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Diversity of plasmids, antibiotic-resistance phenotypes and UV resistance among ESBL- producing E. coli isolated from WWTP effluent in Hong Kong
No full textAre ESBL-producing E. coli isolated from a WWTP effluent more resistant to UV light at different wavelengths?
No full textGlobal integrated surveillance of the dissemination of extended spectrum β-lactamase-producing E. coli using “One Health” approach is proposed by World Health Organisation. To minimize microbial spread in the environment, conventional, mercury-vapour, UV lamps are commonly employed to disinfect wastewater effluents after traditional treatment processes. Since their disposal is a significant environmental issue, UV-LEDs, are emerging as a sustainable alternative. In this work, we aimed to address certain contradictions about selective microbial responses to UV disinfection. We have investigated UV susceptibility of three ESBL-producing E. coli strains, with different DNA characteristics, and a type-strain (ATCC 25922) upon disinfection with UV-LEDs at 3 different wavelengths (265, 285 and 300 nm). Our current results suggest that, when bacteria are exposed to sublethal doses of UV light, selection of clinically relevant, antibiotic resistant bacteria may occur, resulting in an increased proportion of ESBL-producers in the population released after the treatment
Integrated photocatalytic-biological treatment of triazine-containing pollutants
No full text© 2019 Elsevier Ltd The degradation of triazine-containing pollutants including simazine, Irgarol® 1051 and Reactive Brilliant Red K-2G (K-2G) by photocatalytic treatment was investigated. The effects of titanium dioxide (TiO2) concentration, initial pH of reaction mixture, irradiation time and ultraviolet (UV) intensity on photocatalytic treatment efficiency were examined. Complete decolorization of K-2G was observed at 60 min photodegradation while only 15 min were required to completely degrade simazine and Irgarol® 1051 under respective optimized conditions. High-performance liquid chromatography (HPLC), gas chromatography/mass spectrometry (GC/MS) and ion chromatography (IC) were employed to identify the photocatalytic degradation intermediates and products. Dealkylated intermediates of simazine, deisopropylatrazine and deethyldeisopropylatrazine, and Irgarol® 1051 were detected by GC/MS in the initial phase of degradation. Complete mineralization could not be achieved for all triazine-containing pollutants even after prolonged (\u3e72 h) UV irradiation due to the presence of a photocatalysis-resistant end product, cyanuric acid (CA). The toxicities of different compounds before and after photocatalytic treatment were also monitored by three bioassays. To further treat the photocatalysis-resistant end product, a CA-degrading bacterium was isolated from polluted marine sediment and further identified as Klebsiella pneumoniae by comparing the substrate utilization pattern (Biolog™ microplate), fatty acid composition and 16S rRNA gene sequencing. K. pneumoniae efficiently utilized CA from 1 to 2000 mg/L as a good nitrogen source and complete mineralization of CA was observed within 24 h of incubation. This study demonstrates that the biodegradability of triazine-containing pollutants was significantly improved by the photocatalytic pre-treatment, and this proposed photocatalytic-biological integrated system can effectively treat various classes of triazine-containing pollutants
Study of the efficacy of probiotic bacteria to reduce process-induced toxicant -acrylamide
Get PDFHuman exposure to various potential food contaminants or process-induced food toxicants has an increasing public health concern. Acrylamide is one of the process-induced toxicants that is formed when foods, especially those with high carbohydrate and rich in asparagine, are cooked at high temperature of 120oC or above in the presence of reducing sugar particularly glucose and fructose in Maillard browning reaction. The presence of acrylamide in food arose the public health concern due to its potential carcinogenicity and genotoxicity. In this study, the new approach to reduce acrylamide by probiotic bacteria was investigated. Two major food groups, potato chips and soda crackers, contain relative high acrylamide levels were selected as food samples. The content of acrylamide in selected potato chip and soda cracker samples were analysed by Liquid chromatography–mass