In any sewage after mechanical filtration wastewater are biological treatment. This may apply biofilters or biofilter system using soil filtering mechanisms. System with a biofilter. Biological after post-treatment tank (septic tank) can be implemented in the biofilter. This is a fairly compact container filled with filter loading or filler. As the load can serve a variety of materials, importantly, that they were easy, hard and porous. For example, expanded clay, pozzolana and small stones. Filler particles are covered by biofilm, consisting of aerobic bacteria that consume organic matter.
Gutters served in the biofilter small amounts, and passing through the loading, clean. Attainable degree of purification is about 90%. Biofilter reproduces the same natural process of aerobic oxidation of organic matter, which occurs in the upper soil layers. Anaerobic processes taking place deep underground, are modeled in some structures of the soil or groundwater cleanup. In general, these methods are divided into soil reclamation and soil filtration. In the first case of sewage, freed from mechanical impurities in the sump shall be in an underground facility after treatment – filtering well, tape, or field of underground filtration.
Drains passing through through them, cleaned up and seep deeper into the ground, where the process is finally completed by anaerobic bacteria. When it comes to soil filtration, cleaning means the use of soil properties for purification of waste waters and their subsequent organized abduction. Runoff, as is the case with the soil absorption, are advanced treatment in special facilities – filter trenches, sand and gravel filters.