Treating rice mill effluent using waste rice hull

Abstract

In Sri Lanka, about 95% of the population consume rice as their staple food. The increase of the population leads to an increment of the number of rice mills to meet the demand. This resulted in the generation of huge volumes of waste rice hull and effluent. Rice mill effluent contains high concentration of organics, inorganics and nutrients (especially nitrates and phosphates). The direct discharge of these effluents to the environment causes several environmental impacts. The standards and criteria for the discharge of industrial effluents set by the Central Environmental Authority (CEA) emphasizes the need of a proper wastewater treatment system for rice mills industries. The use of conventional treatment technologies in treating industrial wastewater has been extensively studied in previous researches. However, the recent researches focused on the development of nonconventional and low-cost adsorbents due to natural abundance, locally obtainable and nontoxicity. Several researchers have found that the modified rice husk can be effectively used for the removal of heavy metals. However, the researches on the utilization of rice husk to treat rice mill wastewater, in terms of removing organics and nutrients, are not extensively studied. Therefore, the aim of this study was to evaluate the performance of waste rice husk in removing organics and nutrients from rice mill effluent.