We use the recently extended superposition T-matrix method to calculate scattering and absorption... more We use the recently extended superposition T-matrix method to calculate scattering and absorption properties of micrometer-sized water droplets contaminated by black carbon. Our numerically exact results reveal that, depending on the mode of soot-water mixing, the soot specific absorption can vary by a factor exceeding 6.5. The specific absorption is maximized when the soot material is quasi-uniformly distributed throughout the droplet interior in the form of numerous small monomers. The range of mixing scenarios captured by our computations implies a wide range of remote sensing and radiation budget implications of the presence of black carbon in liquid-water clouds. We show that the popular Maxwell-Garnett effective-medium approximation can be used to calculate the optical cross sections, single-scattering albedo, and asymmetry parameter for the quasi-uniform mixing scenario, but is likely to fail in application to other mixing scenarios and in computations of the elements of the scattering matrix.
International Journal of Environment and Sustainability, 2015
Water is one of the most essential natural resources for daily human activities, yet it is so sca... more Water is one of the most essential natural resources for daily human activities, yet it is so scarce. Treated wastewater and untreated sewage contain bacteria that can be advantageous to the recycling process. The composition of effluent originates from various industries, such as pharmaceutical industries, mining industries, agricultural sector, household waste, chemical industries, and various manufacturing industries, including the oil manufacturers. These introduce potential health-threatening compounds to wastewater. These compounds that remain for a long time without being broken down or changed in their chemical composition and/or structure in the environment are referred to as recalcitrant compounds. Polychlorinated Biphenyls (PCBs) are examples of such compounds. These compounds have serious negative health effects on humans (act as mutagens and carcinogens). The capacity of Polychlorinated Biphenyl's (PCBs) degradation by bacteria (biodegradation) depends on the diversity and characteristics of naturally occurring populations and their response to environmental conditions. Conventional physical and chemical methods that are used to decontaminate wastewater contaminated by these substances are time and energy consuming. The use of Moringa oleifera seeds, which is currently under trial, is also very costly and not sustainable. This threatens the economic security of most developing countries. Biodegradation is the metabolic ability of microorganisms to transform or mineralize organic contaminants into less harmful, non-hazardous substances, which are then integrated into natural biochemical cycles. This process is not only cost effective, but it is also environmentally friendly. Wastewater that has gone through effective biodegradation can be fully recycled, thus conserving raw water and at the same time ensuring safe available water for all.
Polychlorinated biphenyls (PCBs) cause many significant ecological problems because of their low ... more Polychlorinated biphenyls (PCBs) cause many significant ecological problems because of their low degradability, high harmfulness, and solid bioaccumulation.Two bacterial strains were isolated from soil that had been polluted with electrical transformer liquid for more than 40 years. The isolates were distinguished as Lysinibacillus macrolides DSM54Tand Bacillus firmus NBRC15306Tthrough 16S rRNA sequencing analysis.This is the primary report of an agent of the genus Bacillus firmus equipped for the removal of PCBs. The strains could develop broadly on 2-Chlorobiphenyl and 2,4dichlorobiphenyl. GC/MS analysis of individual congeners revealed up to 80% degradation of the xenobiotics in 96h, attendant with cell proliferation of up to two orders of extent. More extensive investigation of the isolates may be helpful in surveying detoxification forms and in planning bioremediation and bioaugmentation strategies.
