Utilization of bamboo biochar in the removal of heavy metals from wastewater stabilization ponds effluent (Kenya)

Rapid population growth and expansion of industries have led to increase in the presence of heavy metals in wastewater. Irregular discharge of such wastewater with little or no treatment has been rampant in developing countries. Exposure to heavy metals has been associated with stunted growth and development, acute and chronic respiratory effects, cancerous effects, autoimmunity and even death. Technological solutions for heavy metal removal that are affordable, environmentally benign, and simple to use are needed to address these issues. The objective of this study was to determine the potential of two differently modified bamboo biochars in removal of selected heavy metals from wastewater stabilization ponds effluent in Embu town, Kenya. Physically activated preparation of biochar involved pyrolysis hourly at 250 ^oC, then at 350 ^oC, and finally at 500 ^oC (AC). The second one was chemically activated using potassium hydroxide pellets in the ratio of 2:1 (bamboo: potassium hydroxide) and then physically activated (AC+KOH). Both biochars’ moisture content, volatile matter content, iodine number, ash content and carbon yield were characterized and resulted to 3%, 82%, 62mg/g, 13.5% and 11.9% for AC and AC+KOH 7%, 91.5%, 259mg/g, 11% and 13.4% respectively. Atomic absorption spectrophotometer analysis of Pb2+, Cd2+, and Cu2+ ions in the WSPs effluents was conducted during the rainy and dry seasons. Microsoft Excel, SPSS version 26 and R studio were used for statistical analysis. Mean concentrations ranged from 0 to 0.355 ppm, 0.004 ppm, and 0.097 ppm, respectively as opposed to the National Environmental Management Authority, 2006, allowable discharge into public water of 0.01 ppm, 0.01 ppm, and 1 ppm for Pb2+, Cd2+, and Cu2+ ions respectively. The lead removal effectiveness of treating polluted effluents with the AC ranged from 86% to 100%, whereas treatments using AC+KOH showed 72% to 90%. There was a significant difference, (p=0.047 < 0.05 between the differently modified bamboo biochar’s. The study concluded that bamboo biochar was effective in treating wastewater contaminated with heavy metal (Pb2+). Adoption of this green strategy would provide cheap, eco-friendly and safe technological sound alternative to conventional approaches.