Makueni County borders Machakos, Kitui, Taita-Taveta and Kajiado Counties. This area falls in south -eastern Kenya, a semi-arid region characterised by erratic rainfall and inadequate surface water from a few rivers. Groundwater, an option to surface water, occurs in the basement complex terrain of this study area which is highly influenced by secondary porosity bed rocks and recent volcanic activity on the Chyulu hills. However, the quality of groundwater at most locations is not fit for human and livestock consumption. Raw water from two boreholes, Kithunzi and Makindu, was tested using the American Public Health Association (APHA) procedures and found to have high levels of iron (> 5.00 Mg/L) with concentration of Manganese being greater than 0.3 Mg/L. The water was passed through a non-motorized aeration/filtration system comprising of a raised platform made of timber and plastic components designed to increase the contact between air and water in a water-to-air process. Several samples were collected from feed water, after aeration, after filtration (filtrate) and after twenty four. For Kithunzi iron reduced from an average of 5.9 Mg/L to 2.34.Mg/L a drop of 61 %. Similarly for Makindu, iron ions reduced by 56.9 % from an average of 5.72 Mg/L to an average of 2.81 Mg/L. Manganese levels also reduced by an average of 36.4 % and 20 % for the two boreholes respectively. Non – motorized aeration /filtration unit can be used to improve groundwater quality.