How the Zabel Filter Works The Zabel Filter performs two primary functions n a septic system installation. It retains the solids in the tank and lowers the BOD (biological oxygen demand). This retention of solids and reduction of BOD's markedly improves the quality of the effluent and assists in the protection of the ground water. The retention of 90% of the solids in the tank is achieved three ways. First, all particles larger than 1/16" are mechanically filtered as they attempt to move through the filter and leave the tank. Second, the filter dramatically slows the velocity of the effluent over the disc dam allowing the particles that are negatively buoyant to fall to the bottom of the tank. And third, particles attach themselves to the bio-mat growing on the filter discs. Anaerobic organisms cause the particles to disintegrate, lose their buoyancy, and fall to the bottom of the tank. Field reports show BOD's have been reduced 45% or more. It is thought that the combined action of the bio-mat growing on the filter discs, the improved effectiveness caused by the retention of the nutrients in the tank, and the reduction of organic solids in the effluent stream achieve these results. The higher concentration of nutrients and increased action help the tank remain fully functional even in cold weather climates. Modulating Flow: The flow Reducer Plate allows the engineer to predetermine the maximum outflow allowed into the dispersal system and thereby control the retention time of the tank. In most residential systems this is not an issue, but is important in some commercial applications. Servicing the Filter: The filter is virtually self cleaning. The continued action of the anaerobic organisms on the filter discs causes lodged particles to disintegrate and fall to the bottom of the tank. The filter usually only requires servicing at the normal inspection and pumping intervals required of a standard septic installation. Because the filter does not require an increase in th frequency of tank pumping or inspection, access to the tank does not have to be modified from the standard septic tank installation. A riser and lid are not required by the manufacturer.
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