Close this search box.

Industry | Practical example | Piping

Stationary comprex® cleaning of a large sewage treatment plant

Cleaning of sludge pipes of the large sewage treatment plant of a European capital city

Deposit formation in a large-scale wastewater treatment plant often resulted in difficulties in plant operation. However, the cleaning process, which had previously been carried out manually, required a great deal of personnel and time. After several weeks of successful test cleaning with COMPREX®, the operator decided to install a fixed COMPREX® module.

The customer order


Sludge lines overgrown with debris

Deposit formation in wastewater treatment plants often leads to increased operating expenses. This is also the case with our customer. Within three months, the floating sludge lines leading from the primary clarifiers became so overgrown with greasy deposits that intensive cleaning was necessary.

However, this cleaning, which had previously been carried out manually, meant a high level of personnel and time expenditure on a quarterly basis. With several people, the lines had to be opened and cleaned over 4 days under difficult working conditions in order to restore the hydraulic capacity.

The innovative approach of those responsible: supplement the previous procedures with cleaning with COMPREX®.


First test cleaning

After an initial meeting in early 2019, it was decided to conduct a first test week with COMPREX®, supported by the use of rock salt as a solid. One month after manual cleaning, on-site test cleanings already showed high effectiveness. The deposits of one month could be largely removed.

The next batch of test cleaning – this time without rock salt addition – after two months of deposit formation was of limited effectiveness.

After the pipes had clogged up to the maximum over a period of four months, the attempt to clean them manually using COMPREX® in combination with the use of rock salt also failed to produce satisfactory results.

The interim conclusion: COMPREX® promises success with correspondingly short cleaning cycles. Already here it became apparent that cleaning would be required at least once a month, but that the costs in the form of cleaning as a service for the provision of manual cleaning would not be sustainable.

The challenge

The challenge, however, was to permanently slow down or even prevent deposit formation. This gave rise to the idea of permanently integrating a COMPREX® unit into the existing cleaning system on site. To enable shorter cleaning cycles, the operator was provided with the prototype of a stationary COMPREX® module (SCM). Different cleaning programs should be tested on different pipelines over several months and compared with each other.

Cleaning with the comprex® process


Integration of the stationary COMPREX® module for pilot operation

Together with those responsible, it was worked out in advance at which points in the pipe network the stationary COMPREX® module could be used and firmly integrated into the cleaning sequence.

Result of comprex® cleaning

First successes after 5 weeks of pilot operation

Visible success after 5-week test operation

Effectiveness proven on the pipe cross-section

Testing of different cleaning intervals

For 13-15 weeks, different lines were now cleaned with COMPREX® at different intervals. After five and after another six weeks, the lines were opened to document the interim status.

The following figures show examples of the various line sections after 5 weeks of test operation. Various cleaning programs are stored in the COMPREX® unit, which are used for the respective assigned pipe section.

The pipelines of two other primary sedimentation tanks (East 1+2) as well as the pipeline into the discharge basin of the primary sedimentation tank East 2 were flushed weekly. For comparison, that pipe was flushed into the discharge basin of the East 1 primary clarifier every 14 days. A primary settling tank (west) was used as a reference, which was not cleaned at all during this time.

Interim results

The result shows: Although the coating could not be completely removed in any section of the pipeline, lower coating thicknesses could be achieved with weekly flushing. The pipe with 14-day flushing has significantly greater deposit thicknesses.

Based on these results, it was decided to clean the lines on a weekly basis in the future. The cleaning programs set for the individual sections were checked and adapted by a HAMMANN project engineer.

Result of comprex® cleaning

Interim conclusion and recommendations

Further reduce cleaning intervals

ideally regular short cleaning

Optimization of the piping system

In the period between October and the end of December 2020, weekly preventive COMPREX® cleanings of the entire scum system of the East primary sedimentation were carried out, while West continued to run as a reference in normal operation (without interim cleaning).

Cleaning with the comprex® process

Further test cleaning with the Stationary COMPREX® Module

Floating sludge line primary clarifier east
weekly COMPREX® cleaning
Floating sludge line primary clarifier west
Without cleaning

The weekly cleanings in the floating sludge pipes of the primary settling tanks east were able to sustainably reduce the grease deposits there by the end of December, while thick grease deposits now adhere in the reference pipes of the primary settling tanks west.

It was shown that with a weekly cleaning rhythm, no new layers of deposits could build up. The East lines could be kept clear for over 13 weeks. As a result, weekly cleanings with COMPREX® are sufficient to replace the feat of manual cleaning at high personnel and time cost.

Outlook for the further procedure

On the part of the customer the following boundary conditions apply:

  • only one basin can be cleaned at a time in order to guarantee the full plant capacity
  • the water level of the pool to be cleaned must be lowered accordingly

For this reason, the integration of a single COMPREX® unit is sufficient for cleaning the four primary settling tanks. Although the COMPREX® pulses are to be fed directly into the pipeline to be cleaned, the connection points of the floating sludge lines West and East are only 5 m apart, so that only short connecting lines have to be installed for VKB-West.

Result of comprex® cleaning

The next steps

Reconstruction of the plant (outlets, electronic control valves)

Integration of a stationary COMPREX® module into the wastewater treatment plant

Regular COMPREX® cleaning

Novel stationary Comprex® modules

The SCM series

Our novel stationary COMPREX® modules are suitable for regular cleaning of, for example, product lines, pig lines and other pipelines in your production. Regular cleaning reliably removes residues from the pipelines before deposits can form.

For more information, please refer to this product sheet:

The SCM series

The advantages of SCM at a glance







Why should you choose us?

With our comprex® process, we offer an effective, sustainable and resource-saving cleaning alternative.

Let us advise you and we will be happy to convince you with a test cleaning at your site.

Posts that might also interest you

PipelinesPractical example

Extinguishing water pipeline logistics and transport company

Comprex® cleaning of several extinguishing water systems including sprinkler systems as well as supply and connection lines
Learn more
PipelinesPractical example

Chemical Park Production Plant

Industry | Practical example | Piping Chemical Park ...
Learn more

Newsletter subscription

Stay up to date on the latest developments, research and practical applications with the comprex process.
Contact form

Thank you for your interest in the CU-3300

Contact form

Thank you for your interest in the MCU-300

Contact form

Thank you for your interest in comprex® ToolClean.

Your inquiry will be forwarded directly to KraussMaffei.

Contact form

Thank you for your interest in our comprex® process.