Monitoring the toxicity of phenolic chemicals to activated sludge using a novel optical scanning respirometer

This paper reports the development of optical scanning respirometer for det ermining the toxicity of chemicals to activated sludge. The respirometer is used to measure the dissolved oxygen concentration by monitoring the lumin escence intensity of ruthenium dye immobilized in a polymer film in contact with the wastewater sample. The intensity is related to the extent of oxyg en quenching of luminescence. The toxicity of chemicals can be evaluated by measuring the inhibition on respiration rate of microorganism using the sc anning respirometer. The IC50 values (concentration of a chemical that exhi bits 50% respiration inhibition) of various phenolic chemicals in activated sludge were determined. The performance of this method is compared with ot her toxicity methods. The experimental results indicate that the reproducib ility and sensitivity of this respirometer are reasonably good.