February 2014, Vol. 26, No.2

Research Notes

LIFT identifies hot technologies of the future

The Water Environment Research Foundation (WERF; Alexandria, Va.) has teamed with the Water Environment Federation in a joint initiative to move innovation into practice in the water quality sector. The Leaders Innovation Forum for Technology (LIFT) is designed to approach this challenge through four avenues.

 

  1. The Technology Evaluation Program provides a means for municipal and industrial facility owners to evaluate and integrate new technologies and share the risk and cost of conducting demonstrations.
  2. The People & Policy component informs policy at the federal, state, and local level to remove barriers and facilitate adoption of new technologies. This includes benchmarking of how utilities accomplish research and development (R&D).
  3. The Communication component provides training, education, and outreach relative to new technologies.
  4. The Informal Forum for R&D Managers allows individuals responsible for technology identification and deployment to share experiences,  activities, and interests. 

     

LIFT provides an avenue for peer-to-peer networking, knowledge sharing, and collaborative technology testing for innovative technologies.Through the LIFT Working Group, which includes more than 200 WERF facility owners, the program has and continues to identify technologies and topics of high priority around which to form focus groups. So far, five high priority technology topics have been identified.

 

Phosphorus recovery 

Phosphorus is both an essential and limiting nutrient, but in excess it has proven detrimental to water quality. Phosphorus recovery technologies are extremely attractive methods for water resource recovery facilities to reduce effluent phosphorus levels.

For example, Clean Water Services (Hillsboro, Ore.) Durham Advanced Wastewater Treatment Plant currently is operating the first phosphorus recovery facility in the U.S. Benefits to date include reduced phosphorus loads, reduced chemicals necessary for supplemental phosphorus removal, and reduced solids handling and disposal costs. This process has the potential to produce a return on investment in as little as 5 years.

 

Shortcut nitrogen removal 

Shortcut nitrogen removal processes in embryonic stages and those that are well-established promise to address increasingly stringent regulations and rising energy and chemical costs associated with nutrient removal. As a result, liquid sidestreams, which can account for up to 25% of nitrogen loading, are the targets of new technologies aimed at addressing nitrogen removal in a cost-effective and efficient manner.

Examples include the New York City Department of Environmental Protection, which currently is operating the largest SHARON® nitrite-shunt process in the world and is engaged in a pilot study in moving bed biofilm reactor-based sidestream deammonification. And since October 2012, the Hampton Roads Sanitation District (HRSD; Virginia Beach, Va.) has been operating DEMON® sidestream deammonification at its York River facility and has an ANITA® Mox sidestream deammonification in design at its James River plant. DC Water (Washington, D.C.) also has fully implemented the single-reactor DEMON sidestream deammonification process and is evaluating methods for anammox retention within the sidestream process.

Digestion enhancements

Predigestion technologies can help enhance anaerobic digestion, thereby reducing biosolids and increasing gas production. They also can help lower the costs of biological nutrient removal by reducing the need for external supplemental carbon for denitrification.

For example, HRSD, the Philadelphia Water Department, and the Orange County (Cailf.) Sanitation District have been exploring pretreating waste activated sludge with pulsed energy fields to achieve cell lysis. Thermal hydrolysis achieves the same result by using heat and water to cleave the chemical bonds of organic solids, reducing the hydraulic retention time in downstream digesters, and lowering capital costs. HRSD and DC Water are very engaged in better understanding this technology, as well as implementing and refining the Cambi process.

Energy from wastewater

Generating energy from wastewater has enormous potential for water resource recovery facilities striving for net-zero energy.

For example, DuPont Co. (Wilmington, Del.) is looking into electrogenic bioreactors, an innovative twist on microbial fuel cell technology, oxidizing organic matter as it would be in conventional treatment while simultaneously producing an electric current. On the West Coast, Delta Diablo Sanitation District (DDSD; Antioch, Ca.) is engaged in a demonstration project to determine the efficacy of hydrokinetic turbines at multiple facilities. During the demonstration, DDSD will gather data, review design, install and maintain the turbines, and develop operational procedures and drawings.

Biosolids to energy

Energy recovery from biosolids technologies comprises one of the most developed opportunities for water resource recovery facilities to engage in energy production practices,explained WERF Executive Director Glenn Reinhardt. Expansions on the two established pathways for energy recovery, anaerobic biodegradation and thermal conversion, are being examined at facilities nationwide.

