Removal of Selected Heavy Metals from the Water of the River Sosiani in Uasin Gishu County Using Cynodon dactylon (Couch Grass)

Abstract

The management of heavy metal pollution in rivers is a growing concern due to the rapid pace of industrialization and urbanization. Rivers are especially susceptible to heavy metal contamination due to various human activities, such as industrial processes, agricultural runoff, mining operations and improper waste disposal. Several studies in Kenya have documented the alarming presence of elevated heavy metal levels in various rivers, raising concerns about environmental and public health impacts. A variety of methods and techniques have been developed and implemented to remove heavy metals from contaminated water however, several of these techniques are expensive. The potential of plants to serve as a bio adsorbent offers a sustainable solution for addressing heavy metal pollution in rivers. This research therefore investigated the efficacy of modified Cynodon dactylon grass as an adsorbent for removing lead (Pb²⁺), manganese (Mn²⁺), cadmium (Cd²⁺) and chromium (Cr⁶⁺) ions from Sosiani River water. Water samples were collected from three purposively selected sites along the Sosiani River in Uasin Gishu County, Kenya and the mean heavy metal concentrations were analysed using Atomic Absorption Spectroscopy (AAS). The batch adsorption experiments were conducted in triplicates for untreated and treated grass. The study also examined the impact of pH levels on adsorption by testing at pH levels of 5, 7 and 9. Data was coded into SPSS software version 20 and analysed using descriptive and inferential statistics. The results indicate that the mean concentration of Cr⁶⁺ and Pb²⁺ in the water samples were 1.49 mg/L and 1.61 mg/L respectively. Both metals ions exceeding the NEMA guideline. However, the concentration of Cd²⁺ and Mn²⁺ was found to be 0.002 mg/L and 0.05 mg/L which is below the NEMA recommended level. Further, the heavy metal concentrations in Sosiani River water samples varied significantly (p<0.05) across different locations. Also, the chemically treated Cyanodon dactylon grass exhibited a higher percentage of adsorption across all tested heavy metals compared to the untreated Cyanodonat pH 5 compared to pH 9. These findings demonstrate the potential of Cynodon dactylon grass as an effective and more accessible alternative for river water purification. Further research is needed to optimize the conditions and modifications for enhanced adsorption performance. dactylon grass. Lastly, there was a higher adsorption efficiency for treated adsorbent