Surface Aerators Help Remove VOCs From Groundwater

The creative use of surface aerators for stripping volatile organic compounds (VOC's) from groundwater has allowed the City of Santa Monica, California, to use existing facilities at a considerable savings for the community, while continuing to rely on groundwater for a vital portion of its drinking water supply. The Santa Monica water treatment plant installed three 15-horsepower and 12 10-horsepower aeration units in a VOC-removal application which has demonstrated the versatility and flexibility of the equipment selected for the project to upgrade the plant.

Santa Monica uses both local groundwater and imported water for its raw water supply. The discovery of VOCs in the groundwater at a time when a long-lasting drought restricted imported water as a reliable source, motivated the city's water operating staff to experiment on a small scale with an Aqua-Lator aerator to determine its potential air stripping capabilities. Encouraged by the early favorable results which indicated that the floating aerator could indeed remove trichloroethylene (TCE) from the groundwater supply, the city contracted with a consulting engineering firm to expand upon the idea.

City personnel and the engineers from Kennedy/Jenks Consultants (of San Francisco) also considered the use of a packed tower aeration method because of its potentially lower operating cost. However, the placement of a tower at the water treatment site located in a residential area of a community outside Santa Monica presented an aesthetic problem. Moreover, the use of the floating aerators allowed the project team to use an existing reservoir, which incurred lower construction costs than would have resulted from selecting the packed tower approach. The installation of floating aerators eliminated also the need to take up additional space on the plant site, a move which will allow expansion in the future.

The 15 Aqua-Lator aerators, which were supplied by Aerators, Inc., of Roscoe, Illinois, operate inside the covered reservoir, spraying the water up into an stream of air. The air is collected and processed and the TCE is adsorbed out of the stream. With a flow rate of 10,000 gpm, and an influent TCE concentration of 35mg/l, the effluent TCE is reduced to less than 5mg/l. Careful monitoring of the influent allows the process to be operated with fewer aerators when the incoming TCE concentrations are at lower levels, which reduces power costs.

Aerators, Inc., can be reached at: Tel. 815-623-2111; Fax. 815-623-6416.