Gossypium hirsutum (cotton) plants. Key growth parameters (plant height, yield and tiller count) and soil properties, such as pH, electrical conductivity, K (potassium) and P (phosphorus), were sanalysed in detail. Compared to crops grown with untreated DOF irrigation, the plants of crops treated with H2O2-treated DOF showed significantly better growth characteristics: the height and grain yield of wheat plants were increased, and plant height and number of leaves of cotton plants were improved. Post-harvest soil analysis was conducted, which revealed improved soil fertility, especially for K and P requirements, in pots irrigated with the treated effluent. This approach has the dual advantage of conserving freshwater and increasing the nutrient content of soil. The One-Way Analysis of Variance (ANOVA) was used to statistically analyse soil data gathered in the experiment, in order to determine whether the differences between the irrigation treatments were significant. The results of the crops irrigated with the distillery effluent treated with H2O2 were found to be statistically significant (p<0.05), which clearly proved that the removal of melanoidin using oxidation had a positive effect on the growth of the plants and on the fertility of the soil.