Biofilters

The floating biofilter is one of a new range of products which Rhenipal ( UK ) Ltd is marketing. The Biofilter was originally developed at Brunswick University, Germany, and the DIRK Group of Companies has secured an exclusive licence to market the product in Europe.

The Biofilter is best described as a floating, double chambered mattress, which is used mainly to reduce odour emissions from sewage sludge lagoons. One chamber contains a floating medium, which supports the second chamber containing filter medium. The filter medium acts as a substrate for micro-organisms which are responsible for the reduction of offending gases such as ammonia, hydrogen sulphide and organic emissions. The micro-organisms incorporate these emissions as part of their metabolism - they detoxify the gases into odourless products.

The Biofilter has a useful second application in that it provides a floating mattress, which is safe to walk on and thereby enabling safe access for maintenance to areas of the lagoon. The flexibility of the Biofilter system enables a filter cover to be made to fit any shape of lagoon with or without sloping sides and large storage tanks. The walk on floating Biofilter is a low cost efficient odour control product. It is designed to withstand UK climatic conditions and has a useful life span of about seven years.

The first U.K. installation of the floating Biofilter was completed at a farm lagoon owned and operated by Anglian Water at Balsham, Cambridgeshire in April of this year. The lagoon is used for the storage of untreated sewage sludge prior to agricultural disposal.
This application demonstrates the flexibility of the Biofilter system in its ability to compensate for the lagoon's sloping sides and fluctuating sludge levels. In this case the design incorporates a gas tight butyl skirt between the lagoon sides and the Biofilter, enabling the filter body to move vertically with the changing sludge level and prevent egress of gas and odour.

The installed design encompasses the Biofilter; a series of bags linked together to form a simple mattress, an intermediate butyl membrane linked by additional Biofilter bags (to provide more filter medium in contact with sludge at high sludge levels ) to the butyl skirt which is anchored and sealed around the perimeter of the lagoon.

Performance testing by Anglian Water and the Technical University of Brunswick has demonstrated compliance with previously agreed performance criteria - "an overall reduction in gaseous emissions (including H2S, Organic emissions and olfactory) of at least 80%."

Biofilter systems can be used to reduce gaseous emissions and odour in a variety of applications, from steel tanks to holes in the ground. Purchase, installation and maintenance costs are significantly less than alternative solutions.