The work reviewed here was published during 2008 and described researches that involve biofilms treating pollutants. This review generally excludes research in medical biofilms, dental biofilms, biofilms causing corrosion and biofilm formation in drinking water treatment and distribution systems. Anaerobic Processes is a separate section of this issue, therefore, anaerobic biofilm treatment systems research is not reviewed here. However, denitrification in biofilm treatment systems is covered when appropriate. Similarly, biofilm systems for the treatment of air pollutants are not covered in this section (subject of the Gaseous Emissions from Wastewater Facilities section).