Submitted to: Water Environment Federation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 6, 1996
Publication Date: N/A
Interpretive Summary: Nitrophenols are pollutants which are commonly found in industrial wastewater. They are toxic to plants, fish and many other organisms. Nitrophenols are listed by the United States Environmental Protection Agency as priority pollutants. Unfortunately, they are accumulating in the environment at a worrisome rate. In this study two bacteria were examined for their ability to degrade a representative member of the nitrophenol family. Both degraded the nitrophenol to benign materials. But, perhaps more importantly, it was also discovered that for good degradation to occur, a specific, proper amount of added bacteria was necessary. That is, too few bacteria or too many bacteria resulted in poor nitrophenol degradation. The research provides fundamental information needed to utilize biologic agents, such as bacteria, to remove environmental pollutants. The research particularly benefits industrial producers of organic chemicals as well as the general populous which is ever more concerned about a cleaner environment.
The effect of inoculum size on the acclimation period and rate and extent of p-nitrophenol (PNP) degradation at high (1-10 ug/ml) and low (26 ng/ml) concentrations for two bacteria was determined in defined media as well as industrial wastewater. One bacterium was isolated from Cayuga Lake water near Ithaca, NY, and was identified as Corynebacterium sp. strain Z-4. The other bacterium was isolated from a former petrochemical complex in Penuela, Puerto Rico, and was identified as Pseudomonas putida. Increased inoculum size did not effect the acclimation period of either bacterium at high (1-10 ug/ml) PNP concentrations. At low PNP concentrations (26 ng/ml), the two bacteria behaved differently. The acclimation period was shortened and both the rate and extent of mineralization of PNP were enhanced by increasing the Corynebacterium sp. inoculum size from 3x10**5 to 3x10**6 cells/ml. Addition of phosphate or elimination of predators also reduced the acclimation period. Conversely, increasing the inoculum size from 3x10**5 to 5x10**6 cells/ml of Pseudomonas putida lengthened the acclimation period and reduced both the rate and extent of mineralization. It is suggested that, in a given environment, the success of an introduced species to enhance the degradation of a chemical depends upon: (1) concentration of the chemical, (2) selection of an appropriate microorganism, and (3) utilization of a suitable inoculum size.