Phytoremediation by benthic microalgae (BMA) and light emitting diode (LED) in eutrophic coastal sediments

In this study, we examined whether phytoremediation using benthic microalgae (BMA) and a light emitting diode (LED) can remediate eutrophic sediments caused by promoting the growth of BMA. A field application experiment was conducted from September 9 to December 3, 2011, in Masan Bay, Korea. Two chambers were used: an experimental site, which included a red LED (650 nm) lamp and replanted Nitzschia sp. on the surface sediment, and a control site, which did not contain an LED lamp and replanted Nitzschia sp. on the surface sediment. Chlorophyll a (Chl. a) concentration increased at the experimental site, and was 2 times the concentration at the control site. Acid-volatile sulfide (AVS) concentration decreased at the experimental site, with a removal rate of AVS as high as 28%. In addition, the removal rates of dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) were as high as 19% and 24%, respectively. The removal fluxes for DIN and DIP were 2.02 mg N/m2/day and 0.22 mg P/m2/day, respectively, at the experimental site, and 0.88 mg N/m2/day and 0.10 mg P/m2/day, respectively, at the control site. These changes indicate that oxygen produced by the replanted Nitzschia sp. may have enhanced aerobic bacterial activity, and the nutrients may have been taken up by the Nitzschia sp.. Therefore, phytoremediation using BMA and LED shows potential as a novel and eco-friendly method for the remediation of eutrophic coastal sediments.