Viable microalgae are known to be able to accumulate heavy metals (bioaccumulation). Against a background of the increasing environmental risks caused by heavy metals. the microalgae Chlorellu vulguris and Spinclina plurensis and their potential for the biological removal of heavy metals from aqueous s o htions were taken as an example for investigation. Smd-scale cultivation tests (50 1) with Cd-resistant cells of Chlorella vulgaris have shown that approx. 40% of the added 10 mg Cd/l was removed from the solution within seven days. At this heavy metal cqncentration sensitive cells died. Non-viable microalgae are able to eliminate heavy metal ions in a short time by biosorption in uncomplicated systems, withcut any toxicity problems. Compared with original biomasses, the sorption capacity of microalgal by-products changes only insignificantly. Their low price makes them economical.

All the Oceans are plentiful with marine algae. Non-viable marine macroalgae are able to adsorb heavy metal ions. Compared with other biosorbents, such as fungi, bacteria, yeasts and microalgae, they have the advantage of being easily available, cheap and having high heavy metal sorption capacities. The by-products of marine phaeophyceae are even more cost-effective heavy metal biosorbers. Experiments of heavy metal sorption using non-viable F u c u vesiculosus, Ascophyllurn nodosum and algal by-products were carried out to investigate the factors influencing and optimizing the heavy metal biosorption. The pH value, biomass concentration, heavy metal concentration, heavy metal species, competing ions, algal varieties and time were the most decisive parameters. The sorption isotherms showed increasing sorption capacities and decreasing sorption efficiencies with an increase in the initial heavy metal concentration. Sorption kinetics of different metals were established. Biomass concentration influenced the sorption efficiencies very much, but reduced the sorption capacity per g biomass. The pH value controlled the sorption (pH 3-7) and desorption (pH 1-2) decisively. Beside heavy metal contaminated model waters, actual industrial effluents were treated successfully by algal sorhents in batch experiments and continuous column tests. Transmission electron micrographs of different contaminated and untreated algal specimens are available.

An extract of Scenedesmus rubescens showed broad activity against markers of UV irradiation-induced cutaneous ageing. It may therefore be used as a preventive or regenerative agent for anti-ageing strategies.