June 2011, Vol. 23, No.6

Going off the grid


A growing number of water and wastewater treatment plants (WWTPs) have incorporated more environmentally sustainable practices into their operations by buying electricity from utilities that use wind power, recovering biogas from anaerobic digesters to heat their facilities, or conducting energy audits. But few have been able to install renewable energy sources that enable them to go “off the grid” for hours or have made it possible to generate so much energy they can power their entire facility and send the remainder back to the grid. Two WWTPs — the 75th Street Wastewater Treatment Facility in Boulder, Colo., and the Lometa (Texas) WWTP — were able to do just that by installing solar arrays onsite.  

Using solar energy has not only helped these plants become more energy independent, but also resulted in cost savings. The City of Boulder expects to save $50,000 in energy costs annually, and the Lower Colorado River Authority, which owns and operates the Lometa facility, expects to save $13,000 annually.

Harnessing solar power in the Rockies

For 2.5 hours in October 2010, the 75th Street Wastewater Treatment Facility was able to generate for the first time from solar panels and its cogeneration system all the power necessary to run its facility.

The 56,775-m3/d (15-mgd) WWTP began the installation of its solar arrays in early 2009 with funding through its contractor, SunEdison (Beltsville, Md.). The $5 million covered the total cost of construction and operations, and continues to fund maintenance, said Chris Douville, coordinator of wastewater treatment for the City of Boulder.

Prior to the installation, the city had another consultant look at several buildings in Boulder, Douville said. “They looked at facilities throughout the city to see what would be the best location for rooftop solar panels,” he said.

These rooftop panels were later installed on Boulder’s recreation centers — one of which is certified under the Leadership in Energy and Environmental Design, or LEED, program, sponsored by the U.S. Green Building Council (Washington, D.C.) — as well as some of its libraries and city hall, said Jonathan Koehn, Boulder regional sustainability coordinator.

But the WWTP has 16 different buildings, making the facility too dispersed to use solar panels on roof tops effectively, Douville said. So instead, the city decided to construct a field of solar arrays, 4464 solar panels in total, which sit east of the WTTP on city-owned land, he said.

“We use the power directly from the solar arrays,” Douville said. “The energy does not go through the grid and then back to us.”

In addition to the solar array installation, the WWTP also has been generating electricity with its cogeneration system since 1986.

“We run one or two engines based on how much biogas the [anaerobic digesters] are producing,” Douville said. Each engine produces a maximum of 240 kW of power.

But even with both solar arrays and the cogeneration system generating power, the city had not anticipated having enough energy to go off the grid.

“That had not been our initial goal,” Koehn said.

Douville said the WWTP demands between 1100 kW and 1400 kW to operate. The city wanted “to get up to 20% of our total energy production for the year,” taking into account the variability of temperature, weather, and time of day and how these factors would affect the solar rays, he said. For instance, electricity production declines drastically during storms and at night.

But the solar arrays and cogeneration system exceeded this goal. Since October 2010, the WWTP has gone off the grid several times a month, usually midday for durations between 5 minutes and 6 hours, Douville said.

So far, it appears that the solar arrays are generating the most energy in cooler temperatures. During fall and winter months, the arrays can produce 900 kW of power, Douville said. In the summer, they average between 750 and 800 kW.

“There are inefficiencies at that time of the year because of the surface temperature of the panels,” Douville explained.

Though the solar arrays are producing a lot more energy than anticipated, Douville does not think the WWTP will ever be able to generate all its electricity through solar energy — even if it does have the additional land to add more arrays.

“We’d have to reduce overall usage significantly in order to do that, and it would probably start to affect the quality of our wastewater treatment,” Douville said.

Renewable energy — deep in the heart of Texas

When the Texas Department of Rural Affairs provided $488,714 to install 442 solar panels on 0.1 ha (0.25 ac) of land near the Lometa WWTP, it knew it was funding a project that would be the first of its kind in Texas, said Travis Brown, renewable energy program manager at the Department of Rural Affairs.

The facility had decided to install solar arrays rather than wind turbines, another popular renewable energy source, because unlike in western Texas, “the wind is not as great here in central Texas,” Brown said.

