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WWTPs increasingly seek to lower energy demand, reduce solids generation, and recover valuable resources
Death and taxes may be the only certainties in life for individuals, but for U.S. wastewater treatment plants (WWTPs) the main certainties in their collective future appear to be higher energy costs, greater restrictions on solids disposal, and more-stringent discharge limits. Faced with these apparent inevitabilities, designers and operators of WWTPs — along with the vendors that hope to attract their business — increasingly are seeking ways to lower energy demand, reduce solids generation, and recover energy and nutrients. In short, WWTPs of the future seem poised to become lean, green, resource-recovery machines.
The increasing emphasis on reducing energy use and recovering resources from wastewater is the result of “opportunity rather than regulations,” said Glen Daigger, senior vice president and chief technology officer at CH2M Hill (Englewood, Colo.). More than ever, the idea of extracting and using the energy and nutrients present in wastewater is “really catching people’s attention,” he said.
Overcoming overdesigned WWTPs
Long driven by the need for “bulletproof compliance,” WWTPs frequently “have been overdesigned by a factor of two or three,” said John Willis, a vice president at Brown and Caldwell (Walnut Creek, Calif.). Therefore, energy use often has been a secondary consideration. However, the recent economic downturn, combined with federal spending for efforts to reduce energy consumption, has prompted greater interest in improving energy efficiency at WWTPs, Willis said.
For a case in point, consider membrane bioreactor (MBR) technology, an energy-intensive process that has grown in popularity as more WWTPs have turned to membrane technology to comply with tighter discharge limits and accommodate growing demand for reclaimed water. Although they offer such advantages as solids-free effluent and a smaller footprint compared to conventional treatment systems, MBRs consume, on average, twice as much energy as their conventional counterparts to achieve the same treatment goals at the same capacity, said Randall Booker Jr., wastewater membrane technology leader at Malcolm Pirnie (White Plains, N.Y.). “The ultimate issue with MBRs remains energy consumption,” he said.
The larger energy demand of MBRs results from the higher solids concentrations in which they operate. Under these conditions, the membranes must be scoured with air to prevent fouling and maintain filtration performance, while oxygen-transfer and aeration efficiency are lower than in a conventional aeration system. However, membrane makers and users are developing “novel ways” to scour membranes, Booker said. For example, intermittent air scouring, rather than the normal continuous approach, “can be used to significantly reduce energy consumption,” he said. At the same time, more-efficient blower technologies are available to reduce overall energy demands. Meanwhile, high-efficiency fine-bubble diffuser systems, such as strip aerators and aeration panels that help compensate for the reduced aeration efficiency common to MBRs, can help decrease energy usage associated with process air requirements, Booker said.
Making the most of waste
Along with saving energy, WWTPs are generating more energy themselves. One increasingly common approach for boosting biogas production involves adding other waste products — including dairy wastes and fats, oils, and grease — to the anaerobic digestion process, Willis said. High in carbon, the waste products are quickly converted to methane. In this way, some WWTPs “have doubled their methane production,” he said.
However, the challenge with biogas is that it “tends to need a very high level of cleaning” if it is to be used effectively, said Cindy Wallis–Lage, global director of technical solutions at Black & Veatch (Overland Park, Kan.). From an economic standpoint, until the cost to clean the biogas is reduced further, WWTPs that enjoy relatively low energy costs will have a hard time justifying the use of biogas, she said.
The future of energy recovery at WWTPs will entail methods for generating methane from dissolved solids present in wastewater, Willis said. Because dissolved solids do not settle out of wastewater, they typically are removed by the energy-intensive activated sludge process. However, using an anaerobic process to convert both settleable and dissolved solids into methane would create significantly more energy than is now possible. In turn, this process would reduce the pollutant load to the activated sludge system, decreasing the power needed to run it. Although significant technical challenges remain, the potential benefits for WWTPs are enormous: “If we can double methane production and cut energy use in half, we’ve got a power plant,” Willis said.
Reducing solids, cutting disposal costs
For most WWTPs, the top two operational expenses pertain to energy and solids disposal. Just as energy costs are expected only to increase in the future, the cost to dispose of solids also is anticipated to rise, said Marc Roehl, product manager for biosolids technologies at Siemens Water Technologies (Warrendale, Pa.). “Options for solids disposal are becoming fewer or at least have been restricted,” he said. “As that occurs, the cost of disposal goes up.”
