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Case Study through the soil, and then surfaces in springs that feed restored wetland plants before discharging to Sylman Creek," explains Baird. "One-third of the water will be used by plants, and one-third of the water over time will find its way to the creek and river in subsurface flow. At some rates, it will go into the ground this summer and go out next year." That's a boon to the river, which runs low in the summer, notes Ron Thames, RUSA general manager. "Normally, when you're taking your discharge out of the river, the river never gets it back," he points out. "We want to put as much polished water as we can back in to augment the river's low summer flows." The combination of constructed wetlands, upland plantings, conveyance, and filtration and irrigation systems totaled $9 million — about one-tenth the cost of the mechanical treatment option. The operating expense is about $2 million per year, about one-third the projected cost of running a mechanical treatment system, says Thames. RUSA drew from capital reserves and secured a 10-year loan from the state's Infrastructure Financing Authority to fund the project. Even after raising monthly sewer fees to $25 per single-family home to pay off the loan, RUSA is still the least expensive wastewater treatment provider in the area by nearly one-third, Thames notes proudly. Integrated System Between May 1 and October 31 — months of low streamflow in the river — RUSA is required to route its wastewater through its new system. After two stages of clarification and chlorination, effluent is pumped to the canyon using 50- and 100-horsepower pumps with variable frequency drives. It emerges through an upwelling energy dissipater aeration fountain into a constructed wetland, where cattails, rushes, sedge, and algae begin drawing out phosphorus and nitrogen. The water flows several hundred feet through dense stands of wetland plants that continue sucking out excess nutrients. A long, curved channel gently slopes around a pond large enough to hold up to two days' worth of treated water. The channel directs the flow to the far end of the complex, introducing it to the pond after it's had a chance to build up enough momentum to maintain a circular flow. That prevents stagnation and limits the buildup of algae on the pond surface, notes Baird. As the irrigation system's 500-hp high-zone turbine or one of its 250-hp low-zone pumps kicks on, water is drawn through a coarse, steel intake screen to one 18 Water Online The Magazine, Wastewater Edition ■ wateronline.com A community of sedges, rushes, and cattails draws nutrients from treated effluent in RUSA's constructed wetland. The suction scanning process minimizes back flush water, generally to less than one percent of total flow. Back flush water at the Roseburg project is piped back to the head of the constructed wetland for further treat- ment and settling. One of the key benefits of the Amiad filters, notes Madison at CH2M Hill, is that they could be specified to perfectly match the flow capacity and level of filtra- tion required for the program. "We have spec'd Amiad filters on many other proj- ects for drip irrigation and wastewater reuse," Madison adds. "The filters are rugged and reliable, and the support network of dealers and suppliers is vast and supportive, so a project that must perform every day is not waiting for parts and support." Past the filters, the water tracks through a manifold system of 8, 10, 14 and 16-inch lines to feed the various irrigation zones throughout the canyon. Governed by a PLC SCADA network tied back to the plant by fiber optic cable, valves open slowly and pumps spin up deliber- of three Amiad EBS automatic self cleaning filters, each equipped with a 130-micron, stainless steel, weave- wire screen to protect the drip emitters and microsprin- kler heads of the irrigation system from clogging. When a target pressure differential is reached between the dirty and clean sides of the screen, the EBS's auto- matic self-cleaning cycle is engaged. An exhaust valve is opened to atmospheric pressure. Higher pressure inside the filter housing pulls water and filter cake — the dense mass of trapped solids — into a set of suction nozzles connected to the exhaust valve. The nozzles concentrate the high-velocity cleaning action on about one square inch of screen at a time, rotating on a scanning armature to clean the entire screen in a 35-second cycle without interrupting filtration.