Quantifying spatio-temporal variation in aquaculture production areas in Satkhira, Bangladesh using geospatial and social survey

Despite Bangladesh being one of the leading countries in aquaculture food production worldwide, there is a considerable lack of updated scientific information about aquaculture activities in remote sites, making it difficult to manage sustainably. This study explored the use of geospatial and field data to monitor spatio-temporal changes in aquaculture production sites in the Satkhira district from 2017–2019. We used Shuttle Radar Topographic Mission digital elevation model (SRTM DEM) to locate aquaculture ponds based on the terrain elevation and slope. Radar backscatter information from the Sentinel-1 satellite, and different water indices derived from Sentinel-2 were used to assess the spatio-temporal extents of aquaculture areas. An image segmentation algorithm was applied to detect aquaculture ponds based on backscattering intensity, size and shape characteristics. Our results show that the highest number of aquaculture ponds were observed in January, with a size of more than 30,000 ha. Object-based image classification of Sentinel-1 data showed an overall accuracy above 80%. The key factors responsible for the variation in aquaculture were investigated using field surveys. We noticed that despite a significant number of aquaculture ponds in the study area, shrimp production and export are decreasing because of a lack of infrastructure, poor governance, and lack of awareness in the local communities. The result of this study can provide in-depth information about aquaculture areas, which is vital for policymakers and environmental administrators for successful aquaculture management in Satkhira, Bangladesh and other countries with similar issues

Spatio-temporal variations in the water quality of the Doorndraai Dam, South Africa: An assessment of sustainable water resource management

The problem of water scarcity and clean water in sub-Saharan Africa is a growing concern. This study aims to quantify the water quality on a temporal scale in the Doorndraai dam site in sub-Saharan Africa to design possible management options. Here, an integrated approach using both in-situ measurements of water quality parameters and remote sensing data was used to derive the water quality index (WQI) and inherent optical properties of water to deduce the factors governing seasonal and annual variability. The results show that all the water quality parameters analyzed fall under the permissible limit of the World Health Organization (WHO) for drinking water, except turbidity. The average value of turbidity for the dry and wet periods was 12.52 and 3.39 NTU, respectively. WQI value ranges from good to excellent during the wet season, and poor in the dry season owing to the high values of turbidity in the water samples. Both in-situ and remote sensing-based analysis shows that during the last five years, the value of suspended particulate matter (SPM) based on Landsat-8 increased gradually in the study area. The Sentinel-2 derived modified normalized difference water index (MNDWI) shows a decreasing trend in the water area due to encroachment. The strong correlation between in-situ and remote sensing data supports the usefulness of remote sensing techniques for water resource management, especially in data-scarce regions. Looking at the spatio-temporal trend of water quality evolution, the findings of this study will help local decision-makers design sustainable plans for water resource management of Doorndraai dam

Hydrochemical indices as a proxy for assessing land-use impacts on water resources: a sustainable management perspective and case study of Can Tho City, Vietnam

Can Tho City is experiencing water stress driven by rapid global changes. This study assesses the spatiotemporal variation in surface water quality (SWQ) through a multivariate statistical approach to provide evidence-based scientific information supporting sustainable water resource management and contributing to achieving the city’s sustainable development goals (SDGs). The complex SWQ dataset with 14 monthly-measured parameters at 73 sampling sites throughout the city was collected and analyzed. The obtained results indicated that average concentrations of biochemical oxygen demand, chemical oxygen demand (COD), dissolved oxygen (DO), total coliform, turbidity, total suspended solids, and phosphate (PO43−) exceeded the permissible national levels. Spatially, cluster analysis had divided the city’s river basin into three different zones (mixed urban-industrial, agricultural, and mixed urban–rural zones). The key sources of SWQ pollution in these three zones were individually identified by principal component/factor analysis (PCA/FA), which were mainly related to domestic wastewater, industrial effluents, farming runoff, soil erosion, upstream sediment flows, and severe droughts. Discriminant analysis also explored that COD, DO, turbidity, nitrate (NO3−), and PO43− were the key parameters discriminating SWQ in the city among seasons and land-use zones. The temporally analyzed results from weighted arithmetic water quality index (WAWQI) estimation revealed the deterioration of SWQ conditions, whereby the total polluted monitoring sites of the city increased from 29% in 2013 to 51% in 2019. The key drivers of this deterioration were the expansion in built-up and industrial land areas, farming runoff, and droughts

