Abstract: In a method for treating wastewater and an associated design of a treatment plant, wastewater in a storage tank is filled from a minimum level to a maximum level. While being filled, a bioreactor is aerated. After subsequent sedimentation of activated sludge at the bottom of the bioreactor, treated water is pumped from a subsurface layer in the bioreactor and wastewater is simultaneously fed from the storage tank into a sludge bed in the bioreactor. When a level of wastewater in the storage tank is lowered to the minimum level, pumping of treated water from the bioreactor and pumping of wastewater into the bioreactor simultaneously stops. The storage tank has a wastewater pump leading to the bottom of the bioreactor. A safety overflow in the bioreactor leads to a treated water drain having a treated water pump.

Abstract: The method of wastewater treatment and the method-applying apparatus in the sequencing batch reactors, where after separating the activated sludge from the treated water the treated water is drawn off via a decanting apparatus from the sub-surface layer of water in the reactor. The decanted water is conveyed by the decanting apparatus to a separate tank, which is separated in a watertight way from the inside of the reactor. The treated water is pumped off from the separate tank to the outlet by the air-lift pump, the inlet of which is located at the level corresponding to the delivery yield of the air-lift pump. The submerged inlet part of the decanting apparatus moves vertically alongside with the fluctuating water level in the reactor.