07 Mar, 2025
Arginta starts new project in Ukraine
One of the most complex projects in the history of UAB Arginta’s activities – the reconstruction of Vilnius wastewater treatment plant (WWTP) has been completed. The first phase of reconstruction was completed a year ago – in September 2023. The ceremony of completing the second phase of reconstruction took place exactly a year later. The amount of investment in both phases of reconstruction is over EUR 50 million. The project average capacity of Vilnius wastewater treatment plant is 129,100 m3/d, the maximum – 225,000 m3/d, the equivalent population – 532,220 PE.
From the very beginning, this project was full of challenges and complexity. It should be started with the fact that the competition itself for the reconstruction of the WWTP was re-announced 4 times. This fact alone shows how many difficulties we have had to overcome, because a critical budget was provided for the necessary work. However, it was decided to submit not only a technical, but a financial proposal so that the city of Vilnius would not remain without the reconstruction of the NVĮ, which was necessary both because of the worn-out equipment and because of the tightening environmental requirements. It is also important that the reconstruction of the first phase of the treatment plant was financed by the solidarity funds of the European Union, which received funding of an intensity of 80% from European Union funds. Thus, these investments will not fall on the shoulders of residents and businesses of the capital.
Finally, after 2 years of preparation, several re-tendering procedures in August 2020. an agreement was signed on the reconstruction of Vilnius WWTP. Most of the formal negotiations and preparations took place during the COVID-19 first lockdown, remotely. Due to the fact that a team of more than 15 engineers from Lithuania and Italy worked on the project, this was a significant challenge.
With the acceleration of reconstruction work, the second wave of COVID-19 began, and later the war in Ukraine. The consequences were immediately felt – the daily increase in the cost of materials and works, the lack of supply, which raised great concerns about both the project budget and the deadlines for completion. Despite the unplanned challenges, the project was completed at the scheduled time.
The largest structure in the cleaner is an aerotank consisting of 6 bioreactors, each of which has 2 sections. Its total length is 138 m, the total width is 216 m, the total depth is 5.7 m. The reconstruction of aerotank structures has received special attention. Knowing that in 1993 there was an accident during construction, when during the hydraulic test the loads were not withstanding the loads and the partition between the two airthink bioreactors collapsed, a series of structural studies and expert examinations were carried out: all the structures of the structure were examined, and an analysis of the existing reinforcement was carried out. The authors of the older generation of the previous project were also contacted, from whom significant help and advice was received on strengthening existing structures. Thus, all the walls and bottoms of each aerotank bioreactor were examined and strengthened according to individually prepared solutions by partially replacing the calibrated reinforcement. Aerotank structures have been successfully reconstructed and have passed all the necessary tests.
From a technological point of view, the reconstruction of the wastewater treatment plant also posed challenges, since both the constant flow of wastewater through the plants and the wastewater treatment process had to be ensured throughout the reconstruction period. Due to the fact that there was no possibility to temporarily interrupt the supply of wastewater to the Vilnius wastewater treatment plant, a number of individual solutions were discussed, adopted and implemented on how to technically carry out switchings and inspections, while ensuring the constant flow of wastewater, their treatment process, safe operation and reconstruction works of the facilities. Thus, the disconnection, switching or bypassing of each element of the wastewater treatment chain – the bioreactor, the precipitator, the distribution or assembly chambers, and the channels, pumping stations, etc. – was carefully planned. The latter works took place in close cooperation with the staff of the wastewater treatment plant of UAB Vilniaus vandenys.
The main works carried out during the reconstruction of Vilnius NVĮ and the installation of technological links:
- The closure chamber was reconstructed and expanded, which was equipped with 4 electrified closures.
- New gutters for the supply of wastewater to pre-treatment have been built, equipped with flow measurement equipment – 2 Venturi gutters with a capacity of 8500 m3/h each.
- A new pre-cleaning building was built, equipped with 6 large grottoes with 10 mm intermittent, 6 small perforated grottoes with 6 mm apertures, as well as equipment for transporting, washing and drying sand carriers and sand.
- A new aerated sandblasting plant consisting of 5 sections, as well as a sandblasting pumping station, was built.
- A new pre-cleaning chain operator building has been built.
