Drinking Water Research

M_dietrich_drinking_water_taste_odorWATER: Interfacing Physical, Life and Behavioral Sciences and Engineering for Healthy Water Applications

Faculty Member: Dr. Andrea Dietrich (with colleagues from College of Engineering, College of Science, College of Agriculture and Life Sciences)

To move society and research forward, disciplines need to integrate their knowledge, research and training to promote drinking water and protect public health.  The WATER Interface faculty and students from the physical, life and behavioral sciences and engineering are applying “convergence science” for intellectual cross-pollination to discover, evaluate, implement, and publicize solutions that deliver and promote sustainable, healthy and aesthetically pleasing drinking water to the nation and then the world. Research and coursework topics being addressed include:

  • determining nutritional, aesthetic, perception, and risk aspects of drinking water;
  • assessing micro- and nano-aerosol droplets from showers as delivery mechanisms of  metals, odorants, and pathogens to humans, then develop strategies for preventing deposition or adsorption of these contaminants;
  • assess release and human exposure to metallic and organic contaminants from water distribution materials;
  • determining chemical, microbiological and ecological changes in source water quality due to new technologies to treat drinking water;
  • transferring knowledge to the public that water quality and the risk of pathogens/contaminants can be influenced by methods not traditionally associated with water consumption;
  • developing guidance for ensuring that water meets accepted standards for safety and minimal risk.

Consumer Perception: Good, Better, and Best Tasting Drinking Water

Faculty Member: Dr. Andrea Dietrich

While treatment and regulations drive practices in production of drinking water, most consumers judge their water based on taste, odor, and visual qualities rather than treatment or reported water quality parameters. For consumers, sustainable water means that the water is safe to drinking and it has a refreshing flavor. Too often drinking water is produced that meant water quality standards but consumers do not like the taste so they resort to applying expensive on-site treatments or purchasing bottled water. Our research is this area is exploring:

  • “off-flavors” or chemicals without know health effects that cause drinking water to have an undesirable flavor;
  • “great flavors” or chemicals that provide water is its refreshing taste;
  • consumer preferences and their ability to discriminate between flavors of water;
  • metal speciation (dissolved, nano, particulate) and its effects on flavor perception – can consumers detect toxic amounts of metals in their water?

Water Quality and Copper Pitting Corrosion

Faculty Member: Dr. Marc Edwards

Rigs set up at a county water utility in Florida allow researchers to initiate, simulate, and monitor copper pitting corrosion. The researchers can then apply and test potential preventative techniques. The primary goal of this work is to identify a level of free Cl2 in WSSC’s Potomac and Patuxent water that would not tend to support copper pitting corrosion. The work also has the goal of determining whether substituting chloramines for chlorine would be beneficial from the perspective of copper pitting, and if dosing of phosphate would counter the effects of chlorine.

Role of Cl2 and Al(OH)3 in non-uniform copper corrosion

Post mortem investigation of copper with pinhole leaks often leads to identification of significant aluminosilicate deposits on the pipe surface. Such deposits are estimate to occur in 30% and 80% of cold and hot water copper pits, respectively (Meyers, 2001), and a significant portion of pits that do not have aluminosilicate deposits have iron deposits instead. The term “aluminosilicate” is a generic name for solids commonly forming in water that contain both aluminum and silica, in addition to other components. Clay is a common aluminosilicate. The goal of this research project is to determine the specific conditions under which aluminosilicate deposits can cause copper pitting corrosion. Preliminary experimental results are presented demonstrating that free Cl2, in combination with Al deposits, can dramatically worsen aspects of copper corrosion and is a likely cause for pit initiation. The specific questions to be answered are:

  1. Does this combination of conditions cause real pits in practice?
  2. What level of free chlorine is required to initiate pits at different pHs?
  3. What level of Al deposits are necessary to initiate pits at different pHs?
  4. Are similar interactions important in hot water pitting?

