BACKGROUND: This study considers batch treatment of saline wastewater in an upflow anaerobic packed bed reactor by salt tolerant anaerobic organisms Holanaerobium lacusrosei. RESULTS: The effects of initial chemical oxygen demand (COD) concentration (COD0 = 1880-9570 mg L-1), salt concentration ([NaCl] = 30- 100 g L-1) and liquid upflow velocity (V-up = 1.0-8.5 m h(-1)) on COD removal from salt (NaCl)-containing synthetic wastewater were investigated. The results indicated that initial COD concentration significantly affects the effluent COD concentration and removal efficiency. COD removal was around 87% at about COD0 = 1880 mg L-1, and efficiency decreased to 43% on increasing COD0 to 9570 mg L-1 at 20 9 L-1 salt concentration. COD removal was in the range 50-60% for [NaCl] = 30-60 g L-1 at COD0 = 5200 +/- .100 mg L-1. However, removal efficiency dropped to 10% when salt concentration was increased to 100 g L-1. Increasing liquid upflow velocity from V-up = 1.0 m h(-1) to 8.5 m h(-1) provided a substantial improvement in COD removal. COD concentration decreased from 4343 mg L-1 to 321 mg L-1 at V-up = 8.5 m h(-1), resulting in over 92% COD removal at 30 g L-1 salt-containing synthetic wastewater. CONCLUSION: The experimental results showed that anaerobic treatment of saline wastewater is possible and could result in efficient COD removal by the utilization of halophilic anaerobic bacteria. (C) 2008 Society of Chemical Industry