NV type wastewater treatment plants

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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.  

Advantages

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).

NV type wastewater treatment plants are of three modifications

1.    NV - a type treatment plant of domestic wastewater: excess sludge is pumped off by  the assenisation machine;
2.    NV - m type treatment plant of domestic wastewater: excess sludge is pumped off into bags of dewatered sludge;
3.    NV - t type treatment plant of domestic wastewater: excess sludge is pumped off into sludge separator.

Declaration of performance characteristics of biological treatment plants of domestic wastewater

NV type biological treatment plants of domestic wastewater meets the requirements of the EU Directive 89/106/EEC and all the provisions of Annex ZA to the standard EN 12566-3:2005+A2:2013 “Small wastewater treatment systems for up to 50 PT – Part 3: Packaged and/or site assembled domestic wastewater treatment plants”.  

Notified body: Public company Certification Centre of Building Products (li, Statybos produkcijos sertifikavimo centras, SPSC), Wastewater Treatment Plant Testing Laboratory (li, Nuotekų valymo įrenginių laboratorija), Linkmenų st. 28, LT-08217 Vilnius, Lithuania, notification No. 1397.

TECHNICAL INFORMATION

About NV 1÷4a type wastewater treatment plants

NV 1÷4a type wastewater treatment plant consists of two chambers present in one tank (Figure 1). At first, wastewater, flowing into the plant, enters into the internal chamber, 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). Biological treatment, i.e. treatment with activated sludge, is based on microorganisms’ activities. Purpose of the process is to bind soluble, colloidal and biogenic substances from wastewater into active 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 the activated sludge takes place in the aeration section. Mixture of the activated sludge from the aeration chamber enters the external chamber (the secondary settling vessel), where, due to gravity forces, the activated sludge separates and falls down into the bottom part of the plant and the separated treated water lifts up and drains away. If the mass of microorganisms increases, the amount of the activated sludge also increases. Excess sludge is removed by the assenisation machine by pumping-off two-thirds of the plant capacity. 

Main structural parts: 

1. Body (GRP) 
2. Lid 
3. Bioload 
4. Aerator 
5. Inflow pipe 
6. Outflow pipe 
7. Air inlet pipe 
8. Airblower 

Additional equipment: 

9. Riser ring 
10. Box for airblower 

Table of parameters for NV 1÷4a type biological treatment plant of domestic wastewater 

The main dimensions of the treatment plant 

The manufacturer reserves the right to change parameters of the product, retaining treatment efficiency. 
H* - adjusted according to the required height. 

INSTALLATION

Installation of NV-a type treatment plant of domestic wastewater

Installation site preparation

  1. Installation of the unit and its performance ensuring systems shall be performed in accordance with technical and/or working project. The designer is responsible for providing calculations, while preparing technical and working projects.
  2. The lid should be accessible for constant inspection and for proper functioning of the system.
  3. Check diameter of the sewage pipe. Do maintain a gradient that is required in order to ensure wastewater natural flow to the unit. 
  4. PREPARATION FOR GROUND WORKS: clean a lager site than the treatment plant itself for at least half a metre around it.
  5. GROUND WORKS: ground works are carried out by strictly following STR 1.07.02:2005 regulation, technical and/or working project and the general construction norms for installation. 
    In case, when, while ground digging works are performed, units or communications not indicated in the designed drawings are encountered, works shall be immediately stopped and the person performing technical supervision of construction or the authorised person shall be informed. Works in such an area can be continued only after receipt of the permission. 
    Finishing ground works to the designed altitude, the foundation shall be check for weak or soaked soil, excavations, etc. Such soil shall be removed to the depth indicated by the person performing technical supervision of construction and shall be filled with a proper soil by compaction. The site shall be prepared to the altitude indicated in the project, soil shall compacted (compaction coefficient shall be from 0.95÷0.98, compaction layer shall be 200–300mm).

Installation of NV-a type treatment plant of domestic wastewater  

1. Installation of wastewater treatment plant shall be performed following EN 976-2 standard.

2. Treatment plant shall be installed according to the technical  and/or working project prepared in advance and harmonized with appropriate institutions.

3. After evaluation of soil properties, an excavation shall follow overhaul dimensions of the plant. Stop digging till 20–30cm to the designed depth of the excavation.  Proceed with manual digging that is dig with the spade. This way the unit shall rest on a fixed soil by its bottom.

4. Before lowering the plant to the excavation, IT IS NECESSARY TO CHECK, if the depth of the wastewater feeding pipe and the height of the treatment plant inflow coupling, and angles of the inflow and outflow pipes of the treatment plant do match.

5. The unit shall be lowered to the excavation by using typical lifting mechanisms. After a careful lowering to the excavation, the unit shall be aligned with the help of the lever. 

6. For an appropriate performance of the treatment plant it is important for the overflow threshold at the top of it t be horizontal.  This is possible by firstly filling the round channel (inner lateral wall is the overflow threshold) at the top with water and by adjusting the position of the whole treatment plant with the help of a level, according to the position of this water surface, in respect of the overflow threshold. Temporary clogging outflow coupling is required for the water not to run-off, when filling the channel.