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Graphene oxide (GO) has become the most attractive material for membrane technology owing to its potential application as a nanofiller in water treatment, purification, and desalination. In this study, we incorporated mica as a cross-linking reagent to increase the interlayer spacing and stability of GO sheets and fabricated a mica/GO (MGO) membrane for the first time. The MGO membrane (260 ± 10 nm) exhibits 100% rejection for biomolecules such as tannic acid (TA) and bovine serum albumin (BSA) and >99% rejection for multiple probe molecules, such as methylene blue, methyl orange, congo red, and rhodamine B. The high rejection of membranes can be attributed to the surface interaction of mica with GO nanosheets through covalent interaction, which enhances the stability and separation efficiency of the membranes for probe ions and molecules. This ultrathin MGO membrane also exhibits much better water permeability at 870 ± 5 L m-2 h-1 bar-1, which is 10-100 times greater than that reported for pure GO and GO-based composite membranes. Additionally, the membrane shows high rejection for salt ions (70%). Furthermore, the stability of the MGO membranes was evaluated under various conditions, and the membranes demonstrated remarkable stability for up to 60 days in a neutral environment.
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Manchar Lake, Pakistan's biggest lake in the arid zone, faces human-induced salinity issues. This study investigated its effects on the multifaceted ecosystem services, including serving as a source of drinking and irrigation water and aquatic health through assessing fish diversity and characteristics. Analyses of 189 water samples from 21 sites revealed spatiotemporal variations in major ions contributing to lake water salinity. The study assessed water suitability for drinking and agriculture using the water quality index (WQI), sodium adsorption ratio (SAR), magnesium hazard (MH), sodium percent (Na%), and Kelly's ratio (KR). The WQI, ranging from 141 to 408, indicated that the lake water was unfit for drinking. In some seasons, such as the pre-monsoon period, the lake water was deemed unsuitable for irrigation due to high SAR values (18 ± 4 g/L, average ± standard deviation), consistently rising MH values exceeding 66 in all seasons and elevated sodium percentages surpassing 66% in both the pre-monsoon and monsoon seasons. The KR remained acceptable (averaging 0.8 to 2.5) in all seasons. Fish health in highly saline conditions was assessed using data from interviews, focus group discussions, and fish sampling (1684 fish from 10 sites). Results depicted that high salt contamination severely impacted fish length and weight. The study found low richness (Simpson's biodiversity: 0.697 and Shannon Weaver: 1.51) and evenness (Pielou's index: 0.48) among the fish populations. Since 1998, Manchar Lake has seen a decline in fish varieties from 32 to 23, with changes in fish species' feeding habits. To improve lake water quality, the study recommends diverting saline water to the sea before and after the monsoon season while utilizing freshwater from alternative sources to fill any water deficit.
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Ecossistema , Poluentes Químicos da Água , Animais , Humanos , Monitoramento Ambiental/métodos , Lagos , Salinidade , Paquistão , Qualidade da Água , Sódio/análise , Poluentes Químicos da Água/análiseRESUMO
Poor water quality exacerbates multidimensional poverty in developing nations. Often centralized treatment facilities generate acceptable water quality, but the water is contaminated during distribution. Methods to assess sources of contamination in water distribution systems are lacking. A case study of two methods, human risk assessment linked to water distribution system sampling was conducted in Hyderabad, Pakistan to determine areas requiring infrastructure rehabilitation. Water samples from source water (i.e., the Indus River), treatment plant effluent and from taps in the water distribution system were analyzed by atomic adsorption spectroscopy for metals and metalloids (As, Cd, Cr, Hg, and Pb) and water quality parameters (dissolved and suspended solids, pH, conductivity, and total organic carbon). Source water exceeded acceptable drinking water levels for As, Cd, total Cr, and Pb, while the treatment plant effluent concentrations were acceptable. Concentrations of all metals and metalloids, except Hg, increased in the water distribution system post-treatment, exceeding safe drinking limits in at least one location, suggesting contamination of the water during distribution. A deterministic and a probabilistic risk assessment were conducted to evaluate two scenarios: (1) unrestricted use of piped water for all household purposes, including as drinking water and (2) restricted use of the water for purposes other than drinking in the household, including only dermal and inhalation exposure pathways. The water was deemed unsafe for unrestricted use as the sole source of drinking water by both risk assessment methods. Yet when an alternative source of drinking water was assumed and the piped water was used only for bathing and dish washing, the probabilistic risk assessment revealed acceptable health risks to the population, while the overly conservative deterministic risk assessment suggested unacceptable risks. The combined methods of water sampling, risk assessment and correlation analysis suggested areas for rehabilitation of the water distribution system in Hyderabad, Pakistan and these methods can be adopted in other developing nations to target limited funds for infrastructure rehabilitation.
