Petroleum liquids are a basic building block of our modern lives. Uses include fuels,
lubricants, and the raw material for manufactured products. The by-product of these
uses has been the inadvertent release of petroleum liquids. A result of our utilization of
petroleum liquids is a legacy of soil and groundwater impacted by petroleum liquids. The
aim of this research is to provide an overview of LNAPLs in South African urban areas,
transport mechanism of the LNAPLs in the subsurface, framework for detecting and
evaluating LNAPLs under South African conditions.
LNAPL is a convenient label for petroleum liquids in soils and groundwater. The
acronym stands for Light Non Aqueous Phase Liquid. âLightâ highlights the fact that
petroleum liquids (i.e., gasoline) are less dense than water; âNon Aqueousâ highlights
the fact that petroleum is not completely miscible in water.
An LNAPL contamination assessment was conducted at a service station after a
complaint was raised by a resident who found free product (petrol) in her borehole. A
multitude of private boreholes were found during the hydrocensus survey. A petroleum
contamination assessment was done through soil vapour survey (SVS), hand auger
holes and rotary percussion drilling. No significant petroleum vapours were detected due
to clay soil which has low transmission of vapours. Hand auger holes were restricted to
shallow depth due to the lack of penetration though the clay soils. Percussion drilling
was needed to gather groundwater information (i.e., quality and quantity). Free product
(petrol) was found within the percussion and some of the private boreholes.
Groundwater samples were collected and analyzed for BTEX (Benzene, Toluene, Ethyl
benzene and Xylenes) compounds. No detectable levels of BTEX were found in the soil
samples. Risk assessment was done suing the RBCA approach and BP RISC software.
BTEX concentrations of groundwater samples have triggered the Tier 1 risk based
screening level for the risk values of carcinogenic and non-carcinogenic through
groundwater ingestion, indoor and outdoor vapour inhalation exposure pathways. BP
RISC was used to conduct Tier 2 evaluation and carcinogenic risk does exist in the
receptor borehole through groundwater ingestion risk pathway. AQUA-WIN finite
element model was used to determine the abstraction rate that could be used to conduct
a pump-and-treat system. Free product could be recovered within two years after
commencing with pump and treat system. Due to the lack of South African regulations
with regard to petroleum contamination, the pump and treat system was stopped as soon as the product was recovered and monitoring of the dissolved phase hydrocarbons
was continued.
The establishment of South African guidelines and risk assessment protocols for
petroleum hydrocarbons is outlined and strongly recommended for implementation.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-08252006-131339 |
| Date | 25 August 2006 |
| Creators | Phophi, Thilivhali Samuel |
| Contributors | Dr BH Usher |
| Publisher | University of the Free State |
| Source Sets | South African National ETD Portal |
| Language | en-uk |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.uovs.ac.za//theses/available/etd-08252006-131339/restricted/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University Free State or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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