ABSTRACT
The presence of heavy metals in wastewater is significant to the extent they are involved in biofouling. Microalgae and other microorganisms play a significant role in the transport of heavy metal ions in the environment while at the same time they are closely related to the formation of minerals in aquatic systems, mainly with the formation of calcium carbonate. Metabolic byproducts of microalgae act as sequestrants of metal ions, thus contributing to the transport of heavy metals on mineral deposits. In this study, the effect of zinc and cadmium in the precipitation of calcium carbonate induced by microalgae was investigated at 25°C, pH 8.5. Living and dead microalgae colonies were used to inoculate calcium carbonate supersaturated solutions. The presence of trace metals resulted in the inhibition of calcium carbonate precipitation, contrary to the accelerating role of microalgae to the crystal growth rate. Also, the presence of metals resulted at the inhibition of microalgae growth and more specifically of photosynthesis, as suggested by the reduction of total chlorophyll measured. The extracellular components of the test microalgae play important role on the nucleation and the subsequent rate of precipitation of calcium carbonate and determine the ability of microalgae for the uptake of heavy metals.