Meanwhile, the trend toward increasingly tighter discharge limits “goes against sludge reduction,” said Richard Tsang, residuals and biosolids discipline leader at CDM (Cambridge, Mass.), “because the more you take out of the wastewater, the more sludge that you produce.” This development is “impacting the solids-handling processes substantially,” he said.
Facilities trying to cope with increasing disposal costs have new options for reducing the amount of solids they generate. For example, the Cannibal® process offered by Siemens Water Technologies is designed to reduce solids yields by conditioning waste activated sludge (WAS). To facilitate this process, a portion of a plant’s WAS is sent to a separate interchange bioreactor that operates under nonaerobic conditions. The resulting biochemical reactions improve the degradability of the solids, which are then returned to the aeration basin in order to undergo further treatment.
By increasing the degradability of WAS and returning it to the aeration system, the Cannibal process results in a “much lower solids yield,” compared to a conventional treatment plant, Roehl said. At the low end, WWTPs using the system generally reduce solids yield between 40% and 50%, he said, while at the high end, facilities may achieve reductions of as much as 80%. “What that means at the end of the day is a significant decrease in sludge disposal costs,” Roehl said. In general, the Cannibal process “fits best” at medium-size plants that use aerobic digestion, he said.
Removing and recovering nutrients
Of all pollutants, nutrients may turn out to have the greatest effect on future treatment methods. Ongoing efforts by the U.S. Environmental Protection Agency (EPA) to develop water quality standards for nutrients will unleash a technological “sea change,” said Denny Parker, director of technology and senior vice president at Brown and Caldwell. In cases in which stringent numeric criteria for nutrients, particularly nitrogen, are translated into effluent requirements for WWTPs as part of the total maximum daily load process, existing treatment methods likely will not suffice or they will cost too much to implement on a large scale. “This is just a huge challenge,” Parker said.
For WWTPs in northern climates, Parker said, the need to decrease nutrient concentrations further will prompt a shift to biofilm reactor technology. Compared to activated sludge systems, biofilm reactors are less sensitive to temperature and require less space. As nutrient requirements become more restrictive in colder regions, an existing trend toward greater implementation of biofilm reactors will become a “landslide,” Parker said.
WWTPs are in the early stages of a shift from simply removing nutrients to recovering them. “We’re seeing a lot of interest in actually recovering nutrients,” said Doug Fredericks, national water infrastructure manager for PBS&J, an Atkins company (Epsom, England). Such interest particularly makes sense regarding phosphorus, Fredericks said, because its current supplies are mined from finite sources that could be exhausted in the coming decades. Wastewater, by contrast, offers the “only renewable source of phosphorus,” he said.
Capitalizing on this fact, Ostara Nutrient Recovery Technologies Inc. (Vancouver, British Columbia) has developed a process to capture phosphorus and ammonia from nutrient-rich wastewater extracted from anaerobically digested solids. Known as the Pearl® Nutrient Recovery Process, Ostara’s proprietary technology comprises a fluidized-bed reactor in which magnesium is added to promote the formation and collection of struvite granules. In this way, the reactor removes nutrients from the wastewater and creates a slow-release fertilizer known as Crystal Green®. Moreover, the process inhibits the formation of struvite scale in pipes, pumps, and valves, a common nuisance at many WWTPs. All told, the process can recover as much as 85% of the phosphorus in the wastewater stream while removing an equal amount of ammonia.
The Pearl process is “ideally suited” for biological nutrient removal facilities that use anaerobic digestion, said Phillip Abrary, Ostara’s president, chief executive officer, and director. To date, the process has been commissioned at four facilities in North America, but Ostara estimates that roughly 200 North American WWTPs would make good candidates for adopting the technology. For WWTPs implementing the process, the cost savings will pay back the investment in equipment in 3 to 5 years, Abrary said. Therefore, the fertilizer revenues are “designed to offset 100% of the operating cost of a facility,” he said.
In addition to reducing nutrients in its effluent, a wastewater agency stands to benefit from the fact that Ostara is responsible for selling the final product, Wallis–Lage said. “Utilities do not usually want to be in the marketing and distribution business,” she noted.
Taking on microconstituents
Even as they fashion themselves into energy-efficient facilities for recovering energy and nutrients, WWTPs can expect to continue to treat an increasing array of pollutants, including microconstituents, contaminants that originate from such items as pharmaceutical and personal care products and pesticides. With recent media attention prompting greater consumer awareness regarding microconstituents, regulatory action is probably not far off, said Jim Farmerie, business development manager of treatment products at ITT Water and Wastewater (White Plains, N.Y.).
