Medium size domestic wastewater treatment technology

Municipal wastewater treatment plants (100 – 5000EO)

  • are used for wastewater with an inflow higher than 30 m3/day (200 EO)

  • are biological wastewater treatment plants with activated sludge in sublime

  • are systems with a discontinuous through-flow (SBR – sequenced batch reactor)

System with discontinuous flow (SBR):

This is technology with an interrupted operation which has been the subject of interest in recent years together with the development of microprocessor control devices. Compared with continuous through-flow treatment plants these water treatment plants do not have a final sedimentation tank.

The process of wastewater treatment is performed in one tank, due to interrupted operation. The total cleaning cycle is divided into several phases:

  • filling,

  • activation,

  • sedimentation,

  • decanting (emptying).

Individual phases can be modified and set in such a manner as to be best adapted to the inflow onto wastewater treatment plant.

Advantages of SBR:

  • managing of unbalanced inflows

  • high and stable quality of water on the outflow

  • lower operating costs compared with the similar systems

  • high flexibility

  • reliability

  • simplicity

  • lower demands for space compared with continuous systems

  • does not have a direct hydraulic connection between the inflow and the outflow



  • biological wastewater treatment plant with interrupted activity

  • consists of two activation tanks

  • the operation is controlled by micro computer with the option to adapt the treatment regime to the quality and volume of inflowing water

  • usually designed for a capacity over 500 PE

The TopolWater company ensures high quality on the outflow (values of BOD5 under 10 mg/l), nitrification, de-nitrification and partial removal of phosphorus.

Advantages of the FLEXIDIBLOK® wastewater treatment plant:

  • high quality of water on the outflow – with sufficiently designed sizes of tanks, BOD5 at the outflow is about 5 mg/l and nitrification, de-nitrification and the partial removal of phosphorus is ensured

  • fully automated operation with remote control system, reduction of costs for servicing

  • high adaptability (option to use wastewater treatment plant for wastewater from septic tanks)

  • maximum protection of the recipient – in the case of failure of one of reactors, the second reactor automatically ensures flowing through the wastewater treatment plant without interruption of the treatment function up to the time of repair

  • low investment costs

  • low costs for servicing

Description of the technological line:

The wastewater flows into the object of rough pre-treatment where sand is removed and on the fine machine screen any other rough dirt is separated. Pre-treated water flows into the distributing tank with an independent filling device for each of pair of SBR reactors.

After filling the reactor all sets of the treatment processes are performed in one tank which is based on the biological removal of nitrogen, organic pollution and the partial removal of phosphorus. Then the reactor is put into inactive status and after sedimentation of the activated sludge at the bottom of the tank there is decantation of the water and, at the end of this, the pumping of excessive sludge to the sludge tank. With this, the treatment process is completed and reactor is ready for further use. Both reactors regularly alter in their activities.

Depending on the volume of the flowing wastewater the computer automatically optimizes the operation in the system in a wide range from 10% to 200% of the designed capacity of the wastewater treatment plant. In the case of a small flow, such a volume of treated water will remain in the system which is necessary to ensure the optimal conditions of the biological processes. At the same time, consumption of electric energy is automatically decreased depending on the decreased flow of raw wastewater. In the case of increased flows, the total length of the treatment cycle is shortened so that before the filling of one of the two reactors the second reactor is empty. Within the range of the arbitrarily adjusted minimum and maximum values of the individual parameters, the wastewater treatment plant will react to the immediate hydraulic loading.