January 2013, Vol. 25, No.1

Research notes

Purifying fracking wastewater

The U.S. National Science Foundation has funded research that may help solve one of the environmental and public health risks associated with hydraulic fracturing, commonly called “fracking.” University of Minnesota (Minneapolis) researchers are developing biotechnology that would purify fracking wastewater, according to a university news release.

During the fracking process, water, sand, and chemicals are forced deep into the Earth, creating fissures that allow natural gas or oil to escape and be recovered. The resulting wastewater contains chemicals used during the process, as well as chemicals present underground. Wastewater treatment methods, such as evaporation and filtration, are expensive and energy-intensive and only reduce chemicals to a concentrated form, the news release says.

The new treatment, however, uses naturally occurring bacteria embedded in porous silica materials to biodegrade contaminants. The technology, originally developed to remove agricultural pesticides from soil and water, is being customized to degrade fracking chemicals. The goal is to make the wastewater suitable for reuse in fracking other wells and to reduce the total amount of water used by the industry, the news release says.

The research project has earned a $600,000 grant from the National Science Foundation’s Partnerships for Innovation program. The program pairs researchers with companies to produce innovative technologies, the news release says. The research team includes lead Larry Wackett, Alptekin Aksan, Michael Sadowsky, and Robert Elde, dean of the university’s College of Biological Science, who will lead interaction between researchers and companies.

The team will work with Tundra Cos. (White Bear Lake, Minn.) on silica encapsulation technologies and Luca Technologies (Golden, Colo.) on using encapsulated microbes to recover natural gas from depleted coal beds, the news release says. The university is tasked with further developing a platform technology that could be used by these and other companies, the release says.

The team also has won a University of Minnesota Futures Grant to explore methods for mitigating the environmental effects of fracking.


Removing resources from wastewater

PARC (Palo Alto, Calif.) scientists received a grant to pursue technology that treats wastewater by separating suspended solids from water into two distinct resources. The California Energy Commission awarded the $1 million grant to demonstrate the new Hydrodynamic Separation (HDS) technology for wastewater treatment in California, according to a PARC news release.

The modular, scalable primary treatment technology separates particles from water without using physical filters and can be implemented in both large treatment facilities and portable applications, the news release says. It recovers solids that can be processed through an anaerobic digester to produce methane and generate electricity.

The process removes much of the organic solids in wastewater, so it can be further treated during a secondary biological process. By reducing organic content in wastewater, there is a lower demand for oxygen and aeration energy in secondary treatment, resulting in energy savings, the news release says.

“The ultimate goal of this project is to help plants become energy neutral,” said Stephen Hoover, PARC CEO, in the news release. “To be able to process millions of gallons of wastewater and provide two types of output — electricity and clean water — which can be repeated across many counties, states, and countries is quite a remarkable project.” The project will help facilities handle an increased flow during storms by providing backup capability that can scale to millions of gallons per day.

PARC plans to work with the Sunnyvale, Calif., municipal water resource recovery facility to demonstrate the HDS pilot system. CDM Smith (Cambridge, Mass.) will support PARC for this project by providing technical expertise in the field of wastewater and stormwater treatment design and engineering review during the field pilot-scale implementation, the news release says.

The technology also can be used for other applications, including algae dewatering, process water, cooling towers, bilge water, mining water, separation of oil or other emulsions from water, distributed/onsite water treatment, and recovery of resources from water, the news release says.


Carbon nanotubes threaten aquatic species

Researchers have determined that carbon nanotubes (CNTs) can be toxic to aquatic animals. University of Missouri (Columbia) and U.S. Geological Survey researchers conducted a joint study showing that CNTs can reduce growth rates or even kill some species of aquatic organisms, according to a university news release.

CNTs are used to strengthen composite materials, such as those used in tennis rackets, and have potential uses in everything from medicine to electronics to construction. The thin, long cylinders of carbon atoms can contain impurities of nickel, chromium, and other metals used in the manufacturing process, the news release says.

Researchers studied CNTs’ effects on mussels, small flies’ larvae, worms, and crustaceans and found that the metal impurities and CNTs themselves can have a negative effect on these species, the news release says.

The study, funded by a $400,000 grant from the U.S. Environmental Protection Agency, was published in the journal Environmental Toxicology and Chemistry. Researchers noted the need for additional studies of CNTs.


Achieving disinfection by combining ozone and ultraviolet radiation

Researchers conducted bench-scale experiments with municipal wastewater effluent samples to examine the feasibility of the combined application of ozone and ultraviolet (UV) radiation for disinfection. The November issue of Water Environment Research contains an article on this work.

Researchers studied effluent samples from the City of Indianapolis’s Belmont and Southport water resource recovery facilities. Effluent samples were subjected to ozonation in semibatch reactors to enable measurement of ozone demand and ozone transfer efficiency, the article says. This yielded high ozone-transfer efficiency and rapid initial ozone demand. Ozone demand resulted in relatively inefficient and variable inactivation of Escherichia coli and required ozone doses of approximately 10 mg/L to approach compliance with discharge permit limitations. Ozonation also yielded small improvements in UV transmittance of effluent samples; preozonation yielded only modest benefits with respect to subsequent UV254 irradiation, the article says.

The study found that compliance with discharge permit limitations could be achieved consistently with a UV254 dose of 12.4 mJ/cm2 at a preozonation dose of 2 to 3 mg/L. Without preozonation, consistent compliance was achieved with a UV dose of 16.5 mJ/cm2. And according to the article, “no evidence of synergism between ozone and UV254 radiation was found in the measured inactivation responses of E. coli.”

The article, “Ozone and UV254 Radiation for Municipal Wastewater Disinfection,” appears in the November issue of Water Environment Research and can be downloaded free at http://goo.gl/PFqHm.