Using microalgae for combined lipid production and heavy metal removal from leachate

Abstract

The remediation of leachate from (municipal) landfills and disposal of hypersaline effluent (from desalination plants) are becoming an increasing challenge for many government authorities and practitioners. There is mounting interest in using bioremediation as a means of stripping contaminants from these waste streams and in the potential for lipid production using microalgae. We present a system dynamics approach to exploring the efficacy of using mixed microalgae populations to treat leachate–hypersaline water. This model evaluates the temporal evolution of metal removal and lipid production using four common marine microalgae species: Nanochloropsis, Pavlova lutheri, Tetraselmis chuii and Chaetoceros muelleri. The uptake kinetics of the metals (removal from the leachate) are modelled using basic adsorption kinetics and the model is primarily parameterised from data obtained through an experimental study where two photobioreactors were dosed with composite leachate–hypersaline solution and seeded with the four microalgae species. After a 10-day period, the microalgae population was found to have removed over 95% of the metals from the solution. Microalgae growth was dominated by Nanochloropsis gaditana and C. muelleri, which are the two species with the highest lipid contents. Overall, this study indicated that the use of microalgae-based bioremediation is a viable method for treating waste streams and lipid-production.