In 2003, the Village of Bartlett in Illinois purchased four fabric-covered buildings to cover aerobic digesters at its wastewater treatment plant. Located just 40 miles from Chicago, the facility handles wastewater for 26,000 people residing in three different counties.
“We have 12 individuals employed with the sewer department who take care of the treatment plant as well as 19 lift stations and the total sewer system within the Village of Bartlett,” said Ron Johnson, Wastewater Supervisor. “This treatment plant is considered a medium to large size treatment facility.”
The four buildings are 62 by 62 feet in dimension and cover two sludge tanks each. They were provided by Cover-All Building Systems and are part of the company’s Legend series.
“The aerobic digesters take in sludge from two parts of our facility. One part is the waste activated sludge from the activated sludge system, and the other is the primary sludge from the primary clarifiers,” Johnson said.
“One of the problems we had in the past was controlling the temperatures during the winter as well as containing odors from drifting into nearby residential areas. Since we have had the Cover-All buildings we’ve been able to hold the heat in during the winter so the bacteria can do its job and we no longer have odor complaints from the surrounding residents,” he said
The Village of Bartlett chose the buildings because of their ability to perform in a corrosive, moist environment.
“We looked at a PVC system that was designed to completely cover the digesters, but that would have caused us problems of getting to the sludge for sampling, temperature readings, etcetera,” Johnson said. “We also looked at aluminum and corrugated steel structures, but the high moisture levels in this type of environment would quickly deteriorate metal structures.”
Friedman Distributing, an authorized Cover-All dealer for Illinois, designed and constructed the buildings.
“We designed each of the Cover-All buildings to have a side access to allow a hoist to be lowered within the tank to clean the digesters or install equipment,” said Paul Smith, Friedman Distributing.
The Legend building design allows for an open clear-span structure using a steel framework supporting the tension fabric membrane outer cover. The buildings are designed with a continuous arch all the way around, allowing for even tension and a smooth support of the cover, eliminating wear points that could cause the cover to stress or loosen and ensures maximum structural load capacity.
The standard galvanized steel-frame system is clad with a triple-coated anti-corrosion barrier and the fasteners and cables were treated with JS500 corrosion resistant protective coating, which is a zinc based chromate sealer. All anchor bolts are stainless steel and the service doors and door frames are manufactured with non-corrosive materials.
The buildings are available in widths from 18 to 82 feet, and can be manufactured to any length. The modular design also allows owners to extend the building at any time to meet changing needs. Engineer sealed drawings are available, ensuring building integrity satisfies local codes and permit requirements.
Although engineered for permanent use, the buildings can be moved with relative ease and re-assembled where they are needed.
“Maintenance on the fabric membrane is minimal since the polyolefin characteristic of the Cover-All DuraWeave membrane is inert to ammonia gasses and is not biodegradable,” Smith said.
Installation of the four 3844-square-foot buildings at the Village of Bartlett was completed in just 12 days and didn’t require the sludge tanks to be emptied. Because of the tight confinements of the site, each truss was assembled on the ground then lifted into place by a crane and a zoom-boom was used to install the purlin bracing and other steel components.
The ventilation system in each of the buildings consists of intake louvers on one end and a 30 inch exhaust fan on the other end. The exhaust fans are operated by a temperature switch which turns the fans on when the temperature hits 95 degrees. The buildings’ design combined with the automated ventilation system allows odors to dissipate into the air and eliminated the need for a scrubber ventilation system which was estimated to be as high as $300,000.
Another benefit with the buildings is the translucent qualities of the fabric membrane.
“We don’t need any natural lighting in the Cover-All buildings, nor do we require the installation of explosive proof fixtures or personnel needing to change light bulbs. The white cover provides us more than enough natural light inside the building, even on gray and overcast days,” Johnson said.
The four buildings have been up for more than a year and the results have been positive.
“The Cover-All buildings themselves are pretty much maintenance free and are working very well for us,” Johnson said. “During the winter months the temperature stays above 70 degrees which enables the microorganisms to be more active and we’ve had zero odor complaints from nearby residents.”
