Determinaton of optimum detention time for refinery oily wastewater treatment with closed separation system

A lot of water is used in the processes of the Petroleum Refineries. As a result of these processes, a high amount of oily wastewater is formed. Treatment of oily wastewater is different from that of municipal wastewater treatment. Gravity separation techniques are used as primary treatment. Separator pools are the primary treatment part of the oily refinery wastewater, conventionally. Equalization Pools are then used for pH and load stabilization. Oily wastewaters found in these open pools cause volatile organic compound emissions. Separation in closed systems is required to prevent this. Closed Separation Tanks were designed and constructed instead of pools, to solve the emission problem at the Waste Water Treatment Unit in TÜPRAŞ Batman Refinery. The operation of these tanks is also based on the principle of separation by gravity. The separation times of the oil / water / sludge phases are determined by Stokes' Law. After the tanks are started up, performance tests have been carried out and proper separation could be performed. In this thesis study; the optimum separation times for these tanks are determined in the actual case. The optimum separation time determination study was carried out in two stages. Firstly, samples were taken from tank outlets at different retention times and Oil & Grease and Total Suspended Solid analyses were made to determine optimum separation time. These results were then compared with weekly analyzes performed during one year in normal operating conditions to determine their feasibility. In addition, the effect of pH changes on separation efficiency was tried to be determined within the scope of thesis study. Closed Separation Tanks in the TÜPRAŞ Batman Refinery can be operated with 10 hours of retention time. Optimum separation time is 12 hours. It has been determined that retention time of over 12 hours does not have a great effect on separation. pH value at the outlet of Closed Separation Tanks is in the range of 6,7 - 8,1. Since there were no high fluctuations, the pH effect on oil separation was not detected.