For industrial facilities such as power plants, meeting the U.S. Environmental Protection Agency (EPA) recommended aquatic standard of 5 µg/L or 5 ppb for selenium discharge could be quite a challenge.
“Five ppb is very close to the detection level of selenium,” explained Yakup Nurdogan, industrial wastewater treatment specialist at Bechtel Corp. (San Francisco). “It is extremely difficult to consistently produce an effluent quality of 5 ppb selenium 365 days a year.”
Nurdogan said it is possible to bring selenium to this level using a combination of technologies. “However, it will be very expensive to achieve 5 ppb,” he said.
For a long time, states, not EPA, had regulated selenium discharge, with standards varying widely from state to state. But as the result of a multiyear study recently conducted by EPA, coal-fired power plants could be asked to meet the selenium discharge limit of 5 µg/L or 5 ppb advocated by many environmentalists or meet an even lower discharge limit after new EPA standards are finalized.
These facilities may have to employ a combination of existing technologies or technologies on the horizon to meet these levels, and some will be required to pay millions of dollars in capital expenditures to do so.
Revising Decades-Old Regulations
In 2009, EPA released Steam Electric Power Generating Point Source Category: Final Detailed Study Report (EPA 821-R-09-008). During its 2005 annual review of effluent guidelines, the agency decided to look further into the steam electric-power-generating industry. At that time, data from the National Pollutant Discharge Elimination System permit program and the Toxics Release Inventory indicated that this industry ranked high in discharges of toxic and nonconventional pollutants.
In the study, EPA specifically investigated discharges from power plants covered by the steam electric power-generating effluent guidelines (40 CFR 423). The study also determined whether the current effluent guidelines for these plants, which were last revised in 1982, should be revised again. In addition, EPA investigated other electric-power and steam-generating activities that are similar to the processes regulated within the steam electric-power-generating point source category but are not subject to the effluent guidelines.
During the course of the study, EPA collected data about the industry by conducting site visits and wastewater sampling episodes at steam electric-power plants; distributing a questionnaire to collect data from 30 coal-fired power plants;reviewing publicly available sources of data; and coordinating with EPA program offices, other government organizations (for example, state groups and permitting authorities), and those in the industry and other stakeholders.
According to the report’s executive summary, EPA evaluated several wastestreams that are generated at these power plants, such as wastewater from wet flue-gas desulfurization (FGD) systems that are used to remove sulfur dioxide from air emissions, fly ash and bottom ash handling, coal-pile runoff, condenser cooling, equipment cleaning, and leachate from landfills and impoundments. Also, EPA reviewed information on integrated gasification combined-cycle and carbon-capture technologies. Wastewaters from flue gas mercury control systems and regeneration of the catalysts used for selective catalytic-reduction nitrogen oxide controls were identified as potential new wastestreams that require attention; however, EPA was not able to obtain characterization data for these wastes.
EPA found the two major sources of pollutants discharged from steam electric-power plants are coal-ash ponds and FGD systems. According to the executive summary, FGD wastewaters generally contain significant levels of metals, including such bioaccumulative pollutants as arsenic, mercury, and selenium, and significant levels of chloride, total dissolved solids, total suspended solids (TSS), and nutrients. Untreated ash-transport waters contain significant concentrations of TSS and metals. The treated effluent from ash ponds generally contains low concentrations of TSS, but metals are still present in the wastewater, predominantly in dissolved form.
EPA identified and reviewed the technologies power plants use to either treat or store this wastewater. To treat FGD wastewater, plants use settling ponds (the most common treatment method), chemical precipitation systems, anaerobic and aerobic biological treatment systems, constructed wetlands, vapor-compression evaporation sys-tems, and other technologies. Coal-fired power plants manage bottom ash and fly ash using either wet or dry handling techniques. For wet handling systems, the plants typi-cally sluice the fly ash, bottom ash, or both to a surface impoundment or settling pond, where most of the solids settle out of the water. Some plants recycle a portion or all of the settled-ash pond effluent, but most plants discharge the pond overflow.
According to EPA, despite these treatment methods, pollutants from power plant wastewater still make their way into the environment, and the agency concluded that many of these pollutants — such as sele-nium, arsenic, mercury, total dis-solved solids, and nutrients — have an impact on wildlife. According to the executive summary of the EPA report, the “primary routes by which coal combustion waste-water impacts the environment are through discharges to surface waters, leaching to ground water, and by surface impoundments and constructed wetlands acting as attractive nuisances that increase wildlife exposure to the pollutants contained in the systems. EPA found the interaction of coal com-bustion wastewaters with the envi-ronment has caused a wide range of environmental effects to aquatic life.”
