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Reference project

No more odor problems at the central harbor

Air treatment .
Complete H2S removal over time
Odor control
Stockholm, Sweden
200 L/s
Min. 98% H2S removal


Our current client is a municipal naval company that is in charge of the operations for all harbours in one of Sweden’s largest cities.

Founded back in 1908, the company handles all sorts of marine traffic in the city harbours, both commercial traffic and ferry cruises. Goods continuously arrive and depart from the harbors, while people use ferries for leisure tours or for traveling to neighbouring countries.


The problem.

This case takes place in the city’s most central harbour, where passenger ferries dock after trips across the Baltic sea.

The problem originated from the ferry wastewater. Normally, it is discharged into a nearby pump station before being transferred to the wastewater treatment plant. However, the pit of the pump station was not completely sealed, so H2S emissions started escaping from the pit.

Whenever ferries docked at the harbour, the H2S concentration frequently spiked, with H2S levels up to 600 ppm. Under such conditions, H2S starts emitting a characteristic unpleasant odor while also becoming an environmental hazard. Therefore, it was absolutely imperative to reduce the H2S concentration levels to 10 ppm, which would be a reduction higher than 98 %.

The solution.

We at Mellifiq were happy to provide the most effective and cost-effective solution for this case: the Nodora™ CAT, which contains the active material called Rubicat™. This granular adsorbent is specifically designed to remove H2S from air streams, even at high concentrations. Unlike similar materials such as activated carbons, it is not flammable and does not need to be disposed of as hazardous material.

A Nodora CAT was connected to the newly built ventilation system. All wastewater emissions were directed into the H2S treatment system, avoiding any leakage. The Nodora CAT was designed to completely remove H2S, lasting for several years without needing any significant maintenance.

Solution facts.
Mellifiq delivery
Nodora CAT
Dimensions (HxWxD)
2,070 x 760 x 2,320 mm
1,500 kg
125 mm circular duct


Since our Nodora CAT system was installed, H2S has been effectively removed with concentration levels being well below the limits. For many weeks, an H2S sensor was placed at the outlet of the treatment system in order to validate the performance, and no significant H2S levels were observed. Even if a tolerance up to 10 ppm was accepted in the process requirements, the Nodora CAT removed 100 % of H2S even during the highest loads.

The system has been operating for a long time now, fulfilling both requirements in terms of performance and low operational costs. Hazardous H2S emissions are a thing of the past for the pump station now, regardless of the wastewater load. The benefits for the surrounding environment are particularly significant, especially considering the crucial central location of the site.