In the face of growing public concern, “more progressive utilities” are beginning to tackle the issue of microconstituents, Farmerie said, rather than waiting to be told to do so by regulators. Depending on the contaminants of concern, WWTPs looking to address microconstituents can select from advanced oxidation processes that involve various combinations of ozone, ultraviolet light, and hydrogen peroxide.
Recovering resources, increasing sustainability
Ultimately, increased efforts to reduce energy use and recover resources will make wastewater agencies more sustainable in the long run, Daigger said. In particular, utilities that minimize their energy use and maximize their energy generation can better withstand variations in energy prices. “We’ve all seen in the not-too-distant past some of the cost shocks of dramatically increased energy costs,” Daigger said. “If you’re making your own [energy], you’re much more isolated from” such shocks, he said.
Four issues to watch in 2011
January is a natural time to survey the legislative and regulatory landscape. Here are some of the main drivers likely to affect the wastewater industry during the coming year.
The varied and diffuse nature of stormwater runoff is reflected in the current complex regulatory framework associated with this type of discharge. The U.S. Environmental Protection Agency (EPA) regulates some sources of runoff as point source dischargers under the National Pollutant Discharge Elimination System permitting program (e.g., industrial facilities, municipal separate storm sewer systems [MS4s], and construction sites) but not others (e.g., agricultural lands, urban areas outside of MS4s, and privately owned storm sewer systems).
However, a national EPA rulemaking begun in December 2009 (74 FR 68617) and continuing throughout 2011 and 2012 seeks to “improve and strengthen” the agency’s stormwater program.
This rulemaking came on the heels of a 26-month study of stormwater management conducted by the U.S. National Research Council. The council’s report on the study, Urban Stormwater Management in the United States, released in October 2008, is critical of many aspects of EPA’s regulations and concludes that “radical changes … are necessary to reverse degradation of fresh water resources and ensure progress toward the Clean Water Act’s goal of ‘fishable and swimmable’ waters.”
In recent years, EPA has faced growing criticism that its regulatory program does not adequately address all of the stormwater impacts on water quality, which are significant and affect all parts of the country. For example, while urban areas cover only 3% of the land mass in the United States, urban stormwater is listed as the primary source of impairment for 13% of all rivers, 18% of all lakes, and 32% of all estuaries.
Some environmental advocates have pressed EPA to impose numeric limits instead of the nonnumeric best management practices (BMPs) that are common to all three of EPA’s general stormwater permits.
In 2009, EPA completed a separate national rulemaking (74 FR 62996) to establish technology-based numeric limits for regulated stormwater dischargers in the construction and development point source category. Some states have done the same.
To date, EPA has resisted across-the-board imposition of water-quality-based numeric limits based on an interim policy adopted in 1996. However, EPA has faced mounting pressure to apply such limits and in fact has done so in a growing number of individual permit proceedings.
The ongoing stormwater rulemaking is expected to focus on discharges from new development and redevelopment, as well as from MS4s. EPA expects to complete the proposed rulemaking in September 2011 and the final rulemaking by November 2012. Stormwater provisions of the rulemaking specifically for Chesapeake Bay states currently are being discussed, with the understanding that the final national rulemaking likely will have many similar elements. EPA officials have said that the changes are expected to be the most significant in the last generation.
One of the nutrient debates likely to play out in 2011 has been working its way downstream for nearly 8 years.
In August 2003, EPA issued a comprehensive strategy for upgrading state water quality standards programs that included EPA’s support to help states adopt numeric nutrient criteria.
Traditionally, states relied on narrative criteria for nutrients that were not always easy to apply to specific control decisions. Particularly vexing was the question of how to translate narrative criteria into total maximum daily loads for individual waterbodies and, thus, into permit limits for dischargers. However, given the scientific complexity of establishing numeric nutrient criteria, states have been slow to do so.
In January 2010, in response to a consent decree, EPA developed a proposed rule for promulgating numeric nutrient criteria for Florida. On Nov. 15, 2010, EPA proposed numeric nutrient criteria for Florida lakes and flowing waters. This proposal will go into effect 15 months after its publication in the Federal Register. EPA is extending the effective date of these criteria for 15 months to enable cities, towns, businesses, and other stakeholders, as well as the State of Florida, a full opportunity to review the controversial standards and develop flexible strategies for implementation.
