Bioremediation of Heavy Metals with Waste Lignocellulosic Biomass

This project had the goal of developing a low-cost alternative for removing toxic heavy metals, in particular arsenic, lead, and cadmium, from industrial wastewater. The proposed process involves using a hybrid batch and continuous process mainly consisting of heavy metal removal in a series of 5 adsorption beds packed with coconut coir coated with P. putida biofilm, then combustion of the saturated coconut for the production of steam. The process goal was to treat 1 MGD of wastewater at a lower cost than ion-exchange plants which cost $0.02/lb of wastewater treated. The proposed coconut-based bioremediation was estimated to cost $0.00304/lb of wastewater treated, 15.2% of the cost of ion exchange, being economically advantageous. In addition, the energy generation in the biomass boiler led it to have a net-negative GHG emissions footprint of -4864 kg CO2e per day. Profitability analysis with clean water being sold at the pricepoint of ion exchange indicates an ROI of 102.5% and IRR of 96%, over the 17-year project in the base case scenario, resulting in an NPV of $146M. Our results suggest that the use of lignocellulosic biomass, especially coconut coir for large-scale wastewater treatment processes for heavy metal removal is a viable alternative to existing treatment mechanisms, being environmentally friendly and economically advantageous.