Biological treatment of saline wastewater in a rotating biodisc contactor by using halophilic organisms

Biological treatment of saline wastewater presents unique difficulties as a result of plasmolysis of microorganisms in the presence of salt. Removal of salt from wastewater before biological treatment by reverse osmosis or ion exchange operations are rather expensive. Inclusion of halophilic organisms in activated sludge culture seems to be a more practical approach in biological treatment of saline wastewater. A synthetic wastewater composed of diluted molasses, urea, KH₂PO₄, MgSO₄ and various concentrations of salt (0–5% NaCl) was treated in a rotating biodisc contactor (RBC). A salt tolerant organism Halobacter halobium was added onto activated sludge culture (50%) and used as inoculum. Effects of important process variables such as A/Q ratio, COD loading rate, feed COD concentration, salt concentration and liquid phase aeration on system performance were investigated. An empirical mathematical model describing the system's performance as a function of important process variables was developed and constants were determined by using the experimental data.