Research Highlights

Drinking Water Researchers Replicate Distribution Pipelines

Distribution system simulator

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“Stuff grows on pipes.” That’s how one drinking water expert sums up the National Risk Management Research Laboratory’s (NRMRL’s) innovative research into the pipe-wall dynamics of the distribution systems that carry finished water from treatment plant to consumer tap.

Although millions of miles of distribution pipes transport drinking water worldwide, surprisingly little is known about pipeline interactions among treatment disinfectants, chemical contaminants, and pipe deposits—the “stuff” that coats pipe walls. To better understand these interactions, NRMRL scientists and engineers have created a model water distribution system at EPA’s Test and Evaluation Facility in Cincinnati, Ohio. The model, called the Distribution System Simulator (DSS), is unique in the United States for its testing capabilities.

Background

Clean, safe drinking water depends on a complex set of interactions among water sources, purification treatments, and distribution systems. Consider just a few:

Source water may contain high levels of calcium carbonate, iron, or manganese, creating “hard water.” If the hardness is not removed at the water treatment plant, biofilm and scale can form on the inner walls of the distribution pipes. Biofilm is made of layers of microorganisms.
The formation of biofilm is further dependent on the type of pipes, whether iron, poly vinyl chloride (PVC), or concrete lined. In turn, biofilm and scale can affect the life span of the pipes, thus playing a role in the cost of the distribution system infrastructure.
Disinfectants (typically chlorine) introduced during the treatment process may react with organic carbons naturally present in the source water to form unwanted disinfection by-products (DBPs).
Biofilm and scale can decrease concentrations of disinfectants. They can also cause taste and odor problems and harbor disease-causing microorganisms or chemical pollutants, possibly releasing them into drinking water in distribution systems.

NRMRL’s DSS allows researchers to study many of these complex interactions.

The “Loops”

The DSS unit is designed to simulate the continuous flow conditions found in a typical distribution system. Five individual 75-foot lengths of 6-inch iron pipes and one 75-foot length of PVC pipe are arranged in a pipe-loop configuration. Above the loop units, two 1,500-gallon reservoir tanks simulate stored water as in a distribution infrastructure system. The loops can be operated individually or collectively in a variety of experimental configurations. Two 2,500-gallon stainless steel holding tanks are used for pre-mixing test water with varying properties (e.g., chloramines versus chlorine).

The model is operated by a computerized data acquisition system that controls experimental variables, including pH, temperature, chlorine, flow, and chemical addition. Biofilm samples can be collected from 18 points in the pipelines and from a 100-gallon recirculation/mix tank.

Current research includes experiments on flow rate, organic carbon concentrations, DBP formation in both iron and PVC pipes, and biofilm sampling methods. Future research, done in collaboration with EPA’s Office of Water and regional offices, will assess the risk of contaminants that can escape many treatment processes intact, and the ways in which they interact over time with biofilm and pipe walls.

By evaluating the physical, chemical, and biological phenomena that occur in drinking water distribution systems, the DSS unit serves EPA’s mission to protect human health and the environment.

Contact

Jane Ice, NRMRL Office of Public Affairs (513) 569-7311

New Publications

Betancourt, D., T.R. Dean, M.Y. Menetrez, and S.A. Moore. (2006). “Characterization of Microbial Volatile Organic Compounds Emitted by Stachybotrys Chartarum.” In: Proceedings Indoor Environmental Quality: Problems, Research, and Solutions, Durham, NC, July 17–19. Abstract

Bowen, T.C., R G. Meier, and L.M. Vane. (2007). “Stability of MFI Zeolite-Filled PDMS Membranes During Pervaporative Ethanol Recovery From Aqueous Mixtures Containing Acetic Acid.” Journal of Membrane Science, 298, 1–2: 117–125. Abstract

Gullett, B.K., A. Touati, L. Oudejans, and D.G. Tabor. (2007). “Real-Time Monitoring of PCDD/PCDF for Transient Characterization and Process Control.” In: Proceedings, Hazardous Waste Combustors Conference 2007, Charleston, SC, March 13–14. Air and Waste Management Association Online Library

Kinsey, J.S., D.C. Williams, Y. Dong, and R. Logan. (2007). “Characterization of the Fine Particle and Gaseous Emissions During School Bus Idling.” Environmental Science and Technology, 41, 14: 4972–4979.

