In 2003, new permitted effluent limits required that the existing 0.85 MGD package-type wastewater treatment plant for the City of Mexia be abandoned. The City hired KSA Engineers, Inc. to upgrade the plant.
KSA completed all civil engineering for the project, including: Preliminary Engineering Report, permitting, environmental assessment, hydraulic profiles, treatment unit sizing, equipment selection/specification, bidding/construction oversight and O&M Manual.
The project involved construction of a new 2 MGD average annual flow wastewater treatment plant with 8 MGD peak 2-hour flow using the extended aeration mode including:
- Mechanical climber-type screen and manual bar screens
- Grit chambers (vortex type)
- Lift station with 4 submersible pumps with VFD’s
- Influent splitter box
- Aeration basins, 2 each with floating aerators
- Two clarifiers with algae sweeps, full radius scum arm, and sludge level meter
- UV disinfection with automatic flow pace and self-cleaning wipers (2 channels, 4 banks)
- Effluent meter with cascade aeration for increased dissolved oxygen
- Sludge pump station with 3 submersible pumps with VFD’s
- Aerobic digester/sludge holding tank with floating aerator
- Digested sludge pump station (grinder and 2 progressive cavity pumps)
- Centrifuge (for sludge dewatering)
- Administration and lab building
- Electrical and generator
- Plant on-site reuse system (pressure tank, pumps, chlorine)
- Site piping, grading, roads, fencing
The project also involved abandonment of the old treatment plant, and it was funded by the Texas Water Development Board - Clean Water SRF program.