| The pilot study scope included an evaluation of RO filtration of the system effluent to determine if the system produced longer RO run times by minimizing membrane fouling and reducing clean-in-place requirements |
A trial at a refinery in Saudi Arabia has led to the development of a MBR-based technology to help with the reuse of wastewater from the petroleum industry. This article examines the trial results from the membrane evaluation of processing this tough to treat industrial water.
By William Cunningham
Wastewater from oil-processing facilities presents a number of challenges for owners and operators contemplating reuse of treated wastewater. The oily wastewater often has a high concentration of dissolved solids that must be removed before reuse as boiler feed water, cooling water and utility water.
Difficult-to-degrade (refractory) organic compounds are also present in refinery wastewater and these compounds must first be removed to protect reverse osmosis (RO) equipment designed to remove the dissolved solids.
Typical biological oxidation methods used to treat these wastewaters often provide inadequate removal of oils and difficult-to-degrade organic compounds, resulting in organic fouling problems in the downstream ultrafiltration (UF) and RO membrane filtration systems.
Wastewater treatment in the oil and gas industry
The petroleum industry traditionally uses very large quantities of water. Refineries, for instance, discharge approximately one-half to one barrel of wastewater for every barrel of crude oil that is processed.
It is becoming increasingly difficult to reduce that figure further because water is an essential component in the refining process. The crude oil distillation tower at the heart of most modern refineries depends on water as a heat exchange mechanism. Water is also used to provide steam as a power source and for washing or desalting crude.
It should come as no surprise that meeting this fresh water requirement through a RO desalination process, and transporting this water to the refineries, is becoming cost-prohibitive for companies like Saudi Arabian oil company - Saudi Aramco.
The company's policy of minimizing the extraction of groundwater and the use (and associated expense) of desalinated seawater for process water use, led them to actively investigate sustainable methods and technologies that will allow wastewater reuse, either as cooling water makeup and/or boiler feed water. Typically, RO treatment of biologically treated effluent is required for reuse. However this leads to excessive organic fouling of RO membranes due to recalcitrant COD remaining in the treated effluent.
