April 2011, Vol. 23, No.4

A new frontier

news

While gas companies, universities, high-tech research firms, and even NASA have waded into the waters of algae-based biofuels, many wastewater utilities have stood along the shoreline watching others as they make the leap. But a few have realized the technology’s potential, growing algae at their wastewater treatment plants in order to remove nutrients. 

They also convert these autotrophic organisms into biofuel that in the far-off future could be used to power the plants or commercialized to raise revenue for their operations.

Since September, the Rockaway Wastewater Treatment Plant in Queens, N.Y., has been engaged in such a project with the assistance of HydroQual Inc. (Mahwah, N.J.), Biohabitats Inc. (Baltimore), the University of Arkansas (Little Rock), and Blackrock Energy Corp. (Williamsburg, Va.). The New York City Department of Environmental Protection (DEP) invested $387,000 into the project, installing an Algal Turf Scrubber®, a patented technology that consists of two 100-m (350-ft) metal sloped troughs. One trough receives 150 L/min (40 gal/min) of effluent, while the other receives 76 L/min (20 gal/min). According to a DEP press release, the troughs’ design is meant to mimic a “stream ecosystem by varying flow currents and using sunlight to promote algae growth.” After sufficient algal growth occurs, usually within a 10- to 14-day time frame, the algae are gathered and the water is removed using wet–dry vacuums. The algae are shipped and converted into butanol by scientists at the University of Arkansas.

So far, the plant has produced 1 L of butanol.

“I know one liter doesn’t sound like a lot of biofuel, but it is, considering that it was made inside a lab with just lab equipment,” said Jamie A. Hestekin, an assistant professor of chemical engineering at the University of Arkansas. “The butanol that we gave them was fuel grade. You could probably run a car on it for about 8 miles [13 km].”

“As far as I know, no one else has made this much [using algae],” said John McLaughlin, director of ecological services at DEP.

Part of an overall plan

The project at Rockaway is part of the Jamaica Bay watershed protection plan, which includes upgrades at other wastewater treatment facilities in New York City, an oyster and eelgrass pilot restoration project, wetlands restoration at Paerdegat Basin, and green infrastructure projects.

When the department put together the watershed protection plan, it focused on “green technologies that had a big stormwater focus, but we were told that nothing was off the table,” McLaughlin said. So DEP decided to move forward with the algae project at Rockaway, he said, because it saw algae as a green technology that treated effluent and could be a source for renewable energy.

The contract was signed last summer, and the algal turf scrubber was operational from September to December.

“Right now we’re going through a seasonal shutdown,” McLaughlin explained.

Even though the algae can still grow in cold temperatures, it has gotten so cold in New York City that the ponds that feed the algal turf scrubber have frozen over.

At press time, McLaughlin had expected the plant to be back up and running by this month.

 

Not a simple formula

The process to convert algae to butanol can be complicated. “We’ve used two methods,” Hestekin said.

Scientists at the University of Arkansas have worked with a standard butanol technology that has been around for almost 100 years, and they have used a newer method that began in the 1990s. With the newer method, the anaerobic fermentation process to convert algae to butanol is broken down into two steps. The first, Hestekin said, is acid-genesis, whereby the starches and carbohydrates in the algae are hydrolyzed and extracted and then made into organic acids. Electrodeionization is used to extract pure butyric acid from this fermentation. In the second step, which is solvent-genesis, the organic acids are made into butanol.

Hestekin said a lot of algae are required to make a little butanol.

“Alga is about 85% to 90% water,” Hestekin said. The water is removed from the alga, and it is possible to do this by drying it on the turf scrubber. “Of the dry stuff, 15% to 40% is sugar. Of the sugar, 40% can be converted to butanol,” Hestekin said. “So keeping that in mind, if you had 100 pounds [45 kg] of wet algae, you would probably get about 1 to 2 pounds [0.45 to 0.9 kg] of biofuel out of it.”

But Hestekin also pointed out that this final product is still a lot compared to how much biofuel can be extracted by corn, another popular renewable fuel resource.

“Standard yield for corn to ethanol is 1 acre [0.4 ha] makes 330 gallons [1250 L] of ethanol per year,” Hestekin explained. “If you assume a growth rate on the algal turf scrubber system of 30 g/m2 day, the maximum yield of butanol is that 1 acre makes 1500-plus gallons [5700 L] of butanol per year. Since butanol is at least as good of a biofuel as ethanol, this means almost 5 times greater fuel production. That’s great, given that the algae on the 1 acre is also serving to clean up wastewater.” 

Moving forward

McLaughlin said DEP plans to evaluate the algae biofuel project for the next 2 years to collect more butanol and improve the data. If it continues to have positive results, it may eventually expand it to other wastewater treatment plants within the system. But it has to keep in mind the geography of New York City and how it could limit the installation of the algal system at other locations.

“In most places where land is plentiful, you can build at any scale,” McLaughlin said. “But in New York, we can’t go farther out. We can only go up.”

