Abstract: In a wastewater treatment plant, the liquid side of the plant has preferably four stages for nitrification and/or denitrification, prior to further treatment such as a clarifier. Energy requirements are reduced by reducing aeration requirements. Four or more tanks/zones comprise serial anoxic and aerobic stages, but in the anoxic stages simultaneous nitrification/denitrification takes place in accordance with the known process of U.S. Pat. No. 5,906,746. By this arrangement the system can achieve a volume ratio of about 20% aerobic tankage to the total tankage volume, as compared to a much higher ratio in a typical prior art system of serial aerobic/anoxic stages, and greatly reducing aeration requirements.

Abstract: An aerobic digester system in a wastewater treatment plant is made more versatile for different conditions by addition of an equalizer basin or in some embodiments, a bypass pipe. If infeed is received from a sequential batch reactor or from a concentrated septage, for example, the equalizer basin can contain one batch, and then deliver the batch out incrementally to a gravity thickener basin. The equalizer basin also enables the gravity thickener of the system to be removed from service when needed, providing increased flexibility for the system. Importantly, the equalizer or bypass enables versatile modes of operation so that a plant designed for a larger, later flow can operate at an initially low flow or at several levels of flow before reaching the largest design flow. This applies to other conditions of variable flow as well such as seasonal.

Abstract: In a wastewater treatment system and process utilizing membrane bioreactors (MBRs), multiple, parallel series of tanks or stages each include, an MBR stage. Under conditions of normal flow volume into the system, influent passes through several parallel series of stages or process lines, which might be, for example, an anoxic stage, an aeration stage and an MBR stage. From the MBR stages a portion of M.L.S.S. is cycled through one or more thickening MBRs of similar process lines, for further thickening and further processing and digesting of the sludge, while a majority portion of the M.L.S.S. is recycled back into the main process lines. During peak flow conditions, such as storm conditions in a combined storm water/wastewater system, all of the series of stages with their thickening MBRs are operated in parallel to accept the peak flow, which is more than twice normal flow. M.L.S.S.