Relationship-Preserving Change Propagation in Process Ecosystems

As process-orientation continues to be broadly adopted – evidenced by the increasing number of large business process repositories, managing changes in such complex repositories becomes a growing issue. A critical aspect in evolving business processes is change propagation: given a set of primary changes made to a process in a repository, what additional changes are needed to maintain consistency of relationships between various processes in the repository. In this paper, we view a collection of interrelated processes as an ecosystem in which inter-process relationships are formally defined through their annotated semantic effects. We also argue that change propagation is in fact the process of restoring consistency-equilibrium of a process ecosystem. In addition, the underlying change propagation mechanism of our framework is leveraged upon the well-known Constraint Satisfaction Problem (CSP) technology. Our initial experimental results indicate the efficiency of our approach in propagating changes within medium-sized process repositories

Biostabilization assessment of MSW co-disposed with MSWI fly ash in anaerobic bioreactors

Municipal solid waste incinerator (MSWI) fly ash has been examined for possible use as landfill interim cover. For this aim, three anaerobic bioreactors, 1.2 m high and 0.2 m in diameter, were used to assess the co-digestion or co-disposal performance of MSW and MSWI fly ash. Two bioreactors contained ratios of 10 and 20 g fly ash per liter of MSW (or 0.2 and 0.4 g g?1 VS, that is, 0.2 and 0.4 g fly ash per gram volatile solids (VS) of MSW). The remaining bioreactor was used as control, without fly ash addition. The results showed that gas production rate was enhanced by the appropriate addition of MSWI fly ash, with a rate of 6.5 l day?1 kg?1 VS at peak production in the ash-added bioreactors, compared to 4 l day?1 kg?1 VS in control. Conductivity, alkali metals and VS in leachate were higher in the fly ash-added bioreactors compared to control. The results show that MSW decomposition was maintained throughout at near-neutral pH and might be improved by release of alkali and trace metals from fly ash. Heavy metals exerted no inhibitory effect on MSW digestion in all three bioreactors. These phenomena indicate that proper amounts of MSWI fly ash, co-disposed or co-digested with MSW, could facilitate bacterial activity, digestion efficiency and gas production rate

Modeling biogas production from organic fraction of MSW co-digested with MSWI ashes in anaerobic bioreactors

This study aims at investigating the effects of MSW incinerator fly ash (FA) and bottom ash (BA) on the anaerobic co-digestion of OFMSW with FA or BA. It also simulates the biogas production from various dosed and control bioreactors. Results showed that suitable ashes addition (FA/MSW 10 and 20 g L?1 and BA/MSW 100 g L?1) could improve the MSW anaerobic digestion and enhance the biogas production rates. FA/MSW 20 g L?1 bioreactor had the higher biogas production and rate implying the potential option for MSW anaerobic co-digestion. Modeling studies showed that exponential plot simulated better for FA/MSW 10 g L?1 and control bioreactors while Gaussian plot was applicable for FA/MSW 20 g L?1 one. Linear and exponential plot of descending limb both simulated better for BA/MSW 100 g L?1 bioreactor. Modified Gompertz plot showed higher correlation of biogas accumulation than exponential rise to maximum plot for all bioreactor

Avaliação da microfiltração para remoção do lodo gerado no processo oxidativo avançado empregando o reagente de Fenton no tratamento de lixiviado de aterro sanitário Evaluation of microfiltration for removal of sludge generated in advanced oxidation process by Fenton reagent in treatment of landfill leachate

Uma alternativa atrativa para o tratamento de lixiviado de aterro sanitário são os processos oxidativos avançados empregando o reagente de Fenton (POA/Fenton). No entanto, a aplicação do POA/Fenton é limitada pela geração de lodo no processo. Esse lodo possui elevada concentração de ferro, o que torna necessária sua separação do efluente tratado. O objetivo desse trabalho foi avaliar a microfiltração para a remoção de lodo gerado no POA/Fenton. A pesquisa foi desenvolvida em unidade de bancada. O POA/Fenton apresentou elevada eficiência na remoção de matéria orgânica (75%) e cor real (95%). O processo de microfiltração foi eficiente na separação do lodo gerado, o qual apresentou baixa sedimentabilidade