McLaughlin said there also is maintenance to consider. “For the most part, the system is self-maintained, but there are occasional leaks, and there is pump wear and tear,” he said.

McLaughlin said for now the hope is to produce enough butanol to use it as an energy source to offset existing fuel costs at the Rockaway plant.

Hestekin said the team at the University of Arkansas also plans to continue to collect data, and it is pursuing other partnerships.

“We’re working with Statoil in Norway as part of a consortium with other universities, like William and Mary and the University of Maryland,” Hestekin said. “They are highly interested in the Chesapeake Bay and open-water areas.”

Hestekin said the team isn’t working with any other municipalities or wastewater treatment plants.

“New York is very forward-looking and thinking in this way,” Hestekin said. “They’re the only ones really doing this. As scientists, we’re used to having far-off ideas of how something can be taken to the next step, but DEP is very big into making this work and getting as much biofuel as possible.”

 

LaShell Stratton–Childers, WE&T

 

 

Chesapeake Bay TMDL calls for steep cuts in nutrient, sediment loads

Despite past reductions, point sources face more stringent discharge requirements

The recently finalized total maximum daily load (TMDL) for the Chesapeake Bay and its tributaries sets ambitious goals for reducing nutrients and sediment entering the waterways. Although the measures necessary for achieving the reductions will not be fully implemented until 2025, point and nonpoint sources must begin reducing pollutant loadings in the next several years. For wastewater treatment plants (WWTPs) within the bay’s watershed, the TMDL likely will require decreasing their nutrient discharges beyond levels that already are among the lowest in the world.

Improving on past efforts

The 20th century witnessed a population boom and rapid development throughout much of the bay’s 166,000-km2 (64,000-mi2) watershed. By the 1970s, large influxes of nutrients and sediment to the bay had diminished water quality and decimated underwater grasses. A series of agreements involving the District of Columbia, various states in the bay’s watershed, and the federal government in 1983, 1987, and 2000 set goals for lowering pollutant loadings to the bay. In some respects, significant progress has been made. For example, annual nitrogen loadings to the bay decreased 27% between 1985 and 2009, dropping from 155 million kg (342 million lb) to nearly 113 million kg (250 million lb) during this period, said Ann Swanson, executive director of the Chesapeake Bay Commission (Annapolis, Md.), which advises the general assemblies of Maryland, Pennsylvania, and Virginia on matters related to the bay. Unfortunately, such advancements have been offset by increased development, she noted.

Some longtime advocates of efforts to improve the bay’s health view the TMDL as a positive step that could succeed where previous measures have fallen short. “For 25 years, the science has very clearly defined how much nitrogen and phosphorus” must be reduced if the bay is to be revived, said William Baker, president and chief executive officer of the Chesapeake Bay Foundation (Annapolis, Md.). “Those limits have been known but never enforced,” Baker said. The new TMDL, he said, “finally puts those limits into a real regulatory regime.”

Mandating further reductions of nutrients and sediment

High levels of nutrients and sediment contribute to several chronic problems plaguing the bay and its tributaries, including excessive algal growth, low concentrations of dissolved oxygen, and reduced water clarity. Therefore, the Chesapeake Bay TMDL, which the U.S. Environmental Protection Agency (EPA)finalized on Dec. 29, calls for major cuts in total nitrogen, total phosphorus, and total suspended solids (TSS) entering the bay and its tributaries annually. For example, EPA allocated 84.3 million kg/yr (185.9 million lb/yr) of total nitrogen, a reduction of 25% compared to the 2009 level. As for total phosphorus, the TMDL sets a limit of 5.7 million kg/yr (12.5 million lb/yr), 24% less than in 2009. Finally, TSS is capped at nearly 2.9 billion kg/yr (6.5 billion lb/yr), a decrease of 20% compared to 2009. Further allocated by jurisdiction and major river basin, the pollution limits are designed to ensure compliance with state water quality standards for dissolved oxygen, water clarity, underwater bay grasses, and chlorophyll a, an indicator of algae levels.

To develop the TMDL, the six states within the Chesapeake Bay watershed — Delaware, Maryland, New York, Pennsylvania, Virginia, and West Virginia — and the District of Columbia each prepared a Phase 1 watershed implementation plan (WIP), a document that outlines how and when each jurisdiction will meet its allocated pollutant loads. Jurisdictions now are developing their Phase 2 WIPs, which “will include additional detail about nitrogen, phosphorus, and sediment controls at the local level,” said Shawn Garvin, regional administrator for EPA Region 3. For example, the Phase 2 WIPs will include “more detail about specific controls, technologies, and practices at the county, conservation district, or other appropriate local scale,” Garvin said. Although originally required to submit Phase 2 WIPs this November, jurisdictions likely will have until early 2012, he said.

Also in 2012, jurisdictions must begin tracking progress against “two-year milestones,” Garvin said. The milestones are part of a series of intermediate deadlines to ensure continual progress as the TMDL is implemented during the next 15 years.

