Phosphorus adsorption by naturally-occurring materials and industrial by-products

Low cost and effective phosphor us adsorbents are required for the treatment of small or decentralized wastewater systems. The goal of this study was to examine phosphorus adsorption on different low-cost media. Bone char and oven dried alum sludge had the highest Freundlich adsorption constants (K-d) of 1.031 and 0.484, respectively. Maximum adsorption density from the Langmuir isotherm plot was 0.674 mg P g(-1) for oven dried alum sludge and 1.787 for air dried alum sludge. PH levels at equilibrium were close to 7 for various dried alum sludge. Experiments conducted at 16 g/L of adsorbent on secondary municipal wastewater showed that all types of dried alum sludge and bone char were the most effective adsorbents of phosphorus. PH levels for oven and air dried sludge were in the range of 6.5-7, whereas the blast furnace slag and cement kiln dust exceeded a PH of 9. Consequently further work was recommended for water plant residuals.