Geophysical characterization of subsurface biofuel contamination and biodegradation

In the last two decades, the production of ethanol (EtOH), one of the most common biofuels in the USA, has substantially increased due to regulations aiming at reducing air pollution and providing a supplement to petroleum. Scenarios of large spills of EtOH during production, transportation and at storage facilities are likely. Accidental release of EtOH and its persistence in the subsurface pose threats to human health and the environment, including the deterioration of municipal water supplies. Thus, there is a need to develop adequate monitoring tools to help with the remediation efforts of subsurface EtOH contamination. Ethanol presence, interaction and biodegradation could substantially alter the electrical properties of geologic materials, thereby potentially leading to distinctive geophysical responses. This dissertation demonstrates the potential application of non-invasive and cost effective complex resistivity (CR) technique for the characterization of biofuel contamination and biodegradation in the subsurface. The first research topic examined the electrical geophysical signatures arising from groundwater contamination by EtOH. Conductivity measurements were performed at the laboratory scale on EtOH-water mixtures (0 to 0.97 v/v EtOH) and EtOH-salt solution mixtures (0 to 0.99 v/v EtOH) with and without a sand matrix. A mixing model was used to simulate electrical conductivity as a function of EtOH concentration in the mixture. It was found that increasing EtOH concentration resulted in a decrease in measured conductivity magnitude ( ), which reflected changes in relative strength of the types of interactions occurring in EtOH-water mixtures. The second research topic explored the electrical properties associated with EtOH-clay interactions using CR measurements on laboratory columns of varying ethanol (EtOH) concentration (0% to 30% v/v) in a sand-clay (bentonite) matrix. A Debye Decomposition approach was applied to fit the CR data. Overall, the results showed a significant suppression (P ≤ 0.001) of the clay driven polarization with increasing EtOH concentration. The suppression effects are associated with alterations in the electrical double layer (EDL) at the clay-fluid interface due to strong EtOH adsorption on clay and complex intermolecular EtOH-water interactions. The persistent EtOH adsorption on clay also indicated strong hysteresis effects in the electrical response. The third research topic investigated changes in electrical properties during EtOH biodegradation processes in sand matrix using CR measurements in conjunction with geochemical data analysis on microbial stimulated (inoculation of bacterial cells) and control (without bacteria inoculation) columns. A Debye Decomposition approach was applied to fit the CR data. Overall, the results showed a clear distinction between the bio-stimulated and control columns in terms of real ( ) and imaginary ( ) conductivity, phase ( ) and apparent formation factor (Fapp). Temporal geochemical changes and high resolution scanning electron microscopy imaging corroborated the CR findings, thus indicating the sensitivity of CR measurements to EtOH biodegradation processes.Ph.D.Includes bibliographical referencesIncludes vitaby Yves Robert Personn

Pore-scale spectral induced polarization (SIP) signatures associated with FeS biomineral transformations

The authors measured Spectral Induced Polarization (SIP) signatures in sand columns during (1) FeS biomineralization produced by sulfate reducing bacteria (D. vulgaris) under anaerboci conditions, and (2) subsequent biomineral dissolution upon return to an aerobic state. The low-frequency (0.1-10 Hz peak) relaxations produced during biomineralization can be modeled with a Cole-Cole formulation, from which the evolution of the polarization magnitude and relaxation length scale can be estimated. They find that the modeled time constant is consistent with the polarizable elements being biomineral encrused pores. Evolution of the model parameters is consistent with FeS surface area increases and pore-size reduction during biomineral growth, and subsequent biomineral dissolution (FeS surface area decreases and pore expansion) upon return to the aerobic state. They conclude that SIP signatures are diagnostic of pore-scale geometrical changes associated with FeS biomineralization by sulfate reducing bacteria

Pore-scale spectral induced polarization (SIP) signatures associated with FeS biomineral transformations

Kerupuk merupakan makanan ringan khas asli Indonesia yang menjadi hidangan pendamping pada beberapa masakan-masakan Indonesia. Proses pembuatan kerupuk meliputi pencampuran bahan baku, pembuatan adonan, pencetakan, pengukusan, pendinginan, pengirisan, pengeringan, dan pemasakan. Dari beberapa proses pembuatan kerupuk tersebut, ada satu proses yang cukup penting diperhatikan yaitu proses pemotongan kerupuk. Hasil pengamatan yang dilakukan di UMKM Srikandi Sumber Laut yang berfokus pada olahan hasil laut menunjukkan bahwa pemillik UMKM masih menggunakan alat pemotong kerupuk secara manual. Untuk memenuhi permintaan konsumen, pemilik menginginkan alat pemotong kerupuk agar dapat menghasilkan kuantitas yang banyak dan kualitas potongan kerupuk yang baik (ukuran dan dimensi kerupuk yang seragam). Dalam penelitian ini digunakan metode TRIZ dalam merancangan ulang alat pemotong kerupuk. Hasil dari penelitian ini yaitu bentuk pisau yang dibuat melengkung, pemotongan 3 adonan dalam 1 rotasi. Penggunaan baja JIS SKD 11 sebagai bahan dasar pisau utama agar dapat memotong lontongan kerupuk dengan bai

Dual effects of a dispersant and nutrient supplementation on weathered Endicott oil biodegradation in seawater

Laboratory-scale experiments were conducted to evaluate the biodegradation of physically (WAF) and chemically dispersed (CEWAF) Endicott oil in seawater (salinity: 29.1‰) from Prince William Sound, Alaska, under low nutrient (LN) (background seawater) and high nutrient (HN) (addition of 100 mg NO3-N/L and 10 mg PO4-P/L to background seawater) at 15 ± 0.5 °C for 42 days. The dispersant was Corexit 9500. The dispersed oil concentration of the WAF (0.019 g/L ± 0.002) was an order of magnitude lower than that in the CEWAF (0.363 g/L ± 0.038). While remaining negligible in the WAF, the total oil removal in the CEWAF was 26% and 44% in LN and HN treatments, respectively. Nutrient supplementation significantly accelerated the rate of oil biodegradation as confirmed by ANOVA coupled with Tukey’s test at 95% confidence intervals (α = 0.05). GC/MS analyses revealed that biodegradation affected mainly alkane compounds. In the CEWAF, O2 consumption, CO2 production and biomass were much larger in HN than in LN treatments, which suggests that chemical dispersion of oil coupled with high nutrient concentration could be very useful in terms of remediation strategies and effective responses to oil spill at sea