Development and Deployment of a Full-Scale Cross-Flow Filtration System for Treatment of Liquid Low-Level Waste at Oak Ridge National Laboratory
A full-scale modular solid/liquid separation (SLS) system was designed, fabricated, installed, and successfully deployed for treatment of liquid low-level waste from the Melton Valley Storage Tanks (MVSTs) at Oak Ridge National Laboratory (ORNL). The SLS module, utilizing cross-flow filtration, was operated as part of an integrated tank waste pretreatment system (otherwise known as the Wastewater Triad) to remove suspended solids and prevent fouling of ion-exchange materials and heat exchange surfaces. The information gained from this testing was used to complete design specifications for the full-scale modular SLS system in May 1997. The contract for detailed design and fabrication of the system was awarded to NUMET in July 1997, and the design was completed in January 1998. Fabrication began in March 1998, and the completed system was delivered to ORNL on December 29, 1998. Installation of the system at the MVST facility was completed in May 1999. After completing an operational readiness assessment, approval was given to commence hot operations on June 7, 1999. Operations involving two of the eight MVSTs were performed safely and with very little unscheduled downtime. Filtration of supernatant from tank W-31 was completed on June 24, 1999 and W-26 processing was completed on August 20, 1999. The total volume processed during these two campaigns was about 45,000 gal. The suspended solids content of the liquid processed from tank W-31 was lower than expected, resulting in higher-than-expected filtrate production for nearly the entire operation. The liquid processed from tank W-26 was higher in suspended solids content, and filtrate production was lower, but comparable to the rates expected based on the results of previous pilot-scale, single-element filtration tests. The quality of the filtrate consistently met the requirements for feed to the downstream ion-exchange and evaporation processes. From an equipment and controls standpoint, the modular system (pumps, valves, sensors, monitors, controls, shielding, and containment) functioned very well during each campaign. Evaluation of the Endress+Hauser Promass 63F Mass Flowmeter (a secondary objective of the project) indicated reasonably accurate and reliable performance. This instrument was installed on the feed pipeline for the SLS system, and it provided very accurate mass flow and density data, and reasonably accurate solids content data. Near the end of tank W-31 processing, the solids content of the feed to the SLS system increased to a very high concentration. This behavior was caused by the increased mixing of liquid and sludge phases within MVST Tank 31 as the level of liquid being decanted from the tank approached the level of the settled sludge. The physical properties of the heavy sludge caused some difficulties in draining and flushing of the system. Other minor equipment problems were encountered, but none resulted in significant downtime or safety issues. Operational data collected during the campaign were useful in evaluating the performance of the system. The 50-ft{sup 2} cross-flow filter was designed to provide filtrate at the rate of 1 to 5 gal/min (flux range of 0.02 to 0.1 gal min{sup -1} ft{sup -2}) of filtrate, and actual production was between 0.6 and 8.0 gal/min (flux range of 0.012 to 0.16 gal min{sup -1} ft{sup -2}). Additional operating data will be needed, however, to assess the long-term performance of the system with wider variations in the composition of the tank waste feed. The SLS will be employed in further processing campaigns during FY 2000, and more performance data will be collected.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- AC05-00OR22725
- OSTI ID:
- 814070
- Report Number(s):
- ORNL/TM-2000/27; TRN: US0303986
- Resource Relation:
- Other Information: PBD: 12 May 2000
- Country of Publication:
- United States
- Language:
- English
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