Sorption of Lead to Slurry Trench Cutoff Wall Backfills Comprised of SHMP-Amended Ca-Bentonite

This study investigated the feasibility of using sodium hexametaphosphate (SHMP)- amended calcium (Ca) bentonite in backfills for slurry trench cutoff walls for the containment of lead (Pb) contamination in groundwater. Backfills composed of 80 wt% sand and 20 wt% either Ca-bentonite or SHMP-amended Ca-bentonite were tested for hydraulic conductivity and sorption properties by conducting laboratory flexible-wall hydraulic conductivity tests and batch isothermal sorption experiments, respectively. The results showed that the SHMP amendment causes a one order of magnitude decrease in hydraulic conductivity of the backfill using tap water (1.9 to 3.0 × 10−10 m/s). Testing using 1000 mg/L Pb solution resulted insignificant variation in hydraulic conductivity of the amended backfill. Moreover, SHMP-amendment induced favorable conditions for increased sorption capacity of the backfill, with 1.5 times higher retardation factor relative to the unamended backfill. The Pb transport modeling through an hypothetical 1-m-thick slurry wall composed of amended backfill revealed 12 to 24 times of longer breakthrough time for Pb migration as compared to results obtained for the same thickness slurry wall with unamended backfill, which is attributed to decrease in seepage velocity combined with increase in retardation factor of the backfill with SHMP amendment. Overall, SHMP is shown to be a promising Ca-bentontie modifier for use in backfill for slurry trench cutoff wall for effective containment of Pb-contaminated groundwater.

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Design and Evaluation of IoT-Enabled Instrumentation for a Soil-Bentonite Slurry Trench Cutoff Wall

Infrastructures ◽

10.3390/infrastructures4010005 ◽

2019 ◽

Vol 4 (1) ◽

pp. 5 ◽

Cited By ~ 2

Author(s):

Alan Marchiori ◽

Yadong Li ◽

Jeffrey Evans

Keyword(s):

Real Time ◽

Web Application ◽

Time Series Data ◽

Sensor Data ◽

Series Data ◽

Raspberry Pi ◽

Transmission Protocol ◽

Cutoff Wall ◽

Bentonite Slurry ◽

Slurry Trench

In this work, we describe our approach and experiences bringing an instrumented soil-bentonite slurry trench cutoff wall into a modern IoT data collection and visualization pipeline. Soil-bentonite slurry trench cutoff walls have long been used to control ground water flow and contaminant transport. A Raspberry Pi computer on site periodically downloads the sensor data over a serial interface from an industrial datalogger and transmits the data wirelessly to a gateway computer located 1.3 km away using a reliable transmission protocol. The resulting time-series data is stored in a MongoDB database and data is visualized in real-time by a custom web application. The system has been in operation for over two years achieving 99.42% reliability and no data loss from the collection, transport, or storage of data. This project demonstrates the successful bridging of legacy scientific instrumentation with modern IoT technologies and approaches to gain timely web-based data visualization facilitating rapid data analysis without negatively impacting data integrity or reliability. The instrumentation system has proven extremely useful in understanding the changes in the stress state over time and could be deployed elsewhere as a means of on-demand slurry trench cutoff wall structural health monitoring for real-time stress detection linked to hydraulic conductivity or adapted for other infrastructure monitoring applications.

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Retention of Pb and Cr(VI) onto slurry trench vertical cutoff wall backfill containing phosphate dispersant amended Ca-bentonite

Applied Clay Science ◽

10.1016/j.clay.2018.11.023 ◽

2019 ◽

Vol 168 ◽

pp. 355-365 ◽

Cited By ~ 7

Author(s):

Yu-Ling Yang ◽

Krishna R. Reddy ◽

Yan-Jun Du ◽

Ri-Dong Fan

Keyword(s):

Cutoff Wall ◽

Slurry Trench

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Non-monotonic piezocone dissipation curves of backfills in a soil-bentonite slurry trench cutoff wall

Journal of Zhejiang University SCIENCE A ◽

10.1631/jzus.a1700097 ◽

2018 ◽

Vol 19 (4) ◽

pp. 277-288 ◽

Cited By ~ 4

Author(s):

Yu-chao Li ◽

Xing Tong ◽

Yun Chen ◽

Han Ke ◽

Yun-min Chen ◽

...

Keyword(s):

Cutoff Wall ◽

Bentonite Slurry ◽

Slurry Trench

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