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Case Study Land Application Of Treated Wastewater Tackles Touchy Challenge Total maximum daily load (TMDL) is solved with out-of-the-box (and off-site) thinking. by Steve Werblow F aced with drastic state-mandated cuts in the amount of phosphorus, nitrogen, and warm water that could be discharged into the south- ern Oregon's South Umpqua River, the Roseburg Urban Sanitary Authority (RUSA) decided to think big about how to modify its wastewater treatment plans — to the tune of 340 acres. The South Umpqua flows through Roseburg, OR. It's a popular fly fishing river renowned for its salmon, steelhead, and trout. In fact, the Umpqua system is home to more wild coho salmon spawners than any other river system in Oregon — 15% of the coho salmon that spawn along the West Coast. with water quality data, a suite of best management practices, and negotiations involving the stakeholders within the watershed, the TMDL process assesses the pollution load and assigns the burdens of reducing it among the stakeholders. In the reach of the South Umpqua that runs through Roseburg, the TMDL dictated reductions in phospho- rus, temperature, and algae (which in turn is tied to tar- get levels of dissolved oxygen, pH, and chlorophyll). The pollutants are tied together, as high levels of nutri- ents feed massive algal blooms, which play havoc with oxygen levels and biological oxygen demand (BOD) in the river as the algae thrive, respire, die, and decom- pose. Elevated water temperatures are also a danger to cold-water fish, whose spawning success and juvenile survival rate suffer as water temperatures rise. In the case of the South Umpqua Basin, the U.S. Geological Survey and Douglas County determined that five wastewater treatment plants contribute less than 15% of the river's flow, but more than 90% of the nitrogen and phosphorus load during the low-stream- flow months of summer. That meant that achieving target reductions would fall squarely on the shoulders of RUSA and neighboring wastewater treatment plants. Expensive Proposition Jim Baird, RUSA's engineering and operations manager, inspects the pump station regularly. That remarkable fishery put the South Umpqua squarely in the sights of state Department of Environmental Quality officials. Under the Clean Water Act, states are required to conduct water quality assess- ments of every water body within their borders. Those found to have excessive levels of pollutants — which could range from chemicals to bacteria, sediment, or temperatures high enough to interfere with fish reproduction and survival — must undergo the total maximum daily load (TMDL) writing process. Working 16 Water Online The Magazine, Wastewater Edition ■ wateronline.com To management at RUSA, bringing its 7.9 million gal- lon per day (MGD) wastewater treatment plant into compliance with the TMDL was shaping up to be an expensive proposition. "There are a couple of different ways you could deal with it," notes Jim Baird, RUSA's engineering and opera- tions manager. "A mechanical and filtration system are most common, but with both up-front costs and energy costs over time, it's expensive." In fact, engineers at CH2M Hill evaluated a similar problem in Spokane, WA and estimated that upgrading to a membrane bioreactor system similar to the alternative Spokane selected would cost RUSA $80 to $100 million. RUSA management and CH2M Hill took a look outside the box, beyond the footprint of the wastewater treatment