DDSD is leading the efforts of the Bay Area Biosolids to Energy Coalition (San Francisco), a coalition of 18 San Francisco Bay area agencies seeking biosolids to energy technologies. They are currently evaluating a process that converts biosolids into biodiesel using the Fischer-Tropsch pyrolysis treatment to chemically degrade organic material with heat, but in anoxic conditions.

 


 

Hybrid solar-microbial system autonomously uses wastewater to produce energy 

 

What do you get when you combine solar energy with a microbial fuel cell (MFC)? A hybrid device capable of using wastewater and sunlight to produce hydrogen gas, according to research conducted by a team at the University of California, Santa Cruz.

The team, led by Yat Li, associate professor of chemistry at the university, developed the device and reported research in a paper published in the American Chemical Society (ACS; Washington, D.C.) journal, ACS Nano. The device combines an MFC with a photoelectrochemical cell (PEC).

In MFCs, electrogenic bacteria generate electricity by transferring metabolically-generated electrons across their cell membranes to an external electrode, the news release says. As bacteria degrade the organic matter in wastewater, the MFC generates electricity. This electricity is delivered to the PEC to assist solar-powered electrolysis that generates hydrogen and oxygen, according to a university news release.

Separately, the PEC and MFC both require a small additional voltage to produce hydrogen gas, adding to the cost and complication of these devices, especially at a large scale. The hybrid device runs entirely on the energy derived from organic matter and sunlight. The self-sustained “bio-battery” provides extra voltage and energy to the PEC to generate hydrogen gas, the news release says.

Initial tests of the device used electrogenic bacteria grown in the lab on an artificial growth medium. Subsequent tests used municipal wastewater from the Livermore (Calif.) Water Reclamation Plant. The wastewater contained both organic nutrients and a mix of microbes that feed on nutrients, including naturally occurring strains of electrogenic bacteria, the news release says.

The team found that when fed with wastewater and illuminated in a solar simulator, the device continually produced hydrogen gas at an average rate of 0.05 m3/d while cleaning the turbid wastewater. Soluble chemical oxygen demand in the water declined by 67% during a 48-hour period, the news release says.

But researches noted a decline in hydrogen generation as organic matter in wastewater declines. Replenishing wastewater in each feeding cycle led to complete restoration of electric-current generation and hydrogen-gas production, the news release says.

The researchers plan on scaling up the laboratory device to a 40-L prototype continuously fed with municipal wastewater and plan to test the device onsite at the water resource recovery facility.“The MFC will be integrated with the existing pipelines of the plant for continuous wastewater feeding, and the PEC will be set up outdoors to receive natural solar illumination,” said Fang Qian, a Lawrence Livermore National Laboratory researcher and study coauthor.


 



Low nutrients limits result in increased costs and pollution with diminishing benefits


Current biosolids regulations prove more than adequate to protect groundwater and human health, according to findings by a study published in the November issue of Water Environment Research. 

Researchers representing Utah State University (Logan, Utah), the U.S. Environmental Protection Agency (EPA), the Water Environment Research Foundation (Alexandria, Va.), and the Utah Division of Water Quality (Salt Lake City), set out to characterize potential human health risks associated with exposure to biosolids pollutants. Using EPA Multimedia, Multi-pathway, Multi-receptor Exposure, and Risk Assessment technology, the team developed a computer-based biosolids groundwater risk characterization screen tool (RCST), according to the report.  

Using RCST at two biosolids land-application sites in Virginia, the researchers determined that pollutant concentrations as large as 10 times the current regulatory limit could safely be applied to land with no apparent human health effects associated with groundwater consumption, the report says.  

Only “unrealistically high” biosolids application rates and pollutant concentrations posed significant health risks associated with groundwater impairment, the report says.  

“The absence of a significant human health risk predicted from biosolids land application modeling efforts as well as no reported incidence of regulated biosolids pollutants negatively impacting groundwater resources further supports maintaining current regulatory requirements,” the report says. 

The report, “Impact of Biosolids Recycling on Groundwater Resources,” is available as an open-access document and can be downloaded free at http://goo.gl/CFldnQ . 
 

Water Environment Research allows open access to one article per issue on a range of important technical topics such as nutrient removal, stormwater, and biosolids recycling.