Membrane processes for the treatment of produced waters

From the oil plants and platforms a large amounts of wastewaters, which are considered a by-product of crude oil extraction, are produced: they are exactly known as "produced waters", and up to now they have been treated and disposed of in deep wells on the onshore platforms or directly discharged into the sea. Extraction technology and reservoir characteristics affect the amount of produced water generated that sometimes may be tenfold the quantity of produced oil. The purpose of this paper is to develop a process suitable for the purification of produced waters, by devising a treatment train aimed at industrial and agricultural reuse. With respect to a municipal wastewaters, produced waters have a very high salinity, that requires specific attention for projecting and managing the specific treatment device. Membranes, commonly used in the production of desalted water, appear to be a suitable technique to overcome the problem; particularly, the vibrating membrane system VSEP (Vibratory Shear Enhanced Processing) turned out to be a reliable and good process to be applied to the produced water, since with a single operation gives an effluent with a high purity degree without the addiction of chemicals. Moreover, if the effluent from secondary membrane treatment is further purified with a reverse osmosis as tertiary treatment, with a previous reduction of nutrients, the effluent has all the necessary attributes required by the law for water reuse. In this paper a process scheme is proposed with a treatment sequence train, in which the a VSEP system is used as secondary treatment, and a Reverse Osmosis process has been implemented as tertiary treatment, simulated with the software IMSDesign Software by Hydranautics. Several case studies have been considered, with waters of different salinity, showing that in all cases a water with very good characteristics is obtained, reusable for different uses.