EPA Tests Water Quality Sensors
Staff at the U.S. Environmental Protection Agency's National Homeland Security Research Center (Cincinnati, Ohio) have been monitoring online drinking water quality at the Test and Evaluation Facility for aberrations that may indicate contamination.

According to the research center, since March 2003 staff have been conducting proof-of-concept experiments demonstrating how water quality sensors respond to contamination in a water distribution system. Staff members inject commonly available contaminants into a recirculating pipe loop and single-pass distribution system simulators and then evaluate the response of commercially available water quality sensors. The experiments used common water quality sensors because water utilities, which may implement contaminant warning systems in the future, are knowledgeable about their operation and maintenance.

This approach also allows for dual benefit applications of water quality monitors. In addition to detecting contaminants, utilities will have more knowledge about the water quality in their distribution system. Problems arising from operational failures that affect water quality have a greater chance of being detected.

More than 25 contaminants were injected into the distribution system simulators. Testing included 20 water quality sensors, employing 17 water quality parameters from 14 different vendors. The most common water quality parameters are free and total chlorine, total organic carbon (TOC), specific conductance, oxidation reduction potential, pH, and turbidity. Of all the water quality parameters tested, free chlorine and TOC changed in response to more of the contaminant injections than the other water quality parameters tested, making them the best trigger parameters for contaminant warning systems.

The recirculation pipe loop is a 240-gallon ductile iron pipe with a mean retention time of 24 hours. Contaminants such as Round-UpĀ® herbicide and Real KillĀ® pesticide produced a large decrease in free chlorine and increase in TOC due to their organic nature. Compounds such as inorganic arsenite decreased free chlorine but did not affect TOC. Biological suspensions of non-pathogenic E. coli and spore-forming bacteria meant to simulate anthrax were injected. When injected with their growth media, free chlorine was consumed and TOC increased. Military agents such as VX, GB (sarin), potassium cyanide and ricin were tested at an off-site facility capable of handling the agents but employing the same experiment design. Free/total chlorine and/or TOC parameters detected all four contaminants.

In addition to the recirculating loop, a single-pass pipe was used. The three-inch diameter, 1,200-foot long pipe is a more realistic representation of a real-world drinking water distribution system. The chart shows the free chlorine response to Aldicarb pesticide. Water quality was monitored at two points in the pipe (80 feet and 1,100 feet from the injection point). The injection lasted for 20 minutes, and the response shows that the contaminant traveled as a slug through the length of the pipe.

Testing of online water quality monitoring for triggering contaminant warning systems has proven feasible in the laboratory. Field deployment is planned for several pilot utilities through EPA's WaterSentinel project. Future challenges to be addressed include:

  • Testing event detection algorithms under various water quality conditions;
  • Determining which commercially available water quality parameters are the best for online monitoring (This requires balancing the number of contaminants that a parameter responds to with the capital and operation and maintenance cost of that parameter); and
  • Performing experiments in drinking water with different residual disinfectants and water quality (Although free chlorine is still a commonly used disinfectant in drinking water, chloramines are becoming increasingly popular. Differences in each system must be evaluated).

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'Nanorust' Used to Clean Up Arsenic from Drinking Water
The discovery of unexpected magnetic interactions between ultra-small specks of rust has led scientists at Rice University's Center for Biological and Environmental Nanotechnology (CBEN) to develop a method for cleaning arsenic from drinking water.

According to the university, the technology holds promise for millions of people in India, Bangladesh, and other developing countries where thousands of cases of arsenic poisoning each year are linked to poisoned wells.

The new technique was described in the Nov. 10 issue of Science magazine."Our approach is simple and requires no electricity," said center director and lead author Vicki Colvin. "While the nanoparticles used in the publication are expensive, we are working on new approaches to their production that use rust and olive oil, and require no more facilities than a kitchen with a gas cooktop."

"Because we had just figured out how to make these particles in different sizes, we decided to study just how big of a magnetic field we needed to pull the particles out of suspension," Colvin said. "We were surprised to find that we didn't need large electromagnets to move our nanoparticles, and that in some cases, hand-held magnets could do the trick."

The experiments involved suspending pure samples of uniform-sized iron-oxide particles in water. A magnetic field was used to pull the particles out of solution, leaving only the purified water. Colvin's team measured the tiny particles after they were removed from the water and ruled out the most obvious explanation: the particles were not clumping together after being tractored by the magnetic field.

