Use of activated carbon from rice husks as a filter medium in treatment of greywater

Abstract

Decentralized grey water treatment in institutions using low-cost and robust technologies offers opportunities to minimize public health risks and to reduce environmental pollution caused by the highly polluted grey water i.e. with a COD and N concentration of 3000-6000 mg L-1 and 3040 mg L-1, respectively. However, grey water usually receives the least attention compared to other environmental aspects like solid waste and black water, particularly in low and medium income countries where it is often discharged untreated into storm water drains and if they exist, sewers. In addition, management and treatment of greywater produced from institutions like schools, hospitals has not been studied extensively and only a few investigations are reported in literature. The objective of this study, therefore, was to suggest a highly carbonaceous agricultural waste which is readily available to prepare granular activated carbon for treatment technology of grey water from a school. Two column filter units were designed and implemented for use. Filter column 1 consisted of only an activated carbon bed while filter column 2 consisted of gravel, sand and activated carbon beds. The gravel and sand were to act as pre-treatment or physical strainers for the grey water. They were monitored at a hydraulic loading rate (HLR) of 10m/h. The removal efficiencies of COD, TP and TN were 13.16%, 55% and 21.88% respectively for filter column 1 and 20.7%, 75% and 26.04% respectively for filter column 2. In addition, the removal efficiency of coliforms for filter column 1 and filter column 2 were 8% and 15% respectively. The results show that activated carbon made from rice husks can be used as a filter medium in the treatment of grey water. Further research is needed to investigate the feasibility of adding a tertiary treatment step to increase the nutrients and microorganisms removal from grey water.