There is concern that these standards could ultimately result in permit limits in some Florida waters requiring publicly owned treatment works (POTWs) to reduce nutrients to a level beyond the current limits of technology.
EPA also will be issuing numeric nutrient criteria for Florida’s coastal waters by August 2012. These numeric nutrient criteria for Florida will set the stage for EPA’s approach for such criteria in other states.
Beyond Florida, EPA is facing litigation from various environmental organizations that may accelerate the issuing of numeric nutrient criteria across the U.S., particularly in the Mississippi River basin.
The possible redefinition of what constitutes secondary treatment is another major regulatory driver. On Nov. 27, 2007, a coalition of environmental groups led by the Natural Resources Defense Council (New York) petitioned EPA to amend the definition of secondary treatment at POTWs to include advanced nutrient controls.
The Clean Water Act requires all POTWs to achieve secondary treatment standards, which currently require the removal of biochemical oxygen demand and suspended solids but do not specifically require nutrient removal. Adding nutrient removal to the standards would necessitate upgrades and construction at most U.S. treatment plants, even in areas where excess nutrient loading is not an issue.
At press time, EPA action on this petition was still pending.
Water quality legislation
Despite considering several infrastructure funding approaches related to wastewater and water, the lame-duck 111th U.S. Congress failed to pass final legislation on any of them. Among the bills was reauthorization of State Revolving Loan Funds and possible innovative funding approaches, including a Clean Water Trust Fund and an infrastructure bank. Congress also considered but did not pass legislation related to Clean Water Act jurisdiction issues on what constitutes “waters of United States” as affected by several U.S. Supreme Court decisions involving wetlands, green infrastructure issues, chemical security, and better stormwater controls under the Federal Highway Act. Climate change initiatives, including necessary adaptation approaches for water and wastewater utilities, also were considered.
For various reasons, no final legislation was passed on any of these concerns; at press time, chances were believed dim for action during the lame-duck session held through December 2010. Thus, these legislative items in all likelihood will be carried forward and reintroduced in the 112th Congress, beginning in January 2011.
Any water-related legislation in the 112th Congress must compete with high-priority congressional legislative concerns. Although predicting the actual congressional agenda is difficult, a number of high-profile bills are likely, including appropriations and deficit reduction, the Farm Bill, the Highway Bill, the Education Reform Bill (No Child Left Behind), a nuclear arms reduction treaty, and action on long-stalled free-trade legislation.
Of particular interest to water quality is the Farm Bill, which will pass in the 112th Congress, as the current 2008 Farm Bill must be replaced. The 2008 Farm Bill included a number of conservation provisions and funding, which supported water quality improvements by addressing agricultural nonpoint source runoff. A coalition of water organizations, including the Water Environment Federation (Alexandria, Va.), is working to help ensure that the 2012 Farm Bill continues to address water quality and nonpoint source issues related to agriculture.
Two proposed rules affecting solids incineration will take center stage in 2011. Approximately 20% of the wastewater residuals generated in the U.S. are incinerated.
First, EPA in June issued a proposed rulemaking (75 FR 31844) that would redefine incinerated biosolids as solid waste, rather than fuel. This change in definition ultimately would mean that the air emissions from these incinerators would be regulated under Sec. 129 of the Clean Air Act, instead of the less stringent Sec. 112.
Several issues surrounding this rule remain unresolved. Could this redefinition affect nonincineration management of biosolids? And does EPA have sufficient operating data for either multiple-hearth or fluid-bed incinerators to establish science-based maximum achievable control technology standards required by the proposed regulation?
Second, EPA in October proposed rulemaking (75 FR 63260) to cut emissions of mercury, particle pollution, and other harmful pollutants from sewage sludge incinerators (SSIs). According to EPA, SSIs represent the sixth-largest source of mercury air emissions in the country. The proposed standards would apply to both multiple-hearth and fluidized-bed incinerators. The proposed rule would set numeric emissions limits for both new and existing SSIs, with separate standards for multiple-hearth and fluidized-bed incinerators. Proposed limits can be found at EPA’s Web site, www.epa.gov/ttn/atw/129/ssi/ssipg.html.
The proposed standards may require approximately 196 of 218 incinerators to install one or more air pollution control devices, such as activated carbon injection, fabric filters, and high-efficiency scrubbers.
is assistant director of public policy at the Water Environment Federation (Alexandria, Va.).
