Heavy metal contaminated wastewater treatment via microalgae

Author: Elene Kakabadze
Keywords: Biosorbtion, toxic and heavy metals, Chlorella emersonii, wastewater, water treatment, bioremediation, environment, microalgae
Annotation:

Water contamination is one of the major environmental problems and holds a great threat to biodiversity, environment and public health. From a vast number of hazardous contaminants that reaches hazardous levels are toxic and heavy metals. Those elements have ability to bioaccumulat in environment, biomagnificat in various food chains and may indulge toxic effects even on trace concentrations. Number of toxic metals can be modified by naturally occurring processes in more hazardous forms. Heavy metals are highly sustainable in environment and have destructive effect on various parts of ecosystem . Due to various human activities like ore mining and industrial processes the natural biogeochemical cycles are disrupted causing increased deposition of heavy metals in terrestrial and aquatic environment There are number of wastewater treatment technologies, such as reverse osmosis, ultrafiltration, ion exchange, chemical precipitation etc. Of course all those methods have their pros and cons, but the main disadvantages of those methods are: low metals uptake capasity, especially on trace amounts, huge expense of energy and reagents , generation of toxic sludge, low efficiency and negative influence on environment. In contrast to above mentioned methods bioremediation has a lot of advantages, in particular biosorption of heavy metals by microalgae is environmental friendly, cost effective, available and highly efficient alternative methodology, because microalgal cells have a remarkable ability to take up and accumulate even trace amounts of heavy metals from their external environment. Biosorption technology offers metal removal even in the trace amounts, metal recovery and biosorbent regeneration, without generation of toxic sludge. The most important part of biomass involved in biosorption is outer cell wall, because metabolism independent uptake takes place on cell periphery and involves bonding between cell wall functional groups and metal ions. The investigated microalgae Chlorella emersonii genus cell wall is mainly form from glucosamine polymers. The potential sites for meta ion binding are: carboxyl, amine, imidazole, phosphate, sulphate, sulfhydryl and hydroxyl. Series of in vivo experiments were performed in batch culture system to establish adsorption rates of heavy metals by fresh water microalgae -Chlorella emersonii, for further application perspectives as biosorbent material. to achieve this goal following objectives has been set: investigation of Chlorella emersonii’s uptake of different concentrations of lead, cadmium and zinc, establishment of the adsorption dynamic of Pb2+- influence of pH on uptake- effects of simultaneous exposer to lead, cadmium and zinc on Chlorella emersonii ‘s adsorption rate. Establishment of the adsorption capacity of alginate immobilized Chlorella emersonii. The results suggested that Chlorella emersonii has high adsorption capacity of lead, cadmium and zinc- Pb2+ adsorption process is rapid and most of the metal ions are adsorbed in less than a minute- adsorption rate of Chlorella emersonii depends on metal concentration and pH value- simultaneous exposure of microalga to Pb2+, Cd2+, and Zn2+ showed incrase in lead adsorption rate - on micromolar concentration immobilized Chlorella emerosnii has greater adsorption capacity of Pb2+ than free cells. The data suggests that Chlorella emersonii has good adsorption capacity of Pb2+, Cd2+, and Zn2+, therefore can be applicable in biosorption processes.

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მძიმე მეტალებით დაბინძურებული წყლის რემედიაცია მიკროწყალმცენარის საშუალებით [ka]