Tryon Creek Wastewater Treatment Plant Disinfection Improvements Phase I
City of Portland, Oregon

The City’s goal for this project was to reduce the number of E. Coli excursions experienced during high plant flows by improving the response time of the chlorine injection system and making effluent chlorine residual easier to manage. One factor contributing to the E. Coli excursions that the City was experiencing was the lack of sufficient chlorine contact time. West Yost is addressing this by moving the chlorine injection points further upstream to allow more chlorine contact time as the effluent travels through the plant. This upstream injection point will also improve mixing of chlorine in the effluent before splitting to parallel chlorine contact chambers.

West Yost designed 1000 feet of neat chlorine pipeline along with three chlorine pumps at Tryon Creek Wastewater Treatment Plant (TCWTP) for the City of Portland (City). Two pipelines were designed consisting of ¾ inch PVC tubing inside 3-inch HDPE secondary containment. These lines deliver sodium hypochlorite to a primary and secondary injection point. Inside the chlorine building, three pumps were upsized to meet high dosage requirements. Another challenge for the City was controlling chlorine dosage with varying flow and water quality parameters. West Yost designed the neat chlorine pipeline with pumps dedicated to each injection point, which made it so that the pump speed was directly correlated to chlorine dosage. This allows operators to easily modify chlorine dosage at each specific injection point, as needed. Finally, West Yost analyzed historic plant flows and dosage data and designed larger pumps that can handle and provide higher chlorine dosages.

Overall, this project will provide the City with more easily controlled chlorine dosage and increase chlorine contact time to combat E. Coli excursions. West Yost also provided valuable input on the historic data and a chlorine system able to deliver more chlorine in order to handle high flow events.