KING COUNTY TO USE MOBILE FOUL AIR TREATMENT UNITS

King County, Washington (Seattle area) has chosen to use mobile foul air treatment units to address odor emissions at collection system and treatment plant locations, as part of a larger odor control study and design project. A team from Brown and Caldwell and Black and Veatch, designed the mobile unit. The design team's goal was to produce a mobile treatment unit that was flexible enough to meet numerous applications, simple to operate and maintain, and configured to minimize capital costs.The unusual design required research and evaluation of earlier mobile unit designs. Mobile foul air treatment units were investigated at the Sacramento Regional Wastewater Treatment Plant in Sacramento, California, and the Hyperion Wastewater Treatment Plant in Los Angeles, California. Successful design features from the existing units were retained and improvements added where necessary.Design criteria to meet the project goals resulted from brainstorming sessions with a Technical Advisory Committee and the King County staff. Experts in odor treatment, mechanical design and wastewater system operation and maintenance fine-tuned the criteria and developed construction drawings. The result is a simple, flexible odor treatment system that can be easily transported to the odor problem.Critical design criteria that grew out of the brainstorming sessions included low operational noise, quick response to collection system odor problems, and corrosion resistant design features. Low operational noise was a key parameter because the mobile units often would be parked in residential areas and operate 24 hours per day. Substituting a noise problem for an odor problem would not be acceptable to King County ratepayers.The mobile units will be self-contained to allow quick response. The units require only a power connection to operate. If no utility power is available, the county has a portable diesel generator with sound enclosure available. The units will include a 100-foot flexible duct that can be quickly connected to a standard manhole.To address foul air corrosion concerns, material selection was an important part of the unit design. Review of the existing mobile units in Sacramento and Los Angeles showed corrosion to be a major concern. Fiberglass or fiberglass-coated components were used for all surfaces in contact with the airflow. Stainless steel was specified for all fasteners in the foul air.The mobile units, now under construction, will provide King County an effective means to address temporary odor problems in the collection system or at treatment plants in response to construction or maintenance projects. The first unit is expected to be in operation by the summer of 2000. After field testing, the County expects to procure six more units.