Pseudomonas aeruginosa was used to assess their potentials to degrade PCBs at concentrations of 1... more Pseudomonas aeruginosa was used to assess their potentials to degrade PCBs at concentrations of 1.0 μg/mL. An aliquot of 1.0 μL of the bacterial suspension with an optical density of 1.0 at 600 nm was used as an inoculum of the assay. Isolates were analysed for their ability to degrade PCB (Aroclor 1260) by measuring a shift in the wavemax using Cary 300 UV-visible spectrophotometer for a period of 96 hours. The presence /absence of the compounds was checked using high performance liquid chromatography (HPLC) UFLC Shimadzu using florescence detector pump RF-20A and system gold column C18 (CTO-20A) after 96 h. PCBs were extracted from wastewater samples from both Gaborone and Mafikeng using the Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) extraction kit, and analysis was performed using the gas chromatography mass spectrometer (GC-MS). The bacteria were able to degrade these compounds under different pH values of 5.0, 7.0, 8.0, and 9.0 and temperatures of 20, 27, 30, and 35 C. Degradation occurred at the most at 35 C and the least at 20 C for PCB samples that were used in the study. The bacteria strain was able to completely degrade Aroclor 1260 that was incoperated into the wastewater samples within 96 h. This was shown by a shift in the wavelength from 224 to 270 nm, which indicated that Aroclor 1260 was degraded and therefore forming a chlorobenzoate derivative. From this finding, it can be concluded that the sewage water samples did not possess PCB (Aroclor 1260) after treatment with bacteria and can be safely recycled.
Bioaccumulation: A process that results in a molecule being taken up into living cells; it remain... more Bioaccumulation: A process that results in a molecule being taken up into living cells; it remains in the cells without enzymatic biodegradation and thus results in biosorptive mechanisms, bioprecipitation and intracellular accumulation. Bio-augmentation: The introduction of bacteria to an area that has been contaminated for purposes of speeding up the removal of the contaminant. Biodegradation: The metabolic ability of microorganisms to transform or mineralize organic contaminants into less harmful, non-hazardous substances, which are integrated into natural biochemical cycles. Biomagnification: The increase in concentration of substances with increase in trophic levels in an ecosystem. Bioremediation: The process whereby organic wastes are biologically degraded under controlled conditions to an innocuous state or to levels below concentration limits established by regulatory authorities. Biotic: The living component of the environment or ecosystem. Biotransformation: A step in the biochemical pathway which leads to the conversion of a molecule into a less toxic product. x Carcinogenic: Any substance that tends to stimulate cancer production or uncontrolled proliferation of cells in a living organism (especially animals). Carbon Catabolite Repression: A regulatory mechanism in bacteria whereby the expression of genes required for the synthesis and activities of proteins necessary for the transport and metabolism of secondary carbon sources is suppressed. Complementary Deoxyribonucleic Acid (cDNA): DNA formed by reverse transcriptase acting on an RNA as the template. Congener: Any single, uniquely defined chemical compound in the PCB category with a specific number of chlorine molecules and their positions. DNA fingerprinting: The process in which genomic DNA base sequence profiles of an organism is obtained. Ecology: A branch of biology that deals with the relations of organisms to each other and to their natural environment or surroundings. Ecological niche: The place or function of a given organism within its ecosystem. Ecosystem: A community of living organisms and their interaction with the non living component of their environment. xi Hydrocarbon: These are organic chemical compounds composed of the elements carbon and hydrogen (alkanes, alkenes, alkynes and aromatic). Pollution: The introduction of contaminants in the environments that cause adverse effects to the biotic and abiotic component of the environment. Polymerase Chain Reaction (PCR): A technique for the rapid production of millions of copies of a particular stretch of DNA or RNA sequence. Primary Treatment: The first stage in the sewage or wastewater treatment process where removal of contaminants is through screening and settling processes, resulting in about 40-50% removal of contaminants. Probable Effect Concentration (PEC): This represents the concentration of a contaminant in bed sediment and thus is expected to adversely affect organisms found/living at the bottom. Recalcitrant Compounds: These are compounds which are non-biodegradable and range from natural organic material such as hair, melanin, lignin, to hydrocarbons and complex polymers such as styrene, pesticides and cyanides. Ribosomal Ribonucleic Acid (rRNA): These are several types or species of RNA that are incorporated into a ribosome. Secondary Treatment: The second stage of wastewater treatment process whereby suspended solids are reduced through biological processes and results to removal of about 85-95% contaminants. xii Standard Reference Materials (SRMs): These are materials that have been well characterised for specific chemical properties such as concentration (denoted as mass fraction) for specific chemical types. Surfactant: These are surface active agents that reduce surface tension in liquids. Tertiary Treatment: The third stage in wastewater treatment process which involves filtration and disinfection, resulting in the removal of up to 99.99% of pathogens and suspended solids. Waste Management: All institutional, financial, technical, legislative, participatory, and managerial aspects related to the handling of wastewater. Wastewater: Water carrying waste from households, businesses and industries and involves a mixture of water and dissolved or suspended solids.
