During the oil production process, oily waste water is coproduced at a rate several times that of oil. This water is known as produced water. Treatment levels and technologies are selected based on disposal method or reutilization objectives, environmental impacts, economics, and other such factors. A 50 m3/day capacity pilot plant was designed, fabricated, and utilized to conduct produced water treatment trials. Pilot treatment trials of produced water from three different oilfelds in Oman were carried out by nitrogen microbubble flotation in conjunction with coagulation/flocculation. Filtration and adsorption treatment processes were tested as well. Oil concentration in one of the produced waters was reduced to below the Omani standard for re-use, through flotation combined with flocculation/coagulation. Oil concentrations in the other two produced waters, which had higherinitial concentrations, were reduced to below the Omani standard for marine discharge. With additional adsorption treatment, these concentrations were further reduced of the level of the re-use standard as well. Additionally, aeration treatment was effective for removal of sulfur compounds such as sulfde from produced water.