Water quality is a critical challenge in Asia in the context of growing industrialization, urbanization, and climate change. Nature-based solutions (NbS) could play an important role in reducing urban water pollution, while generating multiple co-benefits that could make cities more liveable and resilient. In this regard, a number of pilot and demonstration projects have been set up to explore their potential across cities in Asia. Their effectiveness and impacts, however, have not been adequately documented, thus how they can be sustained, replicated and up-scaled remain poorly understood. This study aims to contribute to addressing this challenge by co-developing an integrated assessment framework and employing it to understand how existing evaluations of NbS in the region can be improved. It focuses specifically on a set of nature-based solutions that have been employed for water treatment across six cities in Southeast Asia (two in each Sri Lanka, the Philippines, and Vietnam), namely, floating wetlands, constructed wetlands and maturation ponds. The study also suggests specific methodologies for capturing a set of core indicators considered relevant for assessing the effectiveness and capturing the multi-faceted impacts of the examined NbS. 相似文献
Southeast Asian countries are confronting climate variability, challenging agricultural sustainability and rural livelihoods. However, little research effort has been devoted to exploring how farmers in those countries perceive climate variability and how the perceptions link to adaptive responses. This paper deploys information from three focus group discussions with 30 male farmers; and six in-depth interviews with one female and five male agricultural officers in the Mekong Delta, Vietnam. Recorded 34-year meteorological data in the delta from 1978 to 2011 is also incorporated to demonstrate the actual climate variability of the region. We find that farmers are becoming increasingly conscious of local climate variability issues. However, they have limited understanding of the importance of adaptation to their livelihoods. They also have limited knowledge of where and who to contact for appropriate climate change adaptation information. No opinions about the link between global warming and local climate variability and change were observed. Casual observation via public media and personal experience dominated farmers’ sources of information. Barriers to farmers’ adaptation are not exclusively restricted to socio-economic factors and resource constraints; e.g. land tenure, technical knowledge, market, social relationship, credit, information, health care, and demographics. Maladaptation, habit, and the perception of the importance of climate variability and adaptation are found as additional constraints. Observed differences in farmers’ and agricultural officers’ perspectives regarding barriers to farmers’ adaptation suggest important policy implications. 相似文献
Recently emerging disadvantages in conventional disinfection have heightened the need for finding a new solution. Developments in the use of high pressure carbon dioxide for food preservation and sterilization have led to a renewed interest in its applicability in wastewater treatment and water disinfection. Pressurized CO2 is one of the most investigated methods of antibacterial treatment and has been used extensively for decades to inhibit pathogens in dried food and liquid products. This study reviews the literature concerning the utility of CO2 as a disinfecting agent, and the pathogen inactivation mechanism of CO2 treatment is evaluated based on all available research. In this paper, it will be argued that the successful application and high effectiveness of CO2 treatment in liquid foods open a potential opportunity for its use in wastewater treatment and water disinfection. The findings from models with different operating conditions (pressure, temperature, microorganism, water content, media …) suggest that most microorganisms are successfully inhibited under CO2 treatment. It will also be shown that the bacterial deaths under CO2 treatment can be explained by many different mechanisms. Moreover, the findings in this study can help to address the recently emerging problems in water disinfection, such as disinfection by-products (resulting from chlorination or ozone treatment). 相似文献
The sigma (SIG) coordinate system in ocean circulation simulation models results inevitably in horizontal pressure gradient error. This problem also emerges in models of deep lakes or reservoirs with the same characteristics of underwater terrain mutation. SIG coordinates reflect vertical relative stratification but cannot be used to calculate horizontal pressure gradient force in places with drastic topographic changes; this results in vertical water temperature and circulation errors. In deep lakes or reservoirs, differences in water density caused by the temperature difference between upper and lower water bodies is the primary cause of thermal stratification phenomena. Lake Mead was used as a case study on steep topography based on Environmental Fluid Dynamics Code (EFDC) model in this study. SIG coordinates result in close agreement between the calibrated temperature time series at the top and middle water layers, but disparity in the bottom water layer. The error emerges in the horizontal pressure gradient error due to the SIG coordinate transformation. Neither increasing the vertical resolution nor adjusting the horizontal viscosity coefficient resolve this error. We test the sigma-zed (SGZ) coordinate which combines Z coordinate and SIG coordinate as a replacement for the SIG coordinate to find that they effectively reduce the model’s runtime and simulation efficiency. The vertical temperature distribution in SGZ coordinate mode is more accurate than the distribution in SIG coordinate mode. The Navier-Stokes horizontal gradient and advection diffusion equation results under SIG coordinates are very sensitive to the pressure gradient. The replacement also enhances resolution near the thermocline, facilitates reclosing of the water bottom and the equal sigma surface, lends significant advantages in terms of vertical temperature in the simulation for local deep water with steep terrain, and shortens runtime for 0.14 h. SGZ mixed coordinates are recommended in the simulation of deep lakes or reservoirs wherein the underwater topography is large (with abundant continuous deep trenches or reefs).
