Modelling the adsorption of iron and manganese by activated carbon from teak and shea charcoal for continuous low flow

•Proposing alternative methods of optimizing water treatment for small communities.•Activated carbon has alkaline properties that enhance iron and manganese adsorption.•Increased exhaustion time of activated carbon provides long filter run.•Activated carbon mass and grain size affect rate of iron and manganese adsorption.•Iron and manganese removal on point systems saves boreholes from being abandoned. Nearly 6494 boreholes with iron (Fe) and manganese (Mn) concentrations above permissible limits of 0.3 mg/L and 0.4 mg/L respectively in Ghana have been abandoned because of ineffective water treatment solutions. Activated carbon prepared from teak (Tectona grandis) and shea (Vitellaria paradoxa) charcoal (ACM), of effective grain sizes 0.075–0.2 mm and 0.2–2.0 mm was found to achieve 92.5–100% Fe and Mn removal in batch tests. The experiments, which were repeated for natural groundwater with a low flow similar to boreholes simulated with handpumps and limited mechanized water systems achieved similar Fe and Mn adsorption levels. Data on Fe and Mn adsorption for varying ACM mass and grain sizes, using fixed columns in continuous flow tests were fitted to Adam-Bohart, Thomas and Yoon-Nelson adsorption models to generate data for improvement in water treatment designs. The objective of this modelling process is to develop a prediction mechanism for ACM mass and grain size needed for the design of Fe and Mn removal plants for groundwater with various characteristics. Adsorption constants obtained for Yoon-Nelson; 0.3095 and Adams-Bohart; 0.07335 at R2 values of 0.9728 and 0.9841 respectively are appropriate for generating ACM mass needed, when the target contaminant is Fe and Mn