Assuntos
Água Potável/análise , Metaloides/análise , Metais Pesados/análise , Poluentes Químicos da Água/análise , Purificação da Água/normas , Abastecimento de Água/normas , Água Potável/normas , Monitoramento Ambiental/métodos , Humanos , Paquistão , Medição de Risco , Rios/química , Qualidade da Água/normasRESUMO
The textile wastewater sludge (TWS) treatment and disposal are environmentally challenging due to toxic organics and metals. At the same time, cattle manure (CM), with better combustion performance, i.e., calorific value and uniform burning capability, is still underutilized in many parts of the world. This study evaluated and assessed the TWS and CM blending compatibility to convert them into fuel pellets for the direct combustion option and to stabilize toxic contaminants in TWS. After initial drying, grinding, and particle size control of the raw TWS and CM, both were blended at different ratios. The blended and nonblended TWS and CM samples were converted into pellets and analyzed for proximate and ultimate analyses, namely, moisture content, fixed carbon, CHNO, gross calorific value (GCV), bulk density, ash content, and metals, to evaluate the efficacy for energy applications. Out of three blended ratios, i.e., 75:25 (W/W%; CM/TWS), 50:50, and 25:75, the 75:25 blended pellet composition was found appropriate for fuel application. For the 75:25 blend, the obtained GCV was 12.77 MJ/kg, elemental carbon was 27.5%, volatiles were 41.7%, and residue ash was 42.8% of the total weight. Moreover, the blending ratios of 75:25 and 50:50 revealed that elemental and metal (Fe, Cu, Zn, Ni, Cr, Na, Mg, Mn) concentrations in TWS were stabilized to below threshold limits in the obtained residue ash for safe handling. The explored methods of TWS and CM waste processing, blending, and pelletization proposed a new technique for their sustainable waste valorization into energy sources.
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Herein we report the fabrication of cationic functionalized cellulose nanofibers (c-CNF) having 0.13 mmol.g-1 ammonium content and its ionic crosslinking via the pad-batch process. The overall chemical modifications were justified through infrared spectroscopy. It is revealed that the tensile strength of ionic crosslinked c-CNF (zc-CNF) improved from 3.8 MPa to 5.4 MPa over c-CNF. The adsorption capacity of zc--CNF was found to be 158 mg.g-1 followed by the Thomas model. Further, the experimental data were used to train and test a series of machine learning (ML) models. A total of 23 various classical ML models (as a benchmark) were compared simultaneously using Pycaret which helped reduce the programming complexity. However, shallow, and deep neural networks are used that outperformed the classic machine learning models. The best classical-tuned ML model using Random Forests regression had an accuracy of 92.6 %. The deep neural network made effective by early stopping and dropout regularization techniques, with 20 × 6 (Neurons x Layers) configuration, showed an appreciable prediction accuracy of 96 %.