A simple online headspace solid-phase microextraction (HS-SPME) coupled with the gas chromatography-mass spectrometry (GC-MS) method was developed for simultaneous determination of trace amounts of nine estrogenic odorant alkylphenols and chlorophenols and their derivatives in water samples. The extraction conditions of HS-SPME were optimized including fiber selection, extraction temperature, extraction time, and salt concentration. Results showed that divinylbenzene/Carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fiber was the most appropriate one among the three selected commercial fibers, and the optimal extraction temperature, time, and salt concentration were 70 °C, 30 min, and 0.25 g/mL, respectively. The developed method was validated and showed good linearity (R2?>?0.989), low limit of detection (LOD, 0.002–0.5 μg/L), and excellent recoveries (76–126 %) with low relative standard deviation (RSD, 0.7–12.9 %). The developed method was finally applied to two surface water samples and some of these target compounds were detected. All these detected compounds were below their odor thresholds, except for 2,4,6-TCAS and 2,4,6-TBAS wherein their concentrations were near their odor thresholds. However, in the two surface water samples, these detected compounds contributed to a certain amount of estrogenicity, which seemed to suggest that more attention should be paid to the issue of estrogenicity rather than to the odor problem. 相似文献
This study aimed at finding effective strategies for high-performance removal of reactive blue 19 (RB19) dye from aqueous solution. Chitosan (CS) films had been prepared by using solvent casting with mild drying for this purpose. The CS films were characterized by X-ray diffraction, field-emission scanning electron microscopy, and Fourier transform infrared (FTIR) spectroscopy. The performance of RB19 removal using CS were evaluated by varying contact time, solution pH, initial dye concentration, and adsorbent dosage. Adsorption isotherms, kinetics, and desorption were investigated by batch experiments. Results showed that CS films exhibited the optimal adsorption performance for RB19 removal and high maximum adsorption capacities of RB19, which were 799 and 822.4 mg g?1 at 20 and 40 °C, respectively. Adsorption kinetic data were well described by the pseudo-second-order kinetic model. FTIR analyses further indicated that interactions between RB19 and the CS film occurred during adsorption. The CS films also exhibited satisfactory desorption of RB19 at about 80 % after 30 min of desorption at pH 11. Our study demonstrated that the CS films can be easily prepared and applied for effective removal of RB19 in treatment of wastewater. 相似文献
This study develops a depth-averaged two-dimensional (2D) numerical model using a finite difference method (FDM) on a staggered grid. The governing equations were solved using the Marker and Cell method that was developed at the Los Alamos laboratories by Harlow and Welch in 1965. In the paper, an explicit FDM was used to solve the governing equations. A first-order approximation was used for the temporal derivative. Second-order central difference approximations were used for space discretization. The time step is limited by the Courant–Friedrichs–Lewy (CFL) condition. The time step used in this study depends on the grid spacing and velocity components in the x- and y-directions. The study is divided into two steps: the first step is to develop a depth-averaged 2D numerical model to simulate the flow process. The second constructs a module to calculate the bed load transport and simulate the river morphology in the areas that have steep slopes, torrents, and mountain rivers. Developed model was applied to the artificial channel and a flood event in the Asungjun River section of the mountainous Yangyang Namdae River (South Korea). General simulation results showed that the developed model was in good agreement with the observed data. 相似文献