The department originally had estimated that the roughly $500,000 in funding would enable the WWTP to purchase 50 kW of solar energy. “But because the cost of solar energy went down over time, the bids came in at about half of what we expected,” Brown said. The plant was able to buy twice the amount of power it expected and completed the installation by November 2010. The
100 kW of power was more than what the 379-m3/d (100,000-gal/d) WWTP needed.

Brown said the WWTP will never be able to go completely off the grid. “There are times at night when you can’t use the solar panels or when it’s cloudy outside,” he explained.

But the solar arrays are still producing enough electricity that they are powering the facility 100% of the time, because during the day, the surplus of power they generate goes back to the electric grid operated by Hamilton County Electric Cooperative (Hamilton, Texas).

“So at night, even though the facility is running on electrical power from the grid, the electric cooperative is still crediting us back for the power the solar arrays generated during the day,” Brown said.

Brown said that the department hopes the Lometa WWTP’s solar array installation will serve as a blueprint for other communities, especially small rural communities similar to the City of Lometa where wastewater treatment is their highest energy cost. He said many are deterred by the cost of these projects. The Lometa WWTP was able to secure a grant through the state’s Renewable Energy Demonstration Pilot Program. The Lower Colorado River Authority contributed more than $51,000 in in-kind services and materials. But other smaller communities in the United States only may be able to take out low-cost loans through the U.S. Department of Agriculture, Brown said.

“This project shows that with solar energy renewable projects, there is a payoff in the end,” Brown said.

— LaShell Stratton–Childers, WE&T


A case of too much medicine?

Study shows the level of antiviral drugs and antibiotics used during severe flu pandemics could harm wastewater treatment, waterways

The relationship between influenza and wastewater has been frequently examined. To prepare for flu epidemics, some wastewater treatment plants (WWTPs) have looked at the possible impact a flu outbreak would have on staffing, such as whether mass staff absences due to illness would interrupt operations. Scientists also have conducted research in this area — some into whether the flu virus can be transmitted through wastewater (seeResearch Notes,” WE&T, May 2007). Others have studied how a flu epidemic or pandemic could affect the wastewater treatment process itself.

In March, scientists at the Centre for Ecology and Hydrology (Wallingford, England), the Institute for Scientific Interchange (Torino, Italy), Utrecht University (Utrecht, Netherlands), The University of Sheffield (Sheffield, England), and Indiana University (Bloomington, Ind.), released a paper in the journal Environmental Heath Perspectives that explores the latter. The scientists found that the amount of antiviral and antibiotic drugs used during severe flu pandemics could negatively affect wastewater treatment and lead to the discharge of insufficiently treated wastewater into receiving rivers.


Considering the data, making assumptions

Andrew C. Singer of the Centre for Ecology and Hydrology and lead scientist in the study, said research about the potential problems posed by pharmaceuticals released into the environment through wastewater has been conducted for decades, but “it has always been in the context of an ongoing environmental issue.” Singer gave the example of the birth-control pill and studies that show its prevalence in effluent and its effect on the water ecosystems.

But “the environmental challenges brought about by discrete health events, such as pandemics, had not been previously considered until 2007, when we first published our paper that projected the quantity of Tamiflu to be used during a severe influenza pandemic,” Singer said. “We modeled the amount of Tamiflu that would have reached several river catchments throughout the [United Kingdom] and [United States] and highlighted the human and environmental issues that could be raised from the novel exposure event.”

In the March 2011 paper, “Assessing the ecotoxicologic hazards of a pandemic influenza medical response,” Singer and his colleagues revisited the topic, this time by using a global spatially structured epidemic model to simulate the quantities of antiviral drugs and antibiotics used during a flu pandemic of varying severity, a water quality model applied to the Thames River catchment to determine predicted environmental concentrations, and another computer model to assess the effects antibiotics would have on microorganisms in WWTPs and rivers.

The global spatially structured epidemic model mapped 6 billion individuals, mimicking a worldwide-scale travel and commuting pattern that would simulate the spread of the virus in 220 countries. Each individual was classified as susceptible, latent, infectious symptomatic, infectious asymptomatic, or permanently recovered during each point in time in the simulation. Initial conditions assumed the pandemic starts in Hanoi, Vietnam, on Oct. 1. The pandemic was allowed to evolve during 1 simulated year.