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Celulose , Nanofibras , Celulose/química , Nanofibras/química , Adsorção , Resistência à Tração , Espectrofotometria Infravermelho , ÍonsRESUMO
Zein has drawn attention for its great potential for biodegradability and adsorption of hexavalent chromium Cr(VI) that is a carcinogenic industrial pollutant. Zein is a biopolymer extracted from corn and is used for many purposes, but because of its poor stability in aqueous solution, a novel composite of zein and nylon-6 was used to synthesize a nanofibrous membrane using electrospinning to improve its stability and tensile strength. The scanning electron microscope (SEM) image of the zein/nylon-6 (ZN6) nanofiber membrane showed a smooth, beadless, and continuous structure of the nanofibers, but the Fourier transform infrared (FTIR) spectrum of pristine and Cr(VI) saturated ZN6 showed that peaks of secondary amide, carbonyl, and hydroxyl functional groups were involved in adsorption. Optimized experimental parameters were obtained with pH 2.0, contact time 60 min, adsorbent dosage 25 mg, and adsorbate concentration 5.0 mg Cr-VI/mL. Experimental results show that the ZN6 nanofibers removed 87% Cr(VI) with an adsorption capacity of 4.73 mg/g at ambient temperature. Also, the Langmuir isotherm fits well, and the adsorption process followed a pseudo-2nd-order kinetics with r2 of 0.90 and 0.99 respectively.
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Nanofibras , Poluentes Químicos da Água , Zeína , Adsorção , Caprolactama/análogos & derivados , Cromo/análise , Concentração de Íons de Hidrogênio , Cinética , Polímeros , Espectroscopia de Infravermelho com Transformada de Fourier , Poluentes Químicos da Água/análiseRESUMO
This study was conducted to investigate mechanisms of cross-resistance to chlorine and peracetic acid (PAA) disinfectants by antibiotic-resistant bacteria. Our study evaluated chlorine and PAA based disinfection kinetics of erythromycin-resistant Enterococcus faecalis, meropenem-resistant Escherichia fergusonii, and susceptible strains of these species. Using the integrated second-order disinfectant decay model and first-order Chick-Watson's Law, it was found that the meropenem-resistant Escherichia fergusonii strain showed significantly less log inactivation compared to the susceptible E. fergusonii strain in response to both chlorine and PAA disinfection (p-value = 0.059, 3.5 × 10-6). On the other hand, the susceptible Enterococcus faecalis strain showed similar log inactivation compared to the erythromycin-resistant strain in response to either treatment (p-value = 0.075, 0.28). Meropenem-resistant E. fergusonii showed an increase in gene expression of New Delhi metallo-ß-lactamase (blaNDM-1) gene to chlorine, but there was no increase in expression to PAA. Whole genome sequencing (WGS) was then conducted to elucidate the differences in genes among both resistant and susceptible table E. fergusonii strains. The average nucleotide identity (ANI) analysis of the draft genomes (>97% similarity) suggests that meropenem-resistant E. fergusonii (S1) and meropenem-susceptible E. fergusonii (S2) are the same species but different strains. Both strains have the same genes for oxidative stress pathways, oxidative scavenger genes, and nearly 40 different antibiotic efflux pump genes. The chromosomal and plasmid draft genomes of meropenem-resistant and susceptible E. fergusonii strains each have 65 and 52 antibiotic resistance genes, respectively. Of these, the resistant E. fergusonii strain harbored the extended-spectrum beta-lactamases blaCTX-M-15 and blaTEM-1 genes located on the chromosome, and a blaTEM-1 gene on the plasmid. The overall findings of this study are significant, as they reveal that antibiotic-resistant and susceptible strains of E. fergusonii exhibit different responses towards chlorine and PAA disinfection.
