8 Groundwater Remediation Techniques
Groundwater remediation is a term that refers to the process of filtering and extracting pollutants from groundwater. This is a very important process because it supplies drinking water to almost 50 percent of the entire United States population. Moreover, groundwater is also utilized in agriculture and manufacturing industries. There are many techniques to achieve remediation. It can be done using biological, physical, or chemical technologies, depending on the type of pollutants that can be found in groundwater.
Biological Groundwater Remediation Techniques
In this type of onsite remediation process, indigenous microorganisms like bacteria are used to promote biodegradation of organic substances, such as VOCs (volatile organic compounds) and fuel residuals that are absorbed in the water. Bioventing involves aerating or directly injecting oxygen in subsurface soils that contaminate groundwater. This will trigger growth of indigenous bacteria.
This remediation technique makes use of both vacuum-enhanced pumping systems and bioventing process in order to remove organic contamination, particularly oil from LNAPLs (light non-aqueous phase liquids). A pump is used to draw contaminated water into a needle or slurp, which is a straw-like glass tube. When the organic contaminants are brought to the surface, they are separated from water and air using biological processes.
The process of biosparging is very similar to that of bioventing, except that the oxygen in biosparging is directly injected to the groundwater and not in the soil. The aim of this remediation process is to encourage indigenous microorganisms to biodegrade organic contaminants in the affected area.
This method is effective in removing contaminants such as arsenic, lead, selenium, and other harmful toxins. Phytoremediation is ideal for groundwater that is very close to the soil surface. This technique involves growing on the remediation site certain species of trees or plants, such as brake fern or certain genetically modified plants that are known to absorb toxins from water. Over time, the roots of the plants will tap the contaminated groundwater and take away harmful substances. After the trees or plants have done their job, they are harvested and subsequently destroyed.
Physical Groundwater Remediation Treatments
1. Air Sparging
This is an offsite procedure wherein air is introduced directly into the pumped-out groundwater. As the air comes into contact with the contaminant, any impurity is removed.
2. Pump and Treat Remediation
This method is the most widely used remediation process. It requires pumping groundwater into a facility where contaminants will be removed using either chemical or biological treatment methods. The treated groundwater is then released for consumption.
Chemical Groundwater Remediation Technologies
1. Chemical Precipitation
This type of remediation technology is designed to eliminate heavy metals and excess mineral concentration in groundwater. Here, chemical agents are added to contaminated water, often via a stirred reaction vessel. The chemical reaction between metal ions and the agents convert metallic substances into insoluble compounds or precipitates, which are then removed via filtering or settling processes.
2. Chemical Oxidation
This onsite groundwater treatment method introduces chemical oxidants in the soil subsurface to remove organic contaminants. Oxidants can be in gas form (ozone and oxygen) or liquid form (persulfate compounds and hydrogen peroxide).