Activated charcoal tackles odour nuisance from underground water purification plant
Extreme climate conditions sometimes demand innovative solutions. They realise this in Scandinavia too, where water purification plants are often constructed underground because of the severe cold. This also requires an inventive approach to potential odour nuisance. Activated charcoal proved to be the missing link to address this challenge efficiently and effectively.
A Scandinavian public enterprise is responsible for the purification of wastewater in large cities. The enterprise decided years ago to construct these purification plants underground. This enabled them to avoid the risk that the wastewater would freeze in the piping and process systems.
The construction of underground wastewater purification plants, however, does require an innovative approach to potential odour nuisance. Each time ‘fresh’ wastewater is pumped to the plants, the system needs to be able to vent. The air that is released during this contains concentrations of hydrogen sulphide and is released via venting channels close to a residential area. The public enterprise therefore started to search for a smart solution to avoid odour nuisance.
The choice fell quickly on mobile activated charcoal filters. The venting channels were connected with these filters via above-ground connections. These were successful in adsorbing the H2S concentrations (varying from 10 to 50 ppm, with peaks of 80 ppm), which meant that the presence of hydrogen sulphide was removed completely (0 ppm). The continuous measurement system that the public enterprise installed at the filter output provides daily evidence and enables real-time filtration monitoring.
Filtration in three locations
Until now, Desotec has installed two mobile activated charcoal filters in the Scandinavian city: after the installed AIRCON H (hydraulic discharge to 40,000 m³/h) had already proved its worth for two years, an AIRCON 3000 (hydraulic discharge to 3,500 m³/h) was added to this. Because of the significant results, we will soon be installing a further 3 AIRCON 3000 systems in parallel at a third ‘hot spot’.
The public enterprise is extremely pleased with the total service offered. Its technical department does not actually have the resources and specific expertise to monitor the systems themselves. As contractor, Desotec provides a total service: when the saturated activated charcoal filters need to be replaced we offer temporary hire solutions, which means that good air quality is guaranteed permanently for city residents.
At DESOTEC’s facilities, all used carbon is analysed so the right measures can be taken for handling and removing the saturated carbon out of the mobile filters. All molecules that were adsorbed on the activated carbon at the customers’ site, are desorbed inside DESOTEC’s reactivation furnaces. These contaminants are then fully destroyed, in accordance with National and European legislation, by an incineration and neutralisation setup. The entire installation and it's emissions are under continuous on-line monitoring, which guarantees that only harmless water vapour is seen exiting the chimney.