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Cloro , Ácido Peracético , Desinfecção , Enterococcus faecalis/genética , Escherichia , Expressão Gênica , Genômica , Cinética , Ácido Peracético/farmacologiaRESUMO
Nature has given several unique features to one of the most abundant and inexhaustible biopolymers on the earth, i.e., cellulose. Besides, biodegradability, and cost-effectiveness, cellulose possesses attractive properties such as the ability to undergo chemical and structural modification, plus its light weight and thermal and mechanical stability. Cellulose originates from natural sources, including being significant components of plants (ca. 33%), wood (ca. 50%), and cotton (ca. 90%). It can also be synthesized and modified further into a variety of functionalized nanomaterials for diversified sectors, such as bio-medical, food, customer care, and environmental services. Considering the significant growth in product development and interdisciplinary cellulose-based research, the proposed chapter will let the reader gain knowledge about in-vitro extraction, synthesis of nanomaterials, and applications to resolve ongoing environmental challenges.
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Celulose/química , Nanoestruturas/química , Biodegradação Ambiental , Biopolímeros/química , Recuperação e Remediação Ambiental/métodos , Humanos , Madeira/químicaRESUMO
Primary-school children in low- and middle-income countries are often deprived of microbiologically safe water and sanitation, often resulting in a high prevalence of gastrointestinal diseases and poor school performance. We used Quantitative Microbial Risk Assessment (QMRA) to predict the probability of infection in schoolchildren due to consumption of unsafe school water. A multistage random-sampling technique was used to randomly select 425 primary schools from ten districts of Sindh, Pakistan, to produce a representative sample of the province. We characterized water supplies in selected schools. Microbiological testing of water resulted in inputs for the QMRA model, to estimate the risks of infections to schoolchildren. Groundwater (62%) and surface water (38%) were identified as two major sources of drinking water in the selected schools, presenting varying degrees of health risks. Around half of the drinking-water samples were contaminated with Escherichia coli (49%), Shigella spp. (63%), Salmonella spp. (53%), and Vibrio cholerae (49%). Southern Sindh was found to have the highest risk of infection and illness from Campylobacter and Rotavirus. Central and Northern Sindh had a comparatively lower risk of waterborne diseases. Schoolchildren of Karachi were estimated to have the highest probability of illness per year, due to Campylobacter (70%) and Rotavirus (22.6%). Pearson correlation was run to assess the relationship between selected pathogens. V. cholerae was correlated with Salmonella spp., Campylobacter, Rotavirus, and Salmonella spp. Overall, the risk of illness due to the bacterial infection (E. coli, Salmonella spp., V. cholerae, Shigella, and Campylobacter) was high. There is a dire need for management plans in the schools of Sindh, to halt the progression of waterborne diseases in school-going children.
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Água Potável , Microbiologia da Água , Abastecimento de Água , Doenças Transmitidas pela Água , Criança , Escherichia coli , Humanos , Paquistão , Medição de RiscoRESUMO
This work aims to utilize fly ash from a thermal power station for melanoidin reduction from distillery effluent by adsorption. To accomplish this, coal fly ash was modified through chemical treatment and was then tested for melanoidin adsorption as a function of various melanoidin concentrations, contact time, and pH. The specific novelty of this study is the evaluation of coal fly ash as a low-cost adsorbent for melanoidin removal. Furthermore, the simulation study was carried out using Aspen ADSIM software in order to optimize the commercial usage of the prepared adsorbent. The main results achieved include the maximum removal efficiency of 84% which was reached at initial melanoidin concentration of 1100 mg L-1 (5% dilution), pH 6, and a contact time of 120 min. The Langmuir and Freundlich isotherm models were used to evaluate adsorption isotherms. The maximum adsorption capacity of 281.34 mg/g was observed using the Langmuir isotherm. Furthermore, pseudo-first- and pseudo-second-order and intra-particle diffusion models were used to fit adsorption kinetic data. The pseudo-second-order was best describing the adsorption kinetic with a faster kinetic rate of 0.142 mg g-1 min-1. CFA (coal fly ash) after acidic activation resulted in a slightly higher surface area, average pore volume, and pore size. The maximum breakthrough time and adsorbent saturation time were achieved at initial melanoidin concentration of 1 mol/lit, bed height of 2.5 m, and flow rate of 50 lit/min.
