Moving bed media serving as a growth surface for bacteria that remove soluble carbonaceous BOD, soluble inorganic ammonia nitrogen, phosphorous, nitrate nitrogen or nitrite nitrogen from wastewater are contained in a variable liquid depth, variable volume, hydraulic flow equalization basin. The equalization basin can be divided into different treatment sections by installing separator screens. Fat accumulation on the moving media, which could cause the media to float or in some other way cause the media to be ineffective, can be prevented by a fat, oil, and grease removal process in a dissolved air flotation cell upstream of the flow equalization basin containing the moving bed media. The moving bed media are retained in the basin by a suitable media screen as the liquid level and volume increases or decreases in the basin depending upon the effluent pumping rate vs. the influent flow rate.