The Living Filter
Penn State University's 40-year water
reuse project continues to improve.
A small-scale water reuse experiment that began during the early 1960s has evolved into an essential part of the infrastructure of a major university.
People weren’t talking a lot about water efficiency back in the 1960s. Looking back to those times, it may have seemed the supply of water, like the supply of gasoline and supplies of just about everything else, had no limits. But it was around that time that society began to take a closer look at how our behavior might be affecting the environment. The slogan: “Don’t be a litterbug” began to work its way into the culture.
A Living Filter
Pennsylvania State University’s (PSU) campus hit a growth spurt in the 1960s, coming to rival a mid-sized city in population, and of course, its waste disposal needs grew at the same time. Charles Walker, Professor of Soil and Crop Science at PSU, says that the University’s growth, coupled with population increases in communities around State College, PA, began to cause “a major pollution problem for Spring Creek, the main watercourse for the area.”
|Photo: Gannet Fleming, Pennsylvania State
Water reuse for irrigation is one of the main functions of the University’s water resource management.
Although the University had adequate wastewater treatment, with a fast-growing student population and expanding facilities, the school would soon be generating more effluent than Spring Creek could handle. After a couple accidental chemical spills caused fish kills on the creek, and a multi-year drought that gripped the region threatened to deplete the groundwater supplies during the 1950s and ‘60s, Richard Parizek, along with other researchers at PSU, began exploring ways to try to address both the challenge of water supply and wastewater disposal. With major constraints looming over both farming and residential communities, Parizek began an experiment reusing the University’s wastewater to irrigate croplands that the University owned.
The project, which Parizek dubbed, “The Living Filter,” was conceived to take advantage of the region’s productive agricultural acreage to provide tertiary treatment to the University’s wastewater effluent. Woodland flora and crops grown on farm fields would be used to extract excess nutrients from the water as they grew, while the region’s deep rich top-soil, in some areas plunging down as far as 100 feet, would complete the filtration process, allowing the purified water to gradually cycle back into the groundwater system.
That experiment, which began on May 16, 1963 and continued for the next 20 years, according to Walker, built up such a track record of success that in 1983, “the research application became a full-scale operation.”
Walker says “The Living Filter” is likely the only system of its kind in the region. He says one would be likely to see “a lot more reuse in the western regions of the US, but in our climate, where we’re not in a precipitation deficit region, where we have enough precipitation to grow crops, the system becomes kind of unique.”
Millions of Gallons Per Day
In 1983, the University began directing 100% of its wastewater effluent from its treatment plant, seven days a week 365 days a year, to forests, croplands, and fields, which it owns and manages—providing a much-needed alternative to dumping millions of gallons effluent daily into the surface waters of Spring Creek. And that’s no small task. Serving a campus of nearly 45,000 students, Pennsylvania State’s wastewater treatment plant must dispose of an average of 2.7 million gallons of treated wastewater per day. John Gaudlip, P.E., the engineer who manages the University’s wastewater operations, says the flow rarely slows. “The least we ever see is on Christmas day, when it’s a half-million gallons per day,” he says.
Gaudlip describes the operation as follows: The treated water from the waste treatment plant “flows into a half-a-million-gallon storage tank.”
The same SCADA (supervisory control and data acquisition) system that oversees the operation of the entire plant, as an energy-saving scheme, also controls variable-frequency drives on “three fairly good-sized 300-horsepower pumps,” maintaining pressure at 200 psi, and piping the effluent a distance of two-and-a-half into one of two irrigation networks. The networks fan out into the fields in a series of laterals, covering an area of 600 acres, known variously depending on one’s affiliations, as “the spray fields,” the living filter, or the “land treatment area.”
At a nuts-and-bolts level, the irrigation system is comprised of 96 kilometers of pipe, fitted with 3,100 sprinklers, distributed over 606 acres owned by the University.
