Middle-sized wastewater treatment plants - oval design

čistiarne odpadových vôd Aquatec VFL -  Wastewater treatment plantsAT 30 to AT 225 oval wastewater treatment plants were invented to purify sewage water for blocks of houses, small villages, parts of a village, accommodation properties, restaurants, recreational properties, manufacturing factories, industrial parks. After preliminary purification of industrial wastewater with organic pollution the plants serve as biological treatment for meat processing factories, dairy factories and slaughterhouses, wineries, etc. Furthermore the purified water can either discharge into the surface or underground water, respectively it can be reused for irrigation.

Aquatec VFL oval wastewater treatment plant includes:

  • Biological reactor of wastewater treatment unit.
  • Air pump tank intergrated in the cover of the WWTP.
  • Control unit AQC Basic with GSM remote control.
  • Air pump or Air pumps regarding the type of the WWTP.
  • 230V service plug.
Basic description of VFL® wastewater treatment plants
The compact, “one-tank system” wastewater treatment plants from AT30 oval to AT225 oval are comprised of a single vertical tank with oval ground plan, made from polypropylene - the biological reactor. The dimensions of the plants are ideally suited for transporting in a standard shipping sea container or by a regular truck.
The range of small wastewater treatment plants from AT30 oval to AT225 oval is designed for decentralized and semi-centralized solutions of wastewater treatment in the range of 4,5 up to 33,8 cubic meters per day (30PE-225PE).

The small wastewater treatment systems comprised of the biological reactors from AT30 oval to AT225 oval can be gradually expanded up to the capacity of 135 cubic meters per day (900PE) by installing several units in parallel.

Vertical Flow Labyrinth – VFL® - Treatment process

čistiarne odpadových vôd Aquatec VFL -  Wastewater treatment plantsThe technology uses a continuous-flow activated sludge process with biological nitrogen and phosphorus removal, which combines the following processes in a single tank: mechanical pre-treatment, excess sludge collection, biological treatment using a low-loaded activated sludge process, separation of the treated water from activated sludge in the final clarification chamber, flow balancing of fluctuating inflow of wastewater in the retention chamber. The treatment process consists of several technological processes. Raw wastewater flows into the non-aerated activated sludge chamber with anaerobic and anoxic zones creating and admixture with the recirculated activated sludge, the mechanical pre-treatment of inflowing raw wastewater and the decomposition of coarse impurities, denitrification and accumulation of readily degradable organic contamination is taking place in the non-aerated activated sludge chamber, which is divided by inner partition walls to create a vertical flow labyrinth, where internal circulation is established. 

Furthermore, allowing the admixture flow gravitationally into the aerated activated sludge chamber with includes fine-bubble diffusors. In oxic conditions the biological degradation of organic contamination, nitrification and phosphorus uptake is taking place.  The activated sludge flows into the final clarification chamber, where the activated sludge is separated from the treated wastewater. The treated wastewater is discharged into a water flow, infiltrated or recycled and the separated activated sludge is recirculated by air-lifts.
A flow regulator is installed at the water level in the final clarification chamber which controls the outflow in order to maintain the water level between the normal and maximum level in the tank (integrated retention chamber).
The pressurized air is supplied by blowers for aeration of the activated sludge chamber and for recirculation via air-lift pumps. The recirculation and aeration is controlled by a microprocessor control unit which also enables the wastewater treatment plant to work in various modes depending on the loading. 

The technology Vertical Flow Labyrinth – VFL®, used in the biological reactor, is protected internationally by patent. The treatment technology ensures the high quality of purified water, low investment and operation costs.

The guaranteed and commonly achieved parameters from the outpour of the wastewater treatment plants are shown in the table below:


Commonly  achieved  values

Guaranteed values

čistiarne odpadových vôd Aquatec VFL -  Wastewater treatment plants  


35 mg/l

70 mg/l


10 mg/l

15 mg/l


10 mg/l

20 mg/l


2 mg/l

5 mg/l


15 mg/l

25 mg/l


3 mg/l

7 mg/l

Technical parameters of AT30 - 225 oval wastewater treatment plants:

TYPE Daily inflow
Designed load
[kg BOD5/day]

Usable volume

Length x width x height
of reactor


of reactor


No. of
AT 30 oval 4,5 1,8 11,6 3720 x 2210 x 2250 1700/1500 750 1 0,23
AT 40 oval 6,0 2,4 15,0 4660 x 2210 x 2250 1700/1500 850 1 0,23
AT 50 oval 7,5 3,0 19,5 4850 x 2210 x 2500 2200/1900 940 1 0,36
AT 75 oval 11,3 4,5 19,8 5160 x 2210 x 2500 2200/1900 1040 1 0,46
AT 100 oval 15,0 6,0 25,5 6410 x 2260 x 2500 2200/1900 1400 1 0,72
AT 120 oval 18,0 7,2 28,5 7110 x 2260 x 2500 2200/1900 1460 1 0,90
AT 150 oval 22,5 9,0 35,0 8560 x 2260 x 2500 2200/1900 1750 1 0,90
AT 175 oval 26,3 10,5 40,5 9760 x 2260 x 2500 2200/1900 2000 1 1,08
AT 200 oval 30,0 12,0 45,3 10960 x 2260 x 2500 2200/1900 2230 1 1,35
AT 225 oval 33,8 13,5 49,8 12000 x 2260 x 2500 2200/1900 2360 1 1,35

čistiarne odpadových vôd Aquatec VFL -  Wastewater treatment plants

Wastewater treatment plants installation

Are installed into the prepared hole as underground tanks on a concrete slab with a thickness of about 300 mm so that the top edge of the revision manholes overlaps about 50 mm above the terrain. Wastewater treatment plant is self-supporting, without the need of putting concrete around.
The backfill of the tanks is done with a sorted material.
The backfill should be done by layers, while creating a back pressure by filling the water into the tank. 
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