Building on previous reduction efforts

The central question regarding implementation of the TMDL concerns how to reduce pollution from nonpoint sources that are not addressed by existing regulatory programs related to clean water. For example, agriculture is the largest single source of nutrients and sediment to the bay, contributing approximately 44% of the nitrogen and phosphorus loadings and 65% of sediment loads, according to EPA. By comparison, municipal WWTPs contributed approximately 17% of the nitrogen loadings, 16% of the phosphorus loadings, and a negligible amount of sediment to the bay in 2009. Because of aggressive efforts to reduce nutrient discharges from WWTPs and implementation of conservation practices by farmers, pollutant loadings from point sources and agriculture have decreased substantially over the years. However, the TMDL demands significant further reductions. For example, large WWTPs are required on a combined basis to decrease discharges of nitrogen by 27% and phosphorus by 26% from 2009 levels, Garvin said, while agriculture must cut its loadings of nitrogen by 38% and phosphorus by 31%.

After spending many years and significant amounts of money to reduce their nutrient contributions, some in the wastewater community worry that WWTPs will continue to bear the brunt of efforts to improve the waterbody’s health. For WWTPs, nutrient reductions often have been achieved at considerable expense, as is perhaps best evidenced by the 1.4 million-m3/d (370 mgd) Blue Plains Advanced WWTP in Washington, D.C. To date, the owner of Blue Plains — the District of Columbia Sewer and Water Authority, or (DC Water) has spent more than $1 billion to construct a tunnel system to capture stormwater runoff. In this way, DC Water will reduce combined sewer overflows and decrease the likelihood that peak flows will exceed the advanced treatment capacity of Blue Plains, said George Hawkins, general manager of DC Water. Because water stored in the tunnels will be conveyed to the plant as it is able to treat the flows, more flows will undergo advanced treatment at Blue Plains, enabling DC Water to stop discharging partially treated wastewater following major storms and reduce the amount of nutrients leaving the facility. Meanwhile, DC Water also is spending another $950 million to improve the nutrient-removal capabilities of Blue Plains by 2015.

EPA makes contingency plans

Absent significant nutrient reductions from nonpoint sources, WWTPs and other point sources may be required to reduce their contributions further still. “If a jurisdiction’s plans are inadequate or its progress is insufficient, EPA is committed to take the appropriate contingency actions to ensure pollution reductions,” according to the TMDL. Such actions include “requiring additional pollution reductions from point sources such as wastewater treatment plants,” the TMDL states.

To date, point sources have achieved the “lion’s share of reductions” of nutrients to the bay, Hawkins said, and likely will continue to do so for some time. However, relying predominantly on further reductions from WWTPs ultimately will prove expensive and unproductive, he said. “We’re worried that at some point, the economic efficiency of reducing pollutants from point sources at the margin becomes so ineffective, that it would be much more effective to try to spend similar sums of money” addressing nonpoint sources, Hawkins said.

Compared to more nebulous sources of pollution as air deposition and agricultural runoff, WWTPs offer “easy targets” for additional regulatory requirements, said Karen Pallansch, general manager of the Alexandria (Va.) Sanitation Authority, which is spending $150 million to reduce total nitrogen concentrations in the discharge of its 204,000-m3/d (54-mgd) WWTP to 3 mg/L. “There’s a belief that you can engineer the solution to anything,” she said. However, WWTPs “have already engineered a lot of solutions,” she said. For the TMDL to succeed, “it’s a matter of making sure that everyone bears the same level of responsibility,” Pallansch said.

Of course, money also will be needed for the TMDL to succeed. Although the actions required by the TMDL are technically feasible, finding the means to pay for them is a different matter, said Kimberly Burgess, chief of the Surface Water Management Division within the City of Baltimore’s Department of Public Works. “What it always comes down to with any government service is where the funding might be available” for implementing it, Burgess said.

Legal, legislative challenges loom

Funding questions aside, legal and legislative challenges also could delay or otherwise affect implementation of the TMDL. On Jan. 10, the American Farm Bureau Federation (Washington, D.C.) and the Pennsylvania Farm Bureau (Camp Hill) filed suit against EPA in the U.S. District Court for the Middle District of Pennsylvania, seeking to have the Chesapeake Bay TMDL vacated. The plaintiffs allege that EPA overstepped its authority and used inaccurate information in developing the TMDL, while failing to provide adequate time for public review.

On Capitol Hill, the seeds of a congressional battle over the TMDL were sown on Feb. 18, when the U.S. House of Representatives approved an amendment to an appropriations bill (H.R. 1) that would prevent the federal government from implementing the TMDL. Introduced by Rep. Bob Goodlatte (R–Va.), the amendment passed by a vote of 230 to 195. At press time, the House and Senate still had not resolved their differences on the fiscal year 2011 budget, and the latest temporary spending extension was set to expire on April 8.

 

— Jay Landers, WE&T

 

©2011 Water Environment Federation. All rights reserved.