As utilities continue adapting to the economy, new funding approaches are needed for rehabilitation projects
According to the National Bureau of Economic Research (Cambridge, Mass.), the “Great Recession” — the worst economic recession the United States has experienced since the Great Depression — is already a thing of the past. It began in December 2007 and officially ended in June 2009. But many households and businesses would argue differently. They were still experiencing the aftereffects of the economic downturn nationally and globally in 2010.
At the end of last year, while housing prices remained stable in a few U.S. metropolitan areas, the total number of home sales had declined by as much as 21% from the previous-year quarter, according to the National Association of Realtors (Washington, D.C.). Though the U.S. Bureau of Labor Statistics reported modest job growth, the unemployment rate still hovered between 9% and 10% throughout 2010. (In contrast, the rate was only 5% at the beginning of the recession.)
Utilities also were not immune to the effects of the economic downturn. Last year, many continued to raise rates and scale back capital improvement projects because of the decline in revenues and limited federal funding. Additional changes — including water scarcity, further upheaval in the bond market, and the continued reduction of federal funding — stand to test utilities in the coming year.
Revenues down, rates up
During the housing boom of the late 1990s and early 2000s, subdivisions sprouted up all over the country, particularly in the South and West. With these developments came malls and other businesses. This was a lucrative period for many utilities.
“Our system is a fairly young system with lots of growth in the last 20 years,” said Peter Frank, deputy director of business services at the Gwinnett County (Ga.) Department of Water Resources. “Much of that growth was paid for through the state revolving fund and through [the municipal bond market].”
But when the housing market plummeted, so did the expansion period for many water and wastewater utility systems. The steady flow of new customers not only diminished, but old customers began to disappear with the growing rate of foreclosures. Property assessments began to decline. Subsequently, revenues also took a dive. Many utilities had already planned to make incremental rate increases, but these plans had to be modified to reflect the evolving economic environment. In 2010, some utilities were still making changes to these plans.
The LOTT Clean Water Alliance in Olympia, Wash., already had received approval for rate increases, said Michael D. Strub, executive director of the LOTT Alliance, with the passage in 2009 of a resolution that called for modest water and sewer rate increases until 2015. “But we may have to increase them even more because of the economic slowdown,” he said.
Between 2001 and 2009, the average annual increase in typical residential water bills was 5.3%, and the average increase for typical residential sewer bills was 5.5%, according to the sixth 50 Largest Cities Water and Wastewater Rate Survey released by Black & Veatch (Overland Park, Kan.). According to a Black & Veatch press release, the reasons given by utilities for these rate increases included
· commodity price increases, such asrising costs of electricity, chemicals, and natural gas;
· lower water and wastewater consumption but high fixed costs, such as debt service;
· increased labor costs due to pension obligations and health care benefits;
· implementation of significant capital improvement programs to comply with legal mandates; and
· updating and replacing aging water and wastewater infrastructure.
Between 2001 and 2009, Newport News, Va., experienced an average combined increase in water and sewer rates of 4.5%, said Brian L. Ramaley, director of Newport News Waterworks. The reasons for this increase were complex, involving some of those listed in the Black & Veatch survey, but Ramaley said only “a little” was due to the economy.
“I would say it was a mix of the economy and just modern trends,” Ramaley said. Chemical and energy prices had soared, particularly in 2010, and the closure of a nearby refinery also meant a decline in revenue and the need to raise rates, he said. Whether that refinery was closed due to the economy or if it was an independent business decision by the oil company, no one knows, he said.
In addition to raising rates, some of the harder-hit utilities also have had to take a scalpel to some planned capital improvement projects.
Although the City of Phoenix Water Services Department will continue with its $200 million installation of a granular activated carbon filtration system to meet Safe Drinking Water Act Stage 2 disinfectants and disinfection byproducts rule compliance deadlines by 2012, it must cut back some of its growth-related capital improvement projects, especially now that the city is no longer experiencing growth, said Barbara Glaus, acting director of the department.
“We recognize that this is a tight economy for many of our customers,” Glaus said. Subsequently, the department has cut back on plans for plant expansion and expanding sewer capacity, she said.
Ramaley said Newport News Waterworks had to reduce its overall capital improvement budget last year, but it also has tried to reduce project costs by doing work internally rather than outsourcing to contractors, such as with a recent rehabilitation project to one of its smaller dams.
