Poor Pretreatment Can Increase Refinery Wastewater Load and Variability 

The desalter is the gateway into the refinery and is one of the most critical unit operations, cleaning and processing all crudes entering the refinery. The high temperature desalter effluent is a brine stream, high in impurities and flow volume. Impurities removed by the desalter that are transferred into the effluent include salts, solids, metals and amines. Underperforming desalters can be a major contributor to downstream wastewater treatment plant upsets due to high flows and impurities. Challenging desalter operating conditions result from crude slate changes and/or opportunity crudes which may increase “mud washes”. These purge emulsified material to protect the crude unit and maintain refinery production. When oil, grease and total suspended solids (TSS) are not effectively separated, they pass through the refinery’s primary oil separation treatment (such as API or DAF) directly to the secondary biological treatment. This increases cleaning, treatment and disposal costs and may potentially result in permit non-compliance. 

Improving refinery performance 

Desalter effluent pretreatment increases the capacity of the wastewater treatment plant and improves its operations by reducing load and flow variability to the plant. Recovered water may be returned to the desalter, improving its performance. Increasing capacity in the wastewater treatment plant often enables the refinery to pursue opportunity crude slates to unlock additional profitability. Fewer Total Petroleum Hydrocarbons (TPH) entering the wastewater treatment plant reduces the biosolids to dewater and dispose of. An improvement in OPEX due to reduced tank and equipment cleanings reduces maintenance and chemical spend. Finally, enabling more stable wastewater treatment operations reduces the permit compliance risk.