BIOLOGICAL AERATED FILTERS (BAF) IN EUROPE: 21 YEARS OF FULL SCALE EXPERIENCE

Since the start-up of the first full scale plant in the North of Paris in 1982, Biological Aerated Filters (BAF) have been installed in more than 500 treatment plants worldwide, treating the effluents from more than 50 Million population equivalents. More than ten different technologies are available, although most of the plants have been built with a few dominant systems:downflow countercurrent aeration (Biocarbone)upflow co-current aeration (Biofor)upflow floating filters (Biostyr and Biobead)a sequence of corrugated plastic and granular media (Biopur)Similarly, most plants are implemented in only four countries with high population densities and advanced wastewater treatment requirements, which have more than 50 plants each: France, Germany, Japan and United Kingdom. Denmark and Switzerland also have a high occurrence relative to the number of population, as coastal or mountain locations favour compact plants.Initially BAF application was mainly carbon removal in compact plants, often following chemically enhanced primary treatment on lamella settlers for reduced footprint. This allowed a whole new concept of covered, deodorized wastewater treatment plants, located in sensitive or space-restricted locations on the coast, in mountains or in city centers.As biofilm reactors have shown a particular advantage in the attachment of nitrifiers, in the last ten years, as nitrogen standards were tightened, BAF were recognized as a powerful tool for nitrification. The flexible arrangement of BAFs, integrating aerobic and anoxic reactors, or combinations in one vessel, allowed upgrades of existing plants with limited footprints.