How to ensure a healthy media

By combining its calcified seaweed biofilter media with industrial-strength trickle filter technology, Hibernia hopes to bring new levels of sophistication to biological odour control.

During the early 1990s, Hibernia ETH began championing the use of calcified seaweed as a biofilter media for odour treatment applications. The company believed the seaweed's high surface-to-volume ratio, high porosity and trace elements would deliver favourable performance compared to traditional media. Trials by Thames Water in 1994 validated Hibernia's theory and the material's use became increasingly widespread.

Since then Hibernia has sought to refine its technology and address other problems associated with bulk-media biofilters such as limited operational control, large footprint and the need to replace spent media. The result is the Hibernia BioSiloTM. According to the company's managing director, Richard Berney, it is a "sort of hybrid filter", combining both trickling-filter and calcified-seaweed technologies.

In common with trickling filters, the Biosilo has a layer of inert media, in this case a composite man-made lava, designed to protect the more active biological layers within the calcified-seaweed mix; and this, according to Richard Berney, yields a host of benefits. Firstly, it provides stable load conditions for the delicate biolayers. In biofilter applications it is important to ensure a plentiful supply of healthy 'bugs' in the media to break down pollutants in the airstream. To maintain optimum operating efficiency the biolayer also needs stable conditions. In most applications however this is difficult to ensure and the biolayer can be subject to damaging overloads of contaminated air. The inert media in the Biosilo acts as a roughing layer, preventing uneven inputs from affecting the biolayers. Berney was keen the precise details of how the inert layer protects the seaweed was not described in this article, as it is proprietary.

Secondly, because the calcified seaweed layer in the Biosilo is protected and enjoys a more stable environment, media decay is reduced greatly. This means that with a Biosilo the media will no longer need replacing. All that will be required is simple cleaning and the occasional bed top-up.

Finally, the improved degree of control the Biosilo system affords, makes it easier to balance the nutrient levels essential for improved bacterial growth. As a result it is now possible to tailor the biofilter configuration to more precisely meet the duty conditions occurring on-site.

According to Berney: "Traditional biofilters don't take much rocket science to build. In order to make them smaller and more efficient however you do need a little more rocket science." By combining more sophisticated trickling filter science, designed for handling industrial odour pollution, with its calcified seaweed technology, Hibernia is now able to offer smaller, more efficient biofilters.

To make Biosilo possible, Hibernia acquired a French company, Murgue Seigle "Traitement des Gaz", with expertise in trickling filter technologies developed specifically for volitile organic carbons (VOCs) removal. The Murgue Seigle deal, described by Berney as a "technological acquisition," also put at Hibernia's disposal, state-of-the-art industrial gas treatment technologies, plus patented process know-how developed by Societé d'Application Des Plastiques (SAPS), a company acquired by Murgue Seigle in 1992.

The combination of Murgue Seigle's expertise and Hibernia's calcified seaweed technology, has enabled Hibernia to refine its bio-degradation odour control systems to such a degree that in the Biosilo, Richard Berney believes the company has achieved the "holy grail" of biofilters, a unit which can not only treat STW odours more effectively, but handle VOCs and many other industrial emissions.



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