Trade.Information

Topic Name: Effect of plastic on water quality and odor.

Category: Chemical

Research persons: Andrea M. Dietrich, Ph.D., & Her Team

Location: Department of Civil and Environmental Engineering,200 Patton Hall,,Virginia Tech Blacksburg, VA 24061,, United States

Details

“Fruity plastic” may seem like a connoisseur’s description of the bouquet of a bottle of Chardonnay or Merlot gone bad. However, that was among several uncomplimentary terms that a panel of water “sensory experts” used to describe the odor of drinking water from the plastic piping that is finding its way into an increasing number of homes these days.
The sampling was part of pioneering research on how plumbing materials affect the odor and taste of drinking water, which was reported here today at the 234th national meeting of the American Chemical Society (ACS).
Andrea Dietrich, Ph.D., who reported to the ACS, the world’s largest scientific society, pointed out that a rash of costly pinhole leaks in recent years in commonly used copper water pipes has led to renewed interest in lower priced plastic pipes. Dietrich and colleagues at Virginia Tech are among those scientists leading the way in evaluating how plastic might affect water quality and odor.
“Although water is a complex mixture of organic and inorganic chemicals, most people expect their drinking water to have little or no flavor,” Dietrich noted. With those expectations, any taste or odor in a glass of water can be “highly noticeable.”
Dietrich’s team is using two methods to evaluate odors associated with several types of plastic piping. First, sensory panelists smell and describe the odor of the water after it has sat in the pipes for several days. Then, the water undergoes chemical analyses for metals and organics and basic water quality parameters, such as pH.
Using specially prepared, neutral-smelling water as their control, panelists described the test water samples in terms that included “waxy plastic citrus,” “fruity plastic” and “burning plastic.” Fortunately, the odors are not long lasting, Dietrich said. “We find that after about two months, most of the odors and water quality effects have gone to background.” How quickly the odors disappear depends on the amount of water usage, she added. When a household uses more water, the odors fade faster.
Dietrich told the ACS that her group evaluated several types of plastic piping: cPVC (chlorinated polyvinyl chloride), HDPE (high-density polyethylene), and PEX-aA and PEX-b, which are crosslinked polyethylenes. Each is approved and certified for use in drinking water applications by NSF International, an independent certification, standards and testing organization, and ANSI, the American National Standards Institute.
“We found that cPVC has a low odor potential and it doesn’t seem to release many organic chemicals,” Dietrich said. “HPDE actually had the highest odor production, although it didn’t release very many organic materials. The PEX-b pipe had a moderate amount of odors and also a moderate amount of organic chemicals that were released into the air. PEX-a had fewer odors and organics release than the PEX-b pipe.”
Asked about her personal preference in plastic piping, Dietrich replied: “I would recommend people talk to their neighbors and find out what type of plumbing materials they have and if they are having problems. We do suspect that certain materials are going to be more compatible in certain areas,” due to the differences in water quality from one part of the country to another.
For now, Dietrich’s group is focused mainly on the odors imparted by plastic pipes and the analysis of any organic compounds that may leach into the water from the pipes. Asked if there may be any health effects from the leached compounds, Dietrich said that is still under investigation and she doesn’t have any answers at this point.
 

Water Treatment-
 

Towards a Sustainable Potable Water Infrastructure.
Consumers of potable water are familiar with problems that arise from corrosion of plumbing infrastructure including discolored water (red, brown or blue), metallic and other tastes and odors, and costs associated with replacement of water heaters or repair of damages from leaking pipes. Health problems due to microbial growth or contaminant leaching from metallic, plastic and concrete materials are also a serious public health concern for consumers and regulators. Surprisingly little interdisciplinary research progress has been made in understanding the chemical and biological factors contributing to corrosion, especially in the diverse ecologic niches encountered in residences, and as a result there is no rational basis for decision-making when problems are identified. Moreover, the economic and aesthetic consequences of corrosion in residences have never been quantified, although preliminary estimates and common sense suggest it is a multi-billion dollar per year problem. We have assembled an interdisciplinary research team to advance fundamental understanding of the economic, sociologic and biochemical dimensions to potable water infrastructure corrosion.
Researchers will 1) contribute to a thorough literature review emphasizing private (residential) infrastructure corrosion problems, 2) share their ideas with other members of the team, and then 3) participate in a two and one half day Interactive Information Exchange with practitioners who deal with aspects of corrosion problems on a daily basis and who will contribute their data for innovative scientific analysis. Researchers and students represent six disciplines (Civil and Environmental Engineering, Economics, Food and Sensory Science, Public Health, Regulatory Affairs, Water Treatment and Supply), three countries (USA, Chile, Germany), six different national agencies and associations (including the US Army), and three academic institutions. Participation and team-building among these diverse groups is needed to bring scientific and practical insights to the challenge of providing safe water in a manner that is also tempered by societal and regulatory needs.

Corrosion of Drinking Water Infrastructure by Enhanced Coagulation.
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.

Water Quality and Copper Pitting Corrosion
The primary goal of this work is to identify a level of free Cl2 in WSSCs 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 Super saturation 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 super saturation. 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.

Occurrence Survey for B and Cr in US Drinking Water
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.

About Researchers:
Andrea M. Dietrich, Ph.D.