Norcadia Remover (previously titled Norcadia Eliminator)
Abstract:Hampton Roads Sanitation District's Virginia Initiative Plant (VIP) is a forty million gallon a day biological nutrient removal facility. When the plant switched from coarse bubble to fine bubble diffusers increased level of foam accumulated in the aeration tank. Due to the plant's layout, a blockage in the flow pattern accumulated foam in the aeration tank.
The plant needed an inexpensive and hands free way to remove the foam. Addition of chlorine inhibited nitrification. Polymer added to the secondary clarifiers was very effective, but expensive to use. So a group of plant employees got together and came up with the idea to remove the foam from the surface of the tank and discharge it to the secondary clarifiers. A vacuum device was used at first. A chlorine injector was attached to a free–floating three inch PVC “I” shaped device with a center vacuum connection. Slits were cut in the center vacuum to allow the foam to be removed. The chlorine injector clogged often with debris, due to internal small clearances. So the team designed a four–inch inductor with larger clearances and a straight path through the inductor. This new inductor required more water pressure to create the vacuum, but greatly reduced the plugging. So with this inductor device, the foam was removed from the aeration tanks with the use of existing non–potable water and the PVC inductors. The device removed the foam well as long as the foam was kept moist. So a series of sprayers were installed in the aeration effluent channel. The sprayers were also used to direct the foam toward the inductor.
This system has proved to work well in removing foam that is less than four inches in thickness. It is inexpensive to build and operate, with little attention from plant personnel.
Document Type: Research Article
Publication date: 2000-01-01
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