A Brief Review of Filtration Studies for Waste Treatment at the Hanford Site

Abstract

SummaryThis document completes the requirements of Milestone 1-2, PNNL Draft Literature Review, discussed in the scope of work outlined in the EM-31 Support Project task plan WP-2.3.6-2010-1. The focus of task WP-2.3.6 is to improve the U.S. Department of Energy's (DOE's) understanding of filtration operations for high-level waste (HLW) to enhance filtration and cleaning efficiencies, thereby increasing process throughput and reducing the sodium demand (through acid neutralization). Developing the processes for fulfilling the cleaning/backpulsing requirements will result in more efficient operations for both the Hanford Tank Waste Treatment and Immobilization Plant (WTP) and the Savannah River Site (SRS), thereby increasing throughput by limiting cleaning cycles.The purpose of this document is to summarize Pacific Northwest National Laboratory's (PNNL's) literature review of historical filtration testing at the laboratory and of testing found in peer-reviewed journals. Eventually, the contents of this document will be merged with a literature review by SRS to produce a summary report for DOE of the results of previous filtration testing at the laboratories and the types of testing that still need to be completed to address the questions about improved filtration performance at WTP and SRS. To this end, this report presents 1) a review of the current state of crossflow filtration knowledge available in the peer-reviewed literature, 2) a detailed review of PNNLrelated filtration studies specific to the Hanford site, and 3) an overview of current waste filtration models developed by PNNL and suggested avenues for future model development.This extensive review provides a starting point to help achieve the ultimate goal of the current project, which is to identify technologies such as modifications to the process (e.g., reconfiguration of the filter geometry or changes to operational techniques) or the use of physical property modifiers that increase the sustainability of the filter process. Overall, two avenues of future model development are recommended: 1) determination of long-term filtration dynamics of actual waste and waste simulant slurries and 2) evaluation of the impact of solution chemistry on the rate of filtration and filter fouling. A better understanding of these long-term fouling dynamics and solution chemistry effects will help in developing better predictive models and improved process optimization.v

Filtration Understanding: FY10 Testing Results and Filtration Model Update

“…The results of this literature review are reported in Daniel et al (2010b). The main objective of this report was to identify research areas that would allow improvement of current PNNL models for filtration of HLW (like that proposed in Daniel et al 2010a). To improve the predictive value of PNNL models, the literature review report recommended two areas of additional research:…”

“…Issues of long-term filter dynamics and solution chemistry impacts are discussed extensively in the literature review (Daniel et al 2010a), and as such, readers are referred to that document, and an in-depth discussion of these topics is not provided herein. In contrast, the literature does not extensively discuss chemical cleaning approaches in detail.…”

“…Perform additional filtration testing to provide the underlying data for verification of a filtration model (Subtask 2). The first task objective was completed with the issuance of PNNL-20023 (Daniel et al 2010a) in November 2010. The report is a review of the available information regarding filtration performance with simulated and HLW from SRS and Hanford.…”

“…The state of the art in cross-flow ultrafiltration is discussed in detail in Daniel et al (2010a). The approach in this work is to build a model framework starting from the PNNL model reported in Daniel et al (2010b).…”

“…The approach in this work is to build a model framework starting from the PNNL model reported in Daniel et al (2010b). It was also anticipated that other theoretical approaches discussed in the survey of literature performed in Daniel et al (2010a) would assist in building an understanding of cross-flow filtration behavior.The major findings of Series 1 testing are as follows: Continuous flux decay observed over 100-hour test periods.The filter flux continuously declined for all operating conditions and did not reach a steady-state filter flux. Extrapolation of the observed behavior indicates that the filter may block completely (i.e., exhibit zero flux) at finite time.…”