Apparatus and method for controlling liquor circulation flow in long vertical shaft bioreactors

摘要

This application relates to improvements to long vertical shaft bioreactors for the aerobic biological treatment of wastewater and aerobic digestion of biodegradable sludges. The invention comprises a flow control device and method which improves hydraulic flow, inter-zonal mixing and gas transfer in such bioreactors. The flow control device includes a ported upper plate which is mounted in an upflow chamber of the bioreactor and a lower plate located below the upper plate at the juncture between mix and plug flow zones of the bioreactor which are in fluid communication. At least some of the ports in the upper plate are fitted with adjustable valves for regulating the flow of liquor therethrough and hence the size of a hydraulic head loss imposed by the flow control device. Preferably the upper plate is mounted at a location in the upflow chamber upstream from the inlet where influent is discharged into the bioreactor. The flow control device reduces the circulation velocity of the liquor in an upper circulating zone of the bioreactor and also provides a physical barrier substantially restricting inter-zonal mixing between the mix and plug flow zones.