Hexavalent chromium contaminated soil ex-situ chemical washing project in Changsha
Project Type
Heavy metal pollution
Project Capacity
100TPH
Project Completion
completed
Date
May 2021
Introduction:
Skid- mounted soil washing and remediation equipment is a professional and efficient remediation solutions developed by Desen for ex-situ soil washing.
Characteristics:
* quick installation and easy transfer.
* low maintenance and operating cost.
* 5G intelligent control and operating system.
Related case
The remediation of chromium salt plant
Basic information
Chromium salt is widely used as raw material in many industries, such as the mining, chemical, metallurgy, electroplating, leather, ceramic, dyeing, anti-corrosion, and medical industries, and a large amount of highly toxic solid waste chromium residue is discharged in its long-term production process.
The chromium salt plant was operated 36 years and closed due to environment issues. Based on the sampling data,the main heavy-metal chromium-contaminated soil is about 216300 m³.
| chromium VI exiting state | mass ratio % |
| exchangeable state | 15.98 |
| carbonate-bound state | 24.08 |
| iron-manganese oxide bound state | 34.43% |
| organic matter bound state | 25.51% |
Size distribution
Sample | Size distribution analysis result % | ||||
≤0.075 mm | ＞0.075～0.25mm | ＞0.25～2 mm | ＞2～5mm | ＞5mm | |
Sample 1 | 0.13 | 0.81 | 8.06 | 14.99 | 76.01 |
Sample 2 | 0.20 | 0.78 | 13.36 | 29.18 | 56.48 |
Sample 3 | 0.07 | 0.45 | 31.00 | 25.25 | 43.23 |
Sample 4 | 0.10 | 0.75 | 26.79 | 28.48 | 43.87 |
Sample 5 | 0.12 | 0.68 | 10.33 | 23.84 | 65.03 |
Average | 0.13 | 0.69 | 17.91 | 24.35 | 56.92 |
The Acceptance Indicators for this project is the total reduction rate (S) of earthwork treatment reaches 70% and the total amount of hexavalent chromium in soil and the index of water leaching concentration were effectively reduced.
Through the joint efforts，after many times negotiations, adjustments, and trial runs , Dessen team finally provided the following scheme.
And after the soil washing and remediation process designed by Desen, the total reduction rate of earthwork treatment is achieved to 86.1% and the pollutant reduction is obvious.
Sample soil | Original Cr VI in soil mg/kg | Cr VI in soil after washing mg/kg | Pollutant removal rate % | Original Cr VI leaching mg/L | Cr VI leaching after washing mg/L | Pollutant removal rate % |
Sample 1 | 161 | 89.03 | 44.7 | 4.83 | 0.55 | 88.6 |
Sample 2 | 881 | 436.98 | 50.4 | 18.6 | 2.33 | 87.5 |
Sample 3 | 1620 | 623.7 | 61.5 | 24.6 | 7.29 | 70.3 |
