Various pilot studies with different kinds of membranes and treatment scheme were carried out before freezing the final process scheme. Poly Acrylo Nitrile based Ultra Filtration membranes based on excellent field results were zeroed upon for actual site handling.
The oily water mixture coming out of the heater treater was to be given a residence time of 72 hrs. This water was then to be processed in a Tilted Plate Interceptor followed – Induced Gas Flotation followed by Walnut Shell Filter and finally in an Ultra Filtration system (Sparkle Scope).
The outlet from the ETP is processed in 4 stage process as given above with each stage catering to step reduction of the impurity load. The TPI was to be used to minimise the coarse suspensions as well as the bigger oil particles. This considerably clean water was to be next processed in an Induced Gas Flotation system where fine bubble mechanism is employed to lift the small oil particles to the surface due to the density difference. A dedicated mechanical system skims off this oil and this water is further led to the Walnut Shell Filter for removal of the coarse suspensions and oil particles. Finally, for final polishing an Ultra Filtration system is required to bring down the free oil levels to less than 10 ppm having particle size ≤ 2 microns.
The treated water is