This specialist guide has been written by the environmental experts at Water Treatment Services and considers groundwater remediation techniques for treating contaminated water and surrounding soils. The guide examines three main remediation techniques and looks at wastewater extraction, pumping, treatment and disposal considerations. It also considers specialist in-situ techniques including in-situ chemical oxidation, air sparging and soil vapour extraction.
Groundwater remediation and treatment techniques
Groundwater remediation describes the processes used to treat polluted groundwater by either removing the contamination or pollutants, or by converting them into safe products instead.
There are three main ways of remediating contaminated groundwater and they are:
We’ll now consider each of these techniques in more detail.
Groundwater extraction and disposal
Extraction and disposal is one of the most basic and cost-effective ways of dealing with what is a fairly complex issue.
The key challenges in this method of remediation is to work out exactly how to access the groundwater in the first place, extract it from the ground, and then how to get rid of it safely.
Firstly we’ll consider how to access the groundwater… there are lots of options for finding the water in the ground.
The most common methods are digging boreholes or using sumps.
The exact design of the borehole or sump will depend on the particular circumstances of the land.
The decision about how to get the water out of the ground will typically depend on whether removing the water is a one-off job, or whether ongoing extraction using some sort of pumping system will be needed.
Although basic, manual extraction is a further possibility and can be highly effective.
Although the industry often talks about disposal of wastewater, this usually means sending the water off-site to a registered waste processing centre or third party waste management specialist to separate the water from its contaminants.
Pumping and treatment
Pumping and treatment is one of the most commonly used ways of treating contaminated groundwater.
The process involves pumping the groundwater through a specialist water treatment system, then either returning the treated water into the ground or putting it into the drainage system.
The types of wastewater treatment systems used have a large variation in both size and type.
The set-up of the system will typically be determined by the types of pollutants which need to be removed, the volume of water which is being treated, and budget.
The range of options goes from a basic carbon filter costing very little, to a sophisticated reverse osmosis system costing a lot more.
Once installed, these water treatment systems can run for weeks or even months.
Most, once set-up, require very little maintenance and supervision.
Placing boreholes in the correct locations will draw the water up out of the ground and into the treatment phase of the process.
The pumping and treatment option is particularly useful for situations where you need to reduce contamination in groundwater before moving it offsite, separating water from oil to allow you to reuse the oil, or when trying to clear up a site after a spill.
Techniques for the in-situ treatment of contaminated groundwater
Here we’ll consider three techniques for the in-situ treatment of contaminated groundwater:
In-situ chemical oxidation of groundwater
In-situ chemical oxidation is a very useful way of treating contaminated groundwater without extracting it from the ground first.
Chemical oxidation, or “Chemox” as it is sometimes called, can also be used to reduce the levels of contamination in the surrounding soil.
There are a number of products which can be used to oxidise contamination affecting the soil.
Some of these treatment products used are naturally occurring, but in most cases, specialist synthetic or man-made treatment products are more appropriate.
In order to work out the best products to use to treat contaminated land you’ll first need to carry out soil testing of the land to work out which contaminants are present.
The technique of air sparging is the default choice when the contaminants which require to be removed include fuel, oil or other hydrocarbons.
A layman’s explanation of what air sparging is that it involves pumping air through water.
There are two ways in which this helps to treat hydrocarbon contamination:
- The contaminants are forced into the air and out of the water.
- It introduces oxygen into the water. This has the effect of speeding up the action of bacteria on the contaminants which helps break them down further.
Air sparging is most often used in conjunction with other groundwater decontamination methods.
It can also be used as a standalone treatment technique when the concentration of contamination in the groundwater is relatively low.
Soil vapour extraction (SVE)
Soil vapour extraction (SVE) is used to remove fuel odours from either contaminated soil or groundwater.
A good way of thinking about this technique is that the method is similar to vacuuming smells out of the ground.
The extracted vapour then passes through layers of carbon filter until is it safe enough to exhaust to the air.
Vapour extraction doesn’t have a huge impact when used on its own, and is most often combined with other methods of contaminant removal.
If for example, the Chemox method is used to try to deal with contamination, then vapour extraction can also be used to deal with the additional vapour produced during this process.
Contaminated groundwater analysis and remediation solutions
Water Treatment Services offer a comprehensive range of groundwater analysis and remediation solutions to support organisations involved in the management and redevelopment of contaminated land and brownfield sites.
With offices in London serving the South and South East England, Manchester (North West), Birmingham (Midlands), Bristol (South East England and Wales), Leeds (North and North East) and Glasgow (Scotland), supported by regional teams of specially trained technicians and consultants we can offer professional, cost effective contaminated land and groundwater remediation solutions across the whole of the UK.
Contact us today to learn how our professional environmental solutions can help you deal more effectively with contaminated groundwater, land and brownfield sites.
Learn more about soil testing and analysis of contaminated land.