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1RAS INE <br /> ENVIRONMENTAL CONSULTING <br /> DRAFT MEMORANDUM <br /> Date: 10 June 2020 Job No.: 16312-13.02673 <br /> To: Jowin Jung, SFPUC <br /> From: Bruce Abelli-Amen and Yilin Tian, Baseline Environmental Consulting <br /> Subject: REVISED DRAFT Waste Classification of Mercury-Contaminated Water from On-line <br /> UV Lamp Breaks at the SFPUC Tesla Water Treatment facility in Tracy, California <br /> Introduction <br /> Ultraviolet (UV) light disinfection technology is commonly used in water treatment facilities to <br /> inactivate microbial pathogens. UV light can be produced by mercury vapor lamps (UV lamps), <br /> which contain an inert gas and a small amount of liquid mercury. UV lamps volatilize liquid <br /> mercury into a vapor phase, which facilitate ionizing, and emit UV light as a result. When used <br /> in UV reactors, the UV lamps are usually enclosed in a quartz sleeve for protection, and <br /> oriented perpendicular to the direction of water flow. The UV lamps and sleeves can break and <br /> release mercury into water while water is flowing through the reactor. This technical <br /> memorandum provides a regulatory review and discusses waste classification of the mercury- <br /> contaminated water that is collected and temporarily stored on-site after a UV lamp break at <br /> the Tesla Treatment Facility. <br /> Characteristics of Mercury in UV Lamps <br /> Based on information provided to Baseline from SFPUC staff, each UV lamp contains <br /> approximately 2.3 grams of elemental mercury. Elemental mercury is the most volatile form of <br /> mercury with a vapor pressure of 0.3 Pascal at 25 °C. Liquid-phase elemental mercury has a <br /> relatively low solubility in water, only about 0.06 mg/L at 25 °C under standard pressures. <br /> Mercury released in solid or liquid phase does not readily dissolve in water and will tend to <br /> settle in areas of low water velocity due to its much higher density than water. However, <br /> mercury in the vapor phase may be released as very fine particles, which may be more readily <br /> dissolved in water. <br /> Tesla Treatment Facility Containment Measures <br /> When a UV lamp breaks, the UV reactor is shut down and actuated valves on the reactor inlet <br /> and outlet piping close in approximately 10 minutes to isolate the mercury. The water in the <br /> isolated reactor (down to the level of the reactor) drains onto the floor of the reactor building <br /> and flows by gravity into a concrete-lined trench (the remainder of the water in the pipeline is <br /> 5900 Hollis Street,Suite D, Emeryville, CA 94608 1 P: (510) 420-8686 1 www.baseline-env.com <br />