Removing contaminants from soil and solid waste by flushing them out.
Soil washing process
Contaminants tend to concentrate in fine particle agglomerates due to their large specific surface area. Soil washing is based on scrubbing the soil in water (or a solution with chemicals) and separating the individual grain fractions using various wet processes.
While the separated coarse fractions are usually clean after washing, the contamination is concentrated in fine fractions. A further processing or final disposal of dewatered fine fractions is necessary.
However, as a result of the separation process, the volume of contaminated material requiring further treatment or disposal is significantly reduced.
The applicability of soil washing method is mainly affected by the percentage of fines (particles with a diameter less than 0,063 mm) in the soil. If the percentage of fines is high then there will only be a small volume reduction in the amount of treated material and the efficiency of the soil washing process will be low. Generally, it is considered that if the fine content of the soil is above 25% then soil washing process will not be effective.
Plant description
DEKONTA´s SWP-20 soil washing plant is designed as
a transportable modular equipment which consists of the
following main parts:
- Soil feeding unit comprising a soil feeder bin (5 m3), a scalping vibrating screen, a belt weight feeder and a belt conveyer
- Soil washing unit comprising a drum washer (diameter 2,3 m, length 5,5 m) and a trommel screen (size 5 mm)
- Classification unit comprising a spiral classifier (diameter 0,5 m, length 4,0 m), two hydrocyclones (diameter 150 mm), a slurry tank and a slurry pump
- Sludge thickening unit comprising a sedimentation tank (20” container), a bottom sludge scrapper, sludge removal system and two pumps
- Sludge dewatering unit comprising a filter press, equipment for chemicals preparation and dosing, filter cake discharging and collecting equipment (the unit comes in two 20” containers)
- Water treatment unit (20” container)
- Control room with electric switchboard (20” container)
PROCESS FLOW DIAGRAM
The soil washing technology comprises the following main stages:
- Soil scrubbing
- Separation of contaminated fines from the clean coarse soil fractions (using various types of mechanical screens and hydraulic classifiers)
- Thickening, dewatering and final disposal of contaminated sludge
- Wash water treatment and reuse
Technical parameters
- Capacity: up to 20 tons of treated soil per hour
- Dimensions:
- SWP-20 soil washing plant consists of seven 20” containers
- minimum area necessary for the plant installation is 20 x 30 m
- Total electrical input power: 70 kW
- Operational temperature: 0 - 50 °C
Client support services
- Laboratory testing (particle size distribution analyses, chemical analyses, treatability tests)
- Pilot-scale verification trials
- Designing and permitting
- Erection and start-up operation of soil washing plants
- Staff training
- Maintenance