Evaluation of toxic properties of industrial wastewater using on-line respirometry

An on-line respirometric biosensor using activated sludge microorganisms was used in this work for the assessment of toxic properties of industrial effluents and for the evaluation of their effect on the performance of a municipal wastewater treatment plant. Continuous monitoring of combined industrial discharges was carried out for a period of six months, and increased toxicity values were observed during the evening times and the weekends, possibly due to the discharge of partially treated wastewaters from certain processing units. Furthermore, no direct correlation was observed between toxicity values and organic content, indicating that simply monitoring organic load, as it usually happens in most wastewater treatment plants, does not help in predicting the toxic properties of the effluent. Therefore, the installation and operation of an on-line respirometer is required, in combination with chemical analysis, for the protection of the operation of a municipal wastewater treatment plant from toxic shocks. The assessment of toxicity of wastewaters from certain industrial plants showed that bioluminescence inhibition on Vibrio fischeri was generally higher than the respirometric inhibition on activated sludge microorganisms. It was concluded that for the evaluation of potential toxicity of influents on a wastewater treatment plant, activated sludge microorganisms should be preferred as test species.