Although the University historically served to educate the farming community and to help develop the agricultural sciences, its holdings include both farmland and forested areas, with the areas served by the “living filter” distributed more or less evenly, between the two.
|Photo: Gannet Fleming, Pennsylvania State
The University’s spray fields have the only permit in the state that allows irrigation throughout the entire year.
|Photo: Gannet Fleming, Pennsylvania State
The Wastewater Management Committee made the decision to adjust irrigation schedules to correspond to biological growth cycles in the fields.
The University’s wastewater permits allow it to spray its reuse effluent over these farm fields, forests, and grasslands at a rate of 2 inches per acre per week, although they often spray somewhat less, Gaudlip says.
“If you think about that a little bit, that’s a lot of water,” he says. “That’s over 100 inches a year, added to an area that normally sees, maybe 40 inches or 45 inches of water. We’ve got a situation where we’ve got 140 inches over an area that used to see 40 inches.”
Clearly, it would be unreasonable to imagine that adding that much water to the environs would not result in some changes. And such was the case. According to Gaudlip, the upland species of oaks hardwoods that populated the forested areas of the land application area at the outset of the project “weren’t necessarily adapted to a lot of water.”
He explains: “When we converted the areas into using a lot of water, some of the species just didn’t do well. Some of the red pines, and species like that, didn’t survive the first couple of years; they just kind of died off.”
However, Gaudlip says the forestry department at the University invested in research that successfully identified alternative species, such as sycamore, red maple, and aspen that could replace trees lost due to the wetter conditions.
Rain or Shine
The University’s spray fields have the only permit in the State that allows irrigation throughout the entire year; with 2.7 million gallons of water to discharge, rain or shine, any interruption would be most inopportune. However, winter temperatures in central Pennsylvania plummet below freezing on a regular basis, making frozen pipes, burst pipes, or frozen sprinkler heads, and other interruptions, a real
Jim Loughran, University research associate who coordinates the irrigation schedules for the spray fields, says durable commercial-grade sprinkler heads from Rain Bird help to ensure continuous operations. He also says, as an added measure of protection, technicians drain each lateral after use during cold weather.
Loughran says, in addition, most of the close brush in the forested areas near the sprinklers have to be cut back regularly, to facilitate access for maintenance. If the pipes ever do freeze, access roads allow workers to “drive right up” to the laterals in trucks stocked with blowtorches and any other equipment that might be needed to get things flowing again.
In a telephone interview on a cold February afternoon, with snow already piled several inches deep throughout the region, Chuck Walker said he could not recall hearing of any major weather-related problems with the irrigation system. “They actually spray all year-round. It’s snowing out here right now, but if you went out there, they would be spraying.”
The spray valves are manually controlled by a staff of between three, or four, workers. Loughran says manual control provides the flexibility needed for scheduling maintenance operations between uses.
Walker says the manual operations provide an additional public relations advantage over automatic sprayer systems. According to Walker, some sections of the woodlands covered by the irrigation operation have become popular recreational sites for area residents, who come to the area to stroll, walk their pets, or simply commune with nature. And Walker says manual controls allow operators the discretion to avoid any inconvenience to nature enthusiasts. The University’s farmers who use the spray fields to raise crops for animal feed, however, have to put up with a certain degree of inconvenience, “because there’s water there all the time,” says Gaudlip. “They say ‘It’s like farming underwater.’”
Nonetheless, he says, “They have adjusted their operations” accordingly. Loughran, who oversees farming operations, says contrasted to making changes in a water treatment facility, making changes in farming practices are not so much of a problem. “Farming is more flexible than engineering,” he says.
The spray fields have also proven instructive as living laboratories. Walker, who performed his undergraduate and graduate studies at Pennsylvania State, says the spray fields set the stage for his own early research into the impact of irrigation runoff on wetland habitats. And according to Ron Jager, who works with the University as a consultant with Gannett Fleming, in all, over 300 scientific studies have been reported based on research conducted on PSU’s land application area during the past two decades.
A Tough Test
The toughest test for the “living filter” came during the early 1990s, when, Gaudlip says, nitrogen readings from groundwater monitoring wells, already on an upward trajectory since the project went full scale, began to approach the threshold of drinking water quality limits.