The scientists also considered different pharmaceutical mitigation strategies. They differed according to the selected transmission scenarios. In the case of a mild pandemic, the team assumed no large-scale antiviral treatment. For moderate to severe pandemics, they assumed the implementation of antiviral treatment with Tamiflu in all countries that have available stockpiles. That mitigation strategy was modeled assuming a 30% successful detection and antiviral treatment rate. They also evaluated what effects an antiviral preventive medication provided to 0.1% or 1% of the population for 2 to 4 weeks from the start of the outbreak would have on wastewater treatment. The scientists included a scenario in which no preventive medication was given.

Singer said a lot of these assumptions were based on previous studies and data from previous pandemics. “Our assumptions are currently conservative,” he said. “We would expect a moderate or severe pandemic to have higher case detection and treatment rates.”

Assumptions also were made regarding antibiotic treatment for flu-associated complications. They were based on empirical guidelines from the British Infection Society, British Thoracic Society (London), and the Health Protection Agency (London).

The scientists also included a model that estimated drug excretion into WWTPs. For this analysis, pharmaceutical load in the WWTP influent per head per day was assumed to be constant and fixed at a mean peak value throughout the pandemic. In addition, the team assumed that the WWTPs were the only sources of the drugs, the drugs were not removed during the treatment process or degraded in the water column, and the background drug concentrations in the river stretches and lateral inflows were zero.

Singer said they chose to have no removal of drugs during the wastewater treatment process for various reasons.

“The removal of pharmaceuticals from WWTPs depends on the antibiotic, time of year, wastestream, time of day, nature of the WWTP, as well as physical characteristics of the chemical,” Singer explained. “Although it is possible to generate a range of scenarios for how removal might occur, there are far too many variables involved to have any degree of confidence about the outcome.”

Another reason why the scientists decided to go with a “no-loss model” was that “WWTPs might not function properly owing to the bolus of drugs going through them,” Singer said, which would reduce their ability to remove the microconstituent. He also noted that “most antibiotics are not biodegraded to any significant degree in WWTPs, while some are lost by sorption to sludge. As sewage sludge is not a product of all WWTPs in the study region, a no-loss model was likely to be a good first approximation for the fate of many of the drugs modeled in the study.”

With those assumptions made, the scientists then showed the possible effects a flu pandemic would have on microorganisms by creating another model that included eight antibiotics that might be used to treat flu-associated complications: amoxicillin, cefotaxime, cefuroxime, clarithromycin, doxycycline, erythromycin, levofloxacin, and moxifloxacin. (Tamiflu was not included because it has not been shown to exhibit acute toxicity, according to the paper.) The ecotoxicologic hazards posed by each scenario, which included multiple antibiotic mixtures, and antibiotic use patterns were measured in terms of the potentially affected fraction of microbial species within a WWTP or river.


The impact and possible response

The team of scientists concluded that a mild pandemic would pose negligible ecotoxicologic hazard to WWTPs and rivers, but in a moderate to severe pandemic, almost all WWTPs were projected to exceed the threshold for microbial growth inhibition. Mild and moderate pandemics were shown unlikely to pose a significant ecotoxicologic hazard in the Thames catchment, but risks to the river catchment substantially increased during a severe pandemic. Modeling also showed that WWTPs and river stretches located near areas with higher population concentrations, such as London, reached the highest toxicity values.

Based on the data, the authors concluded that there will be “increasing risk during an influenza pandemic of antibiotic-mediated disruption of WWTP microorganisms. … Increased antibiotic exposure could compromise vital and obligate microbial functions in WWTPs, such as ammonium oxidation and nitrogen and phosphorus removal.”

Because the flu usually peaks during winter months, “the highest drug load will pass through WWTPs at [the microorganisms’] least effective time period, thereby maximizing the likelihood of WWTPs breaching compliance on discharged water,” according to the paper.

To combat the impact of pharmaceuticals on wastewater treatment during flu pandemics, Singer said the medical community has to be involved and develop a cohesive plan.