For those reasons, EPA has decided to revise its existing stan-dards for wastewater discharges from coal-fired plants; however, details about these revisions are not currently available.
“We are in the early stages of the rulemaking, so we cannot comment on what the proposed rules will say,” said Enesta Jones, an EPA spokes-woman.
But Jones said EPA does plan to look at the extent of selenium dis-charge levels from power plants.
Overcoming Technology Obstacles
Facilities that are trying to achieve discharge limits for selenium of 5 µg/L or 5 ppb already required by some regulatory agencies are finding it hard to meet these goals, not for the lack of will but because technolo-gies to enable this are still develop-ing, said Cynthia Wagener, an envi-ronmental engineer in the Industrial Water and Wastewater Services divi-sion in the Baton Rouge, La., office of URS Corp. (San Francisco).
Wagener said most facilities are more familiar with using engineered biological systems, constructed wet-lands, and coprecipitation for sele-nium removal. These methods are “the most proven and established for other constituents at higher limits” and the most popular in removing selenium from wastewater, she said. But “if the requirement is meeting a limit in the vicinity of 5 µg/L, every technology will have to prove itself at that level,” she said.
Many of the technologies have yet to be proven beyond bench scale in removing selenium from industrial wastewater, said Jamal Shamas, Middle East and North Africa inter-national business development leader of Industrial Systems–Water and Process in the Dubai, United Arab Emirates, office of CH2M Hill (Englewood, Colo.).
“There are many processes for removing selenium to low levels, but unfortunately not all could work well in the wastewater matrix of power plant discharges or other discharges, as opposed to drinking water treat-ment, for instance,” Shamas said. “The problem is that actual operating data at pilot and full scale in these types of industries are very limited, which makes it difficult to say what current technologies are capable of achieving in terms of effluent selenium levels.”
In addition to technological limita-tions, facilities also face a more prac-tical and basic concern: cost.
Shamas said the cost can vary based on application, technology used, and flow rates. Wagener agrees.
“The cost estimates I’ve seen vary widely and are heavily dependent on the individual characteristics of the facility,” Wagener said. “Some facili-ties will easily spend millions of dollars to implement an effective solution.”
Costs also can be high because a mix of technologies may be required to remove the selenium.
“Iron coprecipitation alone will not achieve the [5-ppb] level,” Nurdogan said. “Membrane treatment and bio-logical reduction methods together can reduce the selenium to the 5-ppb level. Ion exchange and adsorptive media technologies may also produce a 5-ppb selenium residual, but the cost of the media will be prohibitive due to low bed volumes and disposal costs of spent media, which is haz-ardous waste.”
Even if some power plants are able to meet the discharge limits of 5 ppb or lower despite these obstacles, their success may not be easily rep-licated. A “one-size-fits-all” approach will not work when it comes to sele-nium removal. It will require some trial and error, Shamas said.
“Some technology providers may disagree with the statement that less than 5 µg/L is difficult to achieve,” Shamas said. “I agree that in certain applications, these levels may be achievable; however, every wastewater discharge has unique characteristics that make the process perform differently.”
Desalination Permitting Challenges
Permitting U.S. desalination projects can be challenging and time-consuming, but new initiatives and public outreach could help ease the process
The 190,000-m3/d (50-mgd) Carlsbad Desalination Plant, which is being built by Poseidon Resources (Stamford, Conn.), is anticipated to be fully operational sometime before the end of 2012, but not before the project spent 5 years in California’s permitting process, despite the fact the facility was proposed more than a decade ago.
Desalination projects in the United States face a number of environmental challenges that can make the permitting process cumbersome. The process is especially difficult in California, where environmental groups have a strong voice and the environmental laws are some of the most stringent in the nation.
In environmentally sensitive coastal areas, there is a great deal of awareness about the potential impacts from desalination projects, said Lisa Henthorne, director and past president of the International Desalination Association (Topsfield, Mass.) “The environmental considerations for new desalination projects include greenhouse gas emissions, impingement and entrainment concerns of marine life at intake valves, as well as potential adverse effects from concentrate disposal, which has approximately twice the salinity of seawater and can also contain water-treatment chemicals,” she said.
However, desalination proponents have made significant strides in mitigating the potential impacts in all of these areas, Henthorne said. “At intake valves, proper designs can be implemented to bring about a negligible impact on marine life, and at outfalls, a number of dispersal technologies are available to dissolve concentrates very quickly, thus minimizing potential impacts,” she said. “The industry has also made drastic improvements in lowering the amount of energy used in the desalination process, which has significantly reduced the amount of greenhouse gas emissions. Additionally, many plants around the world now use renewable energy to power the desalination process.”
