Cadmium interaction with microalgal cells, cyanobacterial cells, and seaweeds; toxicology and biotechnological potential for wastewater treatment.

The accumulation of cadmium (Cd) by Tetraselmis chuii and Spirulina maxima was studied with dead and growing cells. Results indicated that the 2 microorganisms accumulated Cd by 2 different means according to the mechanisms involved-metabolism-dependent or metabolism-independent sorption. The mechanism involved in Cd accumulation on Tetraselmis chuii was restricted to surface phenomena, while in Spirulina maxima, Cd was accumulated on different layers of the cyanobacterium surface. In order to select a suitable immobilization support for the cells, several seaweeds were tested. Two types of seaweed were selected for experiments, using a small continuous pilot unit: Sargassum sp., a strong Cd adsorber, and Ulva sp., a poor one. The column reactors of the continuous system were filled with the algal supports and covered with dense microbial biofilms of Tetraselmis chuii or Spirulina maxima. The results obtained proved the success of the association between living microbial cells and dead seaweeds for operation of the continuous system.