“It has always been the case that the existence and widespread use of universal influenza vaccine would preclude the conditions described in our paper,” Singer said. “This is a very cost-effective manner of tackling the problem, as it saves the population from associated illness and the economy from the associated financial burden of the pandemic. The development of a universal influenza vaccine should be of the highest priority for all these reasons.”

But in light of the absence of such a vaccine, Singer said “the availability of a rapid diagnostic tool to assess the nature of secondary infections might cut down the amount of antibiotics needed for treatment by roughly half, as only bacterial secondary infections require the use of antibiotics.” The less antibiotics used would mean less harm to the microorganisms involved in the wastewater treatment process.

— LaShell Stratton–Childers, WE&T


Changing perceptions

Strategic public outreach is helping overcome opposition to indirect potable reuse projects

Unreliable water supplies and the persistent threat of drought are pushing many communities to explore alternative options for meeting current and future water demands. With improved and more cost-effective treatment technologies, indirect potable water reuse is increasingly being considered as a viable solution, but this option also presents challenges due to the potential sensitivity of the public.

Indeed, as has been shown, negative branding — especially from misleading headlines — can create community anxiety, and strong public and political opposition effectively can shut down indirect potable reuse projects. However, by implementing outreach that incorporates “early engagement, effective communication, more stakeholder involvement, and is designed and targeted to the specific community, municipalities can establish higher levels of public support, leading to successful projects,” said Jeff Mosher, executive director of the National Water Research Institute (Fountain Valley, Calif.).

“Indirect potable reuse will have higher success rates if outreach is transparent, begins well before any decisions have been made, and is perceived by the community as a collective effort toward evaluating the options and deciding on the best course of action,” Mosher said. “The process cannot involve a decision with limited stakeholder involvement followed by an announcement to the public. In this sense, the industry has turned a corner.”

Progress in outreach strategies has resulted due to renewed efforts in establishing authentic public involvement programs, according to Linda Kelly, managing director of communications for the Water Environment Federation (Alexandria, Va.). “What has been learned is that every community has its opinion leaders, and in some cases, they will make opposing a reuse project their sole cause,” Kelly said. “However, by locating the most likely opponents of the project early in the process and asking them to assume a role in terms of problem solving, reviewing the facts, and considering the alternatives, the likelihood of public buy-in has been shown to increase. With indirect potable reuse, building credibility through public involvement is the best way to arrive at a workable solution. All effort can be lost if the public is not on board.”

New research by Linda Macpherson, reuse principal technologist at CH2M Hill (Englewood, Colo.), and Paul Slovic of Decision Research (Eugene, Ore.), also has shed light on the public’s perception of water reuse and how the public responds to images and terminology in the context of how water reuse is described. “Certain language can have the inverted effect of stigmatizing the idea of water reuse,” Macpherson said. “Words such as ‘sewage’ and ‘treated wastewater’ conjure unattractive images and deter people from accepting reuse. However, positive words, especially ‘pure’ and its derivatives, have shown to enhance acceptance.”

Research studies found a starting misalignment between scientific understanding and the public’s comprehension of water, according to Macpherson. “The public tends to interpret water as a linear process, when in reality water is actually a component of an interconnected system,” she said. “All water in the world is reused water. A meaningful knowledge of water reuse cannot occur until the public understands the water cycle and realizes that most of us are downstream of another water user.”

Another important finding was related to the factors that the public views as important for ensuring safe drinking water. “The public actually thinks that water treatment and monitoring are more important for safety than the original source of the water,” Macpherson said. “Therefore, outreach should emphasize the quality of the water instead of where it originated. In short, water quality is more important than where the water has been used previously.”

“Outreach and reuse education also can have more of a positive impact if they help people to better understand what is put into water and how treatment and purification technologies can make it suitable for drinking,” Macpherson said. “Wastewater treatment and advanced purification should be viewed as part of a water cycle management system — not stand-alone technologies,” she said.

With the media, Macpherson noted the importance of taking a proactive approach. “Without information, reporters may inadvertently sensationalize the negative aspects of where water has been, rather than what it can be safely used for,” she said.