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Cinza de Carvão , Poluentes Químicos da Água , Adsorção , Carvão Mineral , Concentração de Íons de Hidrogênio , Cinética , PolímerosRESUMO
Poor urban water quality has been linked to diminished source water quality, poorly functioning water treatment systems and infiltration into distribution lines after treatment resulting in microbiological contamination. With limited funding to rehabilitate distribution lines, developing nations need tools to identify the areas of greatest concern to human health so as to target cost effective remediation approaches. Herein, a case study of Hyderabad, Pakistan was used to demonstrate the efficacy of combining quantitative microbial risk assessment (QMRA) for multiple pathogens with spatial distribution system modeling to identify areas for pipe rehabilitation. Abundance of Escherichia coli, Enterococcus (enterococci), Salmonella spp., Shigella spp., Giardia intestinalis, Vibrio cholera, norovirus GI and adenovirus 40/41, were determined in 85 locations including the source water, treatment plant effluent and the city distribution lines. Bayesian statistics and Monte Carlo simulations were used in the QMRA to account for left-censored microbial abundance distributions. Bacterial and viral abundances in the distribution system samples decreased as follows: 9400 ± 19,800 norovirus gene copies/100 mL (average ± standard deviation, 100% of samples positive); 340 ± 2200 enterococci CFU/100 mL (94%), 71 ± 97 Shigella sp. CFU/100 mL (97%), 60 ± 360 E. coli CFU/100 mL (89%), 35 ± 79 adenovirus gene copies/100 mL (100%), and 21 ± 46 Salmonella sp. CFU/100 mL (76%). The QMRA revealed unacceptable probabilities of illness (>1 in 10,000 illness level) from the four exposure routes considered (drinking water, or only showering, tooth brushing, and rinsing vegetables consumed raw). Disease severity indices based on the QMRA combined with mapping the distribution system revealed areas for targeted rehabilitation. The combined intensive sampling, risk assessment and mapping can be used in low- and middle-income countries to target distribution system rehabilitation efforts and improve health outcomes.
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Microbiologia da Água , Água , Teorema de Bayes , Escherichia coli , Humanos , Paquistão , Medição de RiscoRESUMO
The conventional landfilling does not promote sustainable waste management due to uncontrolled emissions which potentially degrade the environment. Pretreatment of municipal solid waste prior to landfilling significantly enhances waste stabilization, reduces the emissions and provides many advantages. Therefore, pretreatment of municipal solid waste methods were investigated. The major objectives of biological pretreatment are to degrade most easily degradable organic matters of MSW in a short duration under controlled conditions so as to produce desired quality for landfill. To investigate the suitable pretreatment method prior to landfilling for developing countries four pretreatment simulators were developed in the laboratory: (i) anaerobic simulator (R(1)), (ii) aerobic pretreatment simulator by natural convection of air (R(2)), (iii) aerobic pretreatment simulator by natural convection of air with leachate recirculation (R(3)) and (iv) forced aeration and leachate recirculation (R(4)). During the pretreatment organic matter, elemental composition, i.e., carbon, hydrogen, nitrogen and settlement were determined for bench scale experiments. A two-component kinetic model is proposed for the biodegradation of organic matter. Biodegradation kinetic constants were determined for readily and slowly degradable organic matter. The biodegradation of organic matter efficiency in terms of kinetic rate constants for the pretreatment simulators was observed as R(4) > R(3) > R(2) > R(1). Biodegradation rate constants for readily degradable matter in simulators R(4) and R(3) were 0.225 and 0.222 per day. R(3) and R(4) simulators were more effective in reducing methane emissions about 45% and 55%, respectively, as compared to anaerobic simulator R(1). Pretreatment of MSW, by natural convection of air with leachate recirculation R(3) is sustainable method to reduce the emissions and to stabilize the waste prior to landfilling.
