The aim of this research is to focus on adequate treatment technology for handling wastewater discharged from natural gas processing industries. An Egyptian natural gas company located at Alexandria was selected for the study. The study represents a useful reference for treatment of such kind of wastewater. Dark Fenton, biological treatment and the combination of them were carried out. The wastewater produced by subject industries has high concentration of chemical oxygen demand, (COD=52665 mg/L), low biological oxygen demand (BOD=8350 mg/L) and low total suspended solids (TSS=370 mg/L). The value of BOD/COD was low (0.16) which indicates that this wastewater inhibits the metabolic activity of bacterial seed because of their refractory properties causing biodegradability to be difficult. Fenton oxidation treatment raise the BOD/COD to more than 0.36. Biological treatment using both aerobic and anaerobic bioreactors for the treatment of mixture of Fenton pretreated gas processing wastewater and sewage gave satisfactory results. The subsequent anaerobic treatment using UASB reactor at optimum HRT [18h] qualifies the produced wastewater for discharge into the sewerage system. The additional aerobic treatment using the continuous-flow activated sludge at 12h HRT qualifies the treated wastewater for discharge into the sea.