Groundwater Remediation Basics
Groundwater remediation is the process of treating polluted groundwater by removing pollutants or breaking them down chemically into harmless products. The kind of groundwater remediation we will be discussing here, and the kind that Hepure focuses on, is called “in situ.” In in situ groundwater remediation, the water is treated by pumping purifying chemicals directly into the aquifer; there’s no need to pump the water to the surface. This type of treatment is generally more cost-effective and time-efficient than alternative methods.
Obviously, certain remediation treatments are only effective under specific conditions. So, before beginning the groundwater remediation process, here are just some of the considerations we advise our clients to keep in mind:
Site conditions are important when selecting a groundwater remediation technology. We can’t go into too much detail here, but the correct approach will be influenced by the following site conditions:
- Type of aquifer, perched, or true groundwater. Most contamination is trapped in small perched aquifer which are shallow and typically do not contain adequate water for support or the quality does not support use as a water supply. Occasionally, contamination does reach drinking water supplies in deeper aquifers. Factors effecting the selection of a remediation method are, total depth to be remediated, water quality (hardness, mineral content), and permeability.
- Type of Geology. Groundwater can be found in a variety of soil matrix, from fractured bedrock to heavy clays. Understanding the geotechnical factors of a aquifer is very important in selecting a remedial method.
- Type of Contaminate; One of the most important factors is a good understanding of the contaminate or mix of contaminate within the aquifer. General categories are Chlorinated Volatile Organic Compounds (CVOC), Petroleum Hydrocarbons, Metals, Inorganics, Pesticides, Polycyclic Aromatic Hydrocarbons (PAH), and the newest categories of PFOS and PFAS. Some contaminates may be addressed with a single technology (CVOC and Metals) where others will require vastly different approaches (Inorganics and Pesticides).
- Concentration of Contaminates; The concentration and mass of contaminate withing the aquifer (even if all is not needed to be removed) is very important. Many remedial methods work well with lower concentration and some with elevated concentration and/or free product (DNPL for CVOCs).
- Remedial Goals; Understanding the goals is very important in selection of remedial alternative. Reaching drinking water standards would require a vastly different approach than polishing for closure.
- Groundwater Chemistry; One of the most overlooked parameters is general groundwater chemistry. This refers to substances which normally would not be thought of as a contaminate but may interfere with implementation of remedial technologies. Groundwater chemistry includes, pH, Conductivity, hardness, sulfate, nitrate, oxygen, manganese, calcium and other chemicals which are in high concentrations.
The factors discussed above are typically collected and documented in a detailed site assessment. Site assessments will address soil and groundwater conditions as well as document the types of contaminates and potential sources of the release.
In-Situ groundwater remediation can be summarized into the four broad categories discussed below. Each address a contaminate or group of contaminates, and may designed to be effecting in a variety geological settings and groundwater chemistries. The product links provide a more detailed review of how each may be used.
The links connect with additional information in typically uses of these product in groundwater remediation.
A variety of chemical oxidants are available to address different contaminates. Sodium and Potassium Permanganate are extremely effective on CVOCs.
Hydrogen Peroxide and Stabilized Hydrogen Peroxide are used most often for in-situ oxidation of petroleum hydrocarbons and has shown good effect on PAH, and pesticides.
Bioremediation is divided into two categories, aerobic and anaerobic. Aerobic is most effective on petroleum hydrocarbons and aerobic is most effective on CVOC. In some setting anerobic treatment of metals can be effective.
Calcium peroxide supports aerobic remediation by providing oxygen which is typically the limiting factor. Hydrogen peroxide in low concentrations is also applied to support aerobic remediation.
Emulsified vegetable oil (EVO) with bioaugmentation has proven to be effective in reduction of CVOCs. EVO is a good source of hydrogen, which is a key component in biological dichlorination. Addition of a bioaugmentation culture (TSI TCA-DC Bioaugmentation Culture®) helps insure the bacteria population will support full dichlorination.
Abiotic remediation is specific to the use of Zero Valent Iron. ZVI has been used with great effectiveness with CVOCs and Metals. ZVI has the advantage of a long lifetime in the aquifer.
Metals are often stabilized within the soil matrix to prevent migration. Metal precipitants are fixed into the soil matrix removing them from the dissolved phase of the water. Calcium Polysulfide is most often used.
Most importantly, just contact us. We’ll help diagnose your issue and figure out your best course of action.