Project documentation – The development of a wastewater treatment plant for the agglomeration of Firlej in the city of Serock

The scope of investment was the development of new technological facility, redevelopment of already existing infrastructure and demolition of some technological facilities not used by the plant located in the agglomeration of Firlej in the city of Serock, Firlej municipality.
The aim of this development was to improve the quality of discharged wastewater as well as improvement of quality of wastewater sediments removed from the plant.


The main aim of development and modernisation of the plant was to make the wastewater treatment plant in Firlej meet the current regulations of the Polish law regarding the quality of wastewater discharged from the facility into the receiver as well as improving the quality of sediments that are a by-product in the process of wastewater treatment.


The development consisted in:

  • developing the installation for transferred wastewater,
  • redeveloping screen basket chamber,
  • repairing and redeveloping the pumping station building together with the blower station,
  • developing the technological building,
  • developing a shed for storing dewatered sediment/granulated calcium-sediment,
  • developing a wastewater retention basin with the pumping station:
  • developing an aerobic sludge digestion chamber,
  • developing an anaerobic chamber with separation chamber,
  • developing a multifunctional biological reactor,
  • developing a separation chamber,
  • developing radial-flow secondary settling tanks,
  • developing a pumping station for recirculated and excessive sediments,
  • developing a floating elements pumping station,
  • redeveloping two slow sand filters chambers into technological water pumping station (treated wastewater),
  • redeveloping the existing lighting system – removing some of the existing light posts and erecting new ones,
  • developing a photovoltaic installation,
  • redeveloping power system and control and management instruments,
  • constructing roads, maneuvering area and pavements – within the existing road system,
  • carrying out demolition and deinstallation work.


The redevelopment plan included keeping the existing technology of wastewater treatment using oxygen activated sludge process in a flow-through system with secondary settlement tanks. The project aimed to increase the hydraulic capacity of the plant as well as increasing its inflow load of sediments, especially during summer time. During other seasons the plant would operate with lower loads (given that, during this time one biological treatment line will be inactive).