Produced Water (PW) is the water trapped in underground formations that is brought to the surface along with oil or gas in extraction operations and it is the highest volume liquid waste stream generated by the petroleum industry. Historically, the treatment of PW has been limited to free oil and suspended solids removal and subsequent discharge into water bodies or deep injection in disposal wells. Only a small fraction of the PW is currently being treated to an extent that allows it to be recycled & reused.

However, due to any of a variety of factors including legislation, geological restrictions and local water scarcity, the future will require a greater fraction of the PW to be extensively treated and ultimately recycled & reused. The petroleum industry will have to change how it has historically been managing PW and start to consider PW as a "by-product" of strategic importance and value and not as an operational liability.

This paper focuses on the application of Advanced Water Treatment Technologies (AWTTs) for the treatment of PW. The specific technologies presented include direct membrane filtration, biological treatment in membrane-bioreactors (MBRs), thermal evaporators and advanced oxidation processes (AOPs). In addition to describing their respective advantages and disadvantages, this paper also presents examples of case studies where PW is being treated and recycled & reused through the application of AWTTs in full scale facilities.

This paper also presents a brief overview of a laboratory investigation carried out by ConocoPhillips GWSC, where various treatment processes (membrane filtration, biological degradation, membrane distillation (MD) and ozonation) were evaluated as PW treatment methods.

The case studies reported demonstrate that thermal evaporators and membrane filtration technologies have been proven at various installations to be cost-effective at the full-scale for PW treatment. Data reported in this paper also reveal that PW can be successfully biodegraded or chemically oxidized and hence processes such as MBRs and AOPs, which have been successful in other industries but overlooked by the petroleum industry, will need to be considered. In the long term, hybrid technologies such as MD may also become a cost-effective alternative to treat PW.

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