Recycling Wastewater Proves to be Ideal Solution
Spring Creek reuse project allowed the State College, Pa. area to continue to grow and prosper without adverse effects on the surrounding environment
What do you do when population growth hits a rural community, transforming it into a thriving university center?
When you’re the local wastewater authority, you work to find new solutions to the old problem of wastewater disposal. When you’re the University Area Joint Authority (UAJA) in State College, Pa., those new solutions have to adequately overcome problems that most other northeastern municipalities simply don’t have to face. As a result, UAJA partnered with engineering consulting firm Herbert, Rowland & Grubic, Inc. (HRG) to develop innovative and environmentally sensitive solutions.
Between 1968 and 1990, UAJA grew from a 3.84 mgd contact stabilization plant to a 6.0 mgd complex aeration system that aggressively removed phosphorous. But with the continued growth of the Pennsylvania State University and the entire region, UAJA needed to evolve again to become a 9.0 mgd nutrient removal system.
Unlike most large northeastern cities, State College did not grow up on the banks of a major river, so the standard solution of disposing wastewater by conventional treatment and dilution into the local stream was becoming a problem by the 1990s.
Left unchecked, the treated domestic wastewater from UAJA was quickly becoming the majority of flow in Spring Creek, the largest waterway in the region. The fact that such a large portion of Spring Creek was treated wastewater meant that nutrients, sedimentation and temperature increases in the stream were changing the environment, according to UAJA. Because Spring Creek is also a world-class trout fishery that brings in millions of dollars to the local economy and is protected by the Pennsylvania Department of Environmental Protection (DEP), meeting those challenges was critical for the local community.
Thermal load was the most significant issue. As water use increased, the groundwater reserves were depressed, reducing the cold, clean water that enters Spring Creek via underground seeps and springs. When the water made its way through homes, bodies and UAJA’s wastewater treatment plant, it resulted in increased thermal load being added to the stream, which was already low on clean, cold water—and getting lower.
The problem identified, UAJA and HRG set out to find the ideal solution.
Addressing the problem
Study of the problem began in the early 1990s even as the plant was being expanded to 6.0 mgd and included 14 alternatives such as relocation of the discharge, spray irrigation, chilling of the treated water and reuse.
Ultimately, the beneficial reuse alternative was selected as the alternative-of-choice in 1998 and testing and design began on the processes necessary to make the system work, according to HRG officials.
“This Beneficial Reuse Project is vital to allow the State College area to continue to grow and prosper without adverse effects on the surrounding environment,” said E.C. Wunz, executive vice president and Environmental Group principal in charge at HRG.
The project involved the expansion of the existing wastewater treatment plant to 10.4 mgd with the addition of a biological nutrient removal (BNR) treatment system.
In addition, Wunz said an advanced water treatment system was built to withdraw a portion of this flow and produce 3.0 mgd of potable-grade quality water. The advanced water treatment consisted of microfiltration, reverse osmosis, ultraviolet irradiation, chemical buffering and chlorine disinfection. Upon completion of the alternatives study, UAJA and HRG formed a project management team with members of the community, key decision-makers, the DEP, and a number of technical experts, according to Wunz.
As the work of the engineers and scientists involved in the implementation of the project progressed, the project management team provided an audience for discussion of goals and critique of performance. By involving leaders and experts in the local community, UAJA and HRG were able to not only get valuable feedback on the proposed solution, but also effectively bring the public on board to support the project.
One change that came about through the project management team was the replacement of direct injection of the reuse water with stream augmentation. Everyone on the project management team agreed that recycling water was a good idea, but felt that the direct injection of recycled water into the groundwater table represented an unnecessary risk. The project was changed so that the reclaimed water would be introduced into the environment at the top end of the watershed, augmenting the base stream flow of Slab Cabin Run (a tributary of Spring Creek) instead of into the groundwater through a series of constructed wetlands.
“In addition, a rewarding aspect of the project is that it will actually help reverse the clock on some of the negative impacts that have already happened to Spring Creek Watershed,” said Wunz.
The next step in the process was selecting the equipment, and for that, HRG embarked on a two-tiered pilot test designed to accomplish several goals.
First, the pilot testing results would be used to validate that UAJA could create a water supply that met or exceeded all Safe Drinking Water Act parameters reliably, along with several other water quality indicators.
The pilot testing would also allow UAJA to gain familiarity with membrane filtration technologies and competitively analyze the various membrane filtration manufacturers’ equipment. This competitive analysis allowed UAJA to procure the most cost-effective and operable equipment for full-scale implementation. “One of the things that really appealed to the engineering team was the opportunity to use all of the available technology to develop solutions that meet the needs of the clients,” said Wunz.
Because the ultimate project would include two stages of treatment, microfiltration (MF) followed by hyperfiltration via reverse osmosis (RO), a two-tiered test was necessary to determine the best equipment for each individual stage.
While the water quality of the MF effluents alone did not comply with all water quality goals set for the final product water, all three MF units were able to produce water that met the intermediate goals of the first stage of the two-stage treatment process. After microfiltration, water analysis demonstrated that trace contaminants were nonexistent, but three parameters in particular (TDS, T-N, and T-O) did require further treatment by reverse osmosis. As anticipated, the second phase of the pilot test resulted in levels consistently below target for all three parameters.
Working with the community, the DEP and various experts, UAJA and HRG were able to bring the Beneficial Reuse Project to fruition.
Construction began in 2002 and was completed in March 2005. Along the way, they tested and proved several technological systems and enhanced the environment and community of State College. Because of their efforts, an additional three million gallons of water will be recycled each day in the region and a world-class trout fishery will be preserved.