The Gwinnett County Department of Water Resources had to cut its capital improvement budget by 50%, Frank said. But the utility continues to fund necessary maintenance and repair projects, he said. The department developed an asset management plan to determine where maintenance dollars should go by establishing which projects were of the highest priority. But Frank said the department may have to put off some repair plans down the line.
The department anticipates the eventual redevelopment of older parts of the county, which will require infrastructure repair. “Though because the economy isn’t doing so well, this may not be until well into the future,” Frank said.
Colorado Springs (Colo.) Utilities, which provides water, wastewater, electricity, and natural gas services to the Pikes Peak region of Colorado, has a rigorous capital prioritization process in place to make sure the utility is funding the projects most critical for reliable service, said Eric Isaacson, spokesman for the utility. So far, these projects are largely funded by a combination of cash from operations and municipal bonds, such as Build America bonds, he said. (Build America bonds are taxable municipal bonds that carry special tax credits and federal subsidies for either the bond issuer or the bondholder.) But the economy continues to be a major concern.
“We anticipate the interest rates will increase,” Isaacson said. The utility also is concerned about whether the Build America bond program, which was created under the 2009 American Recovery and Reinvestment Act, will continue and if the federal government will reduce its interest subsidy level for these bonds.
Preparing for the future
The long-term impact of this recession will not be the only challenge utilities face in the future. Dwindling federal funding despite more stringent mandates that require more infrastructure investment will continue to be an obstacle, along with the growing issue of water scarcity in some regions.
“Municipalities are already paying 95% of the cost of clean water,” said Adam Krantz, managing director of government and public affairs at the National Association of Clean Water Agencies (NACWA; Washington, D.C.). But that burden has gotten even heavier since “we’ve suffered the worst economy since the Great Depression,” he said.
Yet in the past few years, states and the U.S. Environmental Protection Agency (EPA) have released rules that lowered acceptable discharge limits for nutrients, requiring more-expensive equipment and in some cases, larger facilities.
“Individual utilities are frustrated that they have to raise rates and go to the bond market to fund these improvements,” Krantz said.
Many utilities accept that the old days when water and wastewater utilities received an influx of federal dollars to address Clean Water Act and Safe Drinking Water Act mandates are over, but with monies being limited, something has to give, Krantz argued. “Utilities need to know what the most important projects are and what the timetables are,” he said.
That is why NACWA initiated the Money Matters campaign in 2010, which calls for water and wastewater utilities to lobby and educate congressional leadership, states, and EPA about the dilemma they are facing.
“The idea isn’t so much that they can give more money to utilities but to say what EPA priorities are and how utilities can dedicate their limited resources,” Krantz said. “The federal government has to understand that we can’t do everything at once.”
While some systems are grappling with how to address new mandates during tough economic times, other utilities are trying to find additional water sources for their systems. Water scarcity could have a great financial impact on their bottom lines and the bond market, according to a recent report issued by Ceres (Boston), a national network of investors, environmental organizations, and other public interest groups interested in sustainable practices.
According to a Ceres press release, the report, The Ripple Effect: Water Risk in the Municipal Bond Market, “evaluates and ranks water scarcity risks for public water and power utilities in some of the country’s most water-stressed regions, including Los Angeles, Phoenix, Dallas and Atlanta.” The report shows that some of the largest U.S. public utilities may face moderate to severe water supply shortfalls in the next decade, yet these risks have not been reflected in the pricing or disclosure of bonds that these utilities rely on to finance their infrastructure projects, according to the release.
Many bond rating agencies do not conduct water risk “stress tests” when rating municipal bonds because of the “sheer number of utilities they’re rating, which are in the thousands,” said Sharlene Leurig, senior project manager of the Insurance Program at Ceres and author of the report.
Leurig said the major problem with the existing municipal bond market “is that sufficiency of supply is almost always assumed to be adequate,” and even though demand in some areas has declined, “we still see water scarcity being a challenge like it has never been before.”
In the Ceres report, Atlanta’s water and sewer system received the second highest water risk score because of its reliance on a key local water supply — Lake Lanier — whose future is jeopardized by a judicial order that may require the city to reduce its withdrawals by as much as 40% in 2012.
Like Atlanta, Gwinnett County also receives much of its water supply from Lake Lanier. Frank said the Gwinnett County Department of Water Resources has been warned that legal drama surrounding this water source could eventually affect its bond rating.
