Petroleum hydrocarbon (PHC) contamination poses a serious threat to aquifer systems worldwide. Accidental releases of PHCs due to gasoline spills and leakage from underground storage tanks can often result in PHC subsurface contamination. The main compounds of concern associated with gasoline spills are benzene, toluene, ethylbenzene and xylenes (BTEX), trimethylbenzenes (TMBs) and naphthalene, due to their high mobility and potential human health risks. Sodium persulphate is one of the newest oxidants to gain widespread use for in situ chemical oxidation (ISCO), however its effectiveness in treating PHCs is not fully understood. In this study, the ability to use unactivated sodium persulphate as a remediation tool in treating dissolved and residual BTEX contamination was tested during a bench-scale laboratory study and within a pilot-scale field investigation. In both cases unactivated sodium persulphate was used at a concentration of 100 g/L. A laboratory-scale degradation potential batch test was conducted to assess the efficacy of unactivated sodium persulphate to oxidize petroleum hydrocarbon contaminated groundwater in conjunction with aquifer material from a field site. Data from the control reactions indicated that persulphate was stable for the entire 35-day experimental period and that the decrease in PHC concentrations for most of the samples followed a first-order degradation. The behaviour and ability for sodium persulphate to oxidize dissolved and residual BTEX contamination was further evaluated in a controlled pilot scale field study. 200 kg of sodium persulphate was dissolved in 2000 L of water and injected into the subsurface. Electrical conductivity (EC), pH, sodium, persulphate, sulphate and BTEX concentrations were all monitored throughout the 158-day study period. Field research showed that there was a strong correlation between EC and sodium concentrations. Hence, this relationship allowed for real-time EC measurements to be used to effectively predict the extent of the injectate. Based on the calculated aqueous density of sodium persulphate at a concentration of 100g/L, predicted simulation model results and observed tracer field results, density effects were present and played a very important role in the transport of the injectate. The heterogeneous geology of the site also greatly influenced the transport of the injectate. The majority of the injectate appeared to have flowed out of the layers with higher hydraulic conductivity that intersected the upper and lower portion of the injection well’s screen length. The extent of the injected slug in the layers with lower hydraulic conductivity located in the centre portion of the injection well’s screen length was less in comparison. In general, areas with elevated tracer, persulphate and sulphate concentrations, also showed a decrease in BTEX concentration. Four main responses were observed. Group 1 consists of sampling points where tracer levels were elevated along with a corresponding short-term decrease in dissolved BTEX. Group 2 consists of sampling points where elevated tracer levels was observed along with a long-term apparent decrease in dissolved BTEX. Group 3 consists of sampling points where the tracer was elevated however dissolved BTEX levels remained essentially at background levels. And finally, group 4 consists of sampling points where the tracer was not observed to be elevated hence no decrease in dissolved BTEX was observed. Laboratory studies showed that the oxidation of BTEX compounds by unactivated sodium persulphate could be very successful. However, field study results showed that complexities such as heterogeneity of the field site and injectate density effects play a key role in the success of the remediation system.

Petroleum hydrocarbon (PHC) contamination poses a serious threat to aquifer systems worldwide. Accidental releases of PHCs due to gasoline spills and leakage from underground storage tanks can often result in PHC subsurface contamination. The main compounds of concern associated with gasoline spills are benzene, toluene, ethylbenzene and xylenes (BTEX), trimethylbenzenes (TMBs) and naphthalene, due to their high mobility and potential human health risks. Sodium persulphate is one of the newest oxidants to gain widespread use for in situ chemical oxidation (ISCO), however its effectiveness in treating PHCs is not fully understood. In this study, the ability to use unactivated sodium persulphate as a remediation tool in treating dissolved and residual BTEX contamination was tested during a bench-scale laboratory study and within a pilot-scale field investigation. In both cases unactivated sodium persulphate was used at a concentration of 100 g/L. A laboratory-scale degradation potential batch test was conducted to assess the efficacy of unactivated sodium persulphate to oxidize petroleum hydrocarbon contaminated groundwater in conjunction with aquifer material from a field site. Data from the control reactions indicated that persulphate was stable for the entire 35-day experimental period and that the decrease in PHC concentrations for most of the samples followed a first-order degradation. The behaviour and ability for sodium persulphate to oxidize dissolved and residual BTEX contamination was further evaluated in a controlled pilot scale field study. 