The anaerobic treatment of wastewater has contributed to the field of environmental protection. Complex wastewaters contain a considerable amount of slowly biodegradable ingredients in the form of suspended solids. The reflection of the accumulation of such ingredients in the reactor without complete digestion induces high dilution of the active biomass. Sludge stabilization and gas production is an important factor. Unlike the aerobic processes, the anaerobic processes are claimed to be self-dependent with respect to the availability of contact between the wastewater and the biomass. Whatever the applied up flow velocity and the inlet system arrangement, the gas production is the basic to provide a good mixing intensity within the fixed bed. The main target of the prevailing research is the assessment of the Anaerobic Treatment of Low-Strength Wastewater. The research was focused on Domestic Sewage because this waste is approximately the largest in volume especially in developing countries which have increasing rates of population. The main purpose of the experimental work is to evaluate the feasibility of the anaerobic treatment of domestic sewage using the Anaerobic Filter through three stages: Up-Flow Filter (AUF), Down Flow Filter (ADF), and Fluidized Bed Filter (AFBF) atthermophilic range of temperatures (25-35oC). Biological Oxygen Demand (BODƽ) removal efficiencies for AF, DSFF and AFB are 70, 55 and 43% respectively. Chemical Oxygen Demand (COD) removal efficiencies for AUF, ADF and AFBF are 63, 51 and 41% respectively. Removal efficiencies showed very little sensitivity to daily fluctuations in influent wastewater quality. Gas production averaged 0.024 L of gas per L of influent wastewater, or 0.11 m³ of gas per kg of influent COD .Gas composition averaged 35 % nitrogen, 60 % methane and 5% carbon dioxide. Ammonia nitrogen and sulfides both increased during treatment. The experimental results showed that the most suitable approach to apply an effective treatment was the using of Up-Flow Anaerobic Filter AF with HRT= 24 hrs. The maximum removal rate that can be obtained in this case is 76% on COD-basis and 85% on BOD-basis.