October 2011, Vol. 23, No.10

Research Notes

Transforming toilets to operate by solar energy and fuel cells

Michael Hoffmann, environmental scientist and engineer from the California Institute of Technology (Caltech; Pasadena), is transforming the portable toilet. He is working to create a solar-powered portable toilet that can turn waste into fuel, according to a Caltech news release.

Hoffman received a $400,000 grant from the Bill & Melinda Gates Foundation (Seattle) as part of the Reinvent the Toilet Challenge to complete the initial design, development, and testing for his concept. He calls it the Self-Contained, PV-Powered Domestic Toilet and Wastewater Treatment system.

Hoffman’s toilet, designed to be used by as many as 500 people per day, requires only minimal maintenance and is sized to fit inside a typical portable sanitation unit. Equipped with a photovoltaic panel, the system generates energy to power an electrochemical reactor. The reactor breaks down water and human waste into hydrogen gas, which can be stored in a hydrogen fuel cell. The stored gas can provide backup energy at night or during periods of low sunlight, the news release says.

Constructing a single workable unit costs $2000, but the price would drop if the toilets were produced in volume, according to Hoffmann. He also envisions equipping units with self-cleaning toilets powered by solar energy and the fuel cell, the Caltech news release says.

“To address the needs of the 2.6 billion people who don’t have access to safe sanitation, we not only must reinvent the toilet, we also must find safe, affordable, and sustainable ways to capture, treat, and recycle human waste,” said Sylvia Mathews Burwell, president of the Global Development Program at the Bill & Melinda Gates Foundation, in the Caltech news release.

In August, all grant recipients will present their prototypes. The winning projects will receive additional funding. The Bill & Melinda Gates Foundation has awarded more than $40 million in new investments as part of its strategy to improve water, sanitation, and hygiene around the world. 

Reducing nitrogen in wastewater treatment provides economic benefits, study says

Reducing nitrogen generated by wastewater treatment plants can result in sizable economic benefits, according to a new study published in Environmental Science & Technology. The researchers found that adding available technology to existing infrastructure could reduce aquatic nitrogen pollution, atmospheric pollution, and energy use, all of which could result in financial gain for treatment plants, according to a Columbia University (New York) School of Engineering news release.

The study also found that creating an emissions crediting system for the wastewater industry could make incorporating new technologies more affordable. “The creation of an emissions trading market could provide the needed incentive for wastewater treatment plants to adopt technologies that would reduce climate pollution, help clean up our waterways, and even save energy and money,” said chief author of the study, James Wang with the National Oceanic and Atmospheric Administration.

The other authors of the study include Steve Hamburg, Environmental Defense Fund; and Water Environment Federation (WEF; Alexandria, Va.) members Donald Pryor, Brown University (Providence, R.I.); Kartik Chandran, Columbia University (New York) and member of the WEF board of trustees; and Glen Daigger, CH2M Hill (Englewood, Colo.).

With stricter wastewater permits, plants encounter increased capital and operating costs, Chandran said in the news release. “Our study shows that, if the reduced emissions associated with well-designed and operated biological nitrogen removal operations can be used to earn CO2 credits, then this could be a big benefit both for the utilities from a cost perspective and for the environment from water quality and air quality perspectives,” he said.

Emissions credits could create an economic incentive of up to $600 million per year for wastewater treatment plants in the United States to reduce nitrogen pollution, with an added benefit of up to $100 million per year in electricity savings, the news release says. Other research has shown that meeting wastewater treatment objectives decreases biogenic nitrous oxide emissions, so adopting better process technologies for improving water quality could reduce these emissions significantly, Chandran said in the release.

In related research, Chandran has led the development of a protocol to measure nitrous oxide emissions and develop a nationwide database of emissions from wastewater treatment plants. The U.S. Environmental Protection Agency has adopted this protocol as the standard practice for detecting these emissions from plants, the release says.

Chandran also received a $1.5 million grant from the Bill & Melissa Gates Foundation (Seattle) to develop a pilot-scale process using esterification and anaerobic digestion to transform wastewater solids into biodiesel and methane, respectively, using the biodiesel to run generators. The project is being developed to aid sanitation and water quality in Accra, Ghana, and create the next-generation urban sanitation facility. Read more about this project in the September issue of WEF Highlights at www.wef.org/highlights.


New protocols to measure low levels of nutrients at treatment plants

With increasingly strict regulations for nutrient concentrations in wastewater treatment plant (WWTP) effluent, facilities need to use more advanced options for measuring dissolved organic nitrogen (DON) and dissolved non-reactive phosphorus (DNRP) at low levels. A new study by researchers from the Illinois Institute of Technology (Chicago) was performed to develop simple, accurate, and inexpensive protocols to measure these nutrients.

The researchers have devised two protocols: one exclusively measures DON; the other measures both DON and DNRP simultaneously.

Currently, measurements for both nutrient levels are calculated indirectly by subtracting dissolved inorganic fractions from the total dissolved concentration, which can result in significant errors, according to the study.

To remove nitrate below detectable levels while providing complete DON recovery, the researchers pretreated wastewater effluent using ion exchange. This method increases the accuracy of the overall DON measurement protocol, the study says. To measure both total dissolved nitrogen and phosphorus accurately, spectrometric methods were combined with persulfate digestion of the samples. Measurement ranges attained were 0.05 to 3 mg N/L for DON and 0.01 to 0.5 mg P/L for DNRP.

“Overall, the protocols proved to be accurate, simple, and economical options to deploy in WWTPs and research laboratories to measure low concentrations of effluent DON and DNRP,” the study says.

This study, “Measurement of Organic Nitrogen and Phosphorus Fractions at Very Low Concentrations in Wastewater Effluents,” appears in the August issue of the Water Environment Federation (Alexandria, Va.) research journal, Water Environment Research. The article can be downloaded free at http://goo.gl/PbbK7.



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