Effluent Filter

Effluent Filter

Effluent filters are devices that can be affixed to outlets of septic tanks and grease traps. The filter is a primary screening barrier designed to reduce the volume of solids passing out of the tank and through to the soil absorption system (SAS). If you were to pour unfiltered effluent from a septic tank into a clear glass and hold it up to the light, you would see that there are many fine particles of organic matter (and some inorganic material like fine grit) floating around.

These particles, some barely visible to the human eye (and some that aren’t) are referred to as suspended solids. The measure of their abundance is referred to as Total Suspended Solids or TSS. The average TSS values from residences is 60-120 PPM. When these particles pass out of the septic tank into the leachfield, they settle in the small spaces between the soil, reducing the capacity of the soil to drain away the effluent.

Given enough time, and aerobic (free exchange of oxygen) conditions, many of these organic particles break down into the basic components of water, carbon dioxide, and other simpler compounds. If too much of this organic matter is deposited on the soil interface however, the soil spaces clog and ponding of the effluent in the leach field occurs. This results in anaerobic (no oxygen) conditions further impeding the complete breakdown of wastes.

By retaining more of the suspended solids in the septic tank and reducing the amount of organic material that “demands” oxygen to breakdown (technically this is called reducing the Biochemical Oxygen Demand or BOD) that passes into the leach field, the performance of the leach field in breaking down waste can be improved.

This results in a longer leach field “life”. The goal of a good effluent filter is to do exactly this – prevent the passage of suspended organic and inorganic materials into the leach field, while not impeding the flow of effluent to the point where it backs up into the building. Effluent filters perform this function by providing either screens or directing the flow across areas where the suspended material becomes trapped or settles out.

The effluent filter is most commonly a simple device that fits into the discharge tee of a septic tank. New tanks can easily accommodate the filter installation, while previously installed tanks can often be retrofitted. In some cases, where an effluent filter is desired but a precast baffle is in place (as opposed to a PVC sanitary tee) it may be necessary to install a filter chamber along the outlet pipe between the tank and D-box.

In addition to acting as a filter, the effluent screen acts as a substrate on which organisms can grow and digest the trapped waste. The mass of organisms and trapped waste eventually grows on the filter to the point where the weight causes it to slough off into the tank below and undergo subsequent anaerobic digestion.

Please contact Affordable Pumping Services for additional information or to schedule the installation of an effluent filter.