Concerning septic tanks, they represent an alternative system of sewage, buried, with the role of purifying the domestic water. This system has maximum efficiency in the situation in which the distance between the exit from the pit (burial rate of the drain) and the level of the groundwater is minimum 4m.
What options do we have?
For ecological septic tanks there are many options on the market, but there are few that meet predetermined criteria of construction, according to European regulations. Each compartment of the septic tanks must be pre-sized, depending on the number of equivalent inhabitants to have the required retention time for the treatment process to get to accepted parameters for discharging the water into the drainage and then into the soil.
The compartmentation in the cylindrical horizontally septic tanks made of reinforced fiberglass polyesters:
1. the primary decanter of the coarse,
2. the secondary decanter (Imhoff-device thus named after a German nationality researcher) with the role of fat separator located in the primary decanter compartment.
3. the clearing chamber
Mode of operation
The treatment system based on ecological septic tanks is compulsory consisting of the septic tank itself and the drainage system, where the last part of the purification process takes place, namely aerobic decomposition. The water that comes out of the septic tank after the decantation, fat separation and the anaerobic decomposition is at about 50% of the whole process. After aerobic decomposition,that takes place in the drainage, with the help of oxygen from the soil, the water is filtered through the 2 layers (sieve / crushed stone – sort 32-70 mm and sand) and then reaches the groundwater.
The waste water, evacuated through the general connection, reaches the first compartment of the trench where the primary coarse settling (solid matter) takes place. The result is a layer of mud on the bottom of the basin where the culture of microorganisms has naturally formed.
The fats from the wastewater that have a lower density than the water, separates at the top of the first compartment, forming a film that stops the exchange of oxygen with the atmospheric environment, thus initiating the anaerobic decomposition process called fermentation.
The fats, due to the special construction of the Imhoff device, are retained and in the second compartment only water containing macro and micro-impurities arrives. After the secondary decantation the suspended particles and the purification process continues by decanting what is left of them, in the clearing chamber. The upper part of the clearing compartment is gravitationally evacuated in the drainage system.