bridges vol. 21, April 2009 / Feature Articles

By Thomas Wirthensohn

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Wastewater treatment in the Washington, DC, area seems to be a family-run business: Sudhir Murthy, son of a wastewater engineer, is research director at the Blue Plains treatment facilities of the DC Water & Sewer Authority, while his wife, Maureen O'Shaughnessy, works at the Alexandria Sanitation Authority in Virginia, on the opposite shore of the Potomac River. One of the challenges the couple faces at work is how to achieve significant long-term reduction of their plants' energy needs. The most power-consuming process is the removal of nitrogen - a nutrient that gets into the wastewater every time you flush your toilet.

Macroscopic view of Anammox bacteria. Bernhard Wett from the University of Innsbruck, Austria, is an expert in nitrogen removal. The environmental scientist joined the Murthy/O'Shaughnessy family in 2005 to introduce a new groundbreaking technique in wastewater treatment within the Washington, DC, area. The "Demon" process, invented by Wett, employs the recently discovered Anammox bacteria. Wett first demonstrated it successfully in a much smaller treatment plant in Strass in the Tyrolean Alps. For the treatment of certain sidestreams with particularly high nitrogen loads, he could decrease the energy consumption by more than 50 percent. Hence, the "Demon" process became a key component in making the Strass plant Austria's most energy-efficient wastewater treatment plant.

The collaboration of Wett with the American scientists has already received well-deserved recognition for outstanding performance in the US:  In February of this year, the US National Association of Clean Water Agencies (NACWA), the nation's biggest independent association for wastewater treatment, selected the DC Water & Sewer Authority together with the Alexandria Sanitation Authority to receive an award in the "Research & Technology" category of its annual National Environmental Achievements Program for "enhancing nitrogen removal and increasing sustainability with innovative sidestream treatment" using the Demon process.

Blue Plains Advanced Wastewater Treatment Plant

"We treat 300 million gallons of water a day," Murthy explains, while driving around the Blue Plains facilities. The distances are too long to
 
Blue Plains - the largest Advanced Wastewater Treatment Plant in the US. cover by walking, since Blue Plains is the largest Advanced Treatment plant in the United States. Serving 2 million people from the Washington, DC, metro area, Blue Plains is far bigger than the other 10 plants in the neighborhood combined.

Wastewater treatment was invented 100 years ago, and Blue Plains was built in the 1930s. Back then, the removal of organic pollution - carbon (C) compounds - was considered sufficient treatment. "Otherwise these carbon compounds get degraded in the rivers or sea. Degradation is an oxygen-consuming process, the fish would die," says Murthy. In the 1970s, however, it turned out that removing the less bulky compounds nitrogen (N) and phosphorus (P) is even more critical (click here to access a "bridges" article with comprehensive background information on the different pollutants found in waste water). These nutrients fertilize the water bodies, thereby enhancing algal bloom, which is again followed by degradation and oxygen depletion. The Blue Plains treatment process (click here to access a "bridges" article with background information on Blue Plains "Advanced Wastewater Treatment") removes carbon and phosphorus and, since 2000, nitrogen as well. Additionally, a sand filter and disinfection by chlorination further improve the effluent quality. "Blue Plains is located at the nicest spot on the Potomac River; sometimes you can even see bald eagles," smiles Murthy. The effluent of the treatment plant has almost drinking water quality. Still, the Potomac River has environmental problems.

Washington's Water Situation: Potomac, Anacostia, and the Chesapeake Bay

Water quality is a serious issue not only for the Potomac, but the same holds true for the Chesapeake Bay, into which the Potomac eventually flows. Nutrient pollution causes "dead zones," big areas without oxygen (click here to access a "bridges" article with background information on the problem of "dead zones" in the Chesapeake Bay). Sixty percent of these nutrients come from agricultural fertilizer use. Legal limitations for fertilizer use, as applied in Austria, do not exist in the U.S.  "Generally, farming has been allowed to take place without any consideration of water quality impacts.  Although there is no reason to think that ensuring a food supply is somehow inconsistent with having agricultural practices that protect the environment," states Adam Krantz of the National Association of Clean Water Agencies (NACWA ).