“We are currently going through debt refinancing,” Frank said. “The three rating agencies reaffirmed our AAA bond rating, but they all made it a point to say that could change, depending on the outcome of the litigation,” he said.
Meanwhile, Gwinnett County is trying to develop other water sources and putting more water back into the lake, Frank said. Also, they have enough capacity to handle current demand.
Phoenix and Glendale, Ariz., utilities and systems also received high water risks scores in the Ceres study because of their high reliance on what Leurig called “increasingly expensive and potentially volatile out-of-state water imports from the Colorado River.”
Glaus took issue with this conclusion. She said when the bond rating agencies review their performance before giving ratings, they are look at everything, including water supply.
“[Ceres’] water supply analysis was poorly done, and they left out many of our current and future water supplies,” Glaus said.
Progressive utilities find that sustainability projects can reap both financial and environmental rewards
In Alexandria, Va., contractors working on a major nitrogen removal upgrade at the city’s water treatment facility receive financial incentives for carpooling to the job site.
In Sonoma County, Calif., the regional water agency is exploring ways to use chicken waste to produce renewable energy, with the residual dried biosolids sold as fertilizer.
In Lawrence, Mass., the historic Wall Experimental Station — “the birthplace of environmental analysis” — is being upgraded to recycle rainwater and include parking for plug-in hybrid cars.
Clearly, these aren’t your grandfather’s wastewater treatment facilities.
Collectively, they reflect a shift in the way many utilities think about their missions. Whether reducing their dependency on fossil fuels, cutting greenhouse gas emissions, or just applying good business practices, all are striving toward the same common goal: meeting the current generation’s needs without compromising the ability of future generations to meet theirs.
Are any of them there yet? No. At least not entirely.
But step by step, with some of the nation’s most forward-thinking utilities leading the way, wastewater treatment in America is becoming more sustainable.
Using stimulus funds to go green
Among those in the forefront is the 53,000-m3/d (14-mgd) Kent County Regional Wastewater Treatment Facility (RWTF; Milford, Del.), which recently became the first treatment plant in the United States to disinfect wastewater using microwave ultraviolet (UV) technology.
The switch from traditional chlorine gas disinfection offers multiple advantages, according to Jim Newton, the utility’s environmental program manager.
“Chlorine gas has always posed health and safety concerns in the plant and surrounding neighborhoods,” Newton said. By replacing it with technology that uses microwaves instead of light to create UV rays, the utility not only eliminated the safety risk, it lowered its operational costs. “Microwave-powered UV lamps last three times longer than traditional ones,” Newton said.
The conversion, which was completed using $3 million in economic stimulus money from the state revolving fund, will net Kent County RWTF $50,000 in savings a year. “It increases our electrical demand by 5%,” Newton acknowledged, “but the cost savings on chemicals far exceeds that.”
The new disinfection process is just one of several sustainability projects under way at the Milford facility. The plant also is using stimulus money to add 1.2 MW of solar power — enough to cover about 20% of its electrical needs.
Stimulus funds also are being used to build a giant greenhouse where a passive solar process will be used to dry biosolids. Newton projects that the solar-powered system, designed to supplement its existing natural gas dryers, will reduce natural gas consumption at the plant by 60% to 70%.
Kent County RWTF also is looking outside the plant’s own footprint for partnerships that someday could redefine its role in the community. For example, plans are in the works for a local landfill operator to use the plant’s dried biosolids to supplement its daily cover. In exchange, Kent County RWTF would treat the landfill’s leachate. “If this works like we think it will, we’d consider shortcutting the process by installing passive solar dryers right at the landfill someday,” Newton said.
Carbon-free by 2015
On the other side of the country, the Sonoma County (Calif.) Water Agency also is using innovative private partnerships to help achieve its sustainability goals — and those goals are ambitious. In 2006, the agency, which oversees the Northern California county’s water, wastewater, and flood control, committed to being carbon-free by 2015, according to Cordel Stillman, its deputy chief engineer.
Since then, the agency has implemented more than a dozen renewable energy, efficiency, and sustainability projects, many involving solar, hydroelectric, and other alternative energy sources. Currently on the drawing board is a project to turn waste from the local poultry industry into energy that can power the Sonoma Valley Wastewater Treatment Plant.
