Laboratory Study for the Phytoremediation of Eutrophic Coastal Sediment Using Benthic Microalgae and Light Emitting Diode (LED)

We investigated the effects of three wavelengths of light (blue; 450 nm, yellow, 590 nm and red; 650 nm) using light emitting diodes (LEDs) on the growth of benthic microalgae (BMA) Achnanthes sp., Amphora sp., Navicula sp., Nitzschia sp. and the harmful algae Alexandrium tamarense. In addition, we confirmed phytoremediation possibilities of eutrophic coastal sediments obtain from Masan Bay in 60 L water tank with LEDs. The growth rates of four BMA species could grow under all irradiance conditions of three wavelengths. However, the growth rate of A. tamarense was stimulated under blue LED and suppressed under yellow and red LED to less than 70μmol/m²/s. In water tank experiments with no light, environmental factors, such as cell density of Nitzschia sp., chlorophyll a (ChI. a), chemical oxygen demand (COD), acid volatile sulfide (AVS), dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP), were no significant increases or decreases. However, in water tank experiments with LED, cell density Nitzschia sp. and chl. a increased, whereas DIN, DIP, and AVS levels decreased. The removal efficiencies for DIN, DIP, and AVS were high in the order of blue LED, fluorescent lamp, red LED, and yellow LED. Thus, in order to remediate eutrophic sediments, red LED may be the most appropriate during the spring and summer when appearances of harmful algae in the genus Alexandrium are present and blue LED may be the most appropriate during other seasons. benthic microalgae,.