CVEN 5534: Biological wastewater Treatment

Spring 2001

Assignment #3:

This is a very hard problem for which a solution is not yet known. Do your best using your understanding of kinetics (especially inhibition kinetics).

An uncoupler is a toxic compound that acts differently than many other toxic compounds. Dinitrophenol (DNP), C₆H₄(NO₂)₂, is an uncoupler that is also a carbon and energy substrate for bacteria. Organic uncouplers disrupt the cell's membrane proton gradient by carrying a proton through the cell membrane into the cytoplasm where it is released, effectively neutralizing the normal charge imbalance at the membrane. Since the proton gradient is necessary for phosphorylation to make ATP, cells can no longer make energy. However, they do continue to oxidize the uncoupler compound and release electrons that are shunted through the electron transport chain to the terminal electron acceptor (usually oxygen). As a result, the substrate and electron acceptor (oxygen) uptake rates both increase, while the growth rate declines due to lack to ATP. That is, unlike conventional heterotrophic growth, substrate consumption and growth are "uncoupled."

1. Develop kinetic expressions for an organic uncoupler compound that shows the effect of uncoupler metabolism on rates of growth, uncoupler consumption, and oxygen uptake.

2. Show by means of graphs how your kinetic expressions behave, assuming that the uncoupling effect gets more severe as the uncoupler concentration increases. You can use any values for the parameters you choose (within reason).

3. Read and comment on BOTH the research and the application proposed in the attached paper on uncouplers: Strand, S.E., G.N. Haren, and H.D. Stensel, "Activated Sludge Yield Reduction Using Chemical Uncouplers." Wat. Environ. Res., 71(4):454-510, 1999.

Instructions: This is NOT a team project. I encourage you to discuss ideas and approaches with fellow students, but the work turned in should be your own. Use any sources you want.

DUE: February 20.