Blog Post 9

Post your response to the blog discussing why refinery wastewater cannot be treated in municipal wastewater treatment plants.

Water and steam are used for treatment in huge quantities in petroleum refining. Of course a refinery thus generates a lot of waste water. The waste water faces many different levels of contamination based upon its usage within the refinery. The steam or water that comes into direct contact with the hydrocarbons or crude oil is the most highly contaminated and should be treated separately on its own. In order to have the best and most efficient water treatment process the key is segregation of the waste streams. This is because of the different forms of contamination. For example, desalting you don’t really need to use fresh water, you can use waste water that is contaminated with hydrocarbons but doesn’t contain salt to remove salt from crude oil as the very first process before undergoing distillation. Process water contaminated with hydrocarbons can be used effectively for desalting instead of fresh water. Different wastewater streams have different levels and different kinds of contaminants.  Combining them would increase the load on wastewater treatment facilities.

The units within a refinery that generate the largest amount of wastewater are desalting, distillation, cracking processes, coking, heat exchangers, and storage tanks The four types of refinery wastewater include cooling water, process water and steam, storm water, and sanitary sewage water. Storm water may be contaminated because of incidental exposure to pollutant sources on refinery surfaces and other accidental spills such as oil from automobiles.  Pollutants found in the wastewater streams include hydrocarbons that have a particular concern for toxic aromatic compounds, heteroatom compounds, dissolved gases, acids, and suspended or dissolved solids.  Cooling water and sanitary sewage water are forms that may not require much treatment before they are sent to public water treatment facilities due to their contamination levels. The most important thing to keep in mind is to avoid mixing different types of wastewater streams to reduce the load on the treatment units.

According to the lessons we have learned so far, various processes involve with hydrogen consumption and would produce wastewater. Cooling water, process water and stream, storm water, and sanitary sewage water are the four types of wastewater that were introduced in lesson 10. Process water and stream is the most polluted wastewater among four since it directly contact with petroleum fraction. Storm water could also be toxic due to exposure to pollutants and spills by accident. The pollutants that found in wastewater include toxic aromatic compounds, heteroatom compounds, strong acids, dissolved gases, suspended and dissolved solids. Compare to process water and storm water, cooling water and sanitary sewage water are less toxic and need less treatment to directly send to public treatment plants.

Refinery wastewater cannot be treated in municipal wastewater treatment plants mainly due to its capacity of treating heavy toxic chemical wastewater. Most public wastewater facilities are building to treat household wastewater and wastewater from industrial. There are some heavy chemical wastewater plants, but not many of them. As we talked about refinery wastewater previously, it contains different types of heavy toxic chemical such as H2S that municipal wastewater treatment plants hardly to treat and probably will harm the plants. It is important that refinery wastewater go through primary treatment which is physical treatment to strip H2S and remove oil and solids. Refinery wastewater also needs to go through the secondary treatment which uses microorganisms to further remove organic contaminants. After these two treatments, refinery wastewater became more applicable for public treatment facilities.

References:

1. F SC 432 class website lesson 10

https://cms.psu.edu/section/content/default.asp?WCI=pgDisplay&WCU=CRSCNT&ENTRY_ID=F20C6357261A4AE2A750C141B721E8C1

2.EPA. Washington, DC (2004). “Primer for Municipal Waste water Treatment Systems.”

Click to access primer.pdf

3. The Washington State Department of Ecology, “Water Pollution Prevention Opportunities in Petroleum Refineries” Ecology Publication No.02-07-017

Click to access 0207017.pdf

Post your response to the blog discussing why refinery wastewater cannot be treated in municipal wastewater treatment plants.

Among the various supporting processes comes the treatment of wastewater. Refineries use a great amount of water in many different processes including desalting, distillation, cracking, and coking. As stated in Lesson 10, there are a few types of wastewater, including cooling water, process water and steam, storm water, and sanitary sewage water. Process water and steam is usually heavily polluted since it comes in direct contact with petroleum distillates. Several pollutants can be found in wastewater, such as aromatic compounds, heteroatoms like amines, phenols, and cyanides, and acids which all have the potential to harm humans or other wildlife.

It is very important that wastewater be treated prior to being sent off to a municipal wastewater treatment plant. Sour water is contaminated with solid particles that must be stripped of like sulfur in a stripping unit, and oils that must be separated by skimming the oil that floats on top of the denser water. A secondary treatment process utilizes microorganisms as biological contactors to help separate the pollutants from the wastewater. Much of this necessity stems from the implementation of the Clean Water Act of 1972 and the incorporation of National Pollutant Discharge Elimination permits (NPDE). There are multiple stages the wastewater must go through before it is suitable enough to be treated at public facilities.