A phased approach in San Diego

The City of San Diego has limited local water sources and relies on importing approximately 90% of its water supply. To address the need for new, local sources of water, San Diego launched its three-phase Water Reuse Program in 2004. The first phase, the Water Reuse Study, identified reservoir augmentation as the preferred option for maximizing the use of the city’s recycled-water supply.

The Water Purification Demonstration Project, the second phase of the program, includes a purpose to further explore the option of reservoir augmentation by demonstrating the project on a small scale. The Advanced Water Purification Facility is being built and will operate for about 1 year to produce approximately 3800 m3/d (1 mgd) of purified water. Concurrently, a study of the San Vicente Reservoir is being conducted to test the key functions of reservoir augmentation. As part of the demonstration project, the city has initiated a multifaceted outreach program for gaining public acceptance.

“The primary goal of the outreach program is to inform, educate, and engage the city’s local leaders, stakeholders, and residents about the demonstration project,” said Marsi Steirer, deputy director of the San Diego Public Utilities Department. “Political and public opposition can be detrimental to projects involving direct and indirect potable reuse. As such, our efforts have been focused on locating opposition and identifying challenges, so we can better develop strategies to successfully address and overcome them.”

Components of the outreach program include community presentations and events, facility tours, and an extensive stakeholder process. According to Steirer, the outreach team is working with multicultural consultants aware of the cultural factors that may influence a diverse public’s ability to accept a water reuse project. “With this additional insight, the outreach team can adapt messaging so that the concept of the demonstration project is accessible to all San Diegans,” she said.

By incorporating a three-phase effort, the current project takes a different approach than the unsuccessful water reuse project proposed in San Diego in the late 1990s. That project, which would have purified water from the North City Water Reclamation Plant to replenish the San Vicente Reservoir, was stopped after encountering stiff political and public opposition. Resistance to the project was fueled in large part by unfavorable descriptors published by the media.

“The original project was marred by what can only be described as political shenanigans,” said Sara Katz, founder and president of Katz & Associates (San Diego), a public affairs consulting firm specializing in issues-based communication programs for public- and private-sector clients. “The media also latched on and started publishing overly sensationalized headlines and graphics, which helped fuel public [and political] sentiment against the project,” she said.

The project also was led by San Diego’s wastewater department, which raised concerns about whether it was a water supply option or a wastewater solution, Katz said. “Many stakeholders were not comfortable with wastewater engineers as the leading spokespersons,” she added.

However, during that time, competing water resources projects were being considered, and imported water also was considerably cheaper, Katz said. “But since then, the costs for imported water have greatly increased while water purification technology has become more cost-effective,” she said. “The lessons learned from the past have been put into play, but the public also has become more aware of the issues surrounding San Diego’s limited water supplies. They understand the need to develop more local and reliable sources of water and have become more open to the prospect of water reuse.”


A successful model

A blueprint for effective communications can be gleaned from the outreach program associated with the Groundwater Replenishment System, an indirect potable reuse project jointly funded by the Orange County (Calif.) Water District and the Orange County Sanitation District that takes highly treated wastewater and purifies it to near-distilled-quality water for replenishing the Orange County groundwater basin. Operational since January 2008, the project “incorporated a stakeholder involvement process that is considered the gold standard for successful public outreach,” said Patricia Tennyson, executive vice president and director of client relations for Katz & Associates.

“The Orange County project was backed by a strong and energetic staff supported by a team of consultants and dedicated management who worked together to develop and implement a unified, consistent public communications strategy and education program,” Tennyson said. “The districts also conducted extensive research to learn more about key audiences prior to development of the outreach program.”

Orange County’s outreach program also was successful because the leadership was able to gain the trust of the community, according to Mosher. “The communications strategy that was designed achieved wide acceptance for the project and included gathering hundreds of letters of support from local governments, which proved very effective,” he said.

The guiding principles of this approach could be helpful to other municipalities pursuing similar reuse projects, Mosher added. “However, because cultural dynamics can vary greatly between cities, it’s also very important that the strategy is tailored to the individual community,” he said.

Jeff Gunderson, WE&T


©2011 Water Environment Federation. All rights reserved.