February 2007, Vol. 19, No.2

Research Notes

Research Notes

Deodorizing Farms and Reducing Pollution at the Source

Aluminum chloride — an ingredient found in deodorant sticks humans use for hygiene — may also be a good fit for pigs, or at least where they are raised. A U.S. Agricultural Research Service (ARS) scientist has found that aluminum chloride helps minimize the strong odors that emanate from swine and dairy facilities. Aluminum chloride has also been found to treat liquid manure and reduce phosphorus runoff when that manure is applied as a fertilizer.

Philip A. Moore Jr., who works in the ARS Poultry Production and Product Safety Research Unit in Fayetteville, Ark., spent the last 14 years trying to reduce the environmental burdens associated with animal waste, including poultry litter, according to an ARS news release. In 1992, Moore discovered the power of aluminum, in the form of aluminum sulfate, or alum. Alum “grabs onto” the phosphate in poultry waste, keeping it from escaping into waterways. It also reduces the buildup of ammonia gas in chicken houses.

Manure from poultry, dairy, and swine facilities, ARS notes, serves as valuable fertilizer for farmers’ fields, but only if it’s applied in the right dosage. Too much phosphorus-rich waste can foul water supplies and wreck fragile marine ecosystems. More recently, the researcher found an even better aluminum performer for treating the liquid manure associated with pigs and dairy cows — aluminum chloride.

Unlike alum, this compound doesn’t generate smelly, sulfuric gases when applied to liquid waste. Aluminum chloride also can significantly reduce phosphorus runoff and atmospheric ammonia levels that negatively affect water quality by increasing atmospheric nitrogen deposition.

For more information, see the November–December issue of Agricultural Research at www.ars.usda.gov/is/AR/archive.

Device Tests Efficacy of New Orleans Levees

U.S. Agricultural Research Service (ARS) research scientist Gregory J. Hanson of the Hydraulic Engineering Research Unit in Stillwater, Okla., has designed a device capable of measuring the efficacy of New Orleans’ levees through their soils. Originally designed to help evaluate the potential for soil erosion in streambeds and streambanks, the Jet Test Apparatus focuses on how well soil can resist erosion by water.

“We have conducted a significant amount of research on the erodibility of earthen spillways, embankments — i.e., dam embankments, levees — streambeds and banks, and channels,” Hansen explained to Water Environment & Technology (WE&T). “This has included testing conducted at our laboratory, as well as tests in the field. Based on our experience, we have concluded that erodibility is an important parameter for determining erosion resistance of earthen materials in concentrated flow environments, whether it is a streambank or a levee. The jet erosion tool is capable of testing the erodibility of soil materials in either setting.”

By using a water jet pumping at various flow rates, the device can give rapid determinations of the erodibility of soil used in levees or structures similar to levees, according to an ARS news release. “Erodibility is an important indicator of earthen material erosion resistance to concentrated water flow, such as overtopping or internal erosion,”making it a good indicator of a levee’s durability, Hansen told WE&T.

In the past, the ARS news release notes, there has not been an objective way to measure erodibility, so resistance to erosion has not been included in levee specifications. A report now being finalized by U.S. Army Corps of Engineers research civil engineer Johannes L. Wibowo, with the Army Corps’ Engineer Research and Development Center (Vicksburg, Miss.), may change that.

While the device was originally designed to help evaluate the potential for soil erosion in streambeds and streambanks, Hanson and Wibowo saw the possibility of using the equipment to test new and existing levees.

The levees in New Orleans’ East Parish and St. Bernard Parish — both those that survived Hurricane Katrina intact and those that were repaired after failing — provided the perfect place to test their idea.
The ARS National Sedimentation Laboratory in Oxford, Miss., which also has been using the Jet Test Apparatus in stream erosion and sedimentation studies, provided the device and training to help the Army Corps with the initial testing of the levees.

Levees that successfully held during Hurricane Katrina provided a baseline for acceptable erodibility. Newly repaired levees were matched against that standard.

Measuring the ability of the repaired levees to resist water erosion is especially important, because the soil being used to rebuild them is from a number of locations around Louisiana and Mississippi, and the soil’s resistance to erodibility, once placed and compacted, may not be known.
 
Contact Hanson at greg.hanson@ars.usda.gov.

Today’s Seawater Is Tomorrow’s Drinking Water, Researchers Say

Researchers at the University of California–Los Angeles Henry Samueli School of Engineering and Applied Science have developed a new reverse osmosis (RO) membrane that could reduce the cost of seawater desalination and wastewater reclamation, according to a university news release.

The new membrane, developed by civil and environmental engineering assistant professor Eric Hoek and his research team, uses a uniquely cross-linked matrix of polymers and engineered nanoparticles designed to draw in water ions but repel nearly all contaminants. These new membranes are structured at the nanoscale to create molecular tunnels through which water flows more easily than contaminants.

“All of our tests suggest TFN [thin-film nanocomposite] and traditional RO membranes reject salts, minerals, and dissolved organics similarly,” Hoek told Water Environment & Technology (WE&T). “In some cases, we can nearly double the flux while maintaining the same or better salt rejection. It depends on how we synthesize the nanoparticles, the base polymer chemistry, and how we cast the nanocomposite films.”

Hoek’s membrane contains specially synthesized nanoparticles dispersed throughout the polymer — known as a nanocomposite material.

“The nanoparticles are designed to attract water and are highly porous, soaking up water like a sponge while repelling dissolved salts and other impurities,” Hoek said. “The water-loving nanoparticles embedded in our membrane also repel organics and bacteria, which tend to clog up conventional membranes over time.”

With these improvements, less energy is needed to pump water through the membranes. Because they repel particles that might ordinarily stick to the surface, the new membranes foul more slowly than conventional ones. The result is a water purification process that is as effective as current methods but more energy efficient and potentially much less expensive. Initial tests suggest the new membranes have up to twice the productivity — or consume 50% less energy — reducing the total expense of desalinated water as much as 25%.

In lab tests, Hoek explained to WE&T, TFN membranes exhibited significantly more permeability and fewer tendencies to clog with bacteria when compared to traditional RO membranes. This fouling results in higher energy demands on the pumping system and leads to costly cleanup and replacement of membranes.

“Assuming the early lab results translate when the technology is scaled up, we project a substantial reduction in electrical energy needs and RO plant size,” Hoek said.

“You can replace the [traditional] membranes more frequently, but this does not prevent clogging or the need for periodic cleaning, and it is also very costly,” Hoek explained. “Even a conventional RO membrane is not a cheap razor blade; these are elegantly engineered, high-performance materials — the result of 50-plus years of research and development. An average commercial RO element might cost about $300 each. In a large plant, you might have more than 10,000 elements. Traditionally, the goal has been to develop membranes with the longest possible useful life, because there is an optimal balance between the cost of frequent replacement, the cost of energy consumption, and the cost of chemical cleaning [and] pretreatment. Interestingly, we expect the cost of manufacturing TFN membranes to be about the same as traditional RO membranes.”

Viable alternative desalination technologies are few, though population growth, overconsumption, and pollution of the available freshwater supply make desalination and water reuse ever more attractive alternatives.

With his new membrane, Hoek hopes to address the key challenges that limit more widespread use of RO membrane technology by making the process more robust and efficient.

Hoek anticipates the new membranes will be commercially available within the next year or two.

For more information, contact Hoek at hoek@seas.ucla.edu.