Testing the toxicity of influents to activated sludge plants with the Vibrio fischeri bioassay utilising a sludge matrix

To protect the bioceonosis within activated sludge, a method of predicting the toxic effect of influents to the biological treatment stage of waste wa ter treatment plants, based on DIN method 38412 L 34, has been developed. A population of the luminescent marine bacterium Vibrio fischeri was incorpo rated into a sludge testing matrix derived from a model laboratory and real activated sludge plants. The sludge was challenged with different concentr ations of pure toxicants and complex aqueous samples, and light output by V fischeri monitored. The results were compared to toxicant testing in the a bsence of sludge (standard test). The modified method was found to be less sensitive for some toxicants tested than the standard DIN and other biolumi nescent tests, but considered more realistic as it provides buffering and t akes into account sorption which can affect the sensitivity of the test tow ards some compounds. The method is comparable in terms of ease of use, spee d, reproducibility and cost effectiveness to standard V fischeri luminescen ce methods. (C) 2001 John Wiley & Sons, Inc.