Abstract An upflow anaerobic sludge blanket reactor was employed to treat saline sulfate wastewater.Mesophilic operation (35 ± 0.5 C) was performed with hydraulic retention time fixed at 16 h. When the salinity was 28 g L-1, the chemical oxygen demand and sulfate removal efficiencies were 52 and 67 %,respectively. The salinity effect on sulfate removal was less than that on organics removal. The methane productions were 887 and 329 cm3 L-1 corresponding to the NaCl concentrations of 12 and 28 g L-1,respectively. High salinity could stimulate microbes to
produce more extracellular polymeric substances(EPSs) and granulation could be performed better.Besides, with the high saline surroundings, a great deal of Na? compressed the colloidal electrical doublelayer,neutralized the negative charge of the sludge particles and decreased their electrostatic repulsion.