The FM-AS process is a two-stage aerobic process consisting of a submerged biological aerated filter packed with fibre media as the first stage and activated sludge as the second stage. A separation unit working on the principle of dissolved-air flotation is needed between the two stages to remove the solids and thereby maintain a suitable sludge age for nitrification in the second stage. The FM-AS process produces effluents with good qualities. The highest removal efficiencies, obtained with a hydraulic retention time of 4.6 hrs. and an operating temperature of 16°C, for BOD5. NH3-N and SS were 95%, 95% and 90% respectively. The economic evaluation suggests that the FM-AS process can be more cost effective than the traditional activated sludge process, particularly when used for upgrading.

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