Ion System Treats Sludge Tank Odors

The town of South Windsor, CT, has installed an electric-powered system that uses ionized air to oxidize odors from a sludge thickener tank and a sludge storage tank. The two tanks, in particular the sludge storage tank, had been the source of odors that annoyed nearby residents and even patrons at the public library a distance away.

The South Windsor Water Pollution Control Facility is a secondary waste activated treatment plant with a design capacity of 3.75 mgd. Odor levels before installation of fiberglass covers and the odor control system were measured at 14,500 D/T (dilutions to threshold). Odor levels underneath the installed covers were measured at 25,250 D/T.

With the Bentax Oxygen Ionizers turned on, the odor level 12 inches from the air exhaust is 112 D/T. Twenty feet downwind of the tanks it drops to 36 D/T. There are no odors from the tanks when standing next to them.

Hydrogen sulfide levels at the tanks used to be in the 8 to 16 ppm range. Levels are now non detectable at the exhaust ports of the two tanks, according to Fred Shaw, South Windsor's Superintendent of Pollution Control.

Facility Architectural Engineering was provided by The Maguire Group of New Vernon, CT. Carlin Contracting Co. of Waterford made the installation. The tank covers and the Bentax Weather Shed were provided by Fiberglass Fabricators of Rhode Island. Bentax Oxygen Ionization technology and hardware was provided by Bentax of North America, Ringoes, NJ.

The total contract price for the two tank covers and deodorization systems was $180,000. The price of Bentax hardware with spares, support and training as used in this project was about $40,000. The total power for the four Bentax units is only 160 watts; the system runs off 110 vAC.

The tubes are cleaned about every three to six months, depending on the air quality and the filtration system used.

The Bentax technology is based on work by Albert Einstein and Professor Conrad Habicht of Zurich, Switzerland, around 1910 as a result of scientific curiosity as to why mountain air is healthy and curative. Einstein developed equations that showed that natural ion forces could be replicated with voltage multipliers. Habicht owned an electrical company. He formed the Swiss Bentax Corporation in 1932 after being satisfied that he could successfully make ionization tubes.

Bentax tube coronas strip electrons from oxygen. The electron altered oxygen then groups into ion clusters of 15 to 60 oxygen molecules. The reactive effects of the ions last from a few seconds to several minutes. The ions "kill" VOCs such as hydrogen sulfide, ammonia, formaldehyde, etc. Both gram negative and gram positive bacteria are sterilized. Odors are eliminated and animal oxygen uptake is increased by as much as 10 percent.

In the South Windsor application, air is blown over the Bentax units and becomes ionized. The air then flows under the fiberglass covers where it oxidizes the odor causing gases.

South Windsor has completed design and begun construction on a Phase II Odor Control Program using the ionizers in the plant's biosolids building. The system will be used to treat air in the building's wet well, belt filter press room and roll-out container room, Shaw said.