Reduced plant contamination through installation of a HUBER Rotary Drum Fine Screen ROTAMAT® Ro2 with downstream HUBER Wash Press WAP® at the Rednitzhembach sewage treatment works

HUBER was awarded the contract in early 2024 to supply and install a HUBER Rotary Drum Fine Screen ROTAMAT® Ro2 with a downstream HUBER Wash Press WAP® for renewing the STW’s screening system. These have now been in operation since the end of August 2024.

Technical challenge and solution in the screen channel

A particular challenge in this project was that the screen channel had to be widened from 600 mm to 1000 mm in the area of the screen basket. In order to minimize conversion time, which included demolishing the old channel and continuing to operate the sewage treatment plant with a rental screen system, a prefabricated stainless steel channel was delivered in advance and installed in the area of the screen basket. The entire project, from dismantling and conversion to commissioning, was thus completed in less than two working weeks.

Initial operating experience with the new plant technology

Operations managers Mr Strauß and Mr Rühl report on their experience with operating this new technology in comparison to the previously installed screening system (double bar screen with downstream screenings press):

What were the main reasons for replacing the old screening system?

Ultimately, there were two main reasons that led to the complete replacement of the installed system. 

The first reason certainly lies in the technical process of the plant. Firstly, the old screening system was unable to deliver the required throughput during mixed water peaks, resulting in the emergency bypass being activated. Secondly, the bar spacing was too large for the composition of our wastewater, so that the contamination in the other areas of the sewage treatment plant, such as floating scum on the aeration and secondary clarification tanks and screenings volume at the coarse screen in the return sludge lifting station, was much too high. Of all areas, this was most intense in the manually cleaned coarse screen (e=20 mm). Sometimes, this had to be cleaned by hand twice a day. Despite the relatively coarse bar spacing, the screenings accumulation here was almost as high as with the old 6 mm inlet screen!

Another reason is the ageing equipment and the associated problems with repairing and procuring the necessary spare and wear parts.

The newly installed HUBER fine screen with downstream screenings wash press has been in operation since the beginning of August 2024. What has changed fundamentally since then, in your opinion?

Everything, really. There are no floating scum layers visible in the aeration and secondary settling tank or in the return sludge area. The screen separation efficiency has increased enormously. Under the same boundary conditions, approximately two to three times as much washed and dewatered screenings are now produced. 

The time required for manual cleaning of the coarse screen in the return sludge lifting station has been significantly reduced, from previously about twice a day with a high volume of screenings, to now once a week with a very, very low volume of screenings. A small bucket is sufficient for this.

How satisfied were you with the advice received on improving the operating situation and project planning for the plant, and the work carried out?

It was delivered exactly as promised – exactly as one would ideally imagine.

We would like to thank everyone involved in the project, especially the Rednitzhembach sewage treatment plant employees, the plant manager Mr Strauß, and Mr Rühl, for placing their trust in us and for their excellent cooperation.