New 8-kilometre aeration pipe system helps reduce Danube wastewater load

The second major development phase is coming to an end at the wastewater treatment plant in Újpest, where experts from Colas Alterra Zrt. specialists have recently completed another successful trial run.

Water from eight districts of the capital and the agglomeration is also supplied for purification

The North Pest Wastewater Treatment Plant has been operating since 1980.Since 2007, it has been responsible for treating wastewater from the whole of Districts IV, XV, XVI, XVII and parts of Districts III, X, XIII and XIV using the latest treatment technology. It also receives water from the sewerage networks of part of the agglomeration.
The plant treats 135,000 cubic metres of wastewater in an average of 24 hours, producing 1,500 cubic metres of inorganic waste and around 50,000 tonnes of dewatered sludge per year.

More oxygen, less air, better cleaning efficiency

Last year, specialists from Colas Alterra began modernising the air supply system for the structure. This involved replacing the aeration membranes in two sections of the biological line „B” of the sewage treatment plant and modernising the previous bubble diffuser aerator on line „A” by installing more efficient Flygt Sanitaire membrane technology.

In wastewater treatment, the removal of organic matter and nitrogen in the sludge basins is made possible by the right concentration of dissolved oxygen.
"The final design of the system before the upgrade was completed in 2010. The aerator and its equipment that have just been replaced were installed in the early 2000s", Dániel Tóth, the operations team leader of the FCSM Zrt. North Pest Wastewater Treatment Department, told our portal. The modernisation will make the air intake, a key element in the treatment process, more efficient. The maintenance and operating costs of the new system may also be more favourable than before.

Even during the works, the treatment plant continued to operate

On Line B, the trial operation was successfully completed in mid-March following the renovation and maintenance work carried out on Sections 1 and 3. Here, 6,000 diaphragms were replaced and damaged piping, plates and connections repaired.
After the upgrading on Line A, the 30-day trial run was completed on 18 September. Here all air intake elements were replaced.

A total of 10352 square metres of pipework was dismantled and reinstalled at the bottom of the drained and cleaned pools. The new system will allow air to enter the pools through 9-inch rubber membranes, with approximately 3,450 heads installed per section.
During the renovation work, it was necessary to ensure the continuous and uninterrupted operation of the plant,
which is why the construction work could only be carried out in one pool at a time.

Cleaning in a chain of buckles

Line A consists of 4 parallel sections, each with 4 small and 4 large pools. For the modernisation of the line, the sluice which flows into the section was closed and the mixture of sewage and sludge in it was pumped to the pre-settling tanks by means of bilge pumps. After emptying, the operator flushed the basin several times with treated wastewater from the final sedimentation tank. The dismantling of the existing aeration elements could then begin. In parallel with the excavation of the demolition material, the excavation of the silt-sand and fibrous material remaining at the bottom of the basin was carried out.

The cleaning could not be mechanised due to the size of the structure, so 8-10 people, in chains, used snow shovels and sorghum brooms to push the diluted sludge water from one end of the pool to the other, where 2 high-powered mobile pumps were installed. These pushed the diluted sludge into the working sections.

More than 8 kilometres of pipelines built

A new aeration system was installed on the cleaned concrete surface, with a total of about 8200 fm of piping installed.
The ridge line is connected to the lateral branches with hollander pipe ties, on which 9" aeration plates were installed. The system is installed identically per section for easier adjustment and equal load capacity.

Test run ended in mid-September

After a successful trial run on Line A, Section 4, construction continued in the winter of 2024 with the refurbishment of the two B Line sections, before returning to the A Line in the spring for Section 3. The aeration system was renewed on 730 of the 2700 sqm of the B-line pools.

The project included: cleaning of the aerated spaces and external/indoor washing of the existing system.
During the trial run of the Line A upgrade, which lasted until September 18, the 4 sections were coordinated and the volume of air blown was controlled. This process can be done with the newly installed DN600 and DN200 nozzle valves. Measuring instruments are used to check the operation and efficiency of the new system.

