Tank Waste Treatment Research Articles

Treatment of human waste in small-scale facilities: a prospective review

A sustainable approach to the small-scale treatment of portable toilet and septic tank waste is in need to minimise the associated public health and environmental risks. Treatment of human wastes is highly regulated by legislation in many countries given the high content of organic components and pathogens. In conventional wastewater treatment plants, sewage undergoes a series of treatment stages (primary, secondary and tertiary) before effluent discharge. Delivering this approach on a small scale, to meet demands of temporary events, public gatherings or remote locations provides benefits in reducing transport and bulk handling. For a small-scale treatment process to effectively work, the process steps need to be simplified and minimised. The potential of a new treatment scheme is reviewed where the first step is the solid–liquid fraction separation, followed by anaerobic digestion (AD) of the solid fraction, including energy recovery in a combined heat and power unit. The liquid fraction undergoes a series of filtration and disinfection steps to comply with effluent regulations. Digestate from AD is burned on site to provide local domestic/office heating. This has a great potential for application in different locations where inputs may be sporadic, such as outdoor festivals, disaster response scenarios and construction sites.

Heat capacity of complex aluminoborosilicate glasses

ABSTRACTFor nuclear waste vitrification in the Tank Waste Treatment and Immobilization Plant (WTP) at the Hanford site, waste feed is charged into a continuously fed electric melter and the molten glass is poured into stainless steel containers to solidify. The heat from the molten glass must be removed from the facility within plant operating constraints, making knowledge of thermal properties of the waste glasses critical. The heat capacity of Hanford low‐activity waste glasses with systematic variations in composition were studied using complementary thermal analyses – power‐compensated differential scanning calorimetry (pcDSC) at 50–630°C, heat‐flux differential scanning calorimetry (hfDSC) at 200–800°C, and drop calorimetry at 600–1200°C. Variations of the heat capacity with composition have been observed around the transition temperature (Tg) and above, particularly when B2O3 and Al2O3 is varied. Above Tg, all glasses exhibit decreasing heat capacity with increasing temperature. A correlation was found between this curve and the fraction B[4]2O3 in glasses, suggesting boron coordination plays a role in this anomalous behavior. These measurements will be used as critical input to validate the heat balance calculations used for facility design and thus the overall operation of the WTP.

Insight into ion exchange column dynamics through application of an analytical model of system performance

ABSTRACT The Direct Feed Low-Activity Waste flowsheet provides for the early production of immobilized low-activity waste (LAW) by feeding waste directly from Hanford tank farms to the Hanford Tank Waste Treatment and Immobilization Plant (WTP) for vitrification. Prior to the transfer of feed to the WTP LAW Vitrification Facility, tank waste supernatant will be pretreated by the Tank Side Cesium Removal (TSCR) system to meet the WTP LAW waste acceptance criteria (<3.18E-5 Ci 137Cs/mole of Na). This pretreatment will remove cesium from the waste stream using ion exchange (IX). The selected media for IX is crystalline silicotitanate (CST), product number IONSIV-R9140-B, manufactured by Honeywell UOP LLC (Des Plaines, IL). Testing was conducted to improve the understanding of the parameters that impact dynamic ion-exchange performance and to better define IX processing using Low-Activity Waste Pretreatment System (LAWPS) prototypic IX unit operations. Column testing at full height scale was conducted to gain insight into ion-exchange column dynamics and evaluate the application of an analytical model on system performance. Nominal process conditions used 5.6 M Na simulant processed in a lead/lag column format containing 1.15 L 18 × 15 mesh CST in 2.54-cm-diameter columns, 226 cm tall CST beds. Two process flowrates were tested: 1.30 and 1.82 bed volumes (BV) per hour. This work demonstrated that an analytical method can provide a reasonable estimate of the expected performance within the bounds of the assumptions employed for the analytical solution.

Technetium Getters to Improve Cast Stone Performance

ABSTRACTA cementitious waste form known as Cast Stone is the baseline waste form for solidification of aqueous secondary wastes, including Hanford Tank Waste Treatment and Immobilization Plant (WTP) secondary liquid effluents to be treated and solidified at the Hanford Site Effluent Treatment Facility. Cast Stone is also being evaluated as a possible supplemental immobilization technology to provide the necessary low activity waste (LAW) treatment capacity to complete the Hanford tank waste cleanup mission in a timely and cost effective manner. Two radionuclides of particular concern in these waste streams are technetium-99 (99Tc) and iodine-129 (129I). These radioactive tank waste components are predicted to contribute the most risk to groundwater – the most probable pathway for future environmental impacts associated with the cleanup of the Hanford site. A recent environmental assessment of Cast Stone performance, which assumes a diffusion controlled release of contaminants from the waste form, calculates groundwater in excess of the allowable maximum permissible concentrations for both contaminants. There is, therefore, a need and an opportunity to improve the retention of both 99Tc and 129I in Cast Stone. One method to improve the performance of Cast Stone is through the addition of “getters” that selectively sequester Tc and I, therefore reducing their diffusion out of Cast Stone. In this paper, we present results of Tc and I removal from solution with various getters. Batch sorption experiments were conducted with deionized water (DIW) and a highly caustic LAW simulant with a 7.8 M average Na concentration. In general, the data show that the selected getters are effective in DIW but their performance is compromised when experiments are performed with the 7.8 M Na Ave LAW simulant. The diminished performance in the LAW simulant may be due to competition with Cr present in the 7.8 M Na Ave LAW simulant and to a pH effect that may create a negatively charged surface that can repel negatively charged species.

