Description of the operation

A household sewage treatment plant is an autonomous plant for treatment of domestic sewage (grey sewage and black sewage) and discharging it in a treated state into the ground. Thanks to natural gravitational, mechanical, biochemical and physical phenomena occurring in the devices, they are fully environmentally friendly.

Due to the principle of operation, as well as the method of selecting the appropriate unit capacity depending on the number of users, it should be emphasised that other sewage, such as rainwater and drainage water, should not be directed here. Their volume varies (sometimes, it is very large) and would have a negative effect on the expected purification results.

JPR AQUA, with its many years of experience, offers complete equipment that is fully adapted to all conditions. Technological knowledge and proven raw material suppliers allow us to guarantee you the highest quality equipment.

Advantages and disadvantages of a drainage treatment plant

A household drainage treatment plant has many good points:

  • economic and financial considerations – the investment pays for itself after a relatively short period of time (in comparison with municipal sewage systems or archaic septic tanks),
  • accessibility of use – it basically comes down to the use of appropriate bacteria and removal of sludge which accumulates in the tank, as well as periodical inspection of the device in order to control its proper functioning,
  • gravity flow of liquids (in the vast majority of cases)
  • durability – JPR AQUA grants a ten-year warranty for its equipment, thus assuring that all quality requirements dictated by law and production experience are met; unfavourable weather conditions have no negative impact on the equipment operation
  • no nuisance – no unpleasant smells are emitted (condition: correct execution of high ventilation, in accordance with the art of construction; there is no need to worry about overfilling the tank (flow-through device), or the need for frequent emptying (as in the case of a septic tank),
  • easy to install – the tanks are relatively light, no special equipment is required for setting

For drainage treatment plants, it is necessary to designate an area for the sewage receiver (the area of the infiltration field depends on the population equivalent [p.e.] of the facility and the type of soil), which in the case of limited space at the site of the investment can be a problem (this difficulty does not exist when deciding to build a biological sewage treatment plant, please see our offer for this product).  The life span of the drainage system in good ground conditions (permeable soil) is about 10 years. After this time usually the soil under the drainage field needs to be replaced or the infiltration system needs to be relocated. With regard to drainage sewage treatment plants, or sewage treatment plants in general, it is a myth that the plant emits unpleasant odour (sometimes even perceptible inside the facility). This is only the case if the installation of the plant including high ventilation is faulty.

Principle of operation

Treatment of domestic and economic sewage in a household drainage sewage treatment plant takes place in two successive stages:

  • pre-treatment
  • after-treatment

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]
BOD5300-40090-200
total suspended solids300-40040-120
ammoniacal nitrogen N-NH460-12030-60
total nitrogen6530
total phosphorus10-4010-30

Technological advantages of the JPR AQUA septic tank:

  1. 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.
  2. 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.
  3. 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.
I
II

STAGE II – Effluent after-treatment

The pre-treated sewage from the septic tank goes to the aerobic purification stage by means of a system of pipes and distribution pits. This stage may be carried out by means of various systems, depending on topographical and soil conditions:

  1. Infiltration drainage
    This is a system of drains laid under the surface of the ground. It is designed to introduce pre-treated sewage into the system in a uniform way. This sewage must flow into the drainage ditches in very small doses, therefore the drainage length must be appropriately proportional to the amount of sewage and the permeability of the soil. This is a prerequisite for the further, effective disposal of the sewage. The oxygenation of the drainage channels is carried out by means of closing aeration chambers that provide oxygen in all weather conditions via a mushroom-shaped vent.
  2. Sand filter (vertical and horizontal)
    This is a system for mechanical straining and biological sewage treatment through a biological membrane formed on sand grains. Due to the period of sewage dosing to the sand filter and relatively low hydraulic load, aerobic conditions prevail in the filter layer. This results in the nitrification of the sewage – the better the longer the sewage is in contact with oxygen.
  3. Hydrophilic beds
    A system that uses aquatic or marsh plants (hydrophytes), so-called plant treatment plants, to reduce pollutants through absorption processes, chemical oxidation-reduction reactions and biological plant activity.
  4. Infiltration drainage packages
    This is a system ensuring aerobic treatment of sewage with its simultaneous discharge into the ground by means of a package filled with channels of a specific current-cross construction which increases the active surface of the drainage. The arrangement of the channels of the package causes the infiltration to the sides and downwards. The main advantages of this system are a larger infiltration area, resistance to clogging and ease of installation.

PLEASE NOTE!

Infiltration tunnels have gained great popularity in recent years. However, they can be used as an aerobic sewage treatment system, provided they are installed correctly. A situation where treated effluent is discharged to a single location is unacceptable (the effluent is then not provided with the conditions necessary for the treatment process to take place and is only discharged to the soil in a pre-treated state).

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