Gas Supersaturation and Treatment Plant Performance

“Gases in the influent water may be released in the zone of negative pressure, causing bubbles to accumulate (a process called air binding) during the filter cycle. Such accumulations of gas lead to more rapid development of head loss and poorer quality of filtrate.” from Water Quality and Treatment, 1999 (AWWA)

A breakthrough in monitoring capabilities has improved our ability to analyze gas supersaturation. That is, dissolved gas saturation most commonly arises from the combined activity of nitrogen, oxygen and carbon dioxide in water. In the past, dissolved oxygen was the only surrogate measure for total gas saturation, even though it was obviously deficient. Total dissolved gas (TDG) probes are now available which measure the activity of all gases in water directly and which are no more difficult to operate than a pH meter. The first part of this work will transfer this technology to enthusiastic utility participants, and in the process, begin improving practical knowledge of air binding through site visits. Thereafter, two phases of laboratory work will examine the fundamentals of air binding in coagulation/sedimentation and filtration processes. The goal is to determine when air binding will cause problems, to identify what operational parameters worsen this problem, and to test simple operational strategies that we believe will either prevent air binding or minimize its adverse consequences. The parameters to be tested include choice of coagulant, flocculation rate, filter media type, and degassification techniques such as weirs and aeration.

A final phase of work uses a portion of the project funding (about 4%) to examine the controversial topic of magnetically enhanced gas stripping. Recently, peer reviewed articles have appeared in quality journals (i.e, Env. Sci. and Tech., BioPhysics and Biochemistry) that “prove” magnets work to strip gases from water and blood. These articles are bolstering vendor sales of expensive proprietary magnetic devices to utilities. We will rigorously test this hypothesis in laboratory experiments and in the process, either provide the water industry with a miracle cure or produce hard data to counter overly optimistic vendor claims.

Corrosion of Drinking Water Infrastructure by Enhanced Coagulation

Faculty Member: Dr. Marc Edwards

Production of safe drinking water is the steadfast goal of the water industry, but achieving that goal at reasonable cost is increasingly a challenge. Over the next 20 years, utility spending on infrastructure will at least double the spending on treatment according to AWWA estimates. Occasionally, required changes even accelerate infrastructure degradation, such as the lower coagulation pHs and higher coagulant doses necessary to meet provisions of enhanced coagulation. The current project will attempt to lessen the consequences of this action. We propose a study of infrastructure degradation from coagulation that

  1. synthesizes experiences of utilities and experts in the U.S., Canada and around the world,
  2. conducts some of the first detailed examinations of infrastructure degradation at treatment plants by a team with appropriate expertise, and
  3. executes field research to define changes in corrosivity that occur during coagulation.

Occurrence Survey for B and Cr in US Drinking Water

Faculty Member: Dr. Marc Edwards

The concentration, distribution, sources and sinks of chromium and boron in drinking water are quantified for the US. This is the first step in conducting a cost:benefit analysis of various regulations, determining consumer exposure to these emerging contaminants, and also examining passive removal that is occurring in treatment plants across the US. The national survey of chromium and boron is a multi-step process, consisting of (1) a pre-screening survey to validate field sampling and analytical method procedures of 20 utilities, (2) an initial questionnaire survey of utilities identified in the Water/Stats inventory of systems to identify willing participants for the national occurrence survey, (3) assessment of existing occurrence information to determine whether geographic patterns are important to the design of the survey, (4) final survey design where participants are selected randomly from the willing population, and (5) implementation of the field sampling program.

Exposure to Chemical Contaminants in Drinking Water

Faculty Member: Dr. John C. Little

To establish drinking water standards, potential exposure to the entire range of contaminants must be evaluated. A series of mathematical models is being assembled in a software package that evaluates human exposure to all chemical contaminants found in drinking water, based on their chemical properties. The model predicts exposure via ingestion, inhalation, and dermal sorption. A Monte Carlo analysis is employed to estimate the uncertainties associated with the exposure predictions. The program includes an easy to use visually-based user-interface.