Headworks Does Moving Media

Integrated Fixed-film Activated Sludge (IFAS) systems blend the process flexibility and advanced treatment benefits of activated sludge with the inherent stability and ease of operation of attached growth film systems, increasing capacity and/or level of treatment.

IFAS systems are being applied at an increasing number of wastewater treatment facilities to expand the capacity of the activated sludge system in the same tank volume. Implementation includes the addition of either fixed or free floating media to an activated sludge basin to encourage the growth of biomass and enhance the treatment process. This article provides a high level overview of both types of media along with their unique advantages and disadvantages.

There are a variety of fixed media systems. One type employs rope media, also referred to as looped-cord or strand media. This media takes the form of a woven rope with protruding loops that provide a surface for the growth of biomass. The media consists of a polyvinyl, polyester, or polyethylene material. Rope-type media systems have been applied for carbonaceous removal, nitrification and (to a limited extent) denitrification. Generally, media is installed in the aerobic zone, to enhance BOD removal and for nitrification. Some degree of denitrification occurs in the aerobic zone as the nitrates produced in the nitrifying biomass on the surface diffuse down into the anoxic layers of the biofilm. The amount of denitrification varies, depending on the bulk dissolved oxygen concentration and the amount of carbon available.