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SITUATIONS AND REMEDIES p.1 I MAKING IT WORK p.2 I CASE STUDIES p.2 Why be concerned about oil/water separators? Oil/water separators (OWS) can be costly to maintain, and if not prop- erly managed, can pollute surface and ground water, and lead to costly violations. Have you taken steps to minimize the effects of your OWS on your budget and the environment? This fact sheet discusses the basic operation of OWSs in handling vehicle and floor wash water, and techniques to improve OWS performance and reduce costs and liabili- ties. To make sure your OWS works properly, remember: Eliminate contaminants: Don't rely on the OWS to handle wash water from fuel, coolant, solvent, oil, or paint spills. Instead, clean up spills when and where they occur with dry methods (see the Floor Cleanup fact sheet). Wash without detergents: Emulsifying cleaning compounds dis- perse oil in wash water and make OWSs ineffective—oil passes right through to the sewer. High pressure water or non-emulsifying cleaners are sufficient for most cleaning applications. Minimize loading: Minimize the amount of solids and oils that enter your OWS. The less solids and oils that reach the OWS, the less frequently sludge and floating oil must be removed from the OWS and the better it will work. Also, minimize the amount of wash water reaching the OWS. Excessive water flow can flood an OWS, forcing wastewater through it too fast to allow separation; the result: oil and other contaminants pass right through to the sewer. OWSs should not be used to treat storm water runoff. Best Environmental Practices for Auto Repair and Fleet Maintenance • November 2001 OIL/WATER SEPARATORS OIL/WATER SEPARATORS TROUBLE SITUATIONS POTENTIAL IMPACT REMEDY Chemicals and spills • Sewer discharge violation • Eliminate floor drains from shop reach OWS • Sludge requires disposal • Clean up spills when and where they occur as hazardous waste • Use dry cleanup techniques in shop Sludge builds up in OWS • OWS is less effective because • Eliminate storm water flow into the OWS using berms or curbs solids have less time to settle • Install additional grates and screens on drains • Use sloping pavement and sediment traps around drains Excessive floating oil • Oil discharged to sewer • Pump out accumulated oil on a regular schedule accumulates in OWS during high flow periods • Use oil-only absorbent pads to remove and recycle oil • Use high-pressure, low-volume sprays for vehicle washing Detergents reach OWS • Oil is emulsified and • Do not use oil-emulsifying cleaning solutions (detergents) flows out of OWS to sewer • Wash vehicles and engines less often Heavier or Lighter Than Water? OWSs treat vehicle and floor wash water by allowing substances lighter than water to float and substances heavier than water to sink. Many OWSs also have baffles, coalescers, and oil skimmers to speed-up or enhance separation of these substances. Simplified diagram of OWS operation ---PAGE BREAK--- How do I keep oil and solids out? • Filter filter filter. The best way to reduce OWS sludge is to keep solids out of vehicle and floor wash water. Install progressively finer grates and screens over the drains to the OWS inlet in order to maximize solids separation: - Begin with steel bars spaced 3/4 to 1-inch apart at the OWS drain inlet - Add sequentially finer grates and screens (3/4 and 1/4-inch screens or 1/4-inch expanded steel mesh) - Finish with reusable absorbent material to remove very small particles. • Use oil-only absorbents to separate and recycle oil from your OWS. In some older OWSs, it is not easy to collect and remove separat- ed oil. If your OWS does not have an oil trough or other oil collec- tion device, you can use reusable absorbent pads that absorb only oil and grease. Put these pads on the water surface to collect floating oil. Once saturated, squeeze the oil from the pads; this oil can be managed with your used oil, if the squeezed oil is not cont- aminated with hazardous waste (get data on your wash water quality or analyze a sample at least yearly to verify). The squeezed absorbent pads can be reused. You may avoid permitting and compliance fees by properly main- taining the unit following the preceding guidelines. California regulations allow gravity separation only of hazardous oily water waste without a permit of authorization. If hazardous materials and/or hazardous waste, such as spent solvent, is entering the OWS, the material in the OWS no longer qualifies for the exemp- tion and authorization by DTSC will be needed to operate the unit. • Use microbes to digest oil in your OWS*. Bioremediation is a proven technique to minimize the oil content in OWS effluent and sludge and to reduce OWS cleanout frequency. Microbes added to an OWS break down petroleum products suspended or dis- solved in the wastewater, floating oil, or sludge. Facilities using bioremediation have eliminated wastewater violations and have reported reducing their sludge petroleum content by more than 80 percent. Such reductions can lower the regulatory status of OWS sludge, which will affect the required disposal method and disposal costs. Bioremediation is typically performed under a vendor service contract. Microbes are added to an OWS or inter- ceptor lines on a regular basis to replenish microbe populations. Microbes are nontoxic and completely safe; the main by-products of bioremediation are water and carbon dioxide. Vendor service contracts usually cover all materials and labor; costs range from $75 to $130, depending on the size and contaminant loading of the OWS. * If the waste in OWS unit is determined to be a hazardous waste, bioremediation to reduce oil and grease and phase separation of oil/water mixture are considered hazardous waste treatment by California Law and Regulations and requires authorization to oper- ate. Case studies: Car Repair and Car Wash Salem Boys Auto of Tempe, Arizona used sloping pavement, grates, and screens to minimize OWS loading. These controls, together with biore- mediation, decreased the sludge cleanout frequency and cost by 75%. U.S. Postal Service Fleet Maintenance Facility The Huntington Beach, California facility used bioremediation to reduce OWS effluent hydrocarbon concentration by more than 80%. 2 Oil/Water Separators Best Environmental Practices for Auto Repair and Fleet Maintenance MAKING IT WORK & CASE STUDIES • Lower hydrocarbon levels in OWS effluent • Less contaminated sludge and lower volume of sludge • Reduction or elimination of odor • Microbe populations can be killed by harsh chemicals or pH levels greater than 8.5; do not use detergents that are caustic or contain emulsifiers Limitations of Bioremediation: Bioremediation Benefits: Mention of trade names, products, or services does not convey, and should not be interpreted as conveying, U.S. EPA, California Department of Toxic Substances Control (DTSC) or any local government approval, endorsement, or recommendation. *Second reprint by DTSC, November 2001. Your state or local government environmental agencies have additional information about compliance and pollution prevention opportunities for auto repair shops and fleet maintenance operations in your state or area. For information on California regulatory compliance issues contact your nearest Department of Toxic Substances Control (DTSC) Regional Office by calling 1-[PHONE REDACTED]. You may also access the CAL EPA website at www.calepa.ca.gov for links to California Regulatory Agencies. To obtain additional copies “The Pollution Prevention Tool Kit, Best Environmental Practices for Auto Repair” (Document number 626) or “The Pollution Prevention Tool Kit, Best Environmental Practices for Fleet Maintenance” (Document 625) contact “DTSC’s Office of Pollution Prevention and Technology Development (OPPTD)” at 1-[PHONE REDACTED]. Accompanying videos, “Profit Through Prevention”are available at the same phone number for either auto repair (Document number 1504) or fleet maintenance (Document number 1504). DTSC’s OPPTD also provides technical assistance and pollution prevention resources to businesses and government agencies. Electronic versions of the fact sheets can be found at: www.dtsc.ca.gov/PollutionPrevention/Vehicle_Service_Repair.html