ResinTech WBG30-B / ResinTech SIR-700 Comparative Evaluation
The engineering company CH2M Hill, consulting for the US Department of Energy in 2010, performed an evaluation on a number of ion exchange medias for hexavalent chromate removal from contaminated groundwater. The published report contains data from a third-party side-by-side evaluation on ResinTech WBG30-B and ResinTech SIR-700 for chromate removal
from groundwater. As a result of the findings, ResinTech SIR-700 was installed at the Hanford Site* in Richland, WA in the 100 area Pump and Treat system. Over the last 14 years, the SIR-700 chromate selective resin has outperformed every expectation and is estimated to realize significant savings. Use of the ResinTech SIR-700 at Hanford has saved the US Department of Energy tens of millions of dollars.
The ResinTech SIR-700 starting raw material is WBG30, a granular weak base polyamine resin. Currently the granular raw material is in limited supply and subject to potentially high costs in the future. SIR-700 is being reformulated to use WBG30-B as the starting raw material. WBG30-B is the bead form of WBG30. The capacity, moisture, and other chemical characteristics of the two resins are identical, only the physical particle shape has changed.
Both are polyamine weak base anion exchange resins. WBG30-B has improved hydraulic characteristics, lower pressure drop and easier handling compared to the granular version, WBG30.
WBG30-B is an internal ResinTech part number used in the report. Following suit where WBG-30 was commercialized as SIR-700, I suggest a name change for the commercial product from WBG30-B to SIR-700-B.
The report below and the data presented is from the original report done at the Hanford Site by CH2M Hill. The paper demonstrates the functional equivalency of WBG30-B to the existing ResinTech SIR-700 product for the removal of chromate.
ORIGINAL REPORT:
Resin Evaluation and Test Report to Support DX
Treatment System, SGW-4 1642, Revision 1
Prepared for the U.S. Department of Energy,
Assistant Secretary for Environmental Management
Contractor for the U.S. Department of Energy
under Contract DE-AC06-08RL14788
CH2MHILL Plateau Remediation Company
P.O. Box 1600
Richland, Washington 99352
Approved for Public Release, Further Dissemination Unlimited
RESIN TESTING AND EVALUATION
At the conclusion of the first test, ResinTech SIR-700
remained on the skid for further testing.
The test was used to accelerate the collection of data about the capacity of SIR-700 and WBG30-B resin by using shorter test columns 6.4 to 50.8 cm (2.5 to 20 in.).
TEST DATA
The data discussed are from three resin evaluations, which were performed from March 10 to November 24, 2009. The first test used only virgin resins; The only non-regenerable resin used in the first test, ResinTech SIR-700, ran continuously throughout the duration of testing without breakthrough, for 258 days. The third resin evaluation focused on the non-regenerable resins tested-SIR-700 and WBG30-B (the bead form of SIR-700).
EVALUATION AND IN-PROCESS MODIFICATIONS
The performance of the single-use resin SIR-700 greatly exceeded initial estimates. The original column of this resin operated throughout the entire duration of testing (approximately 54,000 BV) with a single excursion above breakthrough when the pH of the process water was not adjusted to pH 5. Effluent chromium concentrations returned to near 0 parts per billion (ppb) after the situation was corrected. The 50 cm (20-in.) column of SIR-700 echoed the results of the initial column with a couple of excursions above 10 ppb during flowrate or pH anomalies. Effluent
chromium concentrations returned to normal following these anomalies. The 50 cm (20-in.) WBG30-B column performed well until an influent filter failed, causing an obstruction that nearly stopped the flow of water through the column. This allowed chromium to migrate down the column with effluent concentrations reaching 175 ppb chromium before testing was terminated. Breakthrough curves for these columns are presented in Figure 5.
Beginning in early September, a series of very short column tests was started as part of an effort to determine the number of BV to breakthrough for the single-use resins tested, SIR-700 and WBG30-B. Columns ranged from 6.4 to 12.8 cm (2.5 to 5 in.) of bed depth. These columns were very sensitive to changes in flow rate and provided contact times of less than one minute. This proved to be too little time for the effluent to have consistent chromium concentrations below breakthrough (10 ppb). However, an estimate of the number of BV to breakthrough can be made by looking at the breakthrough curves (Figure 6). These short column tests were also beneficial to determine the capacity of the resin based on analysis of the resin.
