Small System with Large Challenges: Operating a Wastewater Treatment Plant that Does Not Follow the Rules

Small community wastewater treatment plants must overcome unique challenges that larger facilities do not face. Small plants often have the same mechanical complexity and effluent standards as larger facilities, but without the benefits of stable flow/loadings, operational flexibility, easy access, and buffered protections from toxicity or industrial loadings. The Stevens Pass Sewer District (SPSD) provides a successful case study of a plant which must weather such challenges and merge a technically advanced treatment system (a 379 m3 /d [0.1 MGD] membrane system with nitrogen removal capabilities) with the unique challenges of small system dynamics. The facility reduces ammonia levels to near non-detect despite being carbon deficient, while also responding to nearly instantaneous shoulder season shifts in influent flows and loading. Staff work through extreme logistics challenges with full winter isolation, while working with residents to address the significant impacts of acute events to the plant process.