The reason refinery wastewater cannot not be treated in a municipal wastewater treatment plant is because of the levels of contaminates that exist in these stream. These contaminates include hydrocarbons, suspended solids, Mercaptans, Phenols, dissolved gases, and acids. In general the entire wastewater treatment process is a very delicate balance of processes. After taking a tour at Penn State’s Wastewater Treatment Plant I was amazing to learn how much attention was taken to ensure that the BOD levels and contaminate levels were suitable for proper digestion from their microorganisms, or as they referred to them as, “their bugs”. This balance was so delicate that the operators had to take samples, multiple times a day, from the wastewater stream to ensure a proper balance. Overall, if the refinery wastewater streams were sent to a municipal wastewater treatment plant it would need to be heavily treated before the actual treatment of the waste stream. According to Penn State’s wastewater treatment facility, the wastewater is treated to remove solids, BOD and other nutrients that cause excessive vegetative growth. [1] The increase of pretreatment may be too much for the plant to handle and would cause the system balance to be thrown off which may harm the microorganisms. All in all, a municipal wastewater treatment plant is an ecosystem of its own. By increasing the levels of nitrogen oxides, sulfur oxides and hydrocarbons, the wastewater ecosystem could be destroyed potentially throwing off the entire treatment process.

Sources:
1. Wastewater Services FAQ. (n.d.). — Office of Physical Plant. Retrieved July 25, 2014, from http://www.opp.psu.edu/about-opp/divisions/ee/util/documents/wastewater-services-faq