STAGE I – pre-treatment of the introduced sewage
The preliminary treatment of domestic sewage takes place in a septic tank. Impurities enter the tank through the inlet pipe which slows down the flow and minimizes the turbulence of flotation substances and mineral and organic deposits (deflector). The particles floating in the sewage fall to the bottom and form sludge which undergoes a slow process of anaerobic digestion. On the surface of the sewage in the septic tank, the so-called “scum” is formed, which is foam created during the fermentation process from various substances contained in the sewage. The particles of impurities are decomposed into water-soluble substances and those insoluble mineral substances which remain at the bottom of the tank. For the fermentation process to be effective, it must take at least 3 days and it is therefore essential to select the appropriate capacity of the vessel depending on the population equivalent and therefore the amount of sewage to be treated. The pre-treated sewage flows additionally through the filter for further treatment (stage II). The additional filter in question is a basket filled with stone – puzzolana, which retains suspended solids and fats and, thanks to its specific properties, reacts with Ca(OH)2 to form silicates and aluminosilicates, which allows phosphorus to be removed from the sewage. The purpose of the septic tank is to reduce the level of pollution in the sewage to the values specified in the table below.
|substance [mg/l]||raw sewage [mg/l]||effluent at the outlet after the septic tank [mg/l]|
|total suspended solids||300-400||40-120|
|ammoniacal nitrogen N-NH4||60-120||30-60|
Technological advantages of the JPR AQUA septic tank:
- Calibrated outlet (visible on the drawing in the structure tab)
Appropriate selection of the settling tank capacity is to ensure three-day retention of sewage in the septic tank. The nature of domestic sewage is the so-called hydraulic blockage, i.e. intensification of sewage flow at certain times related to the users’ life rhythm (i.e. in the morning from 7 to 9, and in the evening from 6 to 9 pm). With sewage flows organised in this way, it is difficult to maintain the preset three-day rhythm. In JPR AQUA septic tanks it is possible thanks to calibrated outlet. The calibrated small hole causes that at mass inflow sewage flows out of the tank very slowly raising its level by a few percent of tank capacity until it overflows the outlet valve in the calibrated outlet. This system guarantees that the sewage is kept for three days for proper treatment.
- Decompression valve (vent) on the inlet parallel plane
This valve is responsible for release of gases from sedimentation tank to ventilation of the building. In JPR AQUA units, it is located on a parallel plane of the inlet, thanks to which it cannot be clogged by solid parts of the sewage when it flows into the settling tank, which could cause, apart from decompression closure, also clogging the inlet with time.
- Corrugated tank structure
JPR AQUA septic tank is made of high density polyethylene, which gives the highest guarantee of resistance to crushing. This resistance is further increased in construction by the corrugated structure of the tank and supports in the walls.