A new generation low-cost biochar-clay composite 'biscuit' ceramic filter for point-of-use water treatment

Approximately 600 million people, the bulk of them in developing countries, still lack access to safe drinking water. A short-term solution for the provision of safe drinking water at household level is the use of ceramic filters, which are cheap, safe, and robust. The aim of this study was to fabricate and evaluate a layered 'biscuit' ceramic filter for point-of-use drinking water treatment using locally available biomass and clays. The specific objectives were to: (1) fabricate and characterise the physico-chemical and pollutant retention properties of a ceramic filter, and (2) perform a preliminary evaluation of the performance of the ceramic filter in removing total hardness (TH), total dissolved solids (TDS), turbidity, and dissolved organic carbon (DOC) from water sampled before and after the sand filtration stage at a local water treatment plant (WTP). A biochar-clay composite ceramic filter (BCF) was fabricated from clay and sawdust, and the control (CF) from clay only. The BCF had a remarkable biochar layer sandwiched between two ceramic layers (i.e. 'biscuit' structure). To the best of our knowledge, the fabrication and application of a low-cost biochar-layered ceramic filter has not been reported in literature. The clay had the characteristic Bronsted and kaolinite functional groups, and the surface morphologies of the materials were heterogeneous, suitable for pollutant removal. Both filters were highly hydrophilic, although BCF was more hydrophilic than CF. The initial flow rate of the filters were 51 and 34 mL/min for BCF and CF, respectively. Overall, BCF was more effective in removing TH (42.5%), TDS (45.8%), and turbidity (67%) compared to CF (14.8, 17.6, and 56%, respectively), and its performance was comparable to the sand filtration stage of the WTP. The results demonstrated that a 'biscuit' ceramic filter is potentially effective for household-scale water treatment. However, further research should focus on increasing the permeate flow rate to more useful levels, functionalizing the biochar layer, and investigate the removal of toxic metals and specific organic pollutants.