Public of IraqMinistry of higher education & researchEngineering college/soil &foundation department

Superviser :Dr. Mahdi O. karkush

:Shahad Duja Ali Written by

Soil washing

introductionSoil washing is the process in which water is used to remove contaminants from soil such an organic ,inorganic and radioactive contaminants . The process works by either dissolving or suspending contaminants in the wash solution. Washing separates the small particles from the large particles by breaking adhesive bonds. The separated material is smaller in volume and is

more easily disposed .

application Soil washing may be used to treat soil

contianing : 1.petroleum2.Radoincludes

3.Heavy metal4.Polychlorinated biphenyls(PCBS)

5.Pentachlorophenol(PCP)6.Pesticides

7.Cyanides8.Creosote

Soil washing is most appropriate for treating noncomplex soil that contain at least 50% sand and gravel and is relatively ineffective in treating soils that are rich in clay and silt. Further soils with a relatively high cation exchange capacity tend to bind pollutants more tightly which can limit the ability of the soil washing process to effectively separate the pollutant

from the soil .

Soil washing processSoil washing can be broken into six

different steps :

PretreatmentSeparationCoarse-grained treatmentFine-grained treatmentProcess water treatmentResiduals management

 

soil washing diagram

Advantage1 -soil washing is very cost effective when it can reduce the

amount of soil that needs further treatment or disposal. Soil washing, when performed under ideal conditions, can lead to a volume reduction of approximately 90% of the

originally contaminated soil .

2 -soil washing is performed on site in a closed system where the conditions, such as pH level and temperature, of the soil being treated can be

controlled and closely monitored .

3-generally the process can be run at a very high rate of around 100 cubic yards per day .

Disadvantage1-Soil washing requires a large area in order to

set up the system .

2 -Soil washing is also predominantly effective with soils that are very coarse. The higher the percentage of coarse grains the more successful soil washing will be at

remediating a contaminated site .

3 -oil washing is ineffective for soils containing more than 30 to 50% silt, clay or organic

matter .

CalculationsAn equation that relates the contaminant concentration in soil washing is:

where Csi is the initial concentration of the contaminant in the soil (mg/kg), Ms is the total dry mass of the soil (kg), Csf is the final concentration of the contaminant in the soil after washing (mg/kg), Vl is the total volume of the washing solution (L), and Cl is the concentration of the contaminant in the solution (mg/L).

……..(1)

(Kd) coefficient of the contaminant

……….(2)

Equation 2 can be substituted into Equation 1 to find the removal efficiency, which is given by:

………..(3)

Or can be founded the removal efficiency by the equation below:-

………(4)

References1-ART Engineering. “Soil Washing at King of Prussia Superfund

Site” < http://www.art-engineering.com/Projects/KOP-Soil/Photos.htm> (Mar. 16, 2013).

2-Fristad, W. E. (1995). “Case Study: Using soil washing/leaching for the removal of heavy metal at the twin cities army ammunition plant.” Remediation, 5(4), 61-72.

3-Griffiths, Richard A. (1995). “Soil-washing technology and practice.” Journal of Hazardous Materials. 40. 175-189.

4-Sharma, Hari D., and Krishna R. Reddy (2004). "Soil Remediation Technologies." Geoenvironmental Engineering: Site Remediation, Waste Containment, and Emerging Waste Management Technologies. Wiley ,Hoboken, NJ, 413-421.

5-USEPA. (1991, September). “Guide for Conducting Treatability Studies Under CERCLA: Soil Washing.” Washington D.C., EPA/540/2-91/020A.