Decatur’s Water Treatment Revolution

CMT developed an innovative approach on the Decatur Clarifier Conversion project, addressing operational inefficiencies and aging infrastructure with a streamlined solution. By consolidating multiple treatment stages into one unit, the facility increased capacity from 18 million gallons per day (MGD) to 20 MGD within a smaller and cleaner footprint. The introduction of single-stage helical upflow solids contact clarifiers (SCCs), also called ClariCones, significantly improved operational efficiency and sustainability by eliminating the need for energy-intensive components such as motor drives and mixers.

Traditionally used in smaller facilities, ClariCone technology integrates primary and secondary treatment within a single unit. Its application in Decatur’s larger-capacity plant marks a notable advancement in water treatment design, optimizing both space and performance.

Built in 1988, the City of Decatur’s lime softening water treatment plant had a capacity of 36 MGD and relied on a two-stage clarification process using 100-foot-by-100-foot square primary clarifiers and 120-foot-by-120-foot square secondary clarifiers. Over time, the plant’s two parallel 18 MGD treatment trains had aged to the point of needing extensive rehabilitation, including upgrades to scraper mechanisms, drives, motors, as well as repainting.

In 2015, CMT conducted a feasibility study to evaluate options for rehabilitating the existing clarifiers or transitioning to SCCs. The study identified SCC conversion as the most efficient and cost-effective solution. As part of the project, the outdated clarifiers were replaced with two 71.5-foot-diameter single-stage SCCs.

This conversion delivered measurable benefits, increasing the plant’s total capacity from 36 MGD to 38 MGD while reducing maintenance demands by approximately 600 man-hours annually. The new system also improved energy efficiency and sustainability by consolidating treatment processes and reducing reliance on electrical components.

The Decatur Clarifier Conversion project exemplifies how thoughtful design and modern technology can extend the lifespan and functionality of critical infrastructure in high-capacity water treatment facilities.