Nutrient Removal Research Uncovers New Innovations and Improved Efficiencies
Yewei Sun, Bryce Danker - Hazen and Sawyer
Regulations on nutrient limits for wastewater treatment facilities have continued to evolve and tighten in recent years. With the likelihood of further limits on the horizon, many forward-looking utilities are exploring new methods to achieve nutrient removal in more cost-effective and energy-efficient ways.
One technology that has come to the fore is partial nitrification-denitrification-anammox (sometimes called PANDA).
This method uses a combination of microorganisms—most notably anammox bacteria—to remove nitrogen from wastewater more efficiently than conventional biological nutrient removal (BNR) systems.
Hazen has been investigating the effectiveness of PANDA in multiple groundbreaking studies with partnering utilities and research organizations across the country. As the scale and variety of Hazen’s PANDA testing has grown, so have the potential cost savings, operational efficiencies, environmental benefits, and technological advancements that have been uncovered.
Top Photo: A Los Angeles County cityscape. Hazen's PANDA research in Southern California and across the country has uncovered significant, beneficial discoveries for nutrient removal facilities.
The Evolution of PANDA Research
Hazen has been exploring new, more efficient avenues for improving nutrient removal processes across treatment stages and configurations for over a decade, with early work taking place in tests in New York and North Carolina. Hazen’s recent research in Southern California specifically traces back to an initial small-scale pilot that proved the feasibility of using PANDA to meet strict nitrogen limits using a tabletop version of a northern Virginia plant’s treatment system. This evolved into the study of a full-scale PANDA operation in a new configuration, which in turn led to an opportunity to test PANDA through a fully remote-controlled system at a Seattle-area wastewater plant.
These research iterations have focused on how to best leverage anammox bacteria—microorganisms that are the heart of successful PANDA systems. Anammox are valuable because they don’t require additional oxygen or organic carbon like many other bacteria do in order to effectively remove nitrogen. This means less energy required to run aeration systems and smaller quantities of supplemental carbon that facilities need to purchase—both resulting in major cost savings.
The Promising Benefits and Future of PANDA
Hazen’s study in Southern California was the first to use PANDA in tandem with a high purity oxygen activated sludge (HPOAS) system, a type of high-rate activated sludge (HRAS), proving yet another successful PANDA configuration.
“People in the wastewater industry have been trying to find ways to take advantage of the efficiencies of using anammox in mainstream treatment for years,” says Bryce Danker, PE, Associate Engineer with Hazen. “By focusing on the fundamentals of how we could make a system like this work, we believe we’ve uncovered how to successfully apply anammox for mainstream treatment across a variety of configurations.”
Most notably, the study demonstrated that primary effluent (PE) carbon can be used as a naturally available carbon source within wastewater to help drive PANDA. If utilities no longer need to rely on purchasing large quantities of costly external carbon for nitrogen removal, these systems become much more economically sound and environmentally sustainable.
While this study proved the potential for a consequential new method of mainstream anammox application at full-scale, the Hazen team continues to test PANDA in as many settings as possible to push the concept’s limits and discover its full benefits for wastewater utilities.
“We believe that PANDA can be incorporated into almost all existing wastewater treatment processes for nitrogen removal to generate savings,” says Yewei Sun, PhD, PE, Senior Principal Scientist at Hazen. “Our goal is to prove that by testing it in as many different ways as we can.”
Hazen’s most recent PANDA research findings have been published in multiple papers with the International Water Association’s Water Research and the Chemical Engineering Journal. These studies are available to subscribers and can be found at the links below.
- “Leveraging primary effluent- and glycerol-driven partial denitrification-anammox within a pilot-scale tertiary step-feed moving bed biofilm reactor treating high-rate activated sludge systems effluent”
- “Kinetic mechanism of methanol-fed partial denitrification anammox in tertiary moving bed biofilm reactors fed with real secondary effluent”
- “Mechanistic understanding of the performance difference between methanol- and glycerol-fed partial denitrification anammox in tertiary moving bed biofilm reactors treating real secondary effluent”
- “Carbon-efficient nutrients removal from real municipal wastewater under conditions of highly variable influent quality and low temperature”
