Anaerobic fixed-film reactors were developed in 1968 and have grown to represent an advanced technology that has been used effectively for treating a variety of industrial wastes. A number of variations have been developed in the intervening years including the fully packed upflow anaerobic filter (AF) , the fully packed downflow anaerobic filter and the upflow hybrid anaerobic filter (HAF).
IRWIN, T. (n.y): A Primer on Anaerobic Filters. Fundamentals and Applications. n/a: Engineering Fundamentals URL [Accessed: 08.04.2013]