Air handling, automation, measurements - What happened during the trial run

The trial operation of Line A could be started after the aeration systems of all four sections had been modified. Speaking about the process, Dániel Tóth, the operations team leader of the FCSM Zrt. North Pest Wastewater Treatment Department, said that the first step was to harmonise the aeration due to the replaced control fittings and aeration elements. The new aeration system should be fully operational under the different operating conditions. The correct adjustment was achieved by means of fixed and hand-held dissolved oxygen gauges in the basins.

After fine-tuning, the automatic mode of the "A" line aeration system was monitored. Continuous online measurements and daily laboratory measurements confirm that the water quality parameters, which varied during the trial run, were kept below the limits. Compliance with the legal requirements is a strict condition for a successful trial run.

The sewage sludge receiving structure has also been modified

The Colas Alterra experts also carried out the modification of the sewage sludge receiving structure at the North Pest Wastewater Treatment Plant. Line 1, which had previously been out of service, was also renovated, and its 3-month trial operation started on 11 September.
As part of the works, the conditions were created to allow a new hydraulic grab to carry out the sludge discharge, with the installation of a double auger hopper and an inclined auger to feed the sewer sludge into the existing coarse material separator Noggerath type drum screen.

The Danube floods have stopped

During the modernisation of the plant, both the contractor and the operator faced a number of challenges. On one occasion, a flood on the Danube interrupted the works, with the specialists working on line A when they had to flood section 4 due to the risk of swamping.
From an execution point of view, the cleaning of the pools was a major professional challenge, as the time it would take could only ever be scheduled on the basis of the current section being drained and the amount of silt and sand at the bottom of the pool. There was also a difference of 1-1.5 weeks between the cleaning of each section depending on the amount of silt.
Another critical point was the bubble test. The difficulty here was that the filling and emptying of the pools took one to one and a half days, so it could take up to 1 week to correct a single detected fault.

Ensuring sufficient cleaning capacity was a major challenge

From the operator's side, the biggest challenge was the parallel construction works on the two biological lines. Dániel Tóth, the operations team leader of the FCSM Zrt. North Pest Wastewater Treatment Department, added that the decommissioning of the sections necessary for the handover of the work areas had to be scheduled so that the plant would be able to treat the entire inflowing wastewater volume with sufficient efficiency and operational safety even in the winter. Serious organisation was needed to ensure that the necessary maintenance could be carried out on the decommissioned basins in addition to the renovation work. Thanks to smooth communication and efficient work organisation, both the contractors and the operators were able to work according to the planned schedule.

More cost-effective cleaning, reduced Danube load

The improvement of the aeration system will allow for optimizing the aeration, thus significantly reducing the electricity consumption of the process and the cost of operating the plant - summarized Dániel Tóth the effects of the investment. He added that the more modern technology will allow for better oxygen dissolution, which will improve the efficiency of sludge treatment and reduce the organic matter and nitrogen content of the treated wastewater. The improved water quality will have less impact on the Danube, the receiving water of the treatment plant.

New developments are already being prepared

Improvements will continue, the operations team leader told us. The North Pest Wastewater Treatment Plant has two biological lines with activated sludge, and the modernisation and fine-tuning of their control is an ongoing task for the operator. In the case of line A, the efficiency of the biological treatment will be increased by expanding the dissolved oxygen probes, which is currently in the preparatory phase. The long-term plans include the continuation of the current modernisation, which includes the extension of the air blowers to provide air supply.

In Csepele, the Ghibli harbour artifact has been renovated

In addition to Újpest, Colas Alterra experts also carried out a very important intervention in Csepel. The corrosion protection of the "Ghibli" structure at the port transfer station had to be overhauled due to the extremely corrosive effect of the wastewater that flows into the structure. PE (polyethylene) sheet lining technology was used to ensure the durability of the concrete surfaces. After dewatering and cleaning the structure, the corroded concrete surface was repaired and PE sheets were installed to form an airtight seal at the joints. This lining protects the structure from chemical damage caused by wastewater in the long term, ensuring the operational safety and service life of the transfer station.