The Anacostia is the second main river in Washington, DC, and is in even worse shape than the Potomac and the Chesapeake Bay. "The Anacostia is particularly challenged," says Jim Connolly from the Anacostia Watershed Society, "since it is a smaller river, with low flow velocity." The pollution comes mainly from municipal stormwater runoff. Asked if there is any major industrial effluent, Connolly replies, "DC is not an industrial city.  Our main industry is government.  However, thousands of federal restrooms contribute to the sewage overflows affecting the Anacostia River, but there is no money for treatment and infrastructure." Connolly addresses the "taxation without representation" issue:  Even though DC has the highest federal taxes per capita and more total tax income than 19 other states, it has no adequate representation in Congress, which makes obtaining any federal funding more difficult.

The District, like several other old cities in the US, mostly uses the same pipes for both stormwater and wastewater. This sewage system is outdated and in bad condition, since maintenance was neglected for years. During heavy rain events, the sanitation system cannot take the load; untreated wastewater is discharged straight into the rivers - that's what is called a combined sewer overflow. In 1999, the Anacostia Watershed Society and other NGOs took action and filed a lawsuit against the DC Water and Sewer Authority (DC WASA ) to change this unacceptable situation. "They [DC WASA] were not properly managed in the past", says Connolly. "There were a lot of mistakes made and responsibilities avoided which negatively affected the effectiveness of the wastewater functions in the region." Eventually, the Environmental Protection Agency (EPA ) intervened and after settlement of the lawsuit, DC WASA was sentenced to a plan which called for a short-term fix and a long-term fix. The short-term measure required DC WASA to perform maintenance of the infrastructure, which had been neglected for years, such as fixing clogged pipes and jammed tidal gates, and replacing old pumps.  This has resulted in a significant reduction of the stormwater runoff by 40 percent.

The long-term measure entails construction of three huge tunnels for the storage of 194 million gallons of storm water. Connolly wishes the need for this expensive project could be reduced: It will cost $2.6 billion, and will take years before it is in operation. Therefore, he would prefer to implement measures for "green infrastructure" such as green roofs and porous pavements to manage storm water in a natural way, reducing the number of sewer overflows into the river.

On the other side of the Potomac River: the Alexandria Sanitation Authorities

Maureen O'Shaughnessy overlooking "her" ASA plant, and Alexandria, where the sewage comes from. Maureen O'Shaughnessy, Sudhir Murthy's wife, is director of Clean Rivers at the Alexandria Sanitation Authorities (ASA ) in Virginia, hence water quality of the Potomac is one of her main concerns, too. Her office is in a neat brick building, "We have architectural standards to fit into the Alexandria style," says Mrs. O'Shaughnessy. Still it's less the architecture than the process that makes ASA the tidy plant that it is. Several processes have been installed to make the facilities environmentally friendly: Heat exchangers provide energy savings, recycling schemes exist for all sorts of materials, and the covering of the aerated basins prohibits odor emissions. The exhaust air is then treated in a filter.

Challenges and Collaborations:  Enter DEMON

"The biggest challenges for wastewater treatment currently are reduction of the energy consumption, reduction of sludge volume, and of course improving our effluent quality, especially regarding nitrogen," Murthy and O'Shaughnessy agree. Nitrogen removal is the most costly part of wastewater treatment. The huge powerful blowers for aeration consume much energy. Furthermore, additional carbon (methanol) is needed as "fuel" for the bacteria. The cost factor is particularly critical for certain sidestreams from dewatering the sludge. These streams are concentrated and have significantly higher nitrogen loads than ordinary municipal wastewater.

