Due to its location on the coast, the city of Stockholm has an intense naval activity, both for commerce and passengers. Goods continuously arrive and departure from the harbors, while people use ferries for leisure tours or for travelling to Finland and the other Baltic countries. Stockholms Hamn AB is the public organization coordinating the operations in the harbors of Stockholm and the nearby municipalities. Founded back in 1908, Stockholms Hamn AB ensures a smooth transit of ships and ferries for the most diverse purposes.
This case is related to the most central harbor in Stockholm: Masthamnen. Here passenger ferries dock after cruising in the Baltic sea. The problem was related to their wastewater, discharged in the nearby pump station, prior being transferred to the wastewater treatment plant. The pit of the pump station was not completely sealed, so emissions of H2S originated from the water. Upon docking, the H2S concentration frequently spiked up to 600 ppm. Under such conditions, H2S causes a characteristic unpleasant odor and an environmental hazard. Therefore, the treatment system was required to reduce H2S concentration down to 10 ppm, meaning a reduction higher than 98 %.
Mellifiq has the most 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 as hazardous material.
A Nodora CAT was connected to the newly built ventilation system from the pit to the air exhaust. All emissions from the wastewaters were conveyed into the H2S treatment system, avoiding leakages in the room. The Nodora CAT was designed to completely remove H2S, lasting for several years without significant maintenance.
“Since the installation of the Nodora CAT, no significant H2S emissions were detected”
– Michael Söderström, Project Supervisor
H2S was effectively removed with the Nodora CAT, with emissions well below the limits since installation. For many weeks, a H2S sensor was placed at the outlet of the treatment system validating the performance. No significant values of H2S 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 in operation for a long time now, fulfilling both requirements in terms of performance and low operational costs. Thanks to the Nodora CAT, there will be no more hazardous H2S emissions from the pump station, regardless the load of wastewater. The benefits for the surrounding environment are particularly significant, especially considering the crucial central location of the site.