CONTINUOUS AND EARLY DETECTION OF TOXICITY IN INDUSTRIAL WASTEWATER USING AN ON-LINE RESPIRATION METER

An on-line toxic detection system for the early and continuous observation of toxicity in the wastewater treatment plant of a petrochemical company which produced phthalic acid is described. The plant treated the wastewater using an extended activated sludge process. During annual shut-down the reactors were cleaned with sodium hydroxide which could possibly reach the biological reactor. The toxicity detector consisted of a contact chamber and an on-line respiration meter. The operation of the on-line detection system and continuous toxicity tests are described. The relationship between organic loading rate and actual respiration rate was studied. A ratio of influent sample flow to activated sludge flow of more than 0.6 was recommended to obtain maximal respiration rate. The system was tested under conditions of high and low pH, cobalt inhibition, and the addition of catalyst wastes.