Southwest Regional Wastewater Treatment Plant Improvements – City of Conroe

Conroe Texas

LAN designed upgrades to the 10.0-mgd existing plant, where much of the equipment had reached or exceeded its normal service life. The plant was expanded over its life through a series of different projects, including the numerous expansion projects, conversion to an activated sludge plant, and addition of aerobic digestion. LAN performed a complete system assessment of the existing plant to identify equipment that was still serviceable. The assessment also included an evaluation of the treatment process, which noted the previous design treated the process trains as three separate plants and did not take advantage of denitrification.

LAN revised the process to allow denitrification, providing an ongoing energy reduction associated with reduced aeration. Process modifications included properly sizing the return activated sludge (RAS) pumps; installing anaerobic zones in the aeration basins; repurposing an abandoned clarifier as a sludge thickener, and eliminating a second stage digester; installing a new lift station; and rehabilitating the headworks.

The existing RAS pumps were oversized, requiring more horsepower than necessary for operation. RAS pump changes were made in conjunction with process modifications which combined all return sludge at a single point, allowing for a unified plant operation.
Since the implementation of these improvements, the plant has realized a 25% reduction in monthly kWh usage.

At a glance

25% reduction in monthly kWh usage

$9,000 average monthly power savings

$13.3 million construction cost

10.0-mgd plant


Complete system assessment

Energy efficiency improvements

Unified plant operation



System Assessment


City of Conroe

Related Work

Wastewater and Reuse