Abstract
Notwane Sewage Treatment Plant is situated on the eastern part of Gaborone emptying its ... more Abstract Notwane Sewage Treatment Plant is situated on the eastern part of Gaborone emptying its effluent into Notwane River which flows along the periphery of Gaborone. The wastewater treatment plant receives wastewater from most major industries, and most of the residential waste water for the city of Gaborone. The wastewater is not recycled despite the great shortage of water in Gaborone and surrounding villages and the drying up of Gaborone dam. Wastewater samples from the treatment plant was collected and taken to Department of Biological Sciences in Mafikeng for analysis of PCB (Aroclor 1260) degradation by bacteria. Biodegradation of polychlorinated biphenyls using MD2 was conducted using Aroclor 1260 added to wastewater obtained from Notwane Sewage Treatment Plant by measuring shift in the wavemax (λmax) nm using Cary 300 UV-visible spectrophotometer, for a period of 96 hours. The presence/absence of the compounds was checked using High Performance Liquid Chromatography (HPLC) UFLC Shimadzu using florescence detector pump RF-20A and system gold column C18 (CTO-20A) after 96 hours. The bacterial strain MD2 was found to have completely degraded the Aroclor1260 in wastewater after 96 hours. A shift in maximum wavelength was observed to be from 224 nm to 270 nm, an indication that Aroclor 1260 was degraded forming a chlorobenzoate derivative. This renders the wastewater free from polychlorinated biphenyls thus can be safely recycled
this is the work we are working on to publish. With my colleagues, we prepared these slides for p... more this is the work we are working on to publish. With my colleagues, we prepared these slides for presentation at the 16th Conference for Math, Science & Technology Education in Africa (COMSTEDA 16) last week. the paper is still at an infant stage and hoping end of Dec 2018, it will be out. We are 3, with Dithebe Mmoloki
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Papers by Spar Mathews
Notwane Sewage Treatment Plant is situated on the eastern part of Gaborone emptying its effluent into Notwane
River which flows along the periphery of Gaborone. The wastewater treatment plant receives wastewater from most
major industries, and most of the residential waste water for the city of Gaborone. The wastewater is not recycled
despite the great shortage of water in Gaborone and surrounding villages and the drying up of Gaborone dam.
Wastewater samples from the treatment plant was collected and taken to Department of Biological Sciences in
Mafikeng for analysis of PCB (Aroclor 1260) degradation by bacteria. Biodegradation of polychlorinated biphenyls
using MD2 was conducted using Aroclor 1260 added to wastewater obtained from Notwane Sewage Treatment
Plant by measuring shift in the wavemax (λmax) nm using Cary 300 UV-visible spectrophotometer, for a period of
96 hours. The presence/absence of the compounds was checked using High Performance Liquid Chromatography
(HPLC) UFLC Shimadzu using florescence detector pump RF-20A and system gold column C18 (CTO-20A) after
96 hours.
The bacterial strain MD2 was found to have completely degraded the Aroclor1260 in wastewater after 96 hours.
A shift in maximum wavelength was observed to be from 224 nm to 270 nm, an indication that Aroclor 1260 was
degraded forming a chlorobenzoate derivative. This renders the wastewater free from polychlorinated biphenyls thus
can be safely recycled
Drafts by Spar Mathews