Development and evaluation of a remediation strategy for the oil lakes of Kuwait
Student thesis: Doctoral Thesis
During the occupation of Kuwait by Iraq in 1990/1991, Iraq’s armed forces destroyed more than 700 oil wells. The resulting oil flowed out and formed a large number of oil lakes. This also led to the contamination of soil, which has been left untreated in the deserts of Kuwait for more than two decades now. The untreated contaminated soil has the tendency to pollute the underground watercourses as well as affecting the ecology and humans health. Laboratory scale experiments were carried out to assess the efficiency of soil washing according to the removal of the oil residue. A non-ionic biosurfactant, “saponin”, was employed under a range of conditions (different water type, washing time, stirrer speed, surfactant concentrations, temperature and mass/volume ratio). Results identified that the optimum washing parameters in terms of time, stirrer speed, surfactant concentrations, temperature, mass/volume ratio were found to be 20 min, 1,000 rpm, 0.5 wt% (weight percent solutions), 50oC and ratio of 1:3, respectively. The optimum washing parameters were investigated under varying washing modes namely, mechanical stirrer, ultrasonication, combination of ultrasonication and mechanical stirrer and combination of mechanical vibration and stirrer. The removal efficiency of oil residue generally enhanced with the sequential washing, results showed that 90 %, 80 %, 75 % and 60 % of total petroleum hydrocarbons (TPH) was removed after the third wash by using the combination of ultrasonication and mechanical stirrer, mechanical stirrer, ultrasonication, combination of mechanical vibration and stirrer, respectively. The soil washing by using combination of ultrasonication and mechanical stirrer reduced the mean values of TPH from 330,000 to 10,000 mg/kg, which are lowered than the upper limits (TPH <10,000 mg/kg) of Kuwait Environmental Protection Agency (KEPA). Samples of contaminated sand were analysed by gravimetric method. This approach of soil washing would be a promising alternative for remediation of Kuwait oil contaminated sand. It was found that the soil washing process aided the oil residue to be transferred from solid to the aqueous phase. Wastewater obtained from soil washing technique was investigated by using various wastewater treatment (adsorption, anoxic treatment, aeration treatment, combination of anoxic treatment with coagulation/flocculation and combination of aeration treatment with coagulation/flocculation). The combination of anoxic treatment with coagulation/flocculation and combination of aeration with coagulation/flocculation were capable of lowering the mean of COD values from 48,000 mg/l to 14,110 mg/l and 4,784 mg/l, respectively. This investigation suggests that combination of aeration with coagulation/flocculation proved an effective technique to treat the oily wastewater. This project investigates the potential use of oil-contaminated sand containing TPH <10,000mg/kg on some engineering properties of hardened concrete by its experimental evaluation of its workability by slump test, compressive strength, hammer test and water absorption test using British Standard (BS) methods. The results of this investigation found that no major change was noted for the slump test conducted either with the contaminated specimens or clean specimens. while sand containing less than 10,000 mg/kg crude oil contaminants was able to reduce the compressive strength of the concrete by about 17.0 %. Enhancement of water absorption on average by the oil contaminated sand was about three times than that of clean sand. Direct detection of saponins in soapnuts (Sapindus mukorossi) using fourier transform infrared (FTIR) spectroscopy is investigated in this project. Potassium bromide (KBr) powder was mixed with dry extracted powder of soapnuts and compressed to a thin pellet for examination process. The outcome of the FTIR spectra of saponin demonstrated characteristic triterpenoid saponin absorptions of OH, C=O, C-H, and C=C, while the glycoside linkages to the sapogenins were indicated by the absorptions of C-O. The significance of this study is that saponin absorption peaks are directly detectable in crude aqueous and 95.0 d% ethanol extracts of soapnuts powder using FTIR spectroscopy thereby eliminating the need of further expensive and exhaustive purification steps. The extracts of soapnuts were screened for saponins along with controls by phytochemical tests, while advanced spectroscopic techniques like ultrafast liquid chromatography (UFLC) and ultra-performance liquid chromatography quadrupole-time of flight-mass spectrometry (UPLC-QTOF-MS/MS) were also implemented to validate the saponins.
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