The presence of organophosphorus pesticides in water is dangerous for the environment and aquatic organisms. Bioremediation uses natural organisms to remove pollutants from the environment. In this study, the potential of Dunaliella salina microalga to remove four organophosphorus pesticides from well water was investigated. Diazinon, chlorpyrifos, ethion, and profenofos at five different concentration (0–10 mg L−1) levels were studied. The growth rate of microalga was declined with the increasing concentration of pesticides. The results showed that at certain concentration of pesticides (5 mg L−1), Dunaliella salina can grow and remove 70.25%, 47.65%, 53.89%, and 41.84% of diazinon, ethion, profenofos, and chlorpyrifos, respectively. Based on gas chromatography–mass spectrometry analysis, the degradation products were identified, and the proposed biodegradation pathways were presented. The kinetic studies showed that the biodegradation rates were 0.0235 d−1 and 0.1769 d−1 with half-lives of 2.76 and 29.49 d for selected pesticides. The results from this study indicated that Dunaliella salina was able to tolerate environmental stress, grow in contaminated water and remove pesticides.

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