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 Turn-Key Solution Eliminates Chain and Scraper Downtime in Grass Valley, CA


​The Grass Valley Wastewater Treatment Plant provides service for a population of about 12,000. The area has some unique challenges from mine drainage and heavy flows during the winter storm season in the Sierra Nevada foothills.

The plant uses chain and scraper systems for sludge collection and scum pipes for scum collection. In 2013, the chain and scraper systems were approaching the end of their service life, placing an increasing burden on the system.

Matters came to a head when the collector system in two of the tanks became inoperable due to a breakdown of the triple-ouput shaft drive system. The outage left just one tank operational and threatened to shut down the entire system.


​Grass Valley commissioned an upgrade project to replace the chain and scraper systems, drive system, and the scum pipes with new equipment. The project was planned and executed as a turn-key solution through MISCOwater, Evoqua's sales partner in Northern California.

Envirex® Chain and Scraper sludge collection systems from Evoqua replaced the current systems. The new chain and scraper systems feature non-metallic chain technology with a lightweight design for easy installation and maintenance. 

Simple lever operated scum pipes were also provided for increased reliability and longer life. The triple-ouput drive system was replaced with three individual drives to reduce costs, improve maintainability, and keep the project on track. 

grass valley secondary clarifier basins


​Evoqua was able to move quickly in order to provide the new equipment under a tight timeline. The installation was completed within 3 weeks of the region's unpredictable winter storm season.

With the new equipment installed, downtime and maintenance issues have been eliminated.  In addition, the new Envirex Chain and Scraper systems have increased the efficiency of solids removal at the plant and operating life has been extended for another 15-20 years.

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