More air! Change of regime in one of Budapest's most important facilities

The work is being carried out on more than 10,000 square metres, in pools four and a half metres deep, at the North Pest Wastewater Treatment Plant, which treats wastewater from eight districts of the capital on behalf of the Budapest Metropolitan Municipality. The experts at Colas Alterra Zrt. are building a new aeration system in four phases.

Eight districts and part of the agglomeration have sewerage networks running to the site

The complex, which was opened in 1980 in Újpest, treats the wastewater from the districts IV, XV, XVI, XVII and parts of districts III, X, XIII and XIV, as well as from the agglomeration areas bordering the first mentioned districts, using the most modern treatment technology, in addition to the total wastewater volume generated in the districts.

The plant treats an average of 130 thousand cubic metres of wastewater per day, which results in the production of 1500 cubic metres of inorganic waste per year and nearly 50 thousand tonnes of dewatered sludge.
The plant is capable of treating 200 thousand cubic metres of wastewater per day.

 

From the kitchen sink to the Danube - using the latest technology to clean wastewater

The North Pest Wastewater Treatment Plant uses state-of-the-art treatment technology, which, together with industry developments, is constantly evolving. The wastewater entering the complex is passed through filter grids, and the mechanical treatment process removes particulate, greasy and oily contaminants first.
Sand is removed by sedimentation, and after a further screening, the wastewater is
directed to the pre-settling tanks. The so-called sludge technology removes organic matter and
plant nutrients such as nitrogen and phosphorus, which cause sludge formation. The mixture of sludge and treated effluent is sent to the final settling tanks, where the sludge is settled.

The purified water is finally discharged into the Danube, and the sludge produced is used in a biogas plant to meet the plant's energy needs, and after dewatering, as compost.

 

More air, less running costs

The experts of Colas Alterra Zrt. are replacing the former straw-blower aerator with the more modern Flyght Sanitaire membrane technology in the biological line "A" of the North Pest Wastewater Treatment Plant, in the first phase of the air supply modernization - said Kassai Zsófia, who explained the details of the ongoing investment. The head of department of the Fővárosi Csatornázási Művek Zrt. North Pest Wastewater Treatment Plant added,

The improvements will make the air intake, a key factor in sludge cleaning, more efficient, the new system will be less expensive to operate and will require significantly less maintenance than the previous system.
 

The expert pointed out that the key to removing organic matter and nitrogen in wastewater treatment is to ensure that the dissolved oxygen concentration in the sludge basins is adequate. This process can be achieved in an energy-efficient way with modern aeration systems. 

Replacing the aeration system over an area of one and a half football pitches at a depth of four to four and a half metres

Biology A is divided into 4 sections. Each section is further divided into four large and four small aerated spaces. The former are each 53.8 metres long, 8.9 metres wide and 4.5 metres deep. The smaller pool is 19.9 metres long, 8.9 metres wide and 4 metres deep.

In the first phase of modernization, the entire air intake element of these aeration basins will be replaced, including the sliding valves needed to regulate the air volume - informed our portal Adám László Szilaski.

The Colas Alterra Zrt. site manager added,
 

The new system is installed in aerated spaces at the bottom of drained pools. The system will be installed over 175m² per small pool and 472m² per large pool. In total, demolition and installation is taking place on about 10,352 m².

 

Construction of the wastewater treatment plant is ongoing

Of course, the treatment plant will continue to operate during the development works. Line A has four sections, only one can be drained at a time during the construction of the aeration system, so the construction will be carried out in four phases.

At the North Pest Wastewater Treatment Plant, the pre-settled wastewater in approximately 50-50% is split between biological line A and B, where it is further split into 4-4 parallel sections. The technicians first installed the new aeration system in section A/4, thus eliminating approximately eighth of the total sludge basin volume from the plant's full capacity during the work.
A similar situation will continue during the period of planned maintenance, so this will not affect the operation of the facility.

Preparing the work area with snow shovels and brooms

To prepare the work area, the sluice at the section was closed. The mixture of sewage and sludge was then pumped to the other sections using bilge pumps. Then the basin was flushed several times with treated wastewater before the construction process began.

The first thing that was dismantled in the empty pool was the former aeration system. At the same time, the silty sand and fibrous material remaining at the bottom of the work area was removed.
Ádám László Szilaski said that the dimensions of the structure did not allow for mechanical cleaning, so five or six people, arranged in chains, used snow shovels and sorghum brooms to push the diluted sludge water from one end of the pool to the two high-powered mobile pumps installed at the other. From there, the equipment pushed the diluted sludge into the operating sections.

Successful bubble test

Ádám László Szilaski said that the installation of the new aeration system in section A/4 has been completed and the bubbling test has been successfully completed, after which the pool will be put back into operation, i.e. it will be refilled with wastewater and sludge.

The new state-of-the-art system delivers air through 9-inch rubber membranes into the pools, where around 3,450 heads per section are installed. The improvement has resulted in a uniform bubbling pattern, which leads to an improved efficiency of oxygen dissolution.

The aerator consists of a PVC backbone and branch pipes branching from it. So-called plates are glued into the latter, to which rubber membranes are attached by retaining rings, which provide a controlled supply of oxygen to the pools.  

First phase of modernisation to be completed by mid-summer

After the basin of section A/4, the works will continue with the two sections on line B, after a similar preparation as the first one, and then return to line A for section 3. The upgrade is scheduled to be completed by August 2025 at the latest.