Advanced Oxidation Remediation And Post Health Risk Assessment Of Petroleum-Contaminated Sediment In The Tidal Flats

In recent decades, oil has become the lifeblood of economic and social development in China, but in the process of offshore oil exploitation and transportation, oil spill accidants often occured that can cause serious ecological environmental crisis at beaches and surrounding waters. The purpose of this paper was to study the remediation effect of oil-polluted tidal flats by advanced oxidation techniques, while the application of post risk assessment in the pollunted flats was also investigated and the risk control value models of TPH was derivated to verify the feasibility of advanced oxidation at tidal flats. The main contents in this thesis included:(1) the removal effect of TPH and each fraction by Fenton, modified Fenton and Na2S2O8, and the tidal action’s influence on the removal of TPH; (2) the removal effect of TPH by activated CaO2, and verified the acitive component; (3) post risk assessment for the polluted flats and establishment the risk control value models of TPH to prove the feasibility of advanced oxidation at tidal flats. The main results were showed below:(1) When the molar ratio of FeSO4/H2O2 or Fe2(SO4)3/H2O2 was 0.1 and the mass ratio of H2O2/sediment was 0.05, the removal rate of TPH was 48.9% and 57.4% by Fention and modified Fenton respectively, and the removal effect by Fenton was greater than modified Fenton. For the degradation of each fraction, the middle carbon fraction(Cio-Ci6) could be easily oxidized into low carbon fractions (<Cio, volatile) and even CO2 and H2O which could volatize away easily. However, for high carbon fractions (>C16), part of them could be directly oxidized into low carbon, volatile compounds and even CO2 and H2O which could be removed easily, there was also part of high carbon compounds which could be oxidized into middle carbon compounds that would still remain in the sediment. Tidal action could promote the degradation effience of TPH by Fenton.(2) When Na2S2O8 was added into the polluted sediment separately, more than 46% of TPH was removed at the Na2S2O8/sediment mass ratio of more than 0.01. The TPH removal rate could be increased by Na2S2O8 that was activated by ferrous salt, alkali or heat. As the mass ratio of Na2S2O8/sediment was 0.01, molar ratio of FeSO4/Na2S2O8, molar ratio of CaO/Na2S2O8 and catalytic temperature were 0.05,0.9 and 50℃, as high as 60.4%,51.3% and 59.8% of TPH respectively were removed respectively. The degradation of each fraction by activated Na2S2O8 was the same as Fenton process, but the tidal action had inhibitory effect on the degradation of TPH by activated Na2S2O8 techique.(3) Petroleum contaminants could be removed by activated CaO2. The order of influencing factors was:reaction time>mass ratio of Na2EDTA/sediment>mass ratio of CaO2/sediment>volume ratio of water/sediment>mass ratio of FeSO4·7H2O/sediment. The corresponding optimal levels of all influencing factors were:168 h,0.05,0.02,2.5 and 0.05. After the reaction at the optimal condition mentioned above, the removal rate of TPH reached to 64.43%; at the same times, quenching experiments proved the existence of active ingredient ’OH.(4) The post assessment results showed that the risk control calculation value of TPH was 1614.2 mg/kg, suggesting that the advanced oxidation technologies could be used in the remediation of the oil-polluted tidal flats.