- To build and install biofilters for cleaning the air from the pre-cleaning circuit, which are equipped with an automatic irrigation system.
- 3 primary sitters were reconstructed by installing new bridges with a diameter of 54 m with scrapers and a screw-type automated floodplain assembly system, which was used for the first time in Lithuania.
- A new system for supplying, separating and dehumidifying the collected outflows has been installed.
- A new primary sludge pumping station was built.
- The biological cleaning chain has been reconstructed – an aeration vessel for the biological removal of organic pollutants, phosphorus and nitrogen. It is equipped with slow-moving mixers, pumps for the sludge mixture, an aeration system with 26, 580 pcs. Diffuser.
- A new blower was built, equipped with 7 blowers of the turbine type. The capacity of each blower is 14,900 N m3/h.
- A new storage and dosing node of the external carbon source was installed.
- A new unit for storing and dosing the reagent is installed for the removal of phosphorus by a chemical method.
- The return sludge pumping station was reconstructed, where 6 Archimedes pumps were renovated, the closures.
- A new secondary precipitator with a diameter of 50 m was built.
- New pumps for emptying excess sludge and tanks have been replaced, communication channels, their equipment and pipelines have been reconstructed, including return sludge pipelines with a diameter of 800 mm.
- A new tertiary cleaning chain was built, where for the first time in Lithuania 6 disc fully submerged 10 μm cloth filters were installed, as well as a system for removing microplastics from washes.
- The local sewage and drainage pumping station was reconstructed, where local wastewater and part of the stormwater wastewater are collected and pumped to the beginning of wastewater treatment.
- Two new modern transformer stations were built and one was reconstructed.
- A new SCADA system has been installed, which allows you to fully automate the wastewater treatment processes, and the installed air supply to the aeration system, which is controlled by the most open valve method, allows to optimize the cost of electricity consumption.
- The first link in the Baltic States for the reception and treatment of the contents of the washing of sewage networks (gravel, pebbles, sand) was built, which allows to protect the equipment of the wastewater treatment plant from mechanical damage.
During the reconstruction, a number of modern technological solutions were implemented using the latest world practice. Some of them are still not applicable in Lithuania, designed and implemented exclusively by uab “Arginta” team.
For the removal and processing of outflows from the primary sitters, an advanced system is installed: the outflows in the primary sitters are assembled by screws attached to the bridge. The latter push the bulges towards the submerged pump, which sucks them off the surface and removes them to the suction cup. It is equipped with two separate groups of pumps, one of which returns the unpolluted wastewater from the bottom of the pumping station to the treatment process. Another group of pumps sucks a mixture of floats and effluents from the surface, which is supplied to the flotator. It is equipped with a melted air flotation system (DAF) that allows you to distinguish not only the influxes visible to the eye, but also emulsified fats from the wastewater. Finally, the outflows are drained with a screw press, from which they enter the container. The efficiency of the removal of spills reaches 95%, after processing the average humidity of the outflows is less than 60%.
The installed tertiary cleaning circuit, which is equipped with disc fabric filters, makes it possible to reduce not only the concentration of drowning substances (on average up to 3.5 mg / l), the amount of other contaminants in the treated wastewater, but also to remove microplastic particles with a bulkiness of more than 10 μm. Drum grilles with a sieve mesh size of 0.5 mm are used to separate microplastics from the washcloths. from which enters the container. The separation efficiency of plastic from washes is more than 70%.
The air supply is equipped with turbine-type blowers, in which the electric motor is connected to the turbine directly, i.e. in addition to the reducer, air-type bearings are used. The number of revolutions is about 15000 rpm, the rotational speed is regulated by a frequency converter. Thanks to the latter solutions, the cost of electricity is optimized. The cost of service is also minimal compared to another type of blower, since there is no gearbox, regular replacement of lubricants is not required.
We are proud that after the reconstruction, vilnius wastewater treatment plant has become one of the most efficient and environmentally friendly wastewater treatment plants of this size in the Baltic States.
UAB “Arginta” has proven for the first time that it is one of the leading companies in the field of water management, able to carry out complex and large water management projects in a high-quality and timely manner, even in adverse economic and geopolitical circumstances.
