Woodard & Curran Wins ACEC Georgia Award for Engineering Excellence

Published: 3/31/2017

Woodard & Curran’s work with Delta Air Lines to design and build a new aeration tank and secondary clarifier at the Hartsfield-Jackson Atlanta International Airport (ATL) has received an Engineering Excellence Award in the waste and storm water category from the Georgia chapter of the American Council of Engineering Companies (ACEC).

Delta’s Technical Operations Center (TOC) in Atlanta is the company’s main maintenance hub, consisting of aircraft maintenance and repair hangars and engine repair, engine test cell, plating, aircraft painting, and carpentry shops. Delta uses four industrial wastewater pretreatment facilities to pretreat the wastewater produced from the aviation-related maintenance that takes place in the TOC before it is discharged to the City of Atlanta sewer collection system. For the past 17 years, Woodard & Curran has partnered with Delta to perform all operations and management at these facilities, performing dozens of improvements throughout the years. In one of Woodard & Curran’s routine site assessments, two major processes were identified as lacking redundancy: the biological treatment and secondary clarification operations at the Oily Waste Treatment Plant (OWTP), one of the four pretreatment facilities at the TOC that treats 300,000 gallons of wastewater per day generated by aircraft maintenance activities.

One of the three existing equalization tanks at the TOC was not in-use at the outset of this project because the original design basis for the plant was for one million gallons per day, and through extensive water conservation efforts, Delta has been able to reduce that volume by a full two-thirds. This meant that the third equalization tank would be available to repurpose as an aeration tank using diffused aeration. This aeration tank provides redundancy for biological treatment as well as a more efficient and maintainable biological process than the former oxidation ditch, as the new aeration blowers provide oxygen more energy-efficiently and are equipped with automated speed control from dissolved oxygen instruments in the tank.

A new secondary clarifier was also built above grade using a welded steel tank built on a concrete foundation. Due to a chronic lack of space within the TOC and at the OWTP, the site selected for the new secondary clarifier was the location of an old, out of service, in ground circular oxidation ditch, whose concrete foundation and walls were removed as part of this project. The above ground design makes this new clarifier easier to operate and maintain, and the cost to build the tank above ground was less than an in ground construction due to unfavorable subsurface conditions. In fact, once the old ditch had been removed, the area had to be preloaded to pre-settle the unfavorable subsurface soil before the new clarifier could be built.

At the outset of this project, the lack of redundancy for biological treatment and secondary clarification meant that if one of these processes were to fail, Delta would have had to ship its wastewater off-site for treatment before discharging to the City of Atlanta. These upgrades ensure that the OWTP will not experience any service interruption should one of these operations fail, and they also greatly reduce the risk of failure as it allows equipment to be taken offline periodically and inspected and maintained appropriately.

The work was completed on-site behind security at ATL, the busiest airport in the world, in close proximity to the runway, making it crucial for the work to be done without interfering in any way with flight scheduling or safety. This required innovative approaches to hauling materials in and out of the site as well as carrying out much of the construction-phase work at night when operations at the airport slowed down. The project was completed three months ahead of schedule and $260,000 under budget while adhering to the high standards of safety and sustainability Delta holds for itself and its partners. The OWTP today runs more energy efficiently, treatment processes are more easily managed, and inspections and maintenance are safer for the plant’s operators.

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