sewage treatment in cork and munster
 

Percolation Area & Polishing Filter Design

The most important component of a conventional septic tank system is the percolation area as it provides the majority of the treatment of the wastewater effluent. Septic tanks remove most of the suspended solids and grease from the wastewater, but it is in the percolation area that the wastewater gets most of its treatment. EN 12566-2:2005 Small Wastewater Treatment Systems for up to 50 PT- Part 2 Soil Infiltration Systems has been published by the NSAI as a Code of practice giving guidance for soil infiltration systems to be used with small wastewater treatment systems.

In the conventional percolation trench method, the wastewater is allowed to flow by gravity into a distribution box, which distributes the flow evenly into the several percolation pipes in the percolation trenches. The depth to the invert of the percolation trench may vary and is dependent on the T test location, layering of the subsoil and any other limiting factors such as water table and depth to bedrock

Wastewater flows out through orifices in the percolation pipes into a gravel underlay, which then distributes it on to the soil, where it undergoes biological, physical and chemical interactions that treat the contaminants. For effective treatment, the wastewater should enter the soil; if the base or walls of the percolation trench are compacted or glazed or otherwise damaged during excavation, they should be scratched with a steel tool such as a rake to expose the natural soil surface. It is equally important that the wastewater remains long enough in the soil; the hydraulic loading and the rate of flow into the sides and base of the trench control the residence time.