[Use of bioreactors for continuous water monitoring]

A commercially available bacterial toxicity monitor ("Toxiguard", BTG Anlagentechnik, Bochum, Germany) was tested for continuous river monitoring. Operating with biofilms, this system shall detect toxic substances in the water. River water passes through two bioreactors forming a biofilm of characteristic river bacteria. The indicating parameter of the biomonitor is the respiration rate of this bacterial biofilter. The remaining oxygen content in the effluent from the biofilter is measured continuously by an oxygen electrode. This value is related to the dissolved oxygen (DO) of the river water measured in a by-pass. In presence of inhibitory substances the DO content in the biofilter increases because of the reduced respiration activity of the bacteria. The addition of nutrients may lead to an increase of biomass and of respiration activity. This results in an increasing oxygen difference between DO contents in the biofilter influent and effluent. Therefore, the degree of poisoning is better perceptible. Moreover each nutrient causes a distinct biofilm with a specific sensitivity against chemicals. This effect will be shown for Sodium-Pentachlorophenolate (Na-PCP).