Normally the Desalter effluent is sent of to a common chemical wastewater treatment that handles composite wastewater and serves the whole refinery. The problem with Desalter effluent is that it is very high in suspended solids and oil, which can gum up valves and piping. The effluent can travel hundreds of yards before it reaches the treatment plant and upsets in the piping are a very common event. Sometimes these upsets can shut down the entire refinery.

We are currently working with a refinery in Northern California to install a vibrating membrane system to filter the Desalter effluent right out of the Desalter to remove TSS and oil and grease. The filtrate from this goes on to conventional treatment, but without the process upsets previously experienced.  The membrane system, called VSEP, handles the wastewater with no chemicals or pretreatment and even accepts the periodical Blowdown as the rag layer is purged from the system.  In this case VSEP with Ultrafiltration membranes is being used.  VSEP with Reverse Osmosis can also be used to make this step also the final water treatment with filtrate suitable for discharge or re-use. The VSEP is not affected by scaling or salt precipitation because of the vibration of the membrane.

The main problem with all of the methods you have shown is that they would require a lot of pretreatment to prevent clogging.  VSEP can be used as a stand-alone treatment with a very small footprint and does not require chemicals. We have a great deal of experience with all types of oily wastewaters. If you would like more specific information, see: www.vsep.com or contact me

Rgds

Greg Johnson
gjohnson@vsep.com

Darren:

I'm prevented from giving specifics, but I can tell you what the membrane system is capable of and how it is used. ÊDesalter effluent is water most of the time. During the blowdown of the rag layer 4-6% suspended solids and oil are discharged. The amount of solids can vary depending on the quality of the crude. The VSEP is used like a kidney on the Desalter to remove suspended solids and micelles of oil. ÊThe Desalter is set up for a near continuous blowdown of the rag layer, say every two minutes. This provides a continuous feed to the VSEP of about 1-2% solids on average (the blowdown is 4-6%). The VSEP then filters the effluent to concentrate the suspended solids and oil to 15% or more as a slipstream in single pass. The VSEP reject is sent back to the Coker and the Filtrate is sent on to the chemical treatment plant.

This would be the case where ultrafiltration is used and VSEP is just balancing the effluent before it goes on to the existing treatment plant. This helps to prevent process upsets caused by dumping the rag layer. The UF filtrate is free of all suspended solid and suspended oil, (<1 ppm). ÊThe VSEP is also capable of being the final treatment for the effluent. Nanofiltration or Reverse Osmosis membrane can be used to produce filtrate that is clean enough to discharge or use as process water. We have experience doing this for Fuel Storage Tank Bottom Water. For a case study on this with specific details, see: www.vsep.com/downloads/ and click on the Fuel Storage Tank link.

200 gpm would be normal for Desalter effluent. VSEP is modular and can be sized for any flow. The largest VSEP installation is processing about 1500 gpm. If you would like more information, please contact me. gjohnson@vsep.com

Rgds

Greg