UAB Traidenis

- Model NV-T Type - Biological Wastewater Treatment Plant



Domestic wastewater treatment system consists of two separate tanks – the NV type biological treatment plant and the sludge thickening device.NV 1÷4t  type wastewater treatment plant of domestic wastewater consists of two chambers present in one tank (Figure 1; I). At first, wastewater, flowing into the plant, enters into the aeration chamber (Figure 1; 1, 2 positions), where it is mixed with the activated sludge with the help of air. Compressed air is necessary for supporting life of activated sludge and internal recirculation of  treated wastewater. Air is provided with the help of the compressor (airblower) (Figure 1; 12 position). Wastewater is mixed with the activated sludge by the air, lifting through the aerator (Figure 1; I, 4 position) from the bottom to the top. Biological wastewater treatment is performed with the help of microorganism’s that decompose organic substances.

Purpose of the process is to bind soluble, colloidal and biogenic substances from wastewater into the activated sludge and separate activated sludge. Flake forming microorganisms multiply and form groups that cause adherence of protozoots and other bacteria. Microorganisms metabolyse (“eat up” and decompose) and destroy organic substances. Decomposition of organic materials and formation of activated sludge performs in the aeration section. Mixture of the activated sludge from the aeration chamber enters the external chamber (the secondary settling vessel) (Figure 1; I, 5 position), where, due to gravity forces, the activated sludge separates and falls down into the bottom part of the plant, from which, with the help of aeration system, once again rises into the aeration section - aerotank. Clarified wastewater enters into the collection duct, installed in the perimeter of the whole secondary settling vessel, and by passing through the flow regulator (Figure 1; I, 7 position), is removed through the outflow pipe.

If the mass of microorganisms increases, the amount of the activated sludge also increases. With the help of the airlift, excess sludge is periodically removed to the sludge thickening device (Figure 1, II). Sludge thickening device consists of two chambers – chambers of excess sludge and collection of clarified water. Particles of sludge settle at the bottom of the tank and the clarified water enters into the chamber of collection of clarified water through the overflow duct. Water is returned to the treatment plant from the collection chamber through a T-joint fitted on the inflow pipe. Excess sludge that dewatered per se is periodically removed from the thickening device by pumping-off.

Main structural parts:
I. Biological treatment plant
II. Sludge thickening device

1. Chamber of collection of clarified water
2. Aeration chamber
3. Bioload
4. Aerator
5. Secondary settling vessel
6. Outflow pipe
7. Outflowing water flow regulator
8. Airlift
9. Sludge chamber
10. Lid
11. Lid
12. Windblower


NV type biological treatment facilities of domestic wastewater, sold in Lithuania, Poland, Russia, Macedonia, have been produced since 1996.

NV type aerobic plants are most often used for treatment of domestic wastewater for private houses. Equipment is installed, where there is no possibility of connection to centralised sewage networks.

NV type biological treatment plants of domestic wastewater are intended for treatment of domestic or similar wastewater from the kitchen, bathroom, toilet and other similar-purpose facilities. Substances that cannot enter the treatment plant are as follows:

  • surface wastewater (off the roof, from the yard, etc.);
  • wastewater from a garage and other non-domestic – purpose facilities;
  • water from a basin or other receptacles that are larger than 1m3;
  • chemical substances, entering into sewage system of which is not provided according to their usage (oil products, agrochemical substances, etc.);
  • water after regeneration of filters of softening/removal of iron;
  • chemicals used at home (washing means, bleaches, softeners, degreasers) shall be use as provided in manufacturer’s recommendations.

Equipment advantages:

  • factory enclosed biological treatment unit for domestic waste;
  • various capacities;
  • high level of treatment, removed 95–98% of pollutants;
  • no internal movable parts to be supervised or replaced;
  • serviceable, light-weight glass-fibre structure (easy transportation);
  • quiet operation and no offensive odour diffusion;
  • treated discharged water – transparent and odourless;
  • minimum power consumption;
  • no need in auxiliary filtering equipment;
  • easy maintenance and process automation;
  • easy installation.

Treatment plant is used as an underground facility. Supplementary collection (riser rings) depends on manifold deepening. Subject to the selected place, treatment plant may be installed in a green lawn or under the roadway (not recommended due to uncomfortable maintenance).

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