Effects of a recycle in upflow anaerobic sludge bed (UASB) systems

Two major problems arise in the operation of UASB systems treating carbohydrate wastes; high influent CODs and inadequate influent alkalinity/influent COD. These cause the minimum pH in the bed to decline below 6,6 which can lead to failure of the system. This paper investigates the use of a recycle from the effluent to the influent to reduce the influent alkalinity requirements per influent COD, and to reduce the effective influent COD concentration