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Eliminação de Resíduos/métodos , Resíduos , Biodegradação Ambiental , Cinética , Modelos Químicos , Resíduos/classificaçãoRESUMO
Ultrasonic treatment can disintegrate sludge, enhance microbial activity and improve sludge dewaterability at different energy inputs. To find their relationship, the three phenomena during ultrasonic treatment were investigated synchronously, and an experimental model was established to describe the process of ultrasonic sludge disintegration. Analysis results showed that the changes of sludge microbial activity and dewaterability were dependent on sludge disintegration degree during ultrasonic treatment. When sludge disintegration degree was lower than 20%, sludge flocs were disintegrated into micro-floc aggregates and the microbial activity increased over 20%. When sludge disintegration degree was over 40%, most cells were destroyed at different degree, and sludge activity decreased drastically. Only when sludge disintegration degree was 2-5%, sludge dewaterability was improved with the conditioning of FeCl(3). It was also found that the sonication with low density and long duration was more efficient than sonication with high density and short duration at the same energy input for sludge disintegration, and a transmutative power function model can be used to describe the process of ultrasonic disintegration.
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Esgotos , Ultrassom , Anaerobiose , Biodegradação Ambiental , Reatores Biológicos , Técnicas de Química Analítica/métodos , Cloretos , Compostos Férricos/química , Resíduos Industriais , Eliminação de Resíduos/métodos , Sonicação , Fatores de Tempo , Eliminação de Resíduos Líquidos/métodos , Purificação da Água/métodosRESUMO
Alkaline and ultrasonic sludge disintegration can be used as the pretreatment of waste activated sludge (WAS) to promote the subsequent anaerobic or aerobic digestion. In this study, different combinations of these two methods were investigated. The evaluation was based on the quantity of soluble chemical oxygen demand (SCOD) in the pretreated sludge as well as the degradation of organic matter in the subsequent aerobic digestion. For WAS samples with combined pretreatment, the released COD levels were higher than those with ultrasonic or alkaline pretreatment alone. When combined with the ultrasonic treatment, NaOH treatment was more efficient than Ca(OH)2 for WAS solubilization. The COD levels released in various sequential options of combined NaOH and ultrasonic treatments were in the the following descending order: simultaneous treatment > NaOH treatment followed by ultrasonic treatment > ultrasonic treatment followed by NaOH treatment. For simultaneous treatment, low NaOH dosage (100 g/kg dry solid), short duration (30 min) of NaOH treatment, and low ultrasonic specific energy (7500 kJ/kg dry solid) were suitable for sludge disintegration. Using combined NaOH and ultrasonic pretreatment with optimal parameters, the degradation efficiency of organic matter was increased from 38.0% to 50.7%, which is much higher than that with ultrasonic (42.5%) or with NaOH pretreatment (43.5%) in the subsequent aerobic digestion at the same retention time.
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Aerobiose , Oxigênio/metabolismo , Esgotos/química , Hidróxido de Sódio/metabolismo , Ultrassom , AnaerobioseRESUMO
The quality assessment of water, supplied to the end user, is an essential part to assess the physical, chemical, and biological status of water, which impacts on human health. For the quality assessment of drinking water treatment plants and distribution systems of Hyderabad City and Mehran University of Engineering and Technology, Jamshoro, Pakistan, 13 surface drinking water samples were collected from three treatment plants, two of Hyderabad City, including WASA treatment plant and its distribution system (n = 5), Hala Nakka treatment plant and its distribution system (n = 6), and Mehran University Employees Cooperative Housing Society (MUECHS) treatment plant and its distribution system (n = 2). Physicochemical parameters of all drinking water samples were in the range compared to EPA and WHO guidelines, except in L-12 sample. Notably, no free-chlorine was detected in all samples. In metagenomics analysis, targeting V3-V4 hypervariable region of 16S rRNA gene, in QIIME2 environment, high bacterial prevalence was observed in all samples. On average, 348 OTUs were observed per sample. Among all samples, treated water sample from the Hala Nakka Treatment Plant (HNTR) was the most diverse sample in bacterial composition (Shannon 7.51 and Simpsons reciprocal indices 0.98). Overall, Proteobacteria, Bacteroidetes, Cyanobacteria, Verrucomicrobia, and Actinobacteria were the five most abundant phyla (relative abundances of 43.6, 37.9, 8.5, 2.5, and 2.4 percent, respectively). Notably, Cyanobacteria are well-known toxin producers which effect the human, and animal health. At genus level, Flavobacterium (4.86%) and Aquirestis (3.77%) were the most abundant genera. Functional predictions, based on 16S rRNA gene by PICRUSt, predicted 6909 KEGG orthologies, relating to 245 KEGG pathways. Among the predicted pathways of KEGG orthologies, pathways to human infections were also found. In conclusion, this study gave a deep insight into bacterial contamination in drinking water samples of Hyderabad City and MUECHS treatment plants and water quality status in Hyderabad and Mehran University of Engineering and Technology.