Colvin, professor of chemistry, said the experimental evidence instead points to a magnetic interaction between the nanoparticles themselves.

Co-author Doug Natelson said that as particle size is reduced, the force on the particles does drop rapidly, and the old models were correct in predicting that very big magnetic fields would be needed to move these particles.

"In this case, it turns out that the nanoparticles actually exert forces on each other," said Natelson, associate professor of physics and astronomy and in electrical and computer engineering. "So, once the hand-held magnets start gently pulling on a few nanoparticles and get things going, the nanoparticles effectively work together to pull themselves out of the water."

Because iron is well-known for its ability to bind arsenic, Colvin's group repeated the experiments in arsenic-contaminated water and found that the particles would reduce the amount of arsenic in the water to levels well below the EPA's threshold for U.S. drinking water.

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Scientists Improve Efficiency Of Oil-spill Cleanup Technology
Scientists with the Donald Bren School of Environmental Science and Management, University of California, Santa Barbara, have been working on a major advancement in the technology for cleaning up oil spills on oceans, lakes, and other waterways.

In a report scheduled for the Dec. 15 issue of Environmental Science & Technology, researchers Victoria Broje and Arturo A. Keller describe construction and field tests of an improved version of the mechanical skimmer, the mainstay device for recovering oil spilled on water.

Relatively unchanged for decades, the typical skimmer consists of a revolving steamroller-like drum that picks up a film of oil on the drum's surface. A scraper then removes the oil, which drops into a collector. Broje and Keller note that traditional skimmers are inefficient, work poorly with thin oils like light crude or diesel, and can be expensive to use in cleaning up large spills.

The new mechanical skimmer uses a grooved surface. With a larger surface area, the grooves scoop up more oil than the smooth-surfaced traditional skimmer. The scraper is machined to precisely match the groove geometry, removing almost 100 percent of the adhered oil with each rotation. The grooves also are coated with an improved oil-adhering polymer. Field tests show that the new skimmer is up to three times more efficient than traditional skimmers, the scientists report.

A pdf of additional information on the report, "Improved Mechanical Oil Spill Recovery Using an Optimized Geometry for the Skimmer Surface," can be accessed here or here.

Busch Award Recipient to Study Effects of Nanomaterials in Wastewater
Paul Westerhoff and his team at Arizona State University will try to provide fundamental knowledge of nanomaterial interactions that will facilitate their control in wastewater treatment plants. The work will be somewhat easier because Westerhoff received the Paul L. Busch Award and an accompanying $100,000 research grant.

The Water Environment Research Foundation Endowment for Innovation in Applied Water Quality Research presented the award to Westerhoff at its annual subscriber luncheon in October at WEFTEC 2006 in Dallas, Texas. Westerhoff was selected for his research investigating the fate of commercial nanomaterials in drinking water and wastewater treatment plants, and their potential human toxicity.

It is hoped that this research will improve operations of existing plant processes (for example, membranes, filters, sedimentation basins, ultraviolet irradiation) and catalyze research opportunities on the beneficial use of nanotechnology in diagnostic tools or treatment processes.

"We need to recognize the new and potential impacts of nanomaterials at wastewater treatment plants today," says Westerhoff. "Let's not wait five or ten years before we find nanomaterials ubiquitously in our rivers."

Nanomaterials -- structures no larger than a billionth of a meter wide -- are becoming increasingly common in manufactured goods and are frequently found in products as diverse as cosmetics and stain-resistant paints. Although this emerging technology brings advanced products and scientific advances to humanity, little scientific information is currently available on nanomaterials' fate in water and wastewater treatment plants, whether they are present in biosolids or effluent, or their potential impact on the treatment processes.

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Florida Center Tests Solar-powered Water Purification
Florida International University's Applied Research Center (ARC) together with U.S. Southern Command unveiled its newest technology in November -- a lightweight water purification system powered by solar photovoltaic cells -- the first project of its kind to merge solar technology with an existing water purification unit.

This equipment was deployed to Honduran military installations last year as part of ARC's research efforts for the Western Hemisphere Information Exchange Program (WHIX), conducted on behalf of the Office of the Secretary of the Army for Installations and Environment.

