Polychlorinated Biphenyls (PCBs) are hazardous and toxic chemicals to both humans and
animals. In the late 1960’s PCBs were discovered to be a harmful pollutant which could cause
environmental contamination due to its slow degradation and even trace amounts of PCBs were
regarded as toxic to both human and animals.
Oil spills are a frequent occurrence at Eskom substations which could contain PCBs. The
contaminated sediments which are easily carried away by rain and wind can further
contaminate the environment and aquatic bodies. Eskom currently disposes of soil and ballast
stones contaminated with PCBs by thermal destruction. This is a costly process as PCBs are
regarded as hazardous materials and needs to be safely transported and disposed of at a licensed
disposal facility.
Based on literature, ozone has been used on a laboratory scale to treat soil contaminated with
PCBs with the addition of chemicals such as hexane and acetone which assist in breaking down
PCBs. The objective of this study was to evaluate whether ozone without the addition of
chemicals could reduce the levels of PCBs present in contaminated soil. In this study, two soil
samples and one ballast stone sample were contaminated with 50 ppm, 200 ppm and 600 ppm
of PCBs and then exposed to 0.4, 0.5 and 0.6 l/min of ozone for a period of 60 minutes to
examine the effects of increasing ozone flow rates on PCB destruction in soil.
The results of the experimental tests showed that ozone gas reduced the concentration of PCBs
in the soil and ballast stone samples for the different total gas flow rates. The literature study
identified that the final products of the ozonation of PCBs are carbon dioxide and water and that
any products formed after this process could possibly be degraded by the soil natural
microorganisms.
Calculations based on the Shin et al. (2004) model proved that ozone was in excess after the
ozonation process. The results of the experiments also confirmed this, as the PCB residuals
were similar for all three total gas flows, which showed that there was no dependence on the gas
flow rates hence, ozone was in excess. The experimental data was then trended with zero, first
and second order reaction equations, which showed that the best fit was obtained with the firstorder
reaction equation. It is recommended that ozone be used for the treatment of PCB
contaminated soil at Eskom substations. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2011.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ukzn/oai:http://researchspace.ukzn.ac.za:10413/5095 |
| Date | January 2011 |
| Creators | Moodley, Shanita Jeewan. |
| Contributors | Milan, C. |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
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