Biological wastewater treatment plants can be adversely affected by influent toxicity. The effects can range from poor clarifier biomass settling and elevated effluent BOD and ammonia levels to total plant kills. These problems could be minimized or eliminated if an effective method existed for continuously monitoring biological wastewater treatment plant influent for toxicity to the treatment plant microorganisms. Current influent screening methods have not been proven to be adequate for adaptation to continuous screening in the field. The primary reasons include the batch-wise nature of the assays and an inadequate correlation between the assays and plant performance. The goal of the research team was to create new bioluminescent biosensors from different types of bacteria found in biological wastewater treatment plants for the development of a multi-channel continuous monitoring system. A system built from multiple biosensors would make it possible to differentiate between potential influent toxicity effects to different classes of bacteria (such as nitrifying and heterotrophic bacteria). The research team found it unexpectedly challenging to apply common microbiological transformation methods for laboratory strains to the wastewater treatment plant strains. The research team generated six new bioluminescent bioreporters from bacteria that are typical constituents of activated sludge. Of particular significance is a bioreporter developed using a Hyphomicrobium sp., which is a slow growing bacterium known to be present in significant numbers in some activated sludge plants. Of the six generated, initial bioluminescence and toxicity screening indicated that one strain (a Pseudomonad) was a particularly promising candidate due to its ease of cultivation and high light production. Further toxicity testing, however, determined that the response of the strain to 48 organic compounds and 8 metals commonly found in wastewater was similar to that of a previously created strain, Shk1 (also a Pseudomonad). Further work is therefore needed in the generation of appropriate biosensors and test conditions for populations not represented by the new heterotrophic biosensor.
