Lawrence Livermore National Laboratory (LLNL) Experimental Test Site (Site 300) Salinity Evaluation and Minimization Plan for Cooling Towers and Mechanical Equipment Discharges
This document was created to comply with the Central Valley Regional Water Quality Control Board (CVRWQCB) Waste Discharge Requirement (Order No. 98-148). This order established new requirements to assess the effect of and effort required to reduce salts in process water discharged to the subsurface. This includes the review of technical, operational, and management options available to reduce total dissolved solids (TDS) concentrations in cooling tower and mechanical equipment water discharges at Lawrence Livermore National Laboratory's (LLNL's) Experimental Test Site (Site 300) facility. It was observed that for the six cooling towers currently in operation, the total volume of groundwater used as make up water is about 27 gallons per minute and the discharge to the subsurface via percolation pits is 13 gallons per minute. The extracted groundwater has a TDS concentration of 700 mg/L. The cooling tower discharge concentrations range from 700 to 1,400 mg/L. There is also a small volume of mechanical equipment effluent being discharged to percolation pits, with a TDS range from 400 to 3,300 mg/L. The cooling towers and mechanical equipment are maintained and operated in a satisfactory manner. No major leaks were identified. Currently, there are no re-use options being employed. Several approaches known to reduce the blow down flow rate and/or TDS concentration being discharged to the percolation pits and septic systems were reviewed for technical feasibility and cost efficiency. These options range from efforts as simple as eliminating leaks to implementing advanced and innovative treatment methods. The various options considered, and their anticipated effect on water consumption, discharge volumes, and reduced concentrations are listed and compared in this report. Based on the assessment, it was recommended that there is enough variability in equipment usage, chemistry, flow rate, and discharge configurations that each discharge location at Site 300 should be considered separately when deciding on an approach for reducing the salt discharge to the subsurface. The smaller units may justify moderate changes to equipment, and may benefit from increased cleaning frequencies, more accurate and suitable chemical treatment, and sources of make up water and discharge re-use. The larger cooling towers would be more suitable for automated systems where they don't already exist, re-circulation and treatment of blow down water, and enhanced chemical dosing strategies. It may be more technically feasible and cost efficient for the smaller cooling towers to be replaced by closed loop dry coolers or hybrid towers. There are several potential steps that could be taken at each location to reduce the TDS concentration and/or water use. These include: sump water filtration, minimization of drift, accurate chemical dosing, and use of scale and corrosion coupons for chemical calibration. The implementation of some of these options could be achieved by a step-wise approach taken at two representative facilities. Once viable prototype systems have been proven in the field, systematic implementation should proceed for the remaining systems, with cost, desired reduction, and general feasibility taken into consideration for such systems.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 973335
- Report Number(s):
- LLNL-TR-424562; TRN: US1001911
- Country of Publication:
- United States
- Language:
- English
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