Anaerobic Waste Treatment Fundamentals

Anaerobic filters (AFs) and upflow anaerobic sludge blanket (UASB) reactors are finding wide-scale acceptance for treating various types of wastewater. They are frequently used for medium to high strength wastewater (2,000 to 20,000 mg/L COD), but have fewer applications to low strength wastewater (< 1,000 mg/L COD). In order to understand the applicability of anaerobic treatment for low strength wastewater, such as domestic sewage, a literature review was performed and a dynamic mathematical model was developed. The review showed two main variations of anaerobic wastewater treatment techniques (AF and UASB) and a number of modifications of these two themes. A total of 136 references were found that documented anaerobic wastewater treatment, ranging in strength from 58 mg/L to 62,000 mg/L COD in 34 different countries. A Monod-type kinetic model, which predicts treatment efficiency and gas production, was developed to describe some of the literature observations. The results of the extensive literature review and model predictions suggests that anaerobic treatment is very promising and economical for treating low strength wastewater. This is contrary to experience in the United States where anaerobic wastewater treatment is seldom