After eight years of work, the Littleton/Englewood Wastewater Treatment Plant (LEWWTP) recently completed a $114 million upgrade designed to reduce nitrate levels in treated effluent discharged into the South Platte River and expand its capacity from 36 million gallons per day (mgd) to 50 mgd. The project also repaired and improved much of the facility's aging infrastructure. The complex construction was completed with daily interruptions to the plant's operations but without compromising treatment.

LEWWTP faced a state mandate to reduce nitrates flowing in the South Platte River, and a regional council of governments required the utility to increase capacity to 50 mgd to meet projected population growth. At the same time, parts of the physical plant were beginning to show signs of age, and the agency's managers hoped tackling all of those challenges together would be more efficient.

The plant contracted with Walnut Creek, Calif.-based Brown and Caldwell to design improvements that would optimize plant performance, ensure affordable sewage treatment and embody environmental stewardship principles. Completed in December, LEWWTP now includes a first-of-its-kind 50-mgd denitrification process that simultaneously removes nitrate and filters the water (tertiary filtration) within the process train. Individual methanol feeds to each filter train were incorporated to reduce chemical use. The process will save the plant thousands of dollars each year in operating costs, produces a higher quality effluent and prepares the facility for future regulatory requirements.

A second innovation is nitrified effluent recycling, in which up to 25 mgd of the effluent from the nitrification process is recycled back into the primary treatment process. That reduces the concentration of the nitrate up to 5 milligrams per liter, and saves thousands of dollars each month by minimizing the amount of methanol added into the denitrification process. An added benefit of the recycled stream is that odors are reduced at the primary clarifiers.

A new Supervisory Control and Data Acquisition (SCADA) system also was installed to automate all of the plant operations. It diagnoses equipment maintenance needs, analyzes the plant's performance, alerts staff to any trouble and integrates an asset management system. The SCADA system allows the larger plant to operate without any additional staff and helps reduce the plant's energy use.

In all, 11 of the plant's existing treatment processes were upgraded, including the biosolids storage system, dewatering facilities and secondary clarifiers. Combined, the upgrades allow the plant to operate more efficiently with the same staff, save millions of dollars in capital improvements and pursue opportunities for energy savings.

Project: Wastewater treatment plant upgrade
Jurisdictions: Littleton and Englewood, Colo.
Agency: Littleton/Englewood Wastewater Treatment Plant
Vendor: Walnut Creek, Calif.-based Brown and Caldwell
Date completed: December 2008
Cost: $114 million