Abstract: A method and apparatus for air scouring a layered filter bed wherein the air is dispersed into the finer particles of the bed without disturbing the coarse large aggregate in the lower portion of the bed to prevent inter-mixing of the fine aggregate with the large aggregate. The filter support generally comprises a corrugated filter support forming channels having peaks to provide air channels for distribution of air into air ducts communicating with the fine particles of the filter bed. The valleys between the peaks provide an area for the coarse large aggregate of the filter bed such that the filtered liquid flows through the upper portion of the bed and into the large aggregate and out outlet apertures in the filter support into the lower portion of the channels formed by the filter support.

Abstract: A method and apparatus to automatically control the concentration of microorganisms in an activated sludge waste treatment system, consisting of establishing certain factors by laboratory measurements and field observations to determine the quantity of organisms or "sludge" to be removed during a predetermined period of time in order to maintain the proper microbial balance for most efficient operation of the system by the provision of automatic control means to remove a predetermined amount of mixed liquor directly from the aeration tank during such predetermined period of time, allowing the sludge to settle in a settling tank to thicken same, returning the excess water back to the aeration tank, and removing the predetermined amount of concentrated sludge from the settling tank during such predetermined period.