spectrometry with solid phase extraction (SPE) clean-up. Three Lactobacillus strains - Lactobacillus casei, Lactobacillus acidophilus and Lactobacillus rhamnosus were selected for investigating the effect of reducing acrylamide. The resulted showed that the acrylamide content in potato chip and soda cracker samples were reduced after i ncubati on with different Lactobacillus strains. Lactobacillus casei had exhibited the highest capability in reducing acrylamide in selected samples The % reduction of acrylamide by three Lactobacillus strains in potato chip samples ranged from 43.80 – 23.67% while in soda cracker samples ranged from 20.23 – 9.50%. The results demonstrated that the acrylamide-reducing capacity of selected probiotic strains was different under different food matrix, probably due to different food composition and processing treatment
Effects of beam-column depth ratio on seismic behavior of non-seismic detailed reinforced concrete beam-column joints
No full textFour reinforced concrete exterior beam-column joints with open anchorage beam reinforcement, which are manufactured to simulate those in existing reinforced concrete framed buildings, are tested under reversed cyclic loads simulating earthquake excitation. The particular emphasis of this project is given to the effects of the beam-column depth ratio and the stirrup ratio in joints on the shear strength and seismic behaviour of the exterior joints without seismically designed details. The experimental results indicate that the stirrup placed in the beam-column joint cores can effectively improve the shear strength of the joint and enhance the seismic performance, and the shear strength of the joints decreases when the beam-column depth ratio increases. The experimental results are also compared with the results predicted by two non-seismic design codes (Eurocode 2 and HK code 2013) and three codes for seismic design (Eurocode 8, ACI 318-14 and NZS 3101). In general, the current non-seismic design codes and seismic design codes of practice cannot accurately predict the shear strength of the exterior joints with non-seismically designed details. It is shown that neglecting the seismic design of beam-column joints may lead to potential damage of reinforced concrete framed buildings in unexpected moderate or low seismic areas
Economic feasibility of gasoline production from lignocellulosic wastes in Hong Kong
Get PDFIn this study, the conceptual process flowsheet was developed and the economic feasibility of woody biomass conversion to biofuel as feedstock was analysed by considering several promising experimental processes for lignin depolymerization, such as hydrodeoxygenation and hydrogenolysis, along with lignocellulosic biomass fractionation processes. The engineering simulation process toward the commercial production of bio-gasoline from lignocellulosic biomass using SuperPro Designer® was modeled. The compatibility of the end products with the current gasoline specifications was evaluated and various blending options were investigated to meet the octane number and Reid vapor pressure requirement of the product. The economic potential of the simulated engineering process was then evaluated from an economic perspective. The operating costs and capital investment of three scenario using three different catalytic systems were estimated and discussed to assess of the potential of commercializing of woody biomass valorization process. The main potential market segments were identified, including the process by-products such as xylose and cellulose pulp. From the economic evaluation study, it was found that selling the biomass fractionation products alone does have a greater profit than valorization of lignin to produce bio-gasoline, with net present value of RMB 22,653,000 and RMB 177,000, respectively at the same return on investment if the plant is set up in Hong Kong. It was also found that catalysts play a pivotal role in determination of the profitability in the valorization process, not only because of the price of the catalyst, but also the product distributions obtained with various types of it. To obtain the same gross profit, the sale price of biogasoline has to be set higher with platinum catalysts than with ruthenium catalysts (nearly 10 folds). Thus, catalyst development and process improvement are crucial in the establishment of bio-based circular economy
Effect of limited tension stiffening on behavior of reinforced concrete panels in shear.
