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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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Reuse of significant quantities of produced water (PW) extracted during gasfield operations requires treatment to remove both organic and inorganic materials. Biological treatment is generally regarded as the most cost-effective method for organics removal. For industrial waste waters, biotreatment faces distinct challenges because the PW composition can dramatically affect sludge settleability, a critical parameter in the operation of conventional biotreatment systems. Membrane bioreactors (MBRs) have an inherent advantage and have proved to be successful in the treatment of industrial waste waters because a membrane filter is used to separate the treated water from the sludge rather than separation being contingent on biomass settleability.The outcomes of a bench-scale experimental study on the application of an MBR to the biotreatment of PW from Qatari gas fields are presented for three operating parameters: hydraulicretention time of 16 to 32 hours, solids-residence time of 60 to 120 days, and temperature of 22 to 38 C. The impact on chemical-oxygen-demand (COD) removal was evaluated through experimental testing by use of three parallel bench-scale MBRs. Low sludge concentrations (0.3-1.5 g/L of volatile suspended solids) were attained throughout, with instantaneous-flux values ranging from 3 to 15 L/(m 2 Áh).Results indicated that the COD removal averaged 60% (54-63%), approximately one-third of this value being attributed to physical removal, with the operating parameter values shown to have no statistically significant effect on removal. Although trends were consistent with some previously reported studies performed on refinery waste water, overall removals were lower than expected. The pH of the bioreactor sludge ranged from 4.9 to 6.0, averaging 5.2, compared with a feedwater pH of 4.3, possibly contributing to the low carbon removal recorded. Adjustment of the feed pH to more than 6.5 caused a precipitate to form that contributed to membrane fouling. However, all feedwater acetate and more than 90% of the oil and grease were removed by the MBR treatment.Treatment appeared to be carbon-limited, accounting both for the absence of nitrification (with all removed organic nitrogen apparently being assimilated into the sludge) and for the low sludge-solids concentrations attained. Evidence suggests the feedwater contains a significant fraction (approximately 40%) of highly recalcitrant organic compounds presumed to be nitrogencontaining field chemicals (e.g., scale inhibitors and corrosion inhibitors).

To explore options for simple, safe, and compact chemical reactors that preserve wanted metastable initial products from sequential unwanted reactions, academic and industrial researchers have tried to repurpose reciprocating piston equipment or an “engine-like” design to be used as a chemical reactor. Piston reactors offer the benefit of achieving very high temperature and pressure conditions at very short and defined residence times. Such conditions offer promise for enhanced performance for several chemical conversions. This paper provides a review of the published literature and patents in the field of piston reactors to provide an overview of the current state-of-the-art. The review covers multiple aspects of piston reactors and their applications, reactor design options and their operation, catalyst and ignition placement, tested reactions, experimental setups as well as modeling and simulation. Several research gaps are highlighted as a motivation for future research in the field. To help interested readers into the topic, basic concepts and fundamentals of piston reactors are provided.