| The activated sludge process has been widely used in publicly owned treatment works (POTW). Toxic loadings can cause upsets in the operations of the activated sludge process. Such upsets include decreased BOD removal, reduction of solids separation efficiency, and modification of sludge compacting properties. In the most severe circumstances, the activated sludge microorganisms may be completely inhibited and the treatment plant has to be shut down. Such toxic effects can be avoided if influent wastewater is screened for toxicity and protective actions are taken.; A strain of luminescent bacteria was created at the Center for Environmental Biotechnology at the University of Tennessee for the purpose of wastewater toxicity testing. The bacterium was designated Shk1. The host strain of Shk1 was a Pseudomonad isolated from the aeration basin in an industrial wastewater treatment plant. We developed a rapid toxicity testing system that employed Shk1. The toxicities of 7 heavy metals and 102 organic chemicals were determined using this system. A comparison of the Shk1 toxicity data with literature data, especially the Microtox® data and the activated sludge respiration inhibition data, indicated that the response of Shk1 to toxicants was more similar to that of the activated sludge microorganisms.; A small field-scale monitoring system based on the laboratory system was constructed and was employed at the Kuwahee Wastewater Treatment Plant of the Knoxville Utilities Board (KUB) located in Knoxville, Tennessee for two months. The field system continuously monitored the toxicity of the influent to the wastewater plant as indicated by Shk1 bioluminescence repression and data were recoded at a rate of once per minute. The signals generated by the Shk1-based system were found to be a meaningful piece of information. However, because treatment efficiency could be affected by factors other than influent toxicity, such as influent BOD, temperature, etc., there was no easily observable correlation between the signals generated by the Shk1-based system and treatment efficiency. |