“There are more than 2 million chickens in Sonoma County,” Stillman said. Because land disposal of nitrate-heavy chicken waste is difficult, local poultry farmers currently transport it 190 km (120 mi) to be processed in another utility’s biodigester, he said.
Not only would a chicken-waste biodigester in Sonoma County save these transportation costs, but the methane gas produced there could generate power for the 1.4-MW fuel cell the agency wants to build at its treatment plant.
“We like projects where everybody wins,” Stillman said. Because a private company will own and operate the digester, sell the power to Sonoma County, and market the biosolids as fertilizer elsewhere, the agency’s financial risk is minimal. But by locating the biodigester at the plant, the partner company also benefits. “They don’t need a separate connection to a municipal water source, which saves them money,” he said.
Will Sonoma County achieve its carbon-free goal by 2015?
“If not, we’ll be very close,” Stillman said. “By then, all of our power — electricity, gas, and fleet — should be powered or covered in some way by a renewable energy source.”
While a sense of environmental leadership may lead some utilities to sustainability, many are also driven by more practical concerns, such as regulatory or financial pressures, or just plain good business sense.
The latter description fits Charlotte–Mecklenburg (N.C.) Utilities , which — along with several other utilities interviewed for this article — is working toward International Organization for Standardization (ISO; Geneva) 14001 certification at its five treatment plants. This involves identifying the environmental impacts of the utility’s activities and establishing an environmental management system to minimize these impacts.
“Historically, our focus was on managing costs and, when necessary, cutting budgets,” said Jackie Jarrell, the utility’s environmental management division superintendent. “But that kind of thinking doesn’t lend itself to improving our performance.”
“The ISO process forces us to look at the way we do our work,” Jarrell said. “For the first time, it also means setting performance targets and measuring our success in achieving them.”
The result? “We not only end up becoming more fiscally responsible, we also do a better job of protecting the environment,” Jarrell said.
The drive for continuous improvement has, for example, led to studies exploring the viability of turning sunflower and canola grease into biodiesel. The utility also is exploring ways to use high-strength biochemical oxygen demand wastewater from local industry — rather than chemicals — to remove nutrients from wastewater.
While sustainability is a high priority, it must be balanced by financial realities, Jarrell said.
“It can sometimes be difficult to build a business case,” Jarrell said. When his utility couldn’t obtain grant funding to convert methane to compressed natural gas for its fleet vehicles, for example, the project was shelved.
Karen Pallansch, general manager of the Alexandria (Va.) Sanitation Authority understands. To meet ever more stringent environmental regulations, the authority is completing a $350 million nitrogen removal upgrade at its wastewater treatment plant (WWTP), including supplemental carbon modifications, centrate pretreatment facilities, and a state-of-the-art nutrient management facility.
“We have to spread the cost of operating a state-of-the-art facility over 26,000 accounts,” Pallansch said. “So we’re under pressure to be as efficient as possible.”
To Pallansch, this means operating more like a private business. “A business doesn’t have ratepayers; it has investors,” she said. “In our case, our investors are investing in a clean environment.”
This change in mindset has, among other things, led the authority to look at its operations holistically and embed sustainable concepts and practices in everything it does, from design and value engineering to construction and operations.
“You must look at the wholesale way you do business,” Pallansch said. “We now consider life-cycle costs, rather than project costs, when making decisions and look for ways to drive out waste and build sustainability in everything we do.”
A paradigm shift
Embracing sustainability represents a significant change in thinking from the 1970s and 1980s, when many of today’s WWTPs were built, according to Kent Nichols, vice president of Weston & Sampson (Peabody, Mass.). “Back then, energy savings wasn’t a major consideration in treatment plant design,” he said.
As a result, many utilities today operate large regional WWTPs that have wastewater piped in from all around them. If Nichols were to start from scratch today, he would likely propose smaller treatment plants that serve more local populations.
“If a user is a long way from the treatment plant, you have to build a pipeline and pump wastewater to the plant, which consumes energy and makes the process less efficient,” Nichols said.
Today, in contrast, engineers look at these plants designed by their predecessors and see great opportunities to drive out waste.
“We’re at a stage where we can take giant leaps forward with big projects that make big impacts,” Newton said. “Moving forward, we’ll take smaller steps.”
But even little steps are worth it. “There are many benefits to running an efficient utility,” Newton said. “If you can reduce your own costs, you keep your costs down for your customers and protect the environment as well.”
— Mary Bufe,
© 2011 Water Environment Federation. All rights reserved.