A small-scale low-cost water treatment system for removal of selected heavy metals, bacteria and particles

Abstract

Abstract Two low-cost sand filtration systems incorporating granular activated carbon (GAC) and non-woven geotextile respectively were assessed for Point-of-Use water treatment. Laboratory scale models were evaluated in respect of selected heavy metals, bacterial and particulate removal when exposed to surface water for five months. System 1 (ISSF-1) incorporated GAC and system 2 (ISSF-2) incorporated non-woven geotextile. Filter-mats were placed on the filter surfaces of both systems. Flow rates ranged between 8 and 15 L/h for longer water contact with the GAC and bio-layer. On average, E.coli removals were 96% and 94%, while fecal coliform removals were 96% and 95%, by ISSF-1 and ISSF-2 respectively. Average TSS removals were 98% and 92%, while turbidity removals were 97% and 91%, by ISSF-1 and ISSF-2 respectively. Average metal removals were: Arsenic (21%), Cadmium (82%), Lead (36%), Iron (65%) and Manganese (94%) by ISSF-1, Arsenic (17%), Cadmium (<LoD), Lead (<LoD), Iron (92%) and Manganese (98%) by ISSF-2. Both models consistently met turbidity guideline (5 NTU) and can remove significant amounts of particles. Both systems can treat the poor-quality water used to provide relatively safe water and could be improved further for heavy metal removal. However, to guarantee continued safe-water supply, supplementary treatment by chlorination is recommended.