Cometabolism of Trihalomethanes by Nitrifying Biofilters Under Drinking Water Treatment Plant Conditions

EPA Grant Number: FP916412
Title: Cometabolism of Trihalomethanes by Nitrifying Biofilters Under Drinking Water Treatment Plant Conditions
Investigators: Wahman, David G.
Institution: The University of Texas at Austin
EPA Project Officer: Jones, Brandon
Project Period: January 1, 2004 through December 31, 2006
Project Amount: $109,344
RFA: STAR Graduate Fellowships (2004) RFA Text |  Recipients Lists
Research Category: Academic Fellowships , Fellowship - Environmental Engineering , Engineering and Environmental Chemistry


The basic thesis of this research is that trihalomethane (THM) removal should be possible within drinking water treatment plants by introducing a biological treatment step based on THM cometabolism by nitrifying bacteria. In this way, cometabolism can be sustained without adding organic carbon to grow the appropriate bacteria. The objective of this research is to develop an innovative treatment process that allows for upstream disinfection (to ensure the microbial safety of drinking water) while at the same time protecting bacteria in the downstream process ( i.e., filtration) from the disinfectant. With this protection, bacteria will be able to biodegrade THMs formed within the treatment plant, thereby resulting in a lower concentration of THMs entering the distribution system. The ultimate result will be to provide consumers with a higher quality drinking water.

The overall objectives of this research are the demonstration of successful THM cometabolism in laboratory-scale biofilters, process modeling, and the development of a fundamental understanding of process performance through the use of molecular biology techniques.


An integrated research program will be used to achieve the stated objectives. The overall effect of the research will be to understand on a fundamental level a practical process that can be applied in many drinking water treatment plants to help them meet current and future disinfection and disinfection by-product regulations. Specific approaches of the research include:

(1) Determination of cometabolism kinetics and the significance of enzyme competition with ammonia for all four THMs with the pure culture organism Nitrosomonas europaea.

(2) Determination of transformation capacity for all four THMs with the pure culture organism N. europaea.

(3) Extension of the kinetics and enzyme competition experiments to mixed-culture nitrifiers typically encountered in drinking water treatment.

(4) Demonstration of THM cometabolism in continuous-flow biofilters receiving only ammonia and THMs in the influent (i.e., no chlorine added).

(5) Demonstration of THM cometabolism in continuous-flow GAC biofilters receiving ammonia, monochloramine, and THMs in the influent.

(6) Development of a mechanistic mathematical model of the process to provide a conceptual framework for designing experiments and interpreting results.

(7) Use of molecular probes to quantify the abundance and spatial distribution of nitrifiers among other microorganisms in the biofilters, thereby improving my ability to interpret process performance data and to model the process.

(8) Identification of important process performance variables and development of a strategy for design and operation based on experimental observations and mathematical modeling.

Supplemental Keywords:

fellowship, trihalomethane, THM, THM cometabolism, nitrifying bacteria, nitrifying biofilter, biodegradation,microorganisms, biological treatment, Nitrosomonas europaea, kinetics, drinking water treatment, water quality, drinking water disinfection, GAC biofilters, model, process modeling,, RFA, Scientific Discipline, Water, Environmental Chemistry, Drinking Water, Environmental Engineering, molecular biotechnologies, trihalomethanes, cometabolism, chemical contaminants, drinking water contaminants, drinking water treatment, nitrifying bacteria