Extremely acidophilic sulfur-oxidising bacteria: New tools for innovation of biofiltration

4.1 Project The governments of many countries are implementing much more stringent policies with respect to the emission of acid-forming compounds. An important group among these compounds are the volatile (organic) sulfur compounds (V(O)SC), which give rise to acidification and odor pollution and in addition may be extremely toxic. Conventional treatment systems (active carbon, incineration, caustic scrubbing) are economically less feasible because large streams (> 50,000 m3/h) with relatively low concentration ( 50,000 m3/h) with relatively low concentrations (< 1000 ppm) result in high operational costs. Therefore, biological treatment is an interesting and economically feasible alternative. In the biotrickling processes currently used CS2 is absorbed and degraded in the same compartment. To prevent acidification, the biotrickling filters are sprayed with tap water which result in a high water use and the production of equal amount of diluted sulphuric acid (1%). These bottle-necks often prevent application. The successful use of extremely acidophilic sulfur-oxidising bacteria as inocula for biotrickling filters filtration will result in reduction of water consumption and the increased concentration of sulfuric acid (10%) makes it more feasible for re-use. Also from an economic point of view the biotrickling system with "acidophiles" is interesting. Cost estimates and feasibility studies have shown that the operational costs of other removal techniques are significantly higher. Compared to the current biotrickling technology especially a reduction in operational costs is expected. To illustrate the economic perspective: The viscose industry alone is responsible for a worldwide emission of 200,000 tonnes CS2 per year. Treatment of this emission will need about 1000 reactor systems with a total sales value of 500-700 million euro. Improvement of the biotrickling systems is an important and unique achievement of Dutch biotechnology. With the necessary extra effort it may become a sustainable and economically important export product that can compete with physical/chemical alternatives and radiates the leading role of The Netherlands in environmental biotechnology.