Aeration system key to keeping customers, retailers happy
Unpleasant odors can be retailers’ worst nightmares, as they give customers tangible reasons to stay away from the affected outlets. When faced with legal action that arose from the presence of foul smells, one California mall developed a thoughtful solution with the use of Mazzei products.
Mall-ed by the smell
A shopping center in Ventura, Calif., with several major retail stores had a sewer odor problem. Hydrogen sulfide stenches flooded the entrances of the stores there, causing customer and employee complaints. The local and corporate divisions of the affected retailers initiated lawsuits against the developer of the property, citing poor traffic due to the disturbing sewer odors. The engineering firm of Moffatt & Nichol was hired to find a solution to this problem in an effort to resolve all litigation issues and restore prosperity to local retailers.
The problem originated from a trap in the gravity sewer line. All sewer lines from the development gravity-fed to a gravity main under the street adjacent to the shopping center. One sewer line was constructed to dip under a telephone duct bank on its path to the gravity main. When the flow of sewer water stopped at the end of the day, the stagnant water in the trap under the telephone duct bank would turn septic, causing noxious gases to backflow into the center’s retail establishments. The engineering firm consulted with California Environmental Controls, Inc., of Whittier, Calif., to design a lift station with aeration to prevent the backflow of disturbing odors to the entrances of the shopping center.
Shopping center solution
The design of the collection system incorporates an aeration/recirculation loop that was installed on the wet well that feeds a force main. The aeration loop consists of a solids-handling self-priming pump, a solids grinder, a Mazzei model 4091 4-in. Injector, and two subsurface Mazzei 4-in. MTM45 nozzles. Differential pressure at the injector allows ambient air to be aspirated and mixed with the recirculation water as the first step in the Mazzei AirJection process. The water becomes saturated with oxygen as the two-phase flow leaves the injector and moves back to the wet well basin. At the wet well, the stream of gas and water moves through the MTM nozzles at high velocity to create a jet of micro-bubbles that continues to transfer oxygen to the bulk liquid. This high-energy mixing assures robust oxygen levels to control odors.
Each piece of equipment, except for the nozzles, was conveniently skid mounted and installed above the wet well for easy access and maintenance. The system was run by a local control panel that included an interval timer, which allowed the Mazzei system to maintain an odor-free environment while consuming less energy than a continuously operating system would.
The system was designed not only to prevent odors, but also to operate with minimal maintenance and operator supervision. It was commissioned in July 2008 and continues to successfully operate. The retailers and customers of the shopping center are no longer subject to the disturbing sewer odors, and court action was avoided.