Abstract
Biosorption of heavy metals using dried algal biomass has been extensively described but rarely implemented. We contend this is because available algal biomass is a valuable product with a ready market. Therefore, we considered an alternative and practical approach to algal bioremediation in which algae were cultured directly in the waste water stream. We cultured three species of algae with and without nutrient addition in water that was contaminated with heavy metals from an Ash Dam associated with coal-fired power generation and tested metal uptake and bioremediation potential. All species achieved high concentrations of heavy metals (to 8% dry mass). Two key elements, V and As, reached concentrations in the biomass of 1543 mg.kg−1 DW and 137 mg.kg−1 DW. Growth rates were reduced by more than half in neat Ash Dam water than when nutrients were supplied in excess. Growth rate and bioconcentration were positively correlated for most elements, but some elements (e.g. Cd, Zn) were concentrated more when growth rates were lower, indicating the potential to tailor bioremediation depending on the pollutant. The cosmopolitan nature of the macroalgae studied, and their ability to grow and concentrate a suite of heavy metals from industrial wastes, highlights a clear benefit in the practical application of waste water bioremediation.
Highlights
The use of algae to remove pollutants from water, algal bioremediation, has been well studied over the past 40 years [1,2,3,4]
Since the 1980s considerable research effort has been devoted to the development of algal biosorbents to remediate pollutants, heavy metals [5]
At the laboratory scale these preparations have proven spectacularly successful at sorbing pollutants, especially heavy metals [5,6]
Summary
The use of algae to remove pollutants from water, algal bioremediation, has been well studied over the past 40 years [1,2,3,4]. The process is complicated when different growth states or age of algal tissue influence the selectivity and concentrations of specific metals [17] In these cases factors that affect growth may impact capacity for bioconcentration, making it essential to simultaneously quantify bioconcentration and algal growth in the relevant waste water stream. Coal fired power stations produce large volumes of polluted waste water when the ash collected in the flue, and that remaining in the furnace after the combustion of coal, is washed out The contaminants in this water vary depending on the source of the coal but commonly include high concentrations of As, V, Mo and Se [22,23,24].
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