Microalgal removal of hazardous chemicals in the environment

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Recently, a variety of chemicals are produced and afterwards discharged in the environment. Some of these chemicals have injurious effects in human health and ecosystem, and they cause a serious social problem. We proposed the utilization of the function of microalgae as a method for the environmental bioremediation. It seems to be very useful to use photosynthetic microalgae for the restoration of the polluted environment, because microalgae can grow under the poor nutrition conditions by utilizing the solar energy. In this study, the basic research for the development of efficient removal systems of heavy metals and hazardous organic compounds in the environment was carried out.1. The heavy metal removal from environmental water by microalgae. Effects of light, agitation, pH, tempenature and medium composition on the cadmium removal were examined using microalgae, and optimal conditions for high cadmium removal was obtained. Then, the effect of Na^+, K^+, Ca^<2+> and Mg^<2+>, which are abundantly found in environmental water such as ground water and seawater, on the heavy metal removal was examined. It was found that the removal ability of microalgae was lowered by Ca^<2+> or Mg^<2+>. In order to enhance selective cadmium removal, various pretreatments of algal cells were investigated, and treatment of the algal cells with sodium hydroxide was effective to remove the cadmium in the presence of Ca^<2+> or Mg^<2+>.2. The preliminary study on the decomposition of hazandous organic compounds. Microalgae were screened for the removal of the hazardous organic compounds such as chlorophenols and nitrophenols. Several microalgae that have high removal ability were obtained for the further studies.