Evaluating wood ash as a low-cost disinfectant for faecal and total coliform removal in bathroom greywater from Low-income communities in Zimbabwe

ABSTRACT This study evaluated the effectiveness of wood ash as a low-cost and sustainable disinfectant for treating bathroom greywater in a low-income community without improved sewer or sanitation infrastructure. The key objective was to assess the capacity of wood ash to inactivate total and faecal coliforms, with a focus on identifying the optimal dosage and disinfection time. A 1:20 wood-ash-to-greywater ratio was determined through titration and applied in all treatments. Greywater samples were incubated and analysed at hourly intervals over a 4-hour period, with changes in pH, total coliforms and faecal coliforms recorded. The pH of the treated water increased from 7.19 to a maximum of 11.89. Maximum disinfection occurred within 2 hours, with over 95% reduction in total and faecal coliforms. A strong correlation (r = 0.895) between total and faecal coliform reduction was established, confirming the efficacy of wood ash. Statistical analyses, including analysis of variance (ANOVA), validated the significance of the observed reductions at p < 0.05. This study supports the use of locally available wood ash as an affordable disinfection option in resource-constrained settings, offering a potential solution for decentralized greywater management.