Plasmonic metal decorated titanium dioxide thin films for enhanced photodegradation of organic contaminants

Photocatalysis using titanium dioxide as photocatalyst is an efficient way for the removal of organic contaminants in water using solar energy. In this study, thin films of copper and silver were deposited on fused silica using the thermal evaporation technique. A 100 nm film of titanium dioxide (TiO2) was then deposited on the plasmonic metal films using a sputter coating technique. The opposite order of deposition of the film was also explored. The prepared thin films were fully characterized using high resolution scanning electron microscopy (HRSEM), X-ray diffraction (XRD), atomic force microscopy (AFM) and Rutherford backscattering spectrometry (RBS). The effect of plasmonic metal film thickness, order of deposition and the use of bimetallic layers on the photocatalytic activity of the TiO2 photocatalyst was evaluated using methyl orange as a model pollutant. It was shown that, the increase in Ag film thickness underneath the TiO2 film increased the photocatalytic activity of the TiO2 photocatalyst until an optimum film thickness of 20 nm was attained. In the case of copper, the increase in film thickness above 5 nm led to reduced photocatalytic activity. Silver was found to be a better plasmonic metal than copper in enhancing the photocatalytic activity of TiO2 under UV light illumination. Cu was found to perform better when deposited underneath the TiO2 film whereas Ag performed better when deposited on top of the TiO2 photocatalyst film. The use of bimetallic layers was found to enhance TiO2 photocatalytic activity more than monometallic layers.IS

Modelling the kinetic of biogas production from co-digestion of pig waste and grass clippings

Abstract: This work investigated the use of laboratory batch anaerobic digester to derive kinetics parameters for anaerobic co-digestion of pig waste and grass clippings. Laboratory experiment data from 10 litres batch anaerobic digester operating at ambient mesophilic temperature of 37 0C and pH of 6.9 was used to derive parameters for modified Gompertz model. The carbon/nitrogen (C/N) ratio of Pig waste was found to be 16.16 and grass clippings to be 20.54. Through co-digestion in ratio of 1:1, the C/N ratio settled at 17.28. The actual biogas yield was found to be 7725 ml/g COD. In the model of biogas production prediction, the kinetics constants of A (ml/g COD), μ (ml/g COD. day), λ (day) was 7920.70, 701.35, 1.61 respectively with coefficient of determination (R2) of 0.9994. Modified Gompertz plot showed better correlation of cumulative biogas production and these results show biogas production can be enhanced from co-digestion of substrates

The kinetic of biogas rate from cow dung and grass clippings

Abstract:In this study, we investigated the use of laboratory batch anaerobic digester to derive kinetics parameters for anaerobic co-digestion of cow dung and grass clippings. The Carbon/Nitrogen (C/N) ratio of cow dung was found to be 17.17 and grass clippings to be 20.54. Through co-digestion, the C/N ratio settled at 19.08. Laboratory experimental data from 10 litres batch anaerobic digester operating at mesophilic temperature of 37 0C and pH of 6.9 was used to derive parameters for Modified Gompertz model. The actual biogas yield was found to be 4370 ml/g COD. In the model of biogas production prediction, the kinetics constants of A (ml/g COD), μ (ml/g COD. day), λ (day) were 4319.20, 939.71, 1.91 respectively with coefficient of determination (R2) of 0.996

Design model selection and dimensioning of anaerobic digester for the OFMSW

Abstract: In this study, we investigated the design model selection and dimensioning of the anaerobic digester for the codigestion of different organics fraction of municipal solid waste (OFMSW) originating from the city’s landfills. The waste quantification and characterization exercise were undertaken at the point of generation, so as to obtain the total amount of waste generated and to ascertain the waste composition. Via the application of the simple multi-attribute rating (SMART) technique of multiple-criteria decision analysis (MCDA) as a decision support tool base on cost, scalability, temperature regulation, ease of construction, operation, and maintenance. The most preferred model option for bioenergy design technology was selected from a list of potential alternatives available in the market. Continuous stirred tank reactor (digester) CSTR scored the highest with 79% and was selected for the design in OFMSW biogas production. The geometry of the biodigester parameters was comparable with the anaerobic digestion (AD) process

Mesophilic anaerobic co-digestion of cow dung, chicken droppings and grass clippings

Abstract: The main focus of this study was mesophilic anaerobic co-digestion of cow dung, chicken droppings and grass clippings using pilot bio-digesters. The biochemical methane potential (BMP) works under batch anaerobic digester operating in ambient mesophilic temperature of 35 oC and 37 0C and pH of 7 to generate biogas. The carbon/nitrogen (C/N) ratio for cow dung and chicken droppings was found to be 17.70 and 63.67 respectively and grass clippings to be 20.54. Through co-digestion in a ratio of 1:1, the C/N ratio for cow dung and grass clippings settled at 19.19 while that for chicken droppings and grass clippings settled at 20.49. The conversion rate of the reaction and biogas production increased with the increase in temperature and hydraulic retention time until an equilibrium state was achieved. At the temperature 37 OC, it was observed to be the suitable mesophilic temperature for anaerobic digestion due to high dissociation and collision leading to high rate of biogas production

Water and Wastewater Digital Surveillance 1 for Monitoring and Early Detection of 2 the COVID-19 Hotspot: Industry 4.0

