There are various treatments to treat surface waters for domestic consumption efficiently. Among these processes coagulation is the best process to remove colloidal particles from the water. Aluminium sulphate is the most widely used coagulant in developing countries such as Kenya. The purpose of this study was to investigate the effectiveness of selected plant based materials as alternative materials in the coagulation of surface waters from River Kiu which provides water for the local residents around Maziwa Estate, Kahawa west through a local water project namely Kiamumbi water project. The materials chosen for this study were Moringa oleifera, Opuntia ficus indica and Aloe vera which were used to treat the water through a series of months from November 2018 through February 2019 by coagulation-flocculation and sedimentation processes using the jar test procedure. Experiments were conducted at various dosages o obtain the optimum dosages in terms of turbidity removal. Measurements of the pH, alkalinity and colour removal were also made. The results obtained from the measurements indicated that Moringa oleifera had the highest efficiency with the highest turbidity removal of 87.1% at 40-50 mg/l while Opuntia ficus indica had an average efficiency in terms of turbidity removal with the highest removal efficiency recorded at 46.2% at 15 mg/l. Aloe vera yielded the lowest removal efficiency with its highest turbidity removal efficiency at about 35% at 17% v/V solution. All materials fell short when compared to the turbidity removal efficiency observed when the water was treated by alum which was at 97.5% at an optimum dosage of 30-40 mg/l. All plant based coagulants showed little effect on the pH of the treated waters which remained relatively constant as compared to waters treated with alum which yielded a significant drop in the pH levels. The alkalinity levels of water treated by the biomaterials also remained relatively constant after application as compared to alum treated waters whose alkalinity dropped after dosage. Moringa oleifera showed the best results in the removal of colour whereas the aloe vera showed the poorest efficiency in terms of colour removal. The results showed that the biomaterials deserve more consideration as alternatives to alum in the coagulation process and makes recommendations on the application of the biomaterials synchronously as a blend with alum.