An algal chemostat system for exposure of adsorbable and volatile organic substances

An algal chemostat system for exposure of adsorbable organic substances with potential application also for volatile organic substances has been developed. Volatilization of the test substance has been reduced to a minimum by applying CO,-enriched air (1–2% CO2) introduced at a low flow rate at the bottom of conical reactors. The adsorption of the toxic test compound to tubes was minimized by dosing the medium and the test substance separately. The medium was dosed through of tubes of polyethylene material at a flow rate of 30 ml/h. The test substance was dissolved in a 40%/60% acetone/water mixture and dosed, at a flow rate of 0.125 ml/h, by means of an infusion pump mounted with glass syringes. The chemostat inlet tubes were capillaries of stainless steel. It was possible to maintain a constant dissolved concentration of the test compound in the chemostat, due to a reduction of both volatilization and adsorption. Exposure regimes for phenanthrene, dichlorodiphenyltrichloroethane, and 2,2′,4,4′,5,5′ polychlorinated biphenyl are presented to illustrate the ability of the system to maintain a uniform test substance concentration.