Primary settling tanks covering to prevent odors emission at the Cambrils Waste Water Treatment Plant
The Catalan Water Agency (ACA) commissioned a project aiming to minimize odor emission from a Wastewater Treatment Plant (WWTP) located in Cambrils (Tarragona) that suffered from bothersome smells coming from the primary settling tanks. Occasionally, these emissions ended up into neighborhood complaints. Bioconservacion was selected as the candidate to carry out an interesting project consisting in preventing the release of gas phase pollutants, mainly H2S, to the atmosphere without any treatment.
The main odor focus at the primary settling tanks is the area where the clarified water overflows onto the following treatment step. This is the point where important amounts of volatile organic and inorganic compounds are released.
Bioconservacion suggested covering the overflow pit area in order to prevent free H2S exhaustion into the atmosphere. Once this headspace was confined, the installation of two active drum scrubber units, packed with specially designed media for H2S abatement, made possible to normally operate without any odor release. Each unit was designed to treat up to 750 m3/h. These two BIO-DS750 SAC units were filled with Bi-On carb OX adsorbent, which has an H2S adsorption capacity as a high as 80% weight by weight.
As it can be seen in Figure 1a, covering the entire 29-meter diameter dome area would imply a solution requiring a volume flowrate of 20.000 m3/h. Instead, confining only the problematic focuses can reduce the flowrate down to 1.500 m3/h (Figures). Moreover, civil construction of two drum scrubbers is much more cost-effective than covering a 29-meter diameter facility. Thus, removable covers were installed all along the primary settling tanks perimeter. This measure enables to have a proper control of the emissions released as well as facilitates maintenance tasks. During periods where only small amounts of pollutants are generated, the covers can be lifted to vent the air without treatment