Lack of sewers inspires a Wrentham, MA, outlet mall to use an onsite wastewater disposal system.
By Carol Brzozowski
Several years ago, American Water’s Applied Water Management Group was given the task of providing a system that would reuse onsite treated wastewater at the Wrentham Village Premium Outlets in Wrentham, MA. Because of the lack of sewers in this portion of Wrentham, town officials, the Massachusetts Department of Environmental Protection, and the Chelsea Property Group—which owns the mall—chose to go with an onsite wastewater disposal system.
Town officials had originally planned to build some sort of wastewater treatment system for the mall and felt the reuse of treated wastewater was the most cost-effective way to maximize water resources used by the mall. The wastewater was to be generated by the 575,000-square-foot outlet center, a 550-seat food court, mall management offices, and a cinema. An onsite wastewater treatment plant would recycle wastewater as flush water for the toilets. A subsurface disposal would recharge the groundwater.
The 130-store mall would be the first commercial water reuse project permitted in Massachusetts. But just how that system would be designed to provide maximum efficiency and meet the goals of treatment and reuse would be up to Applied Water Management Group. The company, headquartered in Hillsborough, NJ, was up to the task. Applied Water Management Group has established a reputation for providing geoscience services, as well as designing, constructing, and operating decentralized water and wastewater facilities.
Wastewater recycling was incorporated into the wastewater system to minimize effluent disposal impacts on the environmentally sensitive wetlands area where the plant would be located. “The space that we had available to us for both the treatment facility and the disposal beds was very limited,” says Andy Zinkevich, P.E., a vice president for American Water’s Applied Water Management Group.
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Photo: Ablestock |
| The mall was the first commercial onsite treatment plant in Massachusetts,
causing lots of questions from the community in the initial stages. |
“We had to both be very compact with the facility and with the disposal beds. Because of the recycling, those disposal beds were adequate for double the water that they would be otherwise.”
To address the challenges, Applied Water Management Group designed a state-of-the-art plant that treats the wastewater using a trash trap, an equalization chamber, a series of aerobic digestion chambers, and a membrane filtration system to separate solids from liquids. The water is further cleaned by carbon absorption and disinfected using ultraviolet (UV) and ozone technologies. The two membrane systems are manufactured by Zenon and Enviroquip (Kubota). The ozone generator is manufactured by Praxir Inc. The UV disinfection system comes from Aquafine Corp. The automation and controls are by Applied Water Management. The original plant measured 34 feet by 96 feet. In 2000, an expansion added another 32 feet by 72 feet and 4 inches and is located next to the mall’s parking areas. Treated effluent not used to flush toilets in the mall is recharged into the groundwater below. A subsequent wastewater treatment and reuse system expansion was to accommodate plans for a hotel and a restaurant. The original system had been so successful that the expansion extended the technology for more extensive use.
The use of both UV and ozone technologies was done to meet state requirements for wastewater reuse that calls for extra disinfection, Zinkevich explains. “In terms of using ultraviolet disinfection in our systems, we’ve done dozens of similar types of systems with this technology; it’s one step up,” he says. “Ozone adds an extra measure of disinfection above ultraviolet. Carbon absorption is there for color removal.
“When we are reusing water; if all we had to do was recharge it back to groundwater through the disposal beds, the limits in terms of the effluent are a little less stringent.
“If we are going to reuse the water for flush water, we want it to be not only more carefully disinfected, but we also want to remove the color, which is when the extra unit processes are required. It’s not so much a choice among alternatives—we just added the unit processes to remove the color and disinfect the water to a higher degree.”
The system treats the wastewater to requirements, which for recharge beds is a biological oxygen demand (BOD5) of < 30 milligrams per liter, total suspended solids (TSS) of < 30 milligrams per liter, total nitrogen of < 10 milligrams per liter, and pH of 6 to 9. For reuse, the treated water meets the requirements of a BOD5 of < 30 milligrams per liter, TSS of < 10 milligrams per liter, total nitrogen of < 10 milligrams per liter, fecal coliform of < 100 organisms per 100 milliliters, turbidity of < 5 nephelometric turbidity units, and pH of 6 to 9.
The membrane system is an important component of wastewater treatment, says Zinkevich. “There are other options for doing tertiary and advanced treatments; however, I think for the recycling systems we’ve tended to use a lot of membranes as a good fail safe, as least in the Northeast,” he says. “Twenty years ago, it was a big deal and something new, but now we’ve had a lot of experience and we’re very happy with the way it works for wastewater treatment.”
The initial contract for Wrentham Village Premium Outlets wastewater treatment extends back to 1996, with an expansion done in mid 2001 to continue the reclaimed water use. “It was possible to expand the plant to treat 100,000-gallons-per-day capacity without increasing the size of the recharge beds,” says Zinkevich. “Because of the use of the water within the mall for the toilet flushing, most of it gets returned back.”
One of the major challenges during the expansion was keeping the system running during the expansion, or, as Zinkevich puts it, “fixing the plane while it was still in the air.”