No full textThe principal tensile strength of cracked concrete is not well defined in existing models for predicting the shear response of reinforced concrete (RC) membrane elements; hence, the shear strength of RC elements is generally overestimated due to the unrealistic decreasing slope of tensile stress as the crack accumulates. In this paper, the effect of limited tension-stiffening behavior of cracked RC panels under pure shear stresses is investigated by proposing an analytical model named as the tension-stiffening fixed-angle truss model (TFTM). The proposed model includes the limited tension-stiffening effect of post-cracking reinforced concrete and adopts the fixed-angle theory. In the analysis of TFTM, an iterative root-finding technique and a search method genetic algorithm are applied for solving the stress-strain relationship. The limited tension-stiffening effect on RC panels is examined with a series of tests. Predictions by the proposed model show very good agreement with experimental results, and the elapsed time for each calculation loop is reduced significantly
A review of renewable energy assessment methods in green building and green neighborhood rating systems
No full textGreen buildings and neighborhoods can help mitigate impacts of buildings on the environment, society and economy. Many rating systems or tools have been developed worldwide to assess and certificate green buildings or green neighborhoods. Renewable energy plays an important role in achieving green buildings/neighborhoods or zero energy buildings/neighborhoods by reducing fuel consumption and pollution emissions. However, substantial differences exist in assessing or quantifying the renewable energy in green building/neighborhood rating systems. This paper therefore provides a comprehensive review on renewable energy assessment methods adopted in green building/neighborhood rating systems, which would be very helpful to understand and then improve the rating systems. These methods are analyzed and discussed regarding to the calculation way, involved renewable energy types, building characteristics and energy conversion. Then a case study is conducted to quantitatively illustrate the difference of typical renewable energy assessment. Suggestions are summarized to improve the assessment methods. This paper will help investors, users and policy makers understand the rating systems more thoroughly and promote the development of green buildings and green neighborhoods
Tree distribution, morphology and modelled air pollution in urban parks
No full textTrees offer a range of ecosystem services and remain important in providing human benefits. However, emerging literature questions the long-accepted view of trees being able to improve air quality in urban parks. The aerodynamic effect of trees was identified as a major reason for the change of pollutant distribution in near-road parks, where trees can act as porous barriers and cause localised concentration increase. Although not yet fully developed, planting strategies aiming to mitigate the negative effect of vegetation on air quality should be encouraged in future park design. In this study, we explored the effect of tree planting design on pollutant diffusion by integrating field surveys in urban parks in Hong Kong with computational fluid dynamic (CFD) modelling. A series of indicators associated with tree morphology and landscape were derived from the surveys and their influence on air pollutant distribution in parks was examined using ENVI-MET. Dense trees with low crown base were found effective in improving air quality within parks when planted as barriers with a width of ~15 m at borders. However, more extensive planting led to a decrease in wind velocity and an increase in pollutant concentrations, which should be avoided. Tall trees tended to have little influence on airflow at the pedestrian level, which means they seem appropriate for small urban parks where wide barriers are not applicable and rapid ventilation should be encouraged. The tree distribution also altered the airflow and pollutant dispersion in parks. Our study provides clues for thoughtful planting strategies which can optimise air quality in urban parks
Study of the efficacy of probiotic bacteria to reduce process-induced toxicant -acrylamide
No full textHuman exposure to various potential food contaminants or process-induced food toxicants has an increasing public health concern. Acrylamide is one of the process-induced toxicants that is formed when foods, especially those with high carbohydrate and rich in asparagine, are cooked at high temperature of 120oC or above in the presence of reducing sugar particularly glucose and fructose in Maillard browning reaction. The presence of acrylamide in food arose the public health concern due to its potential carcinogenicity and genotoxicity. In this study, the new approach to reduce acrylamide by probiotic bacteria was investigated. Two major food groups, potato chips and soda crackers, contain relative high acrylamide levels were selected as food samples. The content of acrylamide in selected potato chip and soda cracker samples were analysed by Liquid chromatography–mass spectrometry with solid phase extraction (SPE) clean-up. Three Lactobacillus strains - Lactobacillus casei, Lactobacillus acidophilus and Lactobacillus rhamnosus were selected for investigating the effect of reducing acrylamide. The resulted showed that the acrylamide content in potato chip and soda cracker samples were reduced after incubation with different Lactobacillus strains. Lactobacillus casei had exhibited the highest capability in reducing acrylamide in selected samples. The % reduction of acrylamide by three Lactobacillus strains in potato chip samples ranged from 43.80 – 23.67% while in soda cracker samples ranged from 20.23 – 9.50%. The results demonstrated that the acrylamide-reducing capacity of selected probiotic strains was different under different food matrix, probably due to different food composition and processing treatment