That's why Murthy and O'Shaughnessy started testing new processes on these sidestreams - in collaboration with Au
 
Microscopic view of Anammox bacteria. strian Berhard Wett . Murthy laughs when he describes their first meeting - on a mountain, of course. Where else would you meet an Austrian? "We were at this conference in Morocco, hiking up the Atlas. I was huffing and puffing, while this slim, tall guy next to me was effortlessly walking, chatting about a new way of nitrogen removal that they just had implemented." At first, Murthy did not take Wett's explanations of the new technique too seriously since "Wett is the most understated, humble person you can imagine." But Murthy and Wett stayed in touch via email after their first meeting, and soon more information revealed to Murthy how promising the Demon concept was. Employing Anammox microorganisms, the process requires no additional carbon and only 40 percent of the oxygen required for conventional nitrogen removal - a significant reduction in methanol and aeration costs, almost a silver bullet for wastewater treatment.

Netherlands, a small but densely populated country that is traditionally a leader in wastewater treatment, built the first Anammox plant in Rotterdam in 2000. Bernhard Wett implemented this technology two years later in Strass, Zillertal, an Austrian winter holiday resort. The Strass plant was the first to eventually be operated successfully under full load in 2005. Recently, Wett even outcompeted the Dutch market leader, Paques , for construction of the then-biggest Anammox plant in Apeldoorn/Netherlands.

After Murthy got increasingly interested in the Demon process, he organized a trip to Innsbruck in 2005 - and another one two years later, including scientists from the New York City Department of Environmental Protection (NYCDEP ). The researchers were impressed with Annamox reactors they saw in Austria, and soon afterwards Bernhard Wett packed two pilots in boxes, to be shipped to the US. The experiments turned out to be successful. Recently, after the pilot stage was completed, Wett joined Murthy and O'Shaughnessy for designing a full-scale plant at the ASA in March 2009.

Another Austrian-American collaboration has involved Dr. Norbert Weissenbacher from the BOKU University in Vienna, an expert in monitoring gaseous emissions from wastewater processes.  Greenhouse gas emissions are a brand new research field in wastewater treatment. Biological nitrogen removal releases small amounts of nitrous oxide, a gas whose greenhouse impact is 300 times greater than that of CO2. Before the Demon process can be fully implemented in the Virginia wastewater treatment plant, investigations have to confirm that the level of greenhouse gas emissions is acceptable - and so far, it seems that even these gases can be reduced by 50 percent.

Appreciating wastewater as a resource

Along with new technologies like Anammox and monitoring greenhouse gases caused by wastewater treatment, the notion of saving energy and recycling the resources has slowly but steadily entered people's minds, even in the United States. "Wastewater was always something we simply wanted to get rid of, but we should perceive it as a resource," urges Murthy. The ASA plant already generates biogas from their sludge, and therefore "turns waste into watts." The biogas produced saves 25 percent of the energy costs. Buildings are heated, hot water and steam are produced, and the heat is especially useful for pasteurizing the residual sludge - making it a certified Class A product , the highest EPA classification for sludge. The biosolids are valuable in land applications and can be found in garden supply stores. And Blue Plains has a different biosolid management: Lime is added for disinfection. Local farmers appreciate this freely available product, particularly since fertilizer prices increased drastically. But Blue Plains is now changing its sludge treatment process towards anaerobic digestion: Six egg-shaped biogas reactors are currently under construction and will start operation in 2014. The biogas will be converted into heat and electricity, thereby reducing energy costs even further.

This project reflects a paradigm change. Until recently, energy in America was considered in much the same way as labor in India or China: a cheap resource that provides a competitive advantage in the global economy. But now things have changed drastically. During a recent hearing in the House of Representatives, Rich Brown, an environmental scientist at the Lawrence Berkeley National Laboratory, pointed out that wastewater treatment consumes 1 - 3 percent of a municipality's energy demand.  Energy savings of 10 - 30 percent are possible with technical investments such as better air diffusers and newer pumps. The American Water Environment Research Foundation (WERF ) has recently launched a program to evaluate and, eventually, reduce the energy consumption of wastewater treatment plants - and the Austrian wastewater treatment facility in Strass is set as a role model in their database. "The Strass plant is almost a benchmark," says Wett proudly. "An evaluation determined that it is the most energy-efficient wastewater plant in Austria." Murthy thinks even further ahead. "Now we use biosolids and generate energy, but at some stage it should also be possible to recover the wastewater nitrogen, which is now removed. Currently we in wastewater treatment simply blow the nitrogen into the air, while the chemical industry employs the energy-intensive Haber-Bosch process to recover atmospheric nitrogen."