In California, the permitting process for desalination projects can get considerably lengthy due to opposition. Project intervention is easy to accomplish, even if it is based on unsubstantial information, said Nikolay Voutchkov, president of Water Globe Consulting LLC (Stamford, Conn.) and a specialist in environmental permitting of desalination projects. “Any group wishing to oppose a project can submit a two-page document, which effectively begins a lawsuit,” he said. “Responding and dealing with claims can take a lot of time and money.”
As a comparison, in Australia, any intervention must be based on more substantive information and documentation, Voutchkov said. “The evidence has to be concrete and the claims specific,” he said. “Also, retaliation against unsubstantiated claims in the U.S. is generally not allowed, while in Australia it is more supported. This discourages organizations from filing lawsuits unless it is based on solid information.”
For the Carlsbad project, Voutchkov said 30% of the total permitting time was dedicated to productive and constructive work, while the remaining 70% of the time was spent dealing with frivolous lawsuits and unnecessary challenges. “The U.S. is the only country in the world where it takes longer to complete the environmental review for a desalination plant than to actually build it,” Voutchkov said.
Employing effective outreach aimed at gaining public approval for desalination projects can be one of the most important aspects for managing opposition and helping streamline the permitting process. In comparison to water reuse projects that can generate public concerns about the health and quality of the potable water supply, Henthorne said desalination concerns are more related to the potential impacts on the marine environment.
“There is definitely a strategy as to how information should be presented to the public,” Henthorne said. “With desalination, it is very important to highlight the effectiveness of mitigation measures. At a recent desalination conference, a psychologist involved in the permitting process for these types of projects spoke about the importance of relaying sound information to the public. It should address people’s concerns and bring them together so they feel like they are part of the process. The goal is for desalination to be seen as a positive for the community and not something that is threatening.”
Another influential barrier to permitting U.S. desalination projects in a timely manner is a lack of federal and state desalination policies. In addition to the Carlsbad plant, Poseidon Resources is building the 190,000-m3/d (50-mgd) Huntington Beach (Calif.) Desalination Facility, a project that was initiated about a year after the start of the Carlsbad plant but is anticipated by Voutchkov to end up taking the same amount of time to permit.
“The Huntington Beach project ran into the same issues and obstacles all over again, because no precedent was set for the environmental review,” Voutchkov said. “Without concrete federal or state regulations specific to desalination, it is very difficult for projects to get approved in a timely manner. Desalination is still a relatively new technology, and because the agencies do not have a framework to follow, the permitting process is extremely slow and complex.”
Permitting costs for both the Carlsbad and Huntington Beach projects are also expensive, Voutchkov said, costing roughly 5% to 10% of the total project costs. This is a pricey expense, he added, considering that permitting for similar projects overseas usually costs between 0.5% to 1% of the total project budget.
If policies are to be developed, Henthorne said, it is much more likely to occur at the state level. “Desalination is linked to water scarcity, an issue that is always changing,” she said. “At the federal level, it is very challenging to develop a policy around something that is not consistent.”
Compared to the United States, permitting in other desalination-heavy countries, such as Australia or Spain, is much more efficient, Voutchkov said, taking approximately 3 to 6 months for smaller facilities and 6 to 12 months for larger projects. “Australia has a streamlined environmental review,” he said. “However, at the same time, they are not cutting corners. Environmentally, they are very thorough. Australia’s policies are established and contain a considerable amount of supportive documentation for desalination.”
Interestingly, Massachusetts is the only state in the United States that has a desalination policy, despite the fact that the only facility to be built in the state is the 37,800-m3/d (10-mgd) Taunton River Desalination Plant. “Massachusetts has a very clear desalination policy, and as such, that facility was permitted in about 6 to 9 months, a very reasonable time period, especially considering it was the first desalination plant in the state,” Voutchkov said.
New Initiative in Texas
In Texas, where, along with California and Florida, most of the U.S. desalination projects are located, the Texas Water Department Board is leading an effort with stakeholder groups and state regulatory agencies to streamline the desalination plant permitting process. “Texas has been very proactive in identifying issues and conducting research that could be used toward simplifying the permitting of desalination projects and avoiding duplicative project studies and efforts,” Voutchkov said. “For example, one area of concern in terms of human health is algal toxins, which can arise during algal blooms. While experience to date shows that reverse-osmosis membranes can reject those toxins, under the current regulations, an algal toxin rejection study has to be completed for every proposed desalination project, which is very expensive and time-consuming. Texas is planning to initiate an extensive state-funded study to research this issue and document rejection of such toxins by the newest available membranes, thereby avoiding the need to redo this study over and over again.”
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