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Água Potável/microbiologia , Monitoramento Ambiental , Metagenoma , Purificação da Água , Actinobacteria/genética , Bacteroidetes/genética , Cloro , Cidades , Cianobactérias/classificação , Habitação , Humanos , Metagenômica , Paquistão , Proteobactérias/genética , RNA Ribossômico 16S/genética , Universidades , Qualidade da ÁguaRESUMO
Herein, we attempt to improve the mechanical stability of anionic functionalized cellulose nanofibers (a-CNF) having 1.25 mmol of carboxymethyl groups per gram of cellulose nanofibers (CNF). The a-CNF and cross-linked a-CNF (za-CNF) then used for water desalination in the continuous mode using a tubular adsorption column. It is worth mentioning that the za-CNF possess 40% degree of cross-linking provided better mechanical stability as the tensile strength improved from 3.2 to 5.2 MPa over a-CNF. The IR spectroscopy was used to confirm the success of chemical modifications. Upon ionic cross-linking, the BET surface area reduced from 13.53 to 7.54 m2·g-1 corresponds to a-CNF and za-CNF, respectively. Moreover, this research was extended to determine the dynamic adsorption capacities for a-CNF and za-CNF, which were found to be 21 and 10 mg·g-1 respectively at a flow rate of 5-mL·min-1 explained by Thomas model.
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Celulose/química , Nanofibras/química , Adsorção , Resistência à Tração/fisiologia , Água/químicaRESUMO
This study investigates the sintering behavior of dried sewage sludge and the related sintering mechanisms, considering sintering temperature and sintering time. Experimental results indicate that the characteristics are primarily influenced by sintering temperature. When the sintering temperature is increased from 1020 to 1050 degrees C, the specimens' compressive strength and bulk density increase significantly, while water absorption decreases obviously, indicating an improvement of densification due to sintering. However, the compressive strength cannot meet the requirement for traditional ceramic products due to the release of organic matters and the formation of big pores in the products. Phosphorus in sewage sludge initially takes reactions with the formation of calcium magnesium phosphate and aluminum phosphate during sintering, which are helpful for enhancing the compressive strength. So, some materials with high contents of Al could be used to enhance the compressive strength of products. Heavy metals are fixed primarily inside the sintered specimens, with the As, Pb, Cd, Cr, Ni, Cu, Zn concentrations in the leachate found to be in the range of China regulatory requirements. These results reveal the feasibility of recycling dried sewage sludge by sintering as a construction material.
