March 2014, Vol. 26, No.3

Research Notes

Process extracts and converts nitrogen in wastewater into energy

A process developed by Stanford University (Stanford, Calif.) postdoctoral scholar Yaniv Scherson both converts nitrogen extracted from wastewater into nitrous oxide gas and uses the gas to increase power output of engines at water resource recovery facilities (WRRFs).  

The patented coupled aerobic-anoxic nitrous decomposition operation (CANDO) converts the most common form of reactive nitrogen, ammonium, into gas and allows facilities to generate renewable energy from wastewater, according to a Stanford Woods Institute for the Environment news release. 

CANDO’s three principal steps include biotic conversion of ammonia to nitrite; abiotic/biotic conversion of nitrite to nitrous oxide; and decomposition or combustion of nitrous oxide to nitrogen, oxygen, and energy, according to Scherson’s nitrogen removal and energy recovery poster. While the first and final steps both are established processes, Scherson’s work focuses on the efficient conversion of nitrite to nitrous oxide. His research presents two partial-denitrifying strategies that involve an abiotic reaction of ferrous iron and nitrite to form nitrous oxide and a biotic pathway using heterotropic denitrifying organisms, the poster says. 

Nitrogen removal and energy recovery offer a potential alternative to treating nitrogen as a waste and an opportunity to improve the efficiency of WRRFs by lowering oxygen demand, reducing biomass production, and increasing energy recovery from organic matter and reactive nitrogen, the poster says.   

Scherson and his team at Stanford have demonstrated the technology’s success in a laboratory with synthetic wastewater. They formed a partnership with Delta Diablo Sanitation District (Antioch, Calif.) as well as conducted a successful bench-scale system in the laboratory. The team is building a pilot-scale demonstration unit at the district’s facility and expects to run the unit for at least 12 months, the news release says. 

 


 

Paul L. Busch award recipient develops biogranule  

Chul Park, associate professor at the University of Massachusetts Amherst, has received the 2013 Paul L. Busch Award. Park and his research group have developed an algal-solids biogranule that improves the ability to treat wastewater and nutrients without aeration, according to a Water Environment Research Foundation (WERF; Alexandria, Va.) news release. 

The biogranule — developed in response to the difficulty with effectively and affordably gathering algae for algae-based wastewater treatment processes — is composed of algae and bacteria within one granular biomass. It can be formed in the wastewater treatment process. Because the algae and bacteria cohabitate within the granule, it offers a consistent and efficient symbiotic treatment process, the news release says. 

The research project potentially could change how wastewater is treated and the levels of energy consumption associated with treatment. Park will use the monetary award to demonstrate the biogranule’s ability to treat wastewater with low oxygen requirements and to efficiently collect biomass that can be anaerobically digested to generate methane, the news release says. 

“This research has the potential to provide a new direction for treatment and can be used for mainstream treatment, for sidestream treatment, or as a tertiary nutrient removal process,” according to John T. Novak, the Nick Prillaman professor emeritus in the department of Civil and Environmental Engineering at Virginia Polytechnic Institute and State University (Blacksburg, Va.), in the news release. 

The WERF Endowment for Innovation in Applied Water Quality Research presented Park with the annual award, which includes a $100,000 grant that will support Park’s research. For more information see www.werf.org/PaulLBusch

 


 

Analyzing ammonia control to limit aeration 

Researchers have evaluated the fundamentals of ammonia control with a focus on feedforward control concepts. An article in the January issue of Water Environment Research presents a case study discussion reviewing different ammonia-based control approaches. 

Ammonia control for limiting aeration is applied either to reduce aeration costs or to reduce ammonia peaks in effluent. Benefits of limiting aeration include energy savings, possible reduction in external carbon addition, and possible improvement in denitrification and biological phosphorus performance, the article says.  

Ammonia control mainly has been based on feedback control to constrain complete nitrification by maintaining approximately 1-2 mg/L of ammonia in the effluent. Recently, feedforward ammonia control has received attention for optimal aeration of activated solids systems. “This paper aims to clarify some of the misconception about this control topic,” the article says. 

The researchers from EnviroSim Associates Ltd. (Hamilton, Ontario, Canada) and Hampton Roads Sanitation District (Virginia Beach, Va.) determined that in most instances, feedback control meets the objectives for both aeration limitation and containment of ammonia peaks in effluent. “Feedforward control, applied specifically for switching aeration on or off in swing zones, can be beneficial when the plant encounters particularly unusual influent disturbances,” the article says.  

But researchers recommend applying careful analysis to determine whether feedforward control offers benefits over standard feedback control. They also recommend using dynamic simulation to develop a tailored design for a specific plant and offering a tool to test whenever process control strategies need to be implemented, the article says. 

The article, “Ammonia-Based Feedforward and Feedback Aeration Control in Activated Sludge Processes,” appears in the January issue of Water Environment Research and can be downloaded free at http://goo.gl/6tsmxX. 

  

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.