Case study - Primary settling tanks covering to prevent odors emission

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Courtesy of Bioconservacion SA

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.

Solution implementation

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

Case study - Primary settling tanks covering to prevent odors emission
Case study - Primary settling tanks covering to prevent odors emission

Preliminary cost evaluation showed savings of up to 50% just for initial inversion. Additionally, a comparison of both alternatives, dome confination or perimetrical confination, confirmed Bioconservacion’s proposal as the most economical alternative.

From the moment the solution was implemented by the end of June 2010, complaints coming from a close residential complex with a golf pitch ceased and the WWTP has been free of nuisance problems since then

After more than 5 years, Bioconservacion has been supplying media to the WWTP and has maintained a tight contact with the plant staff. This implication of the company in each project enables us to advance in media development management, since this constant contact with industrial applications allows the company to better understand the real requirements of each sector. Nowadays, we are developing a new media for odor treatment which has an excellent H2S elimination capacity as well as superior mechanical properties. This media is specially recommended for scenarios where humidity content is above 99%. Soon, our client at the Cambrils WWTP facilities will allow bioconservación to perform industrial trials at the site, which shows the degree to which our client have trust in our products and professionality.

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