Performance evaluation of the main units of a refinery wastewater treatment plant - A case study

Abstract

Petroleum refineries generate great amounts of wastewaters which require proper treatment before being discharged into coastal waters or other aquatic systems. The main pollutants present in these industrial wastewaters include suspended particles, biodegradable and refractory organics, hydrocarbons, sulfides, phenols and nitrogen compounds. The performance of the Porto Refinery wastewater treatment plant (WWTP) was evaluated in this study. Five sampling campaigns were carried out at six sampling points of the (WWTP), with the purpose of analyzing the most relevant physicochemical parameters and determining the removal efficiencies in each treatment step and the WWTP overall efficiency. The obtained results show that the Porto Refinery WWTP operates with removal efficiencies higher than 90% for TSS, VSS, TPH, O&G, sulfides and phenols, between 80 and 90% for COD, BOD<inf>5</inf> and total nitrogen and around 60% for chlorides. The final effluent meets the discharge limits imposed by the Portuguese legislation. A correlation analysis between the most relevant parameters under study was performed, which contributes to define a reliable monitoring plan based on a limited number of parameters, and provides valuable information regarding the process efficiency, at low cost, to the WWTP managers.