Lai, D., T. Dai, J. Zhen, et al. (2007). “SUSTAIN – An EPA BMP Process and Placement Tool for Urban Watersheds.” In: Proceedings Water Environment Federation 2007 Total Maximum Daily Loads (TMDL) Meeting, Bellevue, WA, June 24–27. Abstract

Lavrich, R. and M. D. HAYS. (2007). “Validation Studies of Thermal Extraction-GC/MS Applied to Source Emissions Aerosols. 1. Semivolatile Analytic-Nonvolatile Matrix Interactions.” Analytical Chemistry, 79, 10: 3635–3645. Abstract

Lipfert, G., W.C. Sidle, A.S. Reeve, et al. (2007). “High Arsenic Concentrations and Enriched Sulfur and Oxygen Isotopes in a Fractured-Bedrock Ground Water System.” Chemical Geology, 242, 3–4: 385–399. Abstract

Loughlin, D.H., T. Johnson, C.L. Shay, et al. (2007). “Projecting Future-Year Pollutant Emissions: Emerging Approaches From the EPA ORD Global Change Air Quality Assessment (PDF).” (11 pp, 156 KB) In: Proceedings 16th Annual International Emissions Inventory Conference, Raleigh, NC, May 14–16.

Mayer, P.M., S.K. Reynolds, M.E. McCutchen, and T.J. Canfield. (2007). “Meta Analysis of Nitrogen Removal in Riparian Buffers.” Journal of Environmental Quality, 36 4: 1172–1180. Abstract

Nordwick, S.D., R. Bless, H. Joyce, et al. (2007). “A Greener Butte! Revegetation Through Irrigation Using Treated Mine Water From the Belmont Mine’s Flooded Underground Workings.” In: Proceedings SME Annual Meeting and Exhibit and Colorado Mining Association 109th National Western Mining Conference, Denver, CO, February 25–28. Abstract

Patterson, C.L., C. Impellitteri, K.R. Fox, et al. (2007). “Emergency Response for Public Water Supplies After Hurricane Katrina.” In: Proceedings World Environmental and Water Resources Congress 2007: Restoring Our Natural Habitat, Tampa, FL, May 15–19.

Selvakumar, A., S.D. Struck, T. O’Connor, and P. Estornell. (2007). “Effects of Stream Restoration on In-Stream Water Quality in an Urban Watershed.” In: Proceedings Water Environment Federation 2007 Total Maximum Daily Loads (TMDL) Meeting, Bellevue, WA, June 24–27. Abstract

Shanks, O.C., J.W. Santo-Domingo, J. Lu, et al. (2007). “Identification of Bacterial DNA Markers for the Detection of Human Fecal Pollution in Water.” Applied and Environmental Microbiology, 73, 8: 2416–2422. Abstract

Shen, H. and J. T. Wilson. (2007). “Trichloroethylene Removal From Ground Water in Flow-Through Columns Simulating a Permeable Reactive Barrier Constructed With Plant Mulch.” Environmental Science and Technology, 41, 11: 4077–408. Abstract

Sidle, W. C. and P. Li. (2007). “Impact of Submersible Pumps on Pb Constituents in Residential Wells.” Environmental Geochemistry and Health, DOI 10.1007/s: 10653-007-9090-4. Abstract

Srivastava, R., S. Vijay, and A. Zykov. (2007). “Challenges and Opportunities for Emission Reductions From the Coal-Fired Power Sector in Growing Economies: The Case of Coal-Fired Electric Utility Plants in Russia.” In: Energy Security, Climate Change and Sustainable Development. Anamaya Publishers, New Delhi, India.

Thorneloe, S., K. Weitz, and J. Jambeck. (2007). “Application of the U.S. Decision Support Tool for Materials and Waste Management.” Waste Management, 27, 8: 1006–1020. Abstract

Wilhelm, M., L. Liang, D. Cussen, and D.A. Kirchgessner. (2007). “Mercury in Crude Oil Processed in the United States (2004) (PDF).” (6 pp, 128 KB) Environmental Science and Technology, 41, 13: 4509–4514.

Wilkin, R.T., D. Fine, and N. Burnett. (2007). “Perchlorate Behavior in a Municipal Lake Following Fireworks Displays (PDF).” (6 pp, 180 KB) Environmental Science and Technology, 41, 11: 3966–3971.