SIR-700 was also tested at nominal pH (7.5) to investigate the effect of pH on the resin. Two trials were performed with 6.4 cm (2.5-in.) bed depth columns of SIR-700 resin. Breakthrough occurred at approximately 3,000 and 3,500 BV with effluent chromium concentrations nearing influent concentrations after 10,000 BV. Based on the breakthrough curves in Figure 6 and using 200 µg/L for breakthrough, SIR-700 at pH 5, exhibited breakthrough between 60,000 and 75,000 BV. The 6.4 cm (2.5-in.) bed depth WBG30-B column mirrored the results of SIR-700 with breakthrough occurring around 70,000 BV.
Although ResinTech SIR-700 has the highest capacity, there is a trade-off between the capacity and the cost of resin replacement compared to regeneration and the cost of additional acid and base required for pH adjustment. The estimated cost advantage of in-vessel regeneration compared to single-use resin has decreased because the capacity of ResinTech SIR-700 is much greater than initially estimated. This is attributed to the reduction of Cr(VI) to trivalent chromium by reaction with the resin (Sarkar et al., 2008, “Investigation of Extraordinarily High Cr(VI) Removal Capacity by a Weak-Base Anion Exchange Resin: The Mechanism of Reactive Ion Exchange”), as well as indications that the resin had been oxidized (McGuire et al., 2008, Hexavalent Chromium Removal Using Anion Exchange and Reduction with Coagulation and Filtration).
ResinTech SIR-700 is a granular resin with a higher pressure drop than spherical resins such as Dowex 21K (ResinTech, 2009a, SIR-700 Ion-Exchange Resin), and as such is less readily handled by sluicing than bead resins such as Dowex 21K. ResinTech has formulated a spherical weak-base bead resin, WBG30-B (ResinTech, 2009b, WBG30-B Ion-Exchange Resin); and, as such, which is reported to be functionally equivalent to SIR-700, and it has a lower pressure drop and could mitigate sluicing problems. WBG30-B was tested with the resin evaluation skid (discussed in Chapter 3), and is feasible for use as a single-use resin with similar capacity and cost compared to SIR-700.
PROCESS SELECTION
The focus of the third resin test was to confirm ResinTech SIR-700 chromium removal efficiency that was demonstrated in the first test. The single-use SIR-700 column from the first test continued to run through the second and third tests (over 54,000 BV). To confirm these results, a second and shorter column of SIR-700 was evaluated in the third test, as well as a column of ResinTech WBG30-B (which is a comparable bead form of the resin). The shorter columns with SIR-700 and WBG30-B duplicated the original SIR-700 performance.
The Tri-Party Agreement Milestone M-0 16-111 B plans to expand the current P&T capacity at the100-HR-3 OU to 1,893 L/min (500 gpm) by December 31, 2010. To fulfill this Milestone, CHPRC recommends that no further design changes be made to the DX facility at this time. As noted above, the current design can accept either Purolite A500, ResinTech SIR-700 or WBG30-B resin, either of which a marked improvement is over Dowex 21K.
ResinTech SIR-700 will be used for startup and the facility modified after startup to optimize the treatment using this resin. On the assumption that a single-use resin will be successful in DX, converting the remaining 100 Area facilities for single-use resin should be evaluated. Converting existing facilities could significantly reduce operating costs and alleviate DOE’s concerns regarding offsite regeneration. This approach will be further evaluated in the site-wide analysis.
RISKS OF RESIN DISPOSAL
Disposal of spent resin: Although any resin could be disposed of after a single-use, ResinTech SIR-700 or WBG30-B are the only options evaluated that are cost-effective as a single-use resin. The risks listed below are common to any single-use resin:
- The resin may not pass TCLP testing for chromium and potentially require specialized waste disposal.
RESIN SELECTION
ResinTech SIR-700 has shown high capacity in side-by-side resin testing. Although its theoretical capacity is 2.3 times the capacity of Purolite A500, its actual capacity is greater than 5 times that of Purolite A500 under test conditions. The high capacity of SIR-700, which results from its ability to reduce Cr(VI) to trivalent chromium, compensates for the cost of resin replacement. ResinTech WBG30-B merits consideration because of its spherical bead shape. Although there are still some operational concerns to be addressed, CHPRC recommends the use of ResinTech SIR-700 for the initial DX operation.