In executing the project while keeping mall operations moving, Applied Water Management Group relied heavily on planning ahead in order to logistically execute the project. “It was very important as far as the sequence in which things were installed, because we were both upgrading the equipment and the membrane system that was there; plus we were adding an additional whole section to it as well,” Zinkevich says.
“By careful sequencing and making sure there were enough people there during the critical times and being experienced in knowing when those critical times might be” helped the process run smoothly, Zinkevich notes.
Being that the Wrentham Village Premium Outlets project was the first commercial water reuse project permitted in Massachusetts also meant the company was under a microscope with its approach.
“Of course, there was some pressure,” says Zinkevich. “But we’ve been fortunate that because of the need for these projects—and, I think, they are philosophically a good thing to do—to have good relationships with the Massachusetts Department of Environmental Protection. We were working hand-in-hand with them as we went through. The mall owner also was very cooperative in terms of being patient and making sure things were done right. That was important.”
Zinkevich says Applied Water Management Group used concepts that—while not unique to his company—are different from the established norm in the traditional way of approaching such wastewater reuse projects. One of the aspects about the system that made it unique was that Applied Water Management Group was using two different manufacturers’ types of membranes within the same plant in the solids separation process. “They are both working quite well,” Zinkevich says.
Another first is that the company added additional automation because of the need to provide regular service. “We added a fairly sophisticated auto dialer unit that had a 24-channel system that calls the operator to tell him if anything’s not running smoothly at the plant—for instance, if the equalization tank is starting to get too high—so it gives the operator plenty of notice to get there and do something about it,” he adds.
Given that there is now a history with the system, Applied Water Management Group has learned some lessons to take on to subsequent installations. One is the control system in terms of the automation in order to enable operators to respond relatively quickly, says Zinkevich. “We didn’t put it in with the initial plant, but we put it in with the expansion,” he says.
“To my knowledge, we haven’t had any violations of any sort at that plant. Compliance records look good. This is a much better way of managing that type of system. We are now doing it in a lot of other plants as well where we have a lot of automation there that can bring an operator when he is needed.”
The footprint on the system also was important, Zinkevich notes. “With 100,000 gallons a day, if we were just using the recharged groundwater, we would have had to enlarge the recharge beds as well,” he says. “Because of the successful way and the track record that we had with recycling for flush water, we were able to increase the capacity from 60,000 gallons a day to 100,000 gallons a day without increasing the size of the recharge beds. That was a major difference in the footprint.”
The cost-effectiveness of such a system is a matter of size and application, says Zinkevich. “You would not do the same type of system for every application,” he says. “For this type of system, we have found this to be a very cost-effective way to go, particularly in a system we will own or operate over a long period of time.
“In terms of the option to membranes we would use, such as extended aeration-type plants, in the smaller plants, we find the fact that membranes are a little less likely to upset and their failure mode is much less of a problem than some of the other plants. We find them cost-effective when you take into account life cycle and account operations as well as capital cost.”
Its footprint is cost-effective as well, Zinkevich points out. “Obviously, from the perspective of the end user and developer, being able to put the membrane system into a small footprint and be constantly recycling with the smaller footprint is always advantageous.”
Lower maintenance requirements are also an asset, Zinkevich points out. “With this smaller system—as well as with a lot of the other smaller systems with automation we’ve now installed for the last six years—we really only need an operator to be there on a periodic basis two hours per day,” he says.
Then there is some routine maintenance that would go beyond two hours a day. “But to us that’s a good controlled amount of maintenance,” he says.
Applied Water Management Group designs, builds, owns, and operates a number of systems throughout the country. Applied Water Management Group managers are delighted with the results of the Wrentham Village Premium Outlets project, Zinkevich notes. “It’s doing what it’s supposed to do, and we’re happiest when nobody knows we’re there,” he says.
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Photo: Ablestock |
| In addition to recharged groundwater, the facility uses recycled flush water. |
Executives at Chelsea Property Group, a Roseland, NJ, firm that owns Wrentham Village Premium Outlets among others, know the system is there and are pleased that it is. “The wastewater facility at our Wrentham site allows us the ability to have sewer services at this remote location while producing less total sewerage by recycling highly treated wastewater back through the center’s five sets of restrooms,” notes Steve Cupelli, vice president of operations.
As the Wrentham Village Premium Outlets project was the first commercial water reuse project permitted in Massachusetts, and, it turned out successfully, Zinkevich says he hopes it has paved the way for more such commercial reuse of wastewater.
“There are a lot of benefits to not wasting potable water for non-potable uses,” he says. “The technology is improving. Using the membrane separation technology —which allows us to produce a very low-suspended-solid and low-turbidity effluent—and with the advances in and experiences with disinfection technology, we’ve gotten to the point where we are much better at preparing the water for different types of uses.”
In some cases, water crises drive water reuse projects, but in areas that do not have as many water concerns, it just becomes the “right thing to do,” Zinkevich notes.
And sometimes, it’s a combination of both.
Carol Brzozowski is a journalist in Coral Springs, FL.
OW- November/December 2007
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