Water quality plays a vital role during the operation of ethanol plants and should be a consideration during the feasibility and development phases of an ethanol project. "When you look at water quality, it influences how much capital equipment is required up front to pretreat that water," says U.S. Water Services Marketing Manager Mike Mowbray. "Capital costs ultimately determine the quality and quantity of water for an ethanol plant." Plymouth, Minn.-based U.S. Water Services has been involved in more than 40 ethanol plant designs, start-ups and consulting services. Once a producer decides how much he can spend on water equipment, industry experts recommend identifying eight key areas to consider before choosing a plant site: a viable water source; design requirements; environmental impacts; options for equipment and treatment in the form of required capital and expense outlays; proper control mechanisms to maintain water quality and water system designs; resources to monitor treatment equipment in real time to minimize asset degradation; effluent discharge regulations imposed by a particular state; and preliminary water quality samples taken at anticipated operational levels.
 
 To avoid any potential pitfalls during the project development process, consulting firms such as the Natural Resources Group offer preliminary analysis services such as its "Fatal Flaw Analysis." The purpose of an FFA is to provide ethanol plant developers with an outline of possible site issues that could limit construction on a particular property or cause significant time delays, says Angela Ronayne, project manager of Minneapolis-based NRG's renewable fuels group. Employing a project development advisor such as NRG can prove beneficial in the long run for both the developer and the contractors to avoid any legal consequences that may have been overlooked. "[An FFA] is not a substitute for the permitting stage," Ronayne emphasizes. "It's simply a consulting parameter to follow during the feasibility stage of an ethanol project."
 
 To understand how important water quality management issues are for any ethanol plant in today's expanding industry, project developers must be engaged with the micro-intricacies of water activity inside and outside of a given a facility.
 
 Water Sourcing
 For a typical corn-based ethanol plant, the selection of an appropriate water source and the conducting of preliminary water quality tests is a critical portion of the project development process. Groundwater or well water is a popular choice because it's more readily available and generally higher in quality than surface water from a river or a local municipality. Depending on the scope of the project and how much a producer wants to spend, each water source has its advantages, according to Kent Herbst, a certified water technologist and ethanol team leader for U.S. Water Services. Another option to consider is the use of "grey water" from a wastewater treatment plant. Water companies say that grey water has been used as a supplement to a main water source, but they caution that it's expensive to pretreat. "Well water is probably easier to treat just because it's typically more consistent than surface water," Herbst says. "It's easier to design an ethanol plant based on well water for that sake. Although, there is some pretty bad well water out there that we encourage people to shy away from."
 

 Although groundwater is more consistent than surface water, it can vary drastically among different aquifers within the same geographic location. Additionally, the composition of groundwater can change over time as aquifers become stressed because of continuous use such as in the case of the Ogallala Aquifer—the nation's most abundant groundwater source that stretches from South Dakota to Texas. The pumping rate can also affect water quality. "If you pull out 100 gallons per minute versus 1,000 gpm, you can have different water quality," Herbst says.
 
 As more projects come on line in the Midwest, quality water may become scarce prompting project developers to look elsewhere for plant sites. Locations such as southwest Minnesota, southeast South Dakota, eastern Iowa and Colorado tend to "have some bad, deep aquifers," Herbst says. The East and West Coast areas have better groundwater quality, he adds.
 
 Testing
 Once a water source is identified, water management companies strongly recommend collecting water samples at anticipated operational levels. This is imperative when gauging how the water quality could impact utility systems and processes. "We always try to encourage people to do well testing early in the process and sample a couple of different wells because different areas on the aquifer, and different aquifers within the same region may have vastly different water," Mowbray says. "As a result you may save yourself money and headaches by relocating your plant."
 
 Water sampling conducted during the feasibility stage of an ethanol project determine what type of front-end water pretreatment methods should be utilized. Ultimately, it's up to the ethanol company and the engineer, procurement and construction contractor and the technology firm to come up with solutions to water quality challenges. Carefully testing and monitoring constituent or mineral levels (hardness) relative to the incoming water rate can prevent asset degradation. "What's equally important is making sure that the technology providers in conjunction with the EPC firm don't experience slow downs due to unforeseen water problems," says Tony Stanich, industry development manager for Nalco Co.'s grain/ethanol industry sector. The Illinois-based company provides integrated water treatment and process improvement services and has more than $40 million in global sales in the grain and biofuels processing industries. Nalco, and its joint venture partner Siemens Water Technologies, manage more than $200 million in assets as part of its Treated Water Outsourcing business. "We try to work closely with the EPC, technology provider, and owner in the selection of water treatment equipment, chemical, and control technology to minimize related operational and capital costs specific to the plant site," Stanich says.
 
