Analysis and Reduction of Toxicity in Biologically Treated Petroleum Product Terminal Tank Bottoms Water Objectives of this study were to meas ure toxicity in biologically treated petroleum product terminal tank botto ms waters, identify the chemical constituents causing that toxicity, id entify treatment options, and measure the effectiveness of the treatment tech niques in removing the constituents and reducing toxicity. Nine gasoline and two diesel tank bottoms water samples were collected from petrol eum product terminals at various geographical locations. The samples we re normalized to a fixed chemical oxygen demand, then subjected to bi ological treatment. Treated samples were tested for acute toxicity in 24 - hour exposure tests using Mysidopsis bahia and for chronic toxicity in 7 - day st atic renewal toxicity tests also using Mysidopsis bahia. Biolog ical treatment was observed to effectively remove metals but produced highly variable degrees of chemical oxygen demand, biochemical oxygen demand, and to tal organic carbon