Nitrates pollution of waters is a worldwide problem and its remediation is a big challenge from the technical and the scientific point of view. One of the most used and promising cleaning techniques is the biological treatment of wastewaters operated by bacteria. A freshwater microalgae Chlorella sp. was investigated for its ability to remove both nitrogen and phosphorus from influent. Amount of wastewater containing nitrogen is increasing in the environment due to industrialization.  It is necessary to remove nitrogen from waste as it causes eutrophication. The study was carried out to increase characteristics, efficiency and economy of wastewater by the low-cost microorganism.