And, he says the team no longer felt comfortable with the way that nitrogen that was building up. Although the spray fields had, at times, been subjected to nitrogen loadings that were “above what was recommended during the research portion of the project,” he adds that, ultimately, “our nitrate loading is reflective of our student population—which is very seasonal. The students come in September or August, and they’re gone by the April/May time period.”
|Photo: Gannet Fleming, Pennsylvania State
After the fall harvest, corn silage helps manage nutrient uptake and distribution—a key challenge for water reclamation.
And the growing season, when “The Living Filter” would be most efficient at taking up excess nutrients “is, unfortunately, not during that time period. When the growing season takes place, the student population is down, so it’s out of sync,” says Gaudlip.
To solve the problem, Gaudlip says, “We reversed our management style to more-intensive management. Our farm operations people came up with new cropping schemes, including double cropping and using crop rotations that did a better job of taking nitrogen out.”
Immediately after the fall harvest, growers followed corn silage with overwintering crops, such as winter wheat, to uptake the nutrients during the slow growing season, and then they would “reverse the cycle in the spring.”
On the nutrient distribution end, Gaudlip says the operation had, up to that time, maintained a “very mechanical allocation of the spray” to assure compliance with the permitted allotment of 2 inches of water per acre, per week. “We had a weekly schedule Monday through Monday, that on a Monday morning at seven o’clock, this particular lateral would be turned on, and then 12 hours later, it would be turned off, no matter what was going on in the field—whether there were crops growing in the field or not,” he says.
To help facilitate the removal of nitrogen, Gaudlip says the Wastewater Management Committee made the decision to adjust irrigation schedules to correspond more closely to biological growth cycles in the fields. Under the new system he says, “The farm operations people set the times when the fields will be irrigated, based on their assessment of which of the fields need the water. We never go over the two inches per acre per week, but it’s just a matter of when they’re applied.”
Gaudlip says the same principle applies to the woodlands. “There are certain times that we don’t want to spray the forest areas, so we’ve adjusted the schedule there as well. Unfortunately, we have the water 365 days a year, 24 hours a day, so we have to make the thing work.”
Eventually, the treatment facility was upgraded to include nitrification/denitrification processes, and the nitrate loadings on irrigation water were cut by about half, to less than 15 milligrams per liter. “We had been up over the 20s; it was a substantial improvement,” says Gaudlip. But now, he says, “it’s a juggling act, because the farmers are out farming these areas, and they’re looking for that nitrogen for the crops, so if you take it away at the plant, they still have to make the crops grow—so they have to fertilize.”
Nevertheless, these operational and infrastructure improvements were successful in meeting the immediate goal of reducing nitrogen loads, and Gaudlip says, “Now we’re into a point where nitrogen levels are in a steady state in the groundwater, below around five or six milligrams per liter.”
Under the low-nitrate loadings of the current effluent, Loughran says his cropping goals have “shifted,” once again. Demonstrating the versatility of the agricultural part of “The Living Filter,” rather than emphasizing nutrient removal, he says farm operations have begun to focus on cropping schemes that promote soil and water conservation and “protect the soils from compaction and erosion.”
Big Plans on Campus
“We’ve done a study and identified additional reuse customers on campus, anywhere from hosing dairy barns down to water supplies for our steam plants. We’re looking at reuse very closely,” says Gaudlip.
But that, says Gaudlip, will probably mean meeting multiple sets of treatment standards from the treatment plant. “Right now, it’s a straight secondary plant; to meet the Pennsylvania reclaimed guidelines, we’d need a filtered effluent,” he says. “So we’re doing a study to figure out what we need to get the quality of effluent up to what we need for reclaimed water purposes.”
“Some applications, like the power plants, require an even higher level of treatment, but for those we would put a point-of-use treatment system like RO [reverse osmosis] just for that small stream that we’re tapping off to meet that particular demand, for instance, for a cooling tower or something,” says Jager, of Gannett Fleming, the firm that is working with the University on its reuse and other civil engineering projects.
Jager says Gannet Fleming conducted a study to evaluate potable water use for the entire 45,000-student campus. The study attempted to determine the primary water use for each of 384 water meters on campus.
