Water Reuse

Woodburn, Oregon

When the Oregon Department of Environmental Quality revised the Total Maximum Daily Load for the Pudding River, the city of Woodburn had to decide between lowering the ammonia level in its wastewater or finding an alternative discharge site.  After investigating a variety of options, Woodburn chose to refurbish its treatment plant to include a wastewater reuse facility.

In 1999, Woodburn was ready to discharge treated effluent through micro-spray sprinklers into its newly developed poplar tree plantation.  Poplar trees grow quickly and use lots of water.  The treatment plant generally produces about two million gallons a day.  The 88-acre poplar plantation is watered with 1.5 million gallons a day during the critial dry months from June through September.  The remaining 0.5 million gallons a day are discharged into the receiving waters.  Because the amount of wastewater being discharged into the stream has been greatly reduced, the receiving stream is able to dilute the concentrations of ammonia to meet the required limits.

Wastewater is treated using a biological nutrient removal aeration basin, a clarifier, and sand filters bringing it to tertiary treatment.  Treated effluent is disinfected in an ultraviolet unit and then diverted into a basin for chlorination.  While this level of treatment exceeds the requirements for a nonfood crop, management decided to use the precautions since the treatment plant had the equipment to do it.

After chlorination, the treated effluent is pumped into a manifold system that distributes it to the poplar planation through an underground piping system.  This natural system creates an attractive habitat for wildlife, provides 30 - 50% more evapotranspiration capacity, and provides a new source of revenue.  Trees can be harvested every 7 - 12 years and revenue from the sale of woodchips can be used to offset a portion of the capital and operation and maintenance costs of the system.

The city plans to expand the facility every five years to match population growth.  By 2020, the site will cover 300 acres and will reuse 5 million gallons of wastewater per day.

Woodburn Wastewater Treatment Facilities
 
Source:
McKenzie, C. Wastewater Reuse Conserves Water and Protects Waterways. On Tap. Winter (2005): 46-51.