Realization: 2004 –2006
Number of PE: 80 000
Client: Stredoslovenská vodárenská spoločnosť, a.s.
Value of works: 300 000,– EUR
Reconstruction and Extension of the WWTP in the City of Zvolen, Slovakia
The WWTP Zvolen was reconstructed and extended within the years 2004 – 2006. The main goal of reconstruction was except the modernization of existing objects, the intensification of biological treatment step with focus on increased biological removal of nutrients. The realization of the whole project was followed according to the FIDIC – Conditions of contract for plant Design and Build (yellow book), i.e. the proposal, design, construction phase and operation guaranties were covered by contractor. Reconstructed and intensified WWTP Zvolen is designed as a mechanical – biological treatment plant with anaerobic stabilization (digestion) of sludge and biogas utilization for the energy needs of the plant.
Wastewater to WWTP Zvolen is coming from two independent sewerage pipe collectors. On each pipe collector is equipt with a coarse mechanical treatment (a gravel grabber, coarse and fine screening machines). The both collectors are connected into common aerated grit traps and after them wastewater flows in two independent mechanical – biological lines of treatment. Both mechanical – biological lines at the WWTP Zvolen consist of a radial primary sedimentation tank and pre-denitrification and nitrification steps and an anaerobic stage. One line of 80% capacity of the WWTP is completely new and the other line of 20% capacity of the WWTP is a reconstruction of existing one.
The air is delivered by rotary blowers in dependency of online measurement of dissolved oxygen and ammonia concentration. The phosphorus removal is provided by chemical precipitation with ferric sulfate solution in the both lines. . Tertiary treatment is ensured by a micro drum filters.
A sludge management consists of a mechanical thickening of excess sludge on centrifuge, two anaerobic stabilization tanks (anaerobic digesters) working under mesophilic condition and dewatering of anaerobically stabilized sludge on the centrifuge. Sludge water from thickening and dewatering flows into a discharge pipe of return sludge.
A biogas produced in anaerobic digesters is accumulated in two-membrane gasholder. These membranes are made of high resistant polyester fabric coated with PVC. The biogas is preferably used as a fuel to produce electricity in cogeneration unit for the needs of plant and created heat is used to heat the sludge in anaerobic stabilization tank. The excess biogas is burned in a gas burner.
Measurement and control of the main technological processes is ensured with an online measurement of dissolved oxygen and phosphate phosphorus. The dissolved oxygen concentration is measured directly in the nitirfication tank (in one line). Phosphate phosphorus is measured at the outlet of the plant.