Methods to Avoid Post-Filtration Precipitation in Treatment of High-Level Waste

The Hanford Tank Waste Treatment and Immobilization Plant, currently under construction for treating high level waste at the Hanford Site, will rely on ultrafiltration to provide solids/liquid separation as a core part of the treatment process. A series of bench-scale simulant tests have been performed to evaluate the potential for post-filtration precipitation. These tests focused on identifying precipitation from a range of potential feed compositions and providing the data required to evaluate mitigation options. This data is also important to the Savannah River Site as they are also attempting to dissolve saltcake from their tanks. Inadvertent solids formation after saltcake dissolution, either within a staging tank or in transfer piping can have serious repercussions on the eventual retrieval and transfer of the waste. A series of tests were performed using a variety of simulant samples. These tests identified the expected extent of supersaturation that develops under normal operations and identified and characterized the solids phases that are expected to form when the filtrate solutions are stored. In addition, tests identified the potential to mitigate the formation of these solids through both dilution and the application of increased temperature.

Boehmite Dissolution Model Based on Simulant Data

Several of the Hanford waste tanks contain significant quantities of boehmite. This boehmite will be dissolved through caustic leaching as part of the Hanford Tank Waste Treatment and Immobilization Plant (WTP) currently under construction. Therefore, it is important to fully understand the nature of this dissolution process so that caustic leaching can be effectively deployed on the Hanford tank wastes. This research determined the impact of aluminate ion on the dissolution kinetics of boehmite. In addition, other parameters that impact boehmite dissolution, such reaction temperature, were also assessed and used to develop a semiempirical model of the boehmite dissolution process. A shrinking core model was used to fit data from a series of boehmite dissolution tests with an additional term added to account for the approach to saturation. This revised model provided an adequate fit to the experimental data; however, a superior fit to the experimental data was obtained when a term was added to represent t...

Leaching Characteristics of Hanford Ferrocyanide Wastes

A series of leach tests were performed on actual Hanford Site tank wastes in support of the Hanford Tank Waste Treatment and Immobilization Plant (WTP). The samples were targeted composite slurries...

HAZARDOUS WASTE: GAO Grades Hanford Cleanup

HAZARDOUS WASTE: GAO Grades Hanford Cleanup

Glass wars: The Hanford tank wastes and public participation

AbstractOne of the most difficult remediation challenges facing the U.S. Department of Energy (DOE) is the need to immobilize some 50 million gallons of highly ra‐dioactive, liquid wastes stored in underground tanks at the Hanford site in Washington State. In part as a result of public participation, the technical strat‐egy for tank waste treatment was revised in 1994: high‐activity and low‐activity waste fractions would both be immobilized in a vitrified glass form, although the low‐activity fraction would remain at Hanford. This strategy has been subjected to cycles of reargument, reanalysis, and reconfirmation. As DOE proceeds with remediation of the Hanford tank wastes, it would be to the Department's advan‐tage to understand that public participation has already made positive contribu‐tions to technical decisions. © 2006 Wiley Periodicals, Inc.

Removal of Micron-Size Droplets from an Air Stream by Means of Electric Fields

:In many tank retrieval and waste treatment operations conducted for the U.S. Department of Energy, small droplets of aqueous solutions containing radioactive materials are formed in air streams. These droplets need to be separated before the air is released to the environment. The use of an electric field to separate water droplets from an air stream has been investigated. A test chamber of 10 x 10 cm cross-section and approximately 94 cm long mounted vertically was set up without packing, with two parallel-plate steel electrodes facing each other at a distance of 8 cm. An air stream containing water droplets formed by ultrasonic humidifiers was forced through the chamber. A laser-light-scattering particle-sizing system was used to measure the droplet size distribution. The droplet removal efficiency increased approximately linearly with electric field strength over the range investigated except when the field was raised to 3.0 to 3.50kV/cm, suggesting a saturation effect. The analysis showed that the removal efficiency is a function of the initial droplet concentration. For instance, for a droplet concentration of 24.2 g/m3, the maximum removal efficiency was approximately 85%, while that for a concentration of 8.3 g/m3 was 65% under the same experimental conditions. Droplet size measurements revealed that the average size of droplets did not change significantly with voltage; however, the number distribution of drops did change. Appreciable changes in the number of droplets were observed for droplet sizes in a typical range of 4 to 10 (jurn. The results of this research may be useful in developing effective applications of electric fields for the elimination of mist from air or gaseous streams.

양친매성 유기점토를 이용한 중금속과 유기 오염물질 동시제거 기술

Although clay can sorb significant amounts of inorganic contaminants from soils and wastewater, the hydration of exchangeable cations in clay minerals makes it hydrophilic at the clay mineral surfaces and interlayers. Thus, natural clays are often ineffective in complexing and stabilizing toxic organic contaminants in soils and groundwater environment. But, substituting these hydrated cations with cationic surfactant such as QAC(Quaternary ammonium Compound) can change the natural clay from hydrophilic to hydropobic. Furthermore functionalized organoclay can act as a powerful dual function sorbent for both toxic metals and organic compounds. It also can be used as landfill clay liners, slurry walls, nano-composite materials, petroleum tank farms, waste treatment, and filter systems. To use this modified clay minerals effectively, it is required to understand the fundamental chemistry of organoclay, synthetic procedures, its engineering application, bioavailability of sorbed ion-clay complex, and potential risk of organoclay. In this review, we investigate the use, application and historical background of the organoclay in remediation technology. The state-of-the-art of organoclay research is also discussed. Finally, we suggest some future implications of organoclay in environmental research.