CITY OF WOODBURN LAND-APPLIES LIQUID AND DEWATERED BIOSOLIDS, FACULTATIVE SUDGE LAGOON SUPERNATANT, AND EFFLUENT ON HYBRID POPLAR TREES

The City of Woodburn, Oregon, designed and installed a 34-hectare (ha) (84.1-acre) poplar plantation to beneficially reuse wastewater treatment plant effluent, biosolids, and supernatant. The City chose this approach as a cost-effective and environmentally attractive method of reducing effluent discharges to the Pudding River in the summer when the total maximum daily load restriction for ammonia is most stringent. Consequently, in July and August, the treatment plant pumps 5,034 cubic meters per day of effluent (m3/day) (1.33 million gallons per day (mgd)) to a poplar plantation instead of the Pudding River. In the final development phase, this is expected to increase to 11,393 m3/day (3.01 mgd) irrigating 300 acres.The overall system monitoring and management program was developed based on Oregon Department of Environmental Quality guidelines for land application of municipal effluent and biosolids. Irrigation scheduling is based on National Pollutant Discharge Elimination System permit requirements. Nutrient loading is based on agronomic requirements of the trees and the total nutrients available from the reused waste streams.The capital cost estimate for the 320 acre reuse farm and all reuse equipment is 4,610,000. The operations and maintenance cost per year is approximately 120,000. This paper demonstrates that automated irrigation management and scheduling for a poplar tree plantation is an innovative, cost-effective method of wastewater management that protects public health by enhancing water quality and the environment. It also demonstrates that a reuse farm sized for effluent use can also consume all of the biosolids and supernatant produced at the WWTP.