| Anaerobic wastewater treatment is becoming an accepted technology for treating various types of wastewater. It is frequently used for medium to high strength wastewater (2,000 to 20,000 mg/L COD), but has had fewer applications to low strength wastewater (<1,000 mg/L COD) especially in developed countries. In order to understand the applicability of anaerobic treatment for low strength wastewater, such as domestic wastewater, a literature review was performed. The review showed two main variations of anaerobic wastewater treatment techniques (anaerobic filter and upflow anaerobic sludge blanket reactor) and a number of modifications of these two themes in 34 different countries with influent COD ranging from 58 mg/L to 62,000 mg/L. To better understand and extend this technology to low strength wastewater, a dynamic model that predicts treatment efficiency as well as gas production and composition was developed. The model is composed of 12 ordinary differential equations and uses Monod-type kinetics. The model was verified using experiment results from pilot scale studies.; Anaerobic wastewater treatment has the potential to reduce greenhouse gas emissions. A model was developed to estimate greenhouse gas production from domestic wastewater treatment and to compare the differences between aerobic and anaerobic methods. The greenhouse gas contributors of CO 2 and CH4 are included in the analysis, while N2O is neglected. Anaerobic wastewater treatment reduces carbon dioxide emissions through energy conservation but the dissolved methane in the anaerobic reactor effluent can offset this reduction when treating low strength wastewater. The cross over points range from 300 to 700 mg/L influent wastewater COD, and are dependent on the relative efficiency of the aerobic treatment system. Anaerobic wastewater treatment becomes favorable for concentrations higher than the cross over values. A technology to recover dissolved methane would make anaerobic treatment favorable at nearly all influent strengths.; This research documents the opportunities for anaerobic wastewater treatment. The results of the extensive literature review and model predictions suggest that anaerobic treatment is promising and favorable for low strength wastewaters under certain conditions. |
