Method for Estimating the Toxicity of Chemicals to Activated Sludge. II. A Rapid Determination and Application of Oxygen Uptake Rate by Using Oxygen Electrode.

Abstract

This paper deals with the investigation of simple and rapid method to determine the toxicity value (IC50) of chemicals to activated sludge by using oxygen electrode. In this method, activated sludge was added to various concentrations of test chemicals and 50% inhibition of the oxygen uptake rate (OUR) was measured within 10 min. The IC50 values calculated to be 1.5 mg/l, 1.5 mg/l, 4.0 mg/1, 7.2 mg/l, 14 mg/1, 14mg/l, 20 mg/l, 75 mg/l, 108 mg/l and 2500 mg/l for mercury (II) chloride, copper (II) chloride, mercury (II) acetate, copper (II) acetate, 2, 3, 5-trichlorophenol, pentachlorophenol, p-nitrophenol, 3, 4-dimethylphenol, cyclohexylamine and aniline, respectively, agreed almost well with those reported in the literatures. In addition, the OUR of activated sludge inhibited specifically by mercury (II) chloride was easily recovered by the addition of thiol compounds such as 2-mercaptoethanol, thiosulfate and reductive glutathione, respectively. Reactivation by thiol compounds suggested that mercury (II) form reversible mercaptides with sulfhydryl groups of enzymes concerned in OUR. From these results, the OUR method would be applicable to a rapid determination for biochemical field or biodegradation test in the Law Concerning the Examination and Regulation of Manufacture, etc. Chemical Substances.