Study On TPH Removal Process Of Sea-platform Sewage By Flocculation-hydrocyclone&UBD-degradation

With the development of offshore platform and enhancing standards of environmental protection, the sewage produced by platform has posed a great threat to the ocean ecological environment. The objective of this study was the disposal of sewage produced by CEPK platform in Sui-zhong district. This research combined three different processes, scraper, flocculation-hydrocyclone and UBD degradation, to remove the petroleum hydrocarbon in the sewage.Firstly, UBD was cultivated and domesticated to improve the ability of anti-Cl for the further degradation of sewage with6458mg/L Cl". Domesticated UBD grew and reproduced better, besides the ability to degrade sewage improved. After72h degradation, TPH dropped to116mg/L and the removal increased from68.71%to93.21%. Next, the effect of different degradation conditions on TPH removal was investigated. UBD performed best under the condition of4000μL/L(UBD concentration),20℃and continuous aeration. After72h, TPH removal reached97.5%under the optimized condition, but this still failed to meet the national standards.Secondly, centrifugation, flocculation, activated carbon absorption, sand filtration and membrane separation were screened for a suitable pretreatment of TPH removal. The results showed centrifugation and flocculation were of good effect and easy operation. The TPH removal reached96.28%in2min when centrifugation and flocculation were combined. It improved the separation efficiency, meanwhile shortened the time consumed.Due to the limitations of large bulk and small capacity, it is hard to directly use in offshore platforms for centrifuge. Therefore, hydrocyclone was adopted to substitute the centrifuge in this study. For an exploratory study, FX-50hydrocyclone, available on market, was used to dispose the sewage, but the effect was not good. Then, CFD(computational fluid dynamics) was introduced to improved FX-50hydrocyclone. Through CFD, the internal flow field of hydrocyclone was studied through CFD, and then the structural parameters and operating conditions were optimized to fit the needs of sewage disposal. The cone angle was decreased to6°, the diameter of overflow tube reduced to lcm and the appropriate inlet-velocity could be25m/s based on the results of numerical simulation. New flocculation-hydrocyclone process was built up based on the optimized hydrocyclone. TPH dropped to1153mg/L and the removal reached75.3%via the application of new process. Finally, this study adopted scraper to remove oil slick, flocculation-hydrocyclone for pretreatment and UBD degradation for final deep treatment, in a line, to dispose the sewage from offshore platform. After48h treatment of combined processes, TPH dropped to30mg/L which met the national waste water discharge standards of level3waters.