Biocolloid transport and deposition in porous media: A review

Exploring the Potential of Microbial Coalbed Methane for Sustainable Energy Development

By allowing coal to be converted by microorganisms into products like methane, hydrogen, methanol, ethanol, and other products, current coal deposits can be used effectively, cleanly, and sustainably. The intricacies of in situ microbial coal degradation must be understood in order to develop innovative energy production strategies and economically viable industrial microbial mining. This review covers various forms of conversion (such as the use of MECoM, which converts coal into hydrogen), stresses, and in situ use. There is ongoing discussion regarding the effectiveness of field-scale pilot testing when translated to commercial production. Assessing the applicability and long-term viability of MECoM technology will require addressing these knowledge gaps. Developing suitable nutrition plans and utilizing lab-generated data in the field are examples of this. Also, we recommend directions for future study to maximize methane production from coal. Microbial coal conversion technology needs to be successful in order to be resolved and to be a viable, sustainable energy source.

Influence of citric acid concentrations on the porosity and performance of cellulose acetate-based porous membranes: A comprehensive study

This study investigates the influence of citric acid concentration on the fabrication of porous cellulose acetate (CA) membranes using the Non-Solvent Induced Phase Separation (NIPS) method. A notable aspect is the precise control over membrane properties, particularly pore size and porosity, achieved solely through the adjustment of citric acid concentration, serving as the additive. Higher concentrations of citric acid increase pore size by rendering polymer chains more pliable, whereas lower concentrations lead to smaller, denser pores due to improved dispersion in the CA matrix and altered water interactions during phase separation. A decrease in porosity and Gurley values with reducing citric acid concentrations (from 5 × 10-2 to 1 × 10-3 M ratios) indicates less plasticization of CA chains. However, at very low concentrations (1 × 10-4 and 1 × 10-5), porosity increases, despite the presence of smaller pores, and Gurley values approach those of pure CA in terms of gas permeability. Fourier Transform Infrared (FT-IR) spectroscopy confirms the presence of citric acid and its interaction with carbonyl groups, consistent with the pore size observations from Scanning Electron Microscopy (SEM). Spectral data deconvolution reveals weakened carbonyl bonds due to the reduced presence of citric acid, correlating with the smaller pores observed in SEM. Thermal Gravimetric Analysis (TGA) demonstrates that composite membranes are more thermally stable than pure CA, attributed to the citric acid-induced crosslinking within the polymer chains. Stability increases with decreasing citric acid concentration, with some anomalies at the lowest levels. In conclusion, this study highlights the capability of adjusting citric acid concentration to tailor membrane properties, offering valuable insights for the creation of porous materials across diverse industrial applications.

Enhanced porous membrane fabrication using cellulose acetate and citric acid: Improved structural integrity, thermal stability, and gas permeability

In this study, our primary objective was to enhance the properties of porous membranes by addressing the limitations associated with phase separation. We employed a non-solvent induced phase separation (NIPS) method, utilizing cellulose acetate (CA) in conjunction with citric acid to fabricate these membranes. Citric acid played a dual role: ensuring a uniform pore structure and cross-linking the CA polymer, thereby enhancing its mechanical strength. This approach resulted in the development of a more robust membrane with superior structural integrity. Thermogravimetric analysis (TGA) confirmed enhanced thermal stability, particularly up to 150 °C, as a result of citric acid's cross-linking effect. Beyond 150 °C, the decomposition temperatures of the CA/citric acid membrane were found to be comparable to those of pure CA. Remarkably, a CA/citric acid ratio of 1:0.05 exhibited the slowest decomposition rate as the temperature increased. Scanning electron microscopy (SEM) examination unveiled a sponge-like membrane structure with numerous evenly distributed fine pores. Through the use of citric acid as a plasticizer, we were able to effectively control the penetration of water molecules, preventing the formation of macrovoids and promoting the creation of fine pores. This resulted in the fabrication of a high-porosity membrane, boasting an impressive porosity measurement of 84.9 %. Furthermore, measurements of the Gurley value confirmed efficient gas permeation, a critical characteristic for applications requiring effective gas transport. Fourier transform infrared (FT-IR) spectroscopy attested to the presence of citric acid in the membrane post-phase separation, indicating its successful integration. Our work presents a novel approach to enhance porous membranes, providing improvements in mechanical strength, thermal stability, and gas permeability. These findings offer valuable insights for the development of advanced materials with diverse applications in various fields.

Attenuation of bacterial hazard indicators in the subsurface of an informal settlement and their application in quantitative microbial risk assessment

Pit latrines provide essential onsite sanitation services to over a billion people, but there are concerns about their role in infectious disease transmission, and impacts on groundwater resources. We conducted fieldwork in an informal settlement in Dar es Salaam, where cholera is endemic. We combined plate counting with portable MinION sequencing and quantitative polymerase chain reaction (qPCR) methods for characterization of bacteria in pit latrine sludge, leachate, shallow and deep groundwater resources. Pit latrine sludge was characterized by log₁₀ marker gene concentrations per 100 mL of 11.2 ± 0.2, 9.9 ± 0.9, 6.0 ± 0.3, and 4.4 ± 0.8, for total bacteria (16S rRNA), E. coli (rodA), human-host-associated Bacteroides (HF183), and Vibrio cholerae (ompW), respectively. The ompW gene observations suggested 5 % asymptomatic Vibrio cholerae carriers amongst pit latrine users. Pit leachate percolation through one-meter-thick sand beds attenuated bacterial hazard indicators by 1 to 4 log₁₀ units. But first-order removal rates derived from these data substantially overestimated the longer-range hazard attenuation in the sand aquifers. Cooccurrence of human sewage marker gene HF183 in all shallow groundwater samples testing positive for ompW genes demonstrated the human origin of Vibrio cholerae hazards in the subsurface. All borehole water samples tested negative for ompW and HF183 genes, but 16S rRNA gene sequencing data suggested ingress of faecal pollution into boreholes at the peak of the "long rainy season". Quantitative microbial risk assessment (QMRA) predicted a gastrointestinal disease burden of 0.05 DALY per person per year for the community, well above WHO targets of 10^-4-10^-6 DALY for disease related to drinking water.

Physical Clogging Characteristics and Water Quality Variations by Injecting Secondary Effluent into Porous Media: A Laboratory Column Study

Artificial recharge engineering has been widely used to solve the water resource crisis. However, there are still some safety hazards regarding reclaimed water quality. Here, chlorinated secondary effluent (SE) was injected into saturated porous media composed of high–purity quartz sands. The column experiment was conducted and modeled through a developed numerical model to predict the evolution of physical clogging. Some representative inorganic and organic indicators were measured both at different times and in different column sections. The study showed that the relative hydraulic conductivity (K/K0) decreased significantly by approximately 63.5% in 40 h. Especially for the first 3 cm of the column, the clogging was the most serious, with a decrease of approximately 85.8%. The porous media has a certain degree of filtration effect on turbidity, TOC, protein (Pr) and polysaccharide (PS) but has slight removal for other water quality indicators. Pr is the main component of the intercepted TOC, and its content is higher than that of Ps. Moreover, the inorganic and organic parameter variations along the column further verified that the organic floc particles were mainly retained in the first 3 cm. The 3D excitation/emission matrix (3DEEM) fluorescence spectra illustrated that the humic acids and fulvic acids were easy to release and that their injection may be harmful to groundwater quality. The study will lay a theoretical foundation and provide a guiding scheme for optimizing China’s reclaimed water reuse technology, ensuring the safety of reclaimed water quality.