Trees, trees and more trees proved to be a natural solution for meeting tightened effluent ammonia limits at the City of Woodburn (Ore.) Wastewater Treatment Plant.Poplar trees — 41,000 of them — were planted in 1999 on 84 acres next to the 3.3 mgd (design) activated sludge plant. Flow averages 2.0 mgd from May through October, and during those months the poplars provide tertiary treatment with beneficial reuse for 1.0 mgd.“It works very well,” says Curtis Stultz, plant supervisor, who was part of a brainstorming session with city staff and consultant CH2M HILL that produced the idea. “We were just