 Pretreatment Methods
 Looking through a typical "cookie-cutter" lens, pretreatment models employed by corn-based ethanol plants include reverse osmosis and some type of polishing softeners for the steam boilers to decrease sulfate and mineral levels that contribute to unwanted hardness levels. "Over the past 12 months, we've seen the need for more complex water treatment systems," Stanich says. "In the past most sites only required a simple reverse osmosis system followed by water softener systems."
 
 Iron, manganese and silica are a few of the key elements in water that would limit water treatment measures. "You can handle high hardness relatively easily with lime softening for its precipitation process," Herbst adds. "Once you start getting into sodium, chloride and sulfate, those three are some bad actors that are extremely tough to precipitate out of the water, so you end up just moving it around and you concentrate it and there's no way to physically remove it from the water before it gets discharged."
 
 Conducting appropriate water pretreatment methods tailored to the specific needs of a particular plant's utility and process demands should be of paramount interest as well. Requirements for the two can vary between technology providers. For example, some ethanol facilities need varying amounts of water for utility systems, such as for heat exchangers or heat recovery stream generators as both require high-quality water and high maintenance to mitigate mineral scales or deposits. Incoming water quality also impacts cooling tower operations, which requires the largest amount of water. Correct observation of the "cycles of concentration" is important when monitoring water activity in this process. "The higher the cycles you run the less water and chemicals you use so it's a balance of maximizing the cycles relative to what capital costs you have to do for pretreatment," Herbst says.

 
 Water Output
 Balancing environmental sustainability while maximizing production and minimizing investment can be a difficult feat for any ethanol producer. Water quality effluent is probably one of the most variable process constraints associated with water management in an ethanol operation because each site is different. Understanding the discharge parameters imposed by each particular state dictates front-end pretreatment and/or process technology designs. "If we have a state that chooses to be restrictive then we have limits that are set in terms of how efficiently we can operate," says Chris Sleigher a water specialist with ICM Inc., which is involved with nearly 100 ethanol projects around the country. "Water quality is definitely becoming a much more stringent issue today," Ronayne says. "Of course, certain areas [of the country] are more stringent than others. It really depends on what location and state you're in. I would expect that water quality is going to be more heavily scrutinized as projects move forward in the coming years."
 
 Most process technology firms such as ICM provide zero liquid discharge equipment, which doesn't impact effluent water discharge. However, much of the concern lies in the effluent that comes from the cooling towers. Because it's the central piece of equipment that requires the most and highest quality water, it remains the exclusive contributor to discharge issues. The cooling tower is usually the point where water is reused or recycled, depending on the flexibility of the discharge permit. "States have become more protective of their water quality in recent years so they're not going to let you dump your effluent into a receiving stream without permission," Ronayne says. "If the facility chooses to discharge to a receiving stream the water balance is typically designed around the source water and the discharge limit."
 
 Whether an ethanol plant sources its water from a well, river or local municipality, ethanol developers must be mindful of the increasingly stringent discharge regulations and limitations set forth. "Producers don't want to spend any more money than they have to," Stanich says. "But, they still want to follow environmentally sustainable practices. Balancing the two is where we can help."
 
 Bryan Sims is an Ethanol Producer Magazine staff writer. Reach him at <a href="mailto:bsims@bbibiofuels.com">bsims@bbibiofuels.com</a> or (701) 746-8385.

Mowbray adds coagulants in a gang stir to precipitate unwanted river water solids.

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Tera Ziesmer of U.S. Water Services tests for water quality by gauging its clarity in the light at the company's analytical lab.

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Water quality is equally as important as water quantity in choosing a site for an ethanol plant.  EPM talks to water management and project development consultants about the importance of water testing.

Putting Water to the Test

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