Contaminant Focus - Hydrocarbons
Updated: Jun 8
Our second post in the series on common contaminants will look at crude oil and refined petroleum products (e.g. diesel, gasoline, heating oils) The UK, like most of the world, has historically and continues to rely heavily on oil for its energy needs. Both historical and current day incidents involving oil and refined petroleum products cause small and major contamination events alike.
What are hydrocarbons?
As the name suggests, the compounds in hydrocarbons are predominantly made up of chains of carbon atoms linked to hydrogen atoms, although they can also contain chlorine, fluorine, sulphur etc. Crude oil and products refined from it like fuel oil, petrol, diesel and gas are all types of hydrocarbons. Similar to coal, they are formed when animal and plant matter was subject to high temperatures and pressures, deep within the earth, over millennia.
Whilst much of the legacy and modern day contamination is due to fossil fuels, which will be our focus today, it's worth noting the emergence of new fuel sources, developed as a response to climate change. Examples are biofuels (derived from plant oils), bioethanol and biogas (created by degrading waste plant/animal products), and “synthetic fuels”, which are liquid fuels created from bio- or natural gas. How readily these are naturally degraded remains to be seen due to their rarity and they may present a remediation challenge for future generations.
How can hydrocarbons be remediated?
There are many techniques we use to remediate crude oil and refined petroleum products. The technique depends on the specific hydrocarbons present and the risks to humans and/or the environment. Where free product is present on-site, most treatment involves removal of this in the first instance, followed by one or more secondary treatment processes. Often they are used in combination to get better results. The one we most commonly use are:
Separation and treatment of recovered mixtures for cost effective disposal or re-use
Dual phase vacuum extraction
In-situ chemical remediation (ISCO)
Domestic oil spill clean-up and remediation
Forced ventilation of sub-floor and other vapour accumulation voids
Some of our Hydrocarbon Remediation Projects:
University of Glasgow
We were involved for many years in University of Glasgow’s Campus Development Programme assisting contractor Mulitplex with various SI and remediation work. Much of the contamination on this site, some of it unexpected, was due to hydrocarbons. In total, we have treated over 5,500 tonnes of mostly hydrocarbon impacted soils and treated 80,000 litres of hydrocarbon impacted water. Read more here.
New ALDI Supermarket
In this project, our engineers designed and built a bespoke bioslurping remediation system. Unexpected contamination was discovered during the construction of a supermarket and offsite disposal was not possible. Our solution, requiring 36 wells to control the water table, expose the smear zone and enhance volatilisation of hydrocarbons, allowed construction and operation of the supermarket to take place around the ongoing remediation works. Read more here.
Former Bitumen Refinery
This site in Ayrshire was formerly a bitumen refinery and was heavily contaminated. In addition, being close to the coast meant tidal action had smeared the contamination over 2m. The impacted soil was excavated to allow groundwater treatment, then bioremediation. In all 30,000 m3 of soil was treated, of which 20,000m3 was able to be reused on site, giving significant materials costs savings. Read more here.
This site was contaminated with fuel hydrocarbons from its former life as an HGV depot. In total, 1300 m3 of contaminated soil was excavated and treated by bioremediation in windrows. Read more here.
Domestic Heating Oil Spill
Around 1000 litres of heating oil were lost into the back garden of a property and was migrating towards the house. The contaminated area needed to be property delineated, then affected soils were removed and sent for disposal at suitable licenced facilities. This was then backfilled with clean material, and the fence, turf and gravel driveway re-instated for the homeowner's convenience. Read more here.