Eutrophication is hallmarked by excessive algal growth due to the increased availability of inorganic and organic compounds in the water. Pollution is usually one of the major reason that induces eutrophication. In addition, polluted water is one of the leading factors that induce a wide range of diseases, especially in children. Currently about 45% of U.S. streams, 40% of America’s rivers, 47% of lakes, and 32% of bays are polluted, which are not suitable for drinking, swimming, fishing nor aquatic lives. To ensure the quality, residential water is usually suppled after treatment, and the water treatment also induces toxic components, for example, trichloroacetic acid (TCA) and bromodichloromethane, which both are cancer inducers. The national average concentration of these compounds in tap water are 4.92 ppb (part per billion) and 4.31 ppb respectively. In groundwater, the nitric components are one of the major contaminants, which significantly promote the growth of green algae, leading to eutrophication. Single cell algae Chlorella is one of the common algae that involves in eutrophication, and our recent study indicated it also can help reduce the concentration of some contaminants, including TCA, iron, and nitric oxide. This support our hypothesis that green algae can absorb the pollutants and reduce their concentration in the water to reverse the eutrophication.