Abstract: There are a high number of COVID-19 cases per capita in the world that goes undetected including clinical diseases compatible with COVID-19. While the presence of the COVID-19 in untreated drinking water is possible, it is yet to be detected in the drinking-water supplies. COVID-19 viral fragments have been found in excrete, this call for wastewater monitoring and analysis (wastewater surveillance) of the potential health risk. This raises concern about the potential of the SARS-CoV-2 transmission via the water systems. The economic limits on the medical screening for the SARS-CoV-2 or COVID-19 worldwide are turning to wastewater-based epidemiology as great potential tools for assessing and management of the COVID-19 pandemic. Surveillance and tracking of the pathogens in the wastewater are key to the early warning system and public health strategy monitoring of the COVID-19. Currently, RT-qPCR assays is been developed for SARS-CoV-2 RNA specimen clinical testing and detection in the water system. Convectional wastewater treatment methods and disinfection are expected to eradicate the SAR-CoV-2. Chlorine, UV radiation, ozone, chloramine is been used to inactivate and disinfect the water treatment system against the SARS-CoV-2. Water management and design of the water infrastructure require major changes to accommodate climate change, water cycle, reimaging of digitalization, infrastructure and privacy protection. The water digital revolution, biosensors and nanoscale, contact tracing, knowledge management can accelerate with disruption of the COVID-19 outbreak (water-health-digital nexus)

A Comparative Study of Modified and Unmodified Algae (Pediastrum boryanum) for Removal of Lead, Cadmium and Copper in Contaminated Water

The presence of heavy metals in water is of concern due to the risk toxicity. Thus there is need for their removal for the safety of consumers. Methods applied for removal of heavy metals include adsorption, membrane filtration and co-precipitation. However, studies have revealed adsorption is highly effective technique. Most adsorbents are expensive or require extensive processing before use and hence need to explore for possible sources of inexpensive adsorbents. This research work investigated the use an algal biomass (pediastrum boryanum) as an adsorbent for removal of Lead, Cadmium and Copper in waste water in its raw and modified forms. The samples were characterized with FTIR and was confirmed a successful modification with tetramethylethlynediamine (TMEDA). Sorption parameters were optimized and the material was finally applied on real water samples. It was found that the sorption was best at lower pH values (4.2-6.8). Sorption kinetics was very high as more that 90% of the metals were removed from the solution within 30 minutes. The adsorption of copper fitted into the Langmuir adsorption isotherm indicating a monolayer binding mechanism. Cadmium and lead fitted best the Freundlich adsorption mechanism. Sorption of lead and cadmium was of pseudo-second order kinetics, confirming a multisite interaction whereas copper was pseudo-first order indicating a single site adsorption. The adsorption capacity did not improve upon modification but the stability of the material was improved and secondary pollution of leaching colour was alleviated. This implies that the modified material is suitable for application on the removal of metals from water

Multi-criteria analysis of different technologies for the bioenergy recovery from OFMSW

Abstract: In this study, the multi-criteria analysis model is demonstrated for evaluation and technologies from municipal solid waste (MSW) in City of Johannesburg (CoJ), South Africa. The technologies evaluation and alternation criteria for multi-criteria decision analysis (MCDA) area characterized by reviewing the literature and consulting experts in the renewable energy and waste management. MCDA was the approach employed by decision makers to make recommendation on technique employed to select the most suitable biogas digester technology for organic fraction of municipal solid waste (OFMWS) originating from the city’s landfills base on scalability, relative cost prices, available, temperature regulation, agitation, ease of construction, operation and maintenance. The result for digester type indicated that the “complete mix, continuously stirred anaerobic digester” (CSAD) was preferred with 79% preference to other anaerobic digester technologies for energy recovery

Effect of seawater acidification on physiological and energy metabolism responses of the common Cockle (Anadara antiquata) of Gazi Bay, Kenya

DATA AVAILABILITY : Data will be made available on request.Ocean acidification (OA) is becoming a potential threat to marine organisms, especially in calcifying marine invertebrates. So far, along the Kenya Coast, there has been little research on the impact of OA on cockle (Anadara antiquata), particularly on their physiological impacts induced by exposure to acidified seawater. Hence, this study aimed to investigate the physiological and biochemical responses of Anadara antiquata under present and future predicted seawater pH. In this study, the Anadara antiquata was exposed to three pH treatments (pH 7.90, 7.60, and 7.30) for 8 weeks to mimic future OA and to understand the physiological and biochemical effects on the organisms. Condition index, energy reserves (glycogen and protein), and cellular damage (e.g., lipid peroxidation level) were measured. Condition index (CI) showed no significant difference at different pH treatments (pH 7.90, 7.60, and 7.30), whereas the survival Anadara antiquata was slightly reduced after 8 weeks of exposure to pH 7.30. Glycogen and protein content were not affected at reduced pH (7.60 and 7.30). However, after 8 weeks of exposure to pH 7.60 and 7.30, Anadara antiquata showed a slight decrease in lipid peroxidation, an indication of cellular damage. The physiological and biochemical parameters analyzed (glycogen and protein content; lipid peroxidation levels) showed useful biomarkers to assess ocean acidification impacts in cockle.Kenya Marine and Fisheries Research Institute (KMFRI), University of Johannesburg, International Atomic Energy Agency (IAEA) Coordinated Research Project (K41018) and Western Indian Ocean Marine Science Association (WIOMSA) MASMA.https://www.elsevier.com/locate/marpolbulhj2024ChemistrySDG-14:Life below wate