A technology demonstration took place last in early November at ARC, which is located on the university's Engineering Campus in Miami, Fla., and was led by Harlan M. Sands, ARC executive director and Col. Jerry Miller (retired), ARC associate director of military programs.

The new technology features 50 flexible photovoltaic array cells affixed to the canvas of a collapsible tent to produce electricity. These cells absorb solar energy in low light conditions, even if severely damaged. This easily deployable system is superior for operation where mobility and set-up time are crucial. Uses for this technology include battlefield operations, environmental cleanup, disaster areas, and undeveloped countries, where diesel fuel generators are unavailable or too costly to operate and potable water is scarce but crucial.

Currently, the 40-foot by 50-foot tent requires six trained personnel to set up and have operational in six hours. ARC plans to continue research to improve the design and hopes to successfully implement a system that could be affixed to the top of a large utility vehicle, which would allow more mobility and quick deployment.

The WHIX program is designed to facilitate military to military discussions on environmental issues and the exchange of information, ideas, and best practices.

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University Pairs with Company To Find Water Answers
New Mexico State University and General Electric Co. have begun a collaboration to bring the best minds from the school together with the company?s water expertise to produce affordable technologies that address growing demands for water -- particularly in areas like New Mexico.

The new partners signed a memorandum of understanding last October. The collaboration will further focus action on solving water scarcity problems around the world. The agreement was signed by NMSU President Michael V. Martin and Jeff Connelly, vice president of GE Water & Process Technologies.

The MOU, which includes a broad educational incentive for NMSU students, will work to develop advanced water treatment technologies to reduce the cost of creating new sources of freshwater by 25 percent over the next three to five years.

GE's expertise in developing commercial water technologies will complement the growing interest in water research and development in New Mexico, where the Navy, Sandia National Laboratories, and other federal agencies are carrying out major water desalination projects such as the Tularosa Basin National Desalination Research Facility, which is scheduled for completion this spring.

The NMSU-GE partnership will involve research and development at NMSU and at the GE Global Research Center in Niskayuna, N.Y. It will also focus on water treatment technologies capable of removing harmful source water contaminants often responsible for making human consumption, irrigation, and industrial plant production impossible.

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Researcher Finds Scrap Tires Useful for Filtering Wastewater
Every year, the United State produces millions of scrap tires, and finding adequate uses for these castoffs is a continuing challenge for researchers, regulators, and communities.

Dr. Yuefeng Xie, associate professor of environmental engineering at Penn State-Harrisburg, has developed a method that uses crumb rubber to filter wastewater, according to a Nov. 17 announcement by the university.

"The crumb rubber could be used for treating wastewater, ship ballast water and stormwater," Xie said.

Crumb rubber is produced by chopping up and grinding up waste tires to a desired size, cleaning the rubber, and removing any metal particles. It is currently being used in highway pavement, athletic track surfaces, playgrounds, landfill liners, compost bulking agents, various manufactured products, energy recovery, and as artificial reefs for aquatic life.

For traditional wastewater filtration, gravity downflow granular filters using sand or anthracite as a medium are used. One major problem with these filters is that upon backwashing the particles, the larger ones settle at a greater rate than the smaller ones. The Penn State researcher said that this causes the top of the filter bed to hold the smallest medium particles and the bottom to hold the largest, with the small medium particles or top layer of the filter tending to become clogged quickly.

In his research, Xie has found that crumb rubber can be easily bent or compressed. Through the crumb rubber method, the larger solids are removed at the top layer of the filter, and the smaller solids are removed at a lower level, greatly minimizing the clogging problem.

Several studies conducted by Xie show that the crumb-rubber filter is more cost-effective than conventional sand or anthracite filters. Because of substantially higher water filtration rates and lighter weight in comparison to sand or anthracite, crumb-rubber filters also may be used in a mobile-treatment unit for disaster relief operations, he said.

Because the crumb rubber is compressible, the porosity of the particles is decreased, which resembles an ideal filter medium configuration, the researcher stated. It can then be used at higher filter rates while performing similarly to other media now in use. The crumb rubber media provide better effluent qualities, and larger media allow longer filter runs at higher flow rates.

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This department first appeared in the January/February 2007 issue of Water & Wastewater Products.

This article originally appeared in the 01/01/2007 issue of Environmental Protection.

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