“We looked at what uses could be substituted with reclaimed water,” says Jager. And based on that study, he concludes that, “up to 25% of water used on campus could be replaced with reclaimed water.”
Gannett Fleming engineers devised a lay out for a reclaimed water distribution system on campus, and, although the system has not yet been built, the University has begun installing dual plumbing and purple pipe in new construction where appropriate, “so they’re ready to go when we get the water quality there,” says Jager.
Two or Three Classes of Water
Jager says upgrading the treatment plant to meet reclaimed water criteria, is going to prove an interesting challenge. Parts of the plant, he says, “date back to the turn of the last century. It’s a complicated little plant with dual-treatment trains, trickling filters, and activated sludge and MLE [modified Ludzack-Ettinger] process. And it is going to require extensive rehabilitation.”
Gaudlip adds, “We’re probably talking about microfiltration—maybe something heavier than that. We’re too early in the planning process to determine which way it’s going to go.”
Either way, Jager says, “The idea will be to build one plant that meets most of the quality demands for both the spray fields and reuse, which is basically the filtered effluent.” But, he says, that will require “a tough balancing act because you design for the worst-case scenario, in terms of nutrient reduction.
“But, there are times during the year on the treatment area, where they want the nutrients for their crops,” adds Jager. “So we’re going to try to design a lot of flexibility into the system, so that they can shoot for different targets on nitrogen, for example.
“I think we’ll have multiple trains,” he continues. “When we’re putting in an MLE process, instead of having a fixed anoxic zone, we’ll make them a swing-zone so they can aerate it, and run it just for BOD [Biochemical Oxygen Demand] removal. And then, they can also switch it back to an anoxic aerobic zone sequence, to get up to the level of denitrification they might want. They can run different trains different ways, so they have abundant effluent to meet certain goals. They’ll be able to go from absolutely none, to a pretty high level of denitrification, and pretty much everything in between.”
However, “It will take some operator experience to learn how to run that and appropriately hit certain targets,” says Jager, but he’s confident that PSU staff can handle the task. “They have one of the best groups to run a plant that you could find. They have a P.E. [Professional Engineer] on staff, John Gaudlip, and their plant superintendent is very experienced. It’s Penn State University—they do tend to attract a pretty high-quality staff.”
The Highest Degree of Efficiency
Jager says he has enjoyed working with the University’s wastewater management team, which consists of professors as well as staff from the Office of Physical Plant, led by Guadlip. “They are constantly researching,” he says. “As you might expect, with a lot of professors, they challenge almost everything we come up with. It’s a rigorous vetting process. It’s great; it’s a lot of fun to work with them.”
But Jager says it has been a learning experience as well. “Reuse is still relatively new in the Northeast, so working through the process with them on that has certainly been helpful.”
Jager believes the potential for expanding reuse in the eastern United States is ”very high.” He says, “There are different drivers than you have in the Southeast and Southwest. There, potable water supply is usually what drives it; here, it’s the ability to discharge wastewater. We have a lot of development in the more pristine areas; that’s where people want to live.”
But, he says, these same areas often also house high-quality or exceptional-value watersheds, “and you’re not allowed to increase the discharge or create a new discharge in these areas, unless you can demonstrate that you’ve maximized reuse. So I think we’re going to see a lot of it.”
And the “Living Filter” may also have a long and productive future ahead. Walker found, during a recent study, that not only have the soils of the treatment area tolerated over 40 years of intensive wastewater irrigation “quite well,” but the crop yields from those soils have increased. And in a 2007 study of the spray fields, he concludes, “the soils have, so far, retained most of their capabilities to act as a living filter.”
Gaudlip says the benefits of the reuse project accrue daily, not just to the University, but also to the region as a whole.
“We think we’re recycling our water quite efficiently. It has been estimated that 90% of the water that we use to irrigate out there is going back into our groundwater system in the center region. We’re saying, we’re cleaning this water up and putting it back into the groundwater system, and we’re not discharging it into the local stream, where it would provide no benefit to the local community.”
Writer David C. Richardson is a frequent contributor to Forester publications.