Synthetic saline wastewater composed of diluted molasses, urea, KH2PO4 and different concentrations of salt (0-10%) was biologically treated in a rotating biodisc unit for COD removal. The performance of the system was evaluated under different operating conditions such as disc number (or surface area), COD loading rate (or feed GOD) and salt concentration. COD removal efficiency increased with increasing number of discs (N) or disc surface area (A), but decreased with increasing COD loading rate (L-s) and salt concentration. Experimental results were correlated by an empirical polynomial equation in terms of COD removal efficiency as functions of disc number (N) or disc surface area, feed COD and salt concentrations. Empirical constants were determined using the experimental data.