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Incineração/métodos , Esgotos/análise , Adsorção , Algoritmos , Cerâmica , Metais Pesados/análise , Microscopia Eletrônica de Varredura , Espectrometria por Raios X , Temperatura , Eliminação de Resíduos Líquidos , Água/química , Poluentes Químicos da ÁguaRESUMO
The contribution of biowastes in municipal solid waste (MSW) is increasing day by day and being dumped in open atmosphere along with other wastes in every city of Pakistan. This study was formulated to evaluate the feasibility of biowastes such as fruit, vegetable and yard wastes of different seasons individual and mixing at different ratios to optimize methane production at Hyderabad Sindh, Pakistan. Batch digestion of selected samples was conducted for 40 days under mesophilic condition. Methane yield of individual fruit, vegetable and yard wastes (FrVYW) of summer and winter season was obtained in the range of 0.36-0.40â¯L/g VS and 0.39-0.44â¯L/g VS added respectively. The results of co-digestion of FrVYW of summer and winter season were observed in the range of 0.42-0.45â¯L/g VS added and 0.46 to 0.54â¯L/g VS added respectively. The results of tri-digestion of FrVYW of summer and winter season were achieved in the range of 0.46-0.53â¯L/g VS added and 0.56-0.62â¯L/g VS added respectively. Findings of study showed that methane production potential of tri-digestions were highest than all of others and that of co-digestion were higher than mono-digestion of FrVYW. Overall results of study concluded that tri-digestion of FrVYW at the equal blending ratio reported highest methane potential. Therefore, the study recommended that tri-digestion of FrVYW at equal mixing ratio is an optimal ratio for anaerobic digestion process to yield maximum methane production from FrVYW.
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Reatores Biológicos , Frutas , Eliminação de Resíduos , Verduras , Anaerobiose , Biocombustíveis , Cidades , Metano , Paquistão , Estações do AnoRESUMO
Lead is known for its toxic and non-biodegradable behavior. The consumption of lead-contaminated water is one of the major threat the world is facing nowadays. In this study, polyacrylonitrile (PAN) and magnetite (Fe3O4) composite nanofiber adsorbent was developed for Pb2+ removal in batch mode. The synthesis was done by a simple and scalable process of electrospinning followed by chemical precipitation of Fe3O4. The nanofibers thus obtained were characterized through FTIR, zeta potential analyzer, and scanning electron microscope (SEM) and were analyzed for their adsorption capability for Pb2+ ions. The amount of metal ion adsorbed was influenced by the initial metal ion concentration, the time the adsorbent was in contact, the amount of nanofiber, and the pH of the solution. The experimental data fitted well with pseudo 2nd-order and Langmuir adsorption isotherm model. The nanofibers showed high adsorption capability and could be recommended for Pb2+ removal successfully.
Assuntos
Resinas Acrílicas/química , Óxido Ferroso-Férrico/química , Chumbo/análise , Nanofibras/química , Purificação da Água/métodos , Adsorção , Cinética , Modelos Teóricos , Propriedades de Superfície , Poluentes Químicos da Água/análiseRESUMO
Landfilling is a dominant municipal solid waste (MSW) disposal method in most developing countries. In China, approximately 85% of the generated MSW is being disposed of in the landfills. The amount of MSW is growing rapidly with the rate of approximately 8-10% annually, which contains a high quantity of moisture and organic matters. The problems of leachate treatment and landfill gas (LFG) emissions are increasing gradually. Reducing the hazard before emplacement, pretreatment of MSW before landfilling has become very important for the conventional landfill. In this study, aerobic pretreatment of mixed MSW was used, and much attention has been given to the natural convection of air in the mixed and unshredded MSW for bioconversion of organic matter (OM). This study is an attempt to investigate aerobic pretreatment suitability for the mixed and unshredded MSW at Beijing. A pilot-scale aerobic pretreatment simulator (APS) was developed at Beishen Shu Landfill in Beijing. To work out the biodegradation of the OM in the APS, fresh and pretreated MSW samples were collected and analyzed for OM, moisture content, temperature, chemical oxygen demand, total organic carbon, carbon, nitrogen, hydrogen, lignocelluloses, and biochemical methane potential at various stages of the pretreatment. Furthermore, results of the fresh and pretreated MSW are compared. Significant reduction in the observed parameters of the pretreated waste samples is observed. This work demonstrates that pretreatment is significantly effective in reducing the landfill emissions that is leachate and LFG.