US vs. Austria: water use, treatment, and legislation

Wett (5th from left) surrounded by scientist from Washington and New York at the ASA treatment plant. Also pictured, standing: O'Shaughnessy (2nd from right) and Murthy (left, 1st in 2nd row). Asked about the main differences in wastewater consumption between the US and Austria, Murthy replies that there is no general answer since water use and re-use is very different in the dry south of the US, compared to the water-rich areas in the northeast, like DC. Similarly, there would not be a single uniform European way to supply water and treat wastewater. But generally, the per capita water consumption is about 50 percent higher in the US (300 - 400 l per day) than in Europe.

In wastewater treatment, another difference is more obvious:  Austria does not apply sand filters and disinfection as final polishing steps. "Sometimes, safety chlorination would be used for drinking water to prohibit germs in the water grid," says Wett, "but usually not for wastewater."

Clear differences exist between Austrian and American legislation for wastewater treatment: In Austria the effluent of every wastewater plant has to fulfill certain standards. The American approach, however, is risk assessment: How much pollution can a water body of a certain size in a certain ecological system take? The Chesapeake Bay watershed, where DC and Alexandria are located, is a highly populated area. Therefore the effluent criteria for Blue Plains and ASA are much stricter than in Austria, e.g., the limits for phosphorus effluent concentrations are more than five-fold stricter. "The American immission approach, as opposed to the Austrian emission standards, is actually pretty progressive and smart because it is more flexible and dynamic," says Wett. In return, Murthy has good words for the Austrian approach: "The awareness of wastewater issues is much higher in Austria. The 2008 International Water Association (IWA) conference in Vienna was opened by then-Chancellor Alfred Gusenbauer. You could never imagine a conference like that in the US opened by the President."

Despair and Hope

Wastewater is not a very "sexy" topic, agrees Austrian Guenther Fink, assistant professor of International Health Economics at Harvard's School of Public Health. Fink is currently conducting research in Ghana, and he is particularly interested in the correlation between sanitation and health. "Sanitation and water treatment do not get the kind of funding other areas such as cancer or HIV research do." But that's where people die: Lack of sanitation means a higher disease burden and higher mortality, especially among children.

Currently, 1 billion people have no access to drinking water, and 2.5 billion people have no sanitation. One UN Millennium Development Goal is to reduce these numbers 50 percent by 2015. There might be a chance to succeed with drinking water, but it is impossible to accomplish the sanitation goal. More recently, the awareness of wastewater has increased in US media and politics, not only because of energy demand and effluent qualities, but also because of the rotten water infrastructure all over the United States. Maintenance and investments were neglected for many years; however, with the new US administration, progress may lie ahead.  President Obama has particularly addressed water issues:  He wants to triple the funding for infrastructure projects that protect waterways and drinking water. And the stimulus package assigns a total budget of $3.9 billion to improving the nation's sewage treatment plants and drinking water systems, as well as to projects that protect sources of drinking water. In energy policy matters, bipartisanship was also achieved; some supported the bills for environmental reasons, others in order to achieve independence from Middle Eastern oil supplies. Policy makers now understand that both increased efficiency and green energy are important to achieving energy self-sufficiency. "Americans are becoming aware of environmental issues," says Murthy, "and once Americans become religious about something, they really take it seriously." That sounds promising.

So there is hope! - Who said that again?

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The author, Thomas Wirthensohn, is member of the Waterboys, featuring Werner Fuchs.