Dr. Desmond F. Lawler
Nasser I. Al-Rashid Chair Emeritus in Civil Engineering
University Distinguished Teaching Professor Emeritus, University of Texas
"Natural Organic Matter and Disinfection By-Products in Drinking Water: A New Treatment Approach"
The formation of disinfection by-products (DBPs) has been a primary concern in drinking water treatment since its first discovery nearly 50 years ago. DBPs are formed by the reactions of natural organic matter (NOM) in the water source with the chosen disinfectant, which most often is chlorine; a huge number of DBPs have been identified, but only a few classes of DBPs (trihalomethanes, THMs, and haloacetic acids, HAA5) have been regulated by the EPA. Many of these halogenated organic compounds are, or are suspected to be, carcinogenic. The three approaches to the concentration of DBPs at people’s taps include (1) reducing the amount of NOM available for reaction (primarily accomplished by “enhanced” coagulation or “enhanced” softening(2) changing the disinfectant (e.g., chloramine rather than chlorine) or the mode of disinfection (e.g., UV light), and (3) removing DBPs after formation (by, for example, air stripping). All three of these approaches have limitations; which is a key reason why the issues have remained at the forefront of concern for so long. We have developed a potential major breakthrough to reduce DBPs in drinking water—a hybrid system using electrodialysis (ED) and a pressure membrane (nanofiltration, NF, or reverse osmosis, RO) in a unique series/parallel arrangement. ED is used to temporarily remove inorganic ions from the water but is not effective in removing NOM; the ED diluate is then treated by NF or RO to remove the NOM. Finally, the NF/RO permeate is mixed with (all or part of) the ED concentrate to result in a water with nearly the same inorganic ion concentration of the raw water but drastically reduced NOM. This system is admittedly more complex than the current technologies used to limit DBPs but can drastically improve the reduction of DBPs in many drinking waters. The complexity also means that this system provides designers and operators several more control points (“knobs”) to reduce DBP concentrations in the final water. The same system has other potential uses that we are also exploring, such as reducing boron from ocean waters or from “produced waters” from oil and gas extraction, which would allow agricultural uses of those waters.
March 19,2021
11:00 AM
Zoom Meeting ID:
936 7162 2250
https://unl.zoom.us/j/93671622250
More details at: http://cee.unl.edu