Publicação
Valorization of oilfield wastewater for production of bacterial lipids
| Resumo: | Oil and gas industry are responsible for the generation of large volumes of hydrocarbon-contaminated wastewaters. In order to minimize its negative impact on the environment and public health, strict regulations were developed for its treatment and discharge into the sea, leading to a search for innovative and more sustainable strategies for its management. The aim of this thesis is to explore the feasibility of a biological process for the treatment of mineral oil wastewaters coupled with its valorization towards the production of added-value compounds. The efficient treatment of saline oilfield PW, generated during petroleum extraction process, and lubricant-based wastewater (LW) coupled with neutral lipid production by Alcanivorax borkumensis SK2 and Rhodococcus opacus B4 was demonstrated in a sequencing batch airlift reactor (SBAR). Different operational conditions (e.g. cycle duration and carbon/nitrogen ratio (Total petroleum hydrocarbons (TPH)/N)) were tested in order to optimize the treatment efficiency, 96 % and 80 % of TPH removal efficiencies in SBARAb+PW and SBARR.o+LW, respectively, and maximize lipids accumulation (85 % and 94 % of the cellular dry weight (CDW) in SBARAb+PW and SBARR.o+LW, respectively). The nitrogen availability (low TPH/N ratios) influenced the production of TAGs and WEs by A. borkumensis SK2, while the carbon source concentration (high TPH/N ratios) was determinant for the accumulation of TAGs by R. opacus B4. Furthermore, the effect of oxygen concentration on the treatment of PW in a SBAR operation was evaluated. The selection of the oxygen concentration applied allowed to direct A. borkumensis SK2 metabolism to a particular type of storage compound (TAGs, WEs or polyhydroxyalkanoates (PHAs)) maintaining a TPH removal efficiency of 90 - 95%. A. borkumensis SK2 produced a cell-bound and an extracellular biosurfactant in order to increase hydrocarbons availability and up-take, showing that PW valorization towards the production of surface-active compounds is possible. Finally, the efficient treatment of saline oilfield PW (90 - 92 % of TPH removal efficiencies) and neutral lipids production by A. borkumensis SK2 in a continuous airlift operation was shown. Was observed that the TPH/N ratio applied to the bioreactor did not influence hydrocarbons biodegradation and intracellular lipid accumulation, however an improvement on WEs and TAGs excretion was observed when lower TPH/N ratios were applied. |
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| Autores principais: | Silva, Ana Rita Marques |
| Assunto: | Biological treatment Hydrocarbons bacterial lipids hydrocarbonoclastic bacteria wastewater Tratamento biológico hidrocarbonetos lípidos bacterianos bactérias hidrocarbonoclásticas águas residuais |
| Ano: | 2021 |
| País: | Portugal |
| Tipo de documento: | tese de doutoramento |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade do Minho |
| Idioma: | inglês |
| Origem: | RepositóriUM - Universidade do Minho |
| Resumo: | Oil and gas industry are responsible for the generation of large volumes of hydrocarbon-contaminated wastewaters. In order to minimize its negative impact on the environment and public health, strict regulations were developed for its treatment and discharge into the sea, leading to a search for innovative and more sustainable strategies for its management. The aim of this thesis is to explore the feasibility of a biological process for the treatment of mineral oil wastewaters coupled with its valorization towards the production of added-value compounds. The efficient treatment of saline oilfield PW, generated during petroleum extraction process, and lubricant-based wastewater (LW) coupled with neutral lipid production by Alcanivorax borkumensis SK2 and Rhodococcus opacus B4 was demonstrated in a sequencing batch airlift reactor (SBAR). Different operational conditions (e.g. cycle duration and carbon/nitrogen ratio (Total petroleum hydrocarbons (TPH)/N)) were tested in order to optimize the treatment efficiency, 96 % and 80 % of TPH removal efficiencies in SBARAb+PW and SBARR.o+LW, respectively, and maximize lipids accumulation (85 % and 94 % of the cellular dry weight (CDW) in SBARAb+PW and SBARR.o+LW, respectively). The nitrogen availability (low TPH/N ratios) influenced the production of TAGs and WEs by A. borkumensis SK2, while the carbon source concentration (high TPH/N ratios) was determinant for the accumulation of TAGs by R. opacus B4. Furthermore, the effect of oxygen concentration on the treatment of PW in a SBAR operation was evaluated. The selection of the oxygen concentration applied allowed to direct A. borkumensis SK2 metabolism to a particular type of storage compound (TAGs, WEs or polyhydroxyalkanoates (PHAs)) maintaining a TPH removal efficiency of 90 - 95%. A. borkumensis SK2 produced a cell-bound and an extracellular biosurfactant in order to increase hydrocarbons availability and up-take, showing that PW valorization towards the production of surface-active compounds is possible. Finally, the efficient treatment of saline oilfield PW (90 - 92 % of TPH removal efficiencies) and neutral lipids production by A. borkumensis SK2 in a continuous airlift operation was shown. Was observed that the TPH/N ratio applied to the bioreactor did not influence hydrocarbons biodegradation and intracellular lipid accumulation, however an improvement on WEs and TAGs excretion was observed when lower TPH/N ratios were applied. |
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