200 kg of sodium persulphate was dissolved in 2000 L of water and injected into the subsurface. Electrical conductivity (EC), pH, sodium, persulphate, sulphate and BTEX concentrations were all monitored throughout the 158-day study period. Field research showed that there was a strong correlation between EC and sodium concentrations. Hence, this relationship allowed for real-time EC measurements to be used to effectively predict the extent of the injectate. Based on the calculated aqueous density of sodium persulphate at a concentration of 100g/L, predicted simulation model results and observed tracer field results, density effects were present and played a very important role in the transport of the injectate. The heterogeneous geology of the site also greatly influenced the transport of the injectate. The majority of the injectate appeared to have flowed out of the layers with higher hydraulic conductivity that intersected the upper and lower portion of the injection well’s screen length. The extent of the injected slug in the layers with lower hydraulic conductivity located in the centre portion of the injection well’s screen length was less in comparison. In general, areas with elevated tracer, persulphate and sulphate concentrations, also showed a decrease in BTEX concentration. Four main responses were observed. Group 1 consists of sampling points where tracer levels were elevated along with a corresponding short-term decrease in dissolved BTEX. Group 2 consists of sampling points where elevated tracer levels was observed along with a long-term apparent decrease in dissolved BTEX. Group 3 consists of sampling points where the tracer was elevated however dissolved BTEX levels remained essentially at background levels. And finally, group 4 consists of sampling points where the tracer was not observed to be elevated hence no decrease in dissolved BTEX was observed. Laboratory studies showed that the oxidation of BTEX compounds by unactivated sodium persulphate could be very successful. However, field study results showed that complexities such as heterogeneity of the field site and injectate density effects play a key role in the success of the remediation system.

The contamination of aquifer systems by petroleum hydrocarbons is a global problem. Underground storage tanks used for storing these hydrocarbons often leak, resulting in subsurface contamination. The hazards associated with petroleum hydrocarbon contamination are mainly attributable to the BTEX compounds, namely benzene, toluene, ethylbenzene and xylenes together with trimethylbenzenes (TMBs) and naphthalene due to their potential to impact human health and the ease with which they can enter the groundwater system. In situ chemical oxidation (ISCO) is the delivery of strong chemical oxidants to the subsurface for the purpose of treating organic contaminants. ISCO can be an effective way to remediate organic contaminants from the soil and groundwater. Sodium persulphate is one of the newer oxidants to gain widespread use in treating petroleum hydrocarbon contamination, though without being fully understood. This investigation tested the ability of unactivated sodium persulphate in treating dissolved phase and residual BTEX contamination through bench-scale laboratory tests and a pilot-scale field study. A degradation potential batch reactor test was carried out to assess the efficacy of unactivated sodium persulphate in oxidizing petroleum hydrocarbons present in contaminated groundwater as well as its effect on aquifer material from a field site. This test was carried out at a sodium persulphate concentration of 20 g/L. Results from this test did not follow the expected first-order degradation, and so subsequent experiments were carried out using a sodium persulphate concentration of 100 g/L. A test to determine the degree of interaction between the oxidant and aquifer material was also conducted. It was found that the degree of natural oxidant interaction for the field site in question was very low. 1000 kg of sodium persulphate was dissolved in nearly 10,000 L of water and injected into the subsurface. Electrical conductivity (EC), pH, sodium, persulphate, sulphate and BTEX were all monitored during the subsequent 152-day post-injection monitoring period. An empirical relationship was determined between EC and the concentration of sodium in groundwater. This enabled the use of EC as a real-time tracer to track the progress of the injectate. Field results supported predictions based on a simulation model that density-driven flow would play an important role in the delivery of the injectate. A portion of the injectate was believed to have been missed by the monitoring network. Areas that did show elevated tracer results in some cases showed a decrease in BTEX concentrations. Results were categorized in four ways. The first category had wells that showed strong evidence of injectate presence but little to no change in BTEX levels. The second category was comprised of wells that showed a reduction in BTEX levels along with the presence of injectate. BTEX levels in some wells rebounded towards the end of the study period. The third category consisted of wells that showed the presence of dilute injectate but did not show any reduction in BTEX concentrations. The fourth and final category was of wells that showed no evidence of having been affected by the injectate in any way. BTEX levels were the same as background. The oxidation of BTEX by unactivated sodium persulphate was found to be successful, though the vagaries of oxidant delivery and field sampling made difficult the accurate determination of the degree of success.

The contamination of aquifer systems by petroleum hydrocarbons is a global problem. Underground storage tanks used for storing these hydrocarbons often leak, resulting in subsurface contamination. The hazards associated with petroleum hydrocarbon contamination are mainly attributable to the BTEX compounds, namely benzene, toluene, ethylbenzene and xylenes together with trimethylbenzenes (TMBs) and naphthalene due to their potential to impact human health and the ease with which they can enter the groundwater system. In situ chemical oxidation (ISCO) is the delivery of strong chemical oxidants to the subsurface for the purpose of treating organic contaminants. ISCO can be an effective way to remediate organic contaminants from the soil and groundwater. Sodium persulphate is one of the newer oxidants to gain widespread use in treating petroleum hydrocarbon contamination, though without being fully understood. This investigation tested the ability of unactivated sodium persulphate in treating dissolved phase and residual BTEX contamination through bench-scale laboratory tests and a pilot-scale field study. A degradation potential batch reactor test was carried out to assess the efficacy of unactivated sodium persulphate in oxidizing petroleum hydrocarbons present in contaminated groundwater as well as its effect on aquifer material from a field site. This test was carried out at a sodium persulphate concentration of 20 g/L. Results from this test did not follow the expected first-order degradation, and so subsequent experiments were carried out using a sodium persulphate concentration of 100 g/L. A test to determine the degree of interaction between the oxidant and aquifer material was also conducted. It was found that the degree of natural oxidant interaction for the field site in question was very low. 1000 kg of sodium persulphate was dissolved in nearly 10,000 L of water and injected into the subsurface. Electrical conductivity (EC), pH, sodium, persulphate, sulphate and BTEX were all monitored during the subsequent 152-day post-injection monitoring period. An empirical relationship was determined between EC and the concentration of sodium in groundwater. This enabled the use of EC as a real-time tracer to track the progress of the injectate. Field results supported predictions based on a simulation model that density-driven flow would play an important role in the delivery of the injectate. A portion of the injectate was believed to have been missed by the monitoring network. Areas that did show elevated tracer results in some cases showed a decrease in BTEX concentrations. Results were categorized in four ways. The first category had wells that showed strong evidence of injectate presence but little to no change in BTEX levels. The second category was comprised of wells that showed a reduction in BTEX levels along with the presence of injectate. BTEX levels in some wells rebounded towards the end of the study period. The third category consisted of wells that showed the presence of dilute injectate but did not show any reduction in BTEX concentrations. The fourth and final category was of wells that showed no evidence of having been affected by the injectate in any way. BTEX levels were the same as background. The oxidation of BTEX by unactivated sodium persulphate was found to be successful, though the vagaries of oxidant delivery and field sampling made difficult the accurate determination of the degree of success.

Este trabalho de mestrado descreve a avaliação do emprego de radicais sulfato (SO42-.), obtidos a partir do oxidante persulfato de potássio (K2S2O8) , na degradação de soluções aquosas de fenol. A deterioração dos recursos hídricos tem assumido um caráter preocupante uma vez que as demandas deste bem estão se tornando cada vez maiores. Dentre os compostos responsáveis pela degradação da qualidade dos sistemas aquáticos, destacam-se os compostos orgânicos poluentes como os organoclorados, organofosforados, carbamatos, triazinas, hidrocarbonetos aromáticos polinucleares, fenólicos, etc. Dentre esta série de compostos poluentes, atenção especial tem sido dada ao fenol devido as grandes quantidades em que são gerados e pela diversidade tipos de atividades produtivas que o empregam. Assim, este trabalho avaliou a aplicação de radical SO4 2- do fenol Estudos utilizando ressonância paramagnética eletrônica (EPR) mostraram que o radical SO42- é a principal espécie radicalar obtida a partir da fotólise e termólise do oxidante S2O8-2. A presença de radiação UV contribuiu beneficamente para a degradação do composto orgânicos. Altas temperaturas como 40 0C e 70 <SÙP>0C também levaram a uma maior taxa na degradação do fenol devido a uma maior produção de espécies radicalares oxidantes. Além dos processos fotoassistidos e térmicos, investigou-se também processos de geração dos radicais a partir da ativação do oxidante em diferentes pH (3,0, 5,0, 7,0 e 9,0) e tambem na presença de metais de transição (Co2+, Mn2+, Fe2+, Fe3+ e Cu2+). A processo não foi afetada pelo pH. Com relação a presença dos metais de transição na solução obteve-se um ganho na eficiência do processo principalmente com o emprego do Fe2+, caracterizando a reação como uma reação do tipo Fenton. De uma maneira geral a utilização de SO4 2- na degradação de fenol mostrou-se bastante promissora para uma aplicação deste processo no tratamento de efluentes contendo estes compostos. / This work describes the evaluation of radicals sulphate (SO42-), obtained from the oxidant potassium persulphate (K2S2O8), in the degradation of phenol aqueous solutions. The deterioration of the aquatic resources has been assumed a preoccupying situation, since a time its demands has been increased constantly. Amongst many compounds in the degradation of aquatic systems quality, special attention has been dispensed to organic compounds such as organochlorinated, organophosphorated, aromatic carbamates, triazines, polynuclear hydrocarbons, phenolic, etc. This work evaluated the application of SO42- radicals in the degradation of phenol. Studies using electron paramagnetic resonance (EPR) showed that SO4-2 is the main radical species obtained by the S2O8-2 oxidant photolysis and thermolysis. The presence of UV radiation contributed to improve phenol degradation due to the increase in oxidant radicals production. Higher temperatures (40 0C and 70 0C) have also led to an increment in the phenol degradation rate. Beyond the photoassisted and thermal processes, it was also investigated processes of radicals\' generation from the activation of the oxidant in different pH (3.0, 5.0, 7.0 and 9.0) and also in the presence of transition metals (Co2+, Mn2+ , Fe2+ , Fe3+ and Cu2+ ). The efficiency of the process was not affected by the pH. On the other hand, the presence of transition metals in the solution led to considerably better degradation rates, specially applying Fe2+, which could be characterized as a Fenton-like reaction. In a general way, the use of SO42- in the phenol degradation showed promising results for its future application in the treatment of effluent containing these composites.

Este trabalho de mestrado descreve a avaliação do emprego de radicais sulfato (SO42-.), obtidos a partir do oxidante persulfato de potássio (K2S2O8) , na degradação de soluções aquosas de fenol. A deterioração dos recursos hídricos tem assumido um caráter preocupante uma vez que as demandas deste bem estão se tornando cada vez maiores. Dentre os compostos responsáveis pela degradação da qualidade dos sistemas aquáticos, destacam-se os compostos orgânicos poluentes como os organoclorados, organofosforados, carbamatos, triazinas, hidrocarbonetos aromáticos polinucleares, fenólicos, etc. Dentre esta série de compostos poluentes, atenção especial tem sido dada ao fenol devido as grandes quantidades em que são gerados e pela diversidade tipos de atividades produtivas que o empregam. Assim, este trabalho avaliou a aplicação de radical SO4 2- do fenol Estudos utilizando ressonância paramagnética eletrônica (EPR) mostraram que o radical SO42- é a principal espécie radicalar obtida a partir da fotólise e termólise do oxidante S2O8-2. A presença de radiação UV contribuiu beneficamente para a degradação do composto orgânicos. Altas temperaturas como 40 0C e 70 <SÙP>0C também levaram a uma maior taxa na degradação do fenol devido a uma maior produção de espécies radicalares oxidantes. Além dos processos fotoassistidos e térmicos, investigou-se também processos de geração dos radicais a partir da ativação do oxidante em diferentes pH (3,0, 5,0, 7,0 e 9,0) e tambem na presença de metais de transição (Co2+, Mn2+, Fe2+, Fe3+ e Cu2+). A processo não foi afetada pelo pH. Com relação a presença dos metais de transição na solução obteve-se um ganho na eficiência do processo principalmente com o emprego do Fe2+, caracterizando a reação como uma reação do tipo Fenton. De uma maneira geral a utilização de SO4 2- na degradação de fenol mostrou-se bastante promissora para uma aplicação deste processo no tratamento de efluentes contendo estes compostos. / This work describes the evaluation of radicals sulphate (SO42-), obtained from the oxidant potassium persulphate (K2S2O8), in the degradation of phenol aqueous solutions. The deterioration of the aquatic resources has been assumed a preoccupying situation, since a time its demands has been increased constantly. Amongst many compounds in the degradation of aquatic systems quality, special attention has been dispensed to organic compounds such as organochlorinated, organophosphorated, aromatic carbamates, triazines, polynuclear hydrocarbons, phenolic, etc. This work evaluated the application of SO42- radicals in the degradation of phenol. Studies using electron paramagnetic resonance (EPR) showed that SO4-2 is the main radical species obtained by the S2O8-2 oxidant photolysis and thermolysis. The presence of UV radiation contributed to improve phenol degradation due to the increase in oxidant radicals production. Higher temperatures (40 0C and 70 0C) have also led to an increment in the phenol degradation rate. Beyond the photoassisted and thermal processes, it was also investigated processes of radicals\' generation from the activation of the oxidant in different pH (3.0, 5.0, 7.0 and 9.0) and also in the presence of transition metals (Co2+, Mn2+ , Fe2+ , Fe3+ and Cu2+ ). The efficiency of the process was not affected by the pH. On the other hand, the presence of transition metals in the solution led to considerably better degradation rates, specially applying Fe2+, which could be characterized as a Fenton-like reaction. In a general way, the use of SO42- in the phenol degradation showed promising results for its future application in the treatment of effluent containing these composites.