The Upflow Anaerobic Sludge Bed reactor (UASB) has been used successfully by the food processing, pulp and paper and municipal wastewater industries. High organic strength wastewater, limited space, extended down times and sludge handling and disposal have been critical factors in waste treatment system selection. This study investigated the performance of a laboratory-scale UASB reactor for treating clam-processing wastewater. Virginia state effluent regulations for BOD₅:TSS ranged from 0:0 to 90:90 to as high as 500:500 depending on the facility location. It was found that at a volumetric organic loading rate of 13.8 g COD/L/d the BOD₅ removal efficiency averaged 87% and TSS removal efficiency averaged 83%. The average effluent values for BOD₅ and TSS were 200 ppm and 90ppm, respectively. The conversion efficiency of COD to methane gas was 81%. At an organic loading rate of 4.8 g COD/L/d the effluent values averaged 77 and 66 mg/L for BOD₅ and TSS, respectively. Methane production was inhibited at Na⁺ concentrations above 5,000 ppm in batch experiments. At Na⁺ concentrations above 12,500 ppm inhibition was essentially 100%. Nutrient enrichment did not affect methane production. / Master of Science