2006-03-31_REVISION - M1977208 - Laserfiche WebLink

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TECHNICAL REVISION No. 07 SELENIUM REMOVAL SYSTEM CEMEX LYONS PLANT C-PIT WATER As TR-07 to the permit fox the CEMEX Lyons Plant in Lyons, Colorado, the Division of Minerals and Geology (DMG) requires CEMEX to prepare a design and cost estimate to support the calculation of a bond to cover the cost of implementing a treatment remedy for water remaining in C-Pit in the unlikely event that CEMEX defaults and ceases operations. This document presents a conceptual design and cost estimate for a biological water treatment system to-remove selenium from water that has accumulated in C-Pit at the CEMEX Lyons Plant. Continuous-flow, bench-scale ueatabiliry testing has demonstrated that the process can reduce C-Pit water selenium concentrations from 430 micrograms per liter (µg/L) to below 60 µg/L. The average selenium removal rate exceeded 90 percent. DESIGN OBJECTIVES The proposed system will meet the following objectives: • Remove as much residual water as practicable from C-Pit • Leave no final free water surface in C-Pit • Reduce the selenium concentration of the water to 60 micrograms per liter (µg/L) or lower • Be operable independent of the existing cement manufacturing operations. DESCRIPTION OF PROCESS Figure 1 shows the conceptual design of the biological treatment process. Water is conveyed by the C-Pit pump via the C-Pit line to the treatment area. Concentrated sulfuric acid is injected by a metering pump into the C-Pit line upstream of an in-line mixer, thereby reducing the influent pH to the neutral range of 6-9. The C-Pit pump, C-Pit line, acid storage tank, acid metering pump and in-line mixer are all existing items that are in the process of being installed under the terms of Technical Revision TR-06, dated December 2, 2005. The bulk of the treatment process is provided by Zenon Environmental (Zenon) of Oakville, Ontario, Canada (http://www.zenon.com). Proprietary nutrient solution provided by Zenon is injected by a metering pump into the C-Pit line. This mixture flows to the bottom of Reactor 1, which is a rented 21,000-gallon tank filled with activated carbon and inoculated with selenium-reducing bacteria. Effluent is drawn from the top of this tank and conveyed by gravity to the bottom of an identical Reactor 2. Additional nutrient is pumped into the Reactor 2 feed.