Most small wastewater treatment plants , which are based on the activated sludge or variants of the activated sludge process, are generally designed as smaller versions of large-scale plants but without primary settling facilities.
GORONSZY, M.S. (1979): Intermittent Operation of the Extended Aeration Process for Small Systems. In: Research Journal of the Water Pollution Control Federation: Volume 51 , p. 274-287. URL [Accessed: 04.08.2023]