Effect of Hydraulic Retention Time on the Performance and Cleaning Mechanisms of Coconut Biochar Filtration Systems for Wastewater Treatment

Abstract

Re-purposing wastewater is necessary to circumvent water shortage for vegetable farmers in urban areas and to reduce public health hazards associated with using contaminated water for irrigation. The study investigated the efficiency of 40 cm and 30 cm thick coconut biochar filtration systems in removing Cu, Pb, total coliform, and E. coli from wastewater at 24-, 48-, and 168-hour hydraulic retention times (HRT). Fourier Transform Infrared Spectroscopy analysis and Scanning Electron Microscopy imaging were used to characterise the biochar. Atomic Absorption Spectrophotometer (AAS) was used to analyse Cu and Pb while total coliform and E. coli were analysed using the incubation method. Characterization showed the properties of the biochar that enhances the removal of pollutants in wastewater. The optimal hydraulic retention time (HRT) was 168 hours, at which the biochar filtration systems achieved Pb removal efficiencies of up to 99.9%, Cu removal efficiencies of 100%, and Total Coliform removal efficiencies of up to 94.7%. However, the systems were ineffective in the removal of E. coli. This has implications for further research to explore double filtration systems for the removal of other parameters and emerging pollutants.