Biological treatment of hazardous biomedical waste ash - A sustainable approach

Abstract

Solids, liquids, sharps, and laboratory waste from research institutions and hospitals that are potentially infectious or dangerous are considered bio-medical waste (BMW). Bio-medical waste must be properly managed to protect the general public, specifically healthcare and sanitation workers who are regularly exposed to biomedical waste as an occupational hazard. Incineration is the thermal treatment technology facility which provides complete combustion of waste to render it non-pathogenic and it is the most favourable treatment as it reduces the solid waste to its 1/3rd of the volume. The ash generated due to the incineration of biomedical waste contains large amounts of heavy metals, PAH, which is disposed off in regular landfills results in unfavorable amounts of hazardous materials seeping into the ground and may pollute surface and groundwater. Therefore, it is essential to remove the toxicity of ash before disposal into landfills or reutilization. Several studies have been conducted on the biological treatment which shows that micro-organisms offer a better package to treat solid wastes. The characteristics of raw BMW ash leachate showed increased alkalinity (500 mg/L), hardness (1320mg/L) and chloride (8500 mg/ L) contents which are comparatively higher than the values prescribed by WHO and EPA guidelines for drinking water (alkalinity , 250-350; hardness, 300 mg/L; chloride, 250 mg/L). In this study, we have investigated the metal tolerance level of Bacillus sp. isolated from soil of Thapar university and sludge from the textile industry. The isolate can tolerate upto 75 ppm of metal concentration (Mn, Mo, Cr, Fe, Cu and Zn) in enriched growth medium and upto 50 ppm in minimal medium . This shows that the isolated culture is capable to grow in presence of high concentration of heavy metals and acts as potential biological tool to reduce the negative impact of BMW ash on the environment during landfilling. There is reduction in 50% alkalinity, 25% hardness and 60% chloride contents within 5 days of treatment compared to control when suitable carbon source (glucose and molasses) was given. There was also considerable amount of reduction in metal toxicity after 10 days of treatment in the presence of carbon source. Also, analysis of the ash and soil mixture at different concentrations (pH, Electrical conductivity, Available phosphorous, Available nitrogen, and organic matter) was done for agriculture purposes by growing ladyfinger seeds.