Events

Leachate generated in the Tillamook County Closed Landfill (TCL) has been a continuous environmental hazard due to its high iron and ammonia content. The Tillamook County Department of Solid Waste Prevention and Recycling has called on Oregon State University Environmental Engineering Class of 2021 to produce workable solutions for a sustainable and effective design for treatment of the leachate. Removal of these contaminants is necessary for permitted release offsite to reduce potential risk to human and aquatic life.  

To achieve permitted effluent concentrations of 1.6 and 5.3 mg/L of iron and ammonia, respectively, the team designed a solution based on an evaluation of different treatment options. Criteria for different alternatives were established based on constraints, and an assessment took place that determined the most applicable design. The team selected a design that included an oyster packed bed, cascade aerator, sedimentation basin, and vertical flow wetlands. 

To accomplish effluent concentrations and meet constraints, dimensions of unit operations for a pilot scale were calculated. Leachate will be pumped uphill to achieve gravity flow throughout the system. Leachate will enter a packed bed of oyster shells 2.8 feet in height and 3.5 feet in width which will adjust the pH to make removal of iron in the cascade aerator easier to achieve. Leachate will flow into a cascade aerator 4 feet in height, covering an area of 27 square feet. In this unit process, a large amount precipitation will be formed from the iron oxidation process. A 4-foot-tall sedimentation basin covering an area of 29 square feet will follow to allow iron particles to settle out of the leachate. Ammonia removal will occur in vertical flow constructed wetlands covering an area of 1506 square feet and a depth of 3.28 feet. 

In the coming weeks we will estimate the cost and environmental impact of our design via a cost analysis and life cycle assessment. Additionally, we will continue making amendments and scale up our design to achieve a full-scale treatment process able to operate at 100 gallons per minute.