Some effects of aeration on anaerobic digestion : a thesis presented ... for the degree of Master of Technology

Abstract

Anaerobic treatment is a process which has been used extensively for the stabilisation of strong biologically degradable organic waste materials. This process is commonly used for stabilisation of raw sewage sludge or the sludge produced from aerobic treatment processes. Anaerobic digestion has also been modified and applied to the treatment of some strong industrial wastes, such as meat works wastes. One such process is similar to the activated sludge process and is commonly known as the anaerobic contact process. An essential feature of the anaerobic contact system is that an appreciable amount of the sludge biomass cells in the effluent is concentrated and recycled to the head of the system where it is mixed with the incoming waste water. In this way, Kirach and Sykes (2) reported, a high level of cells is retained in the system, and the hydraulic retention time can be shortened to the economical level of approximately 6-12 hours. This system is similar to aerobic activated sludge process and has been often referred to as the anaerobic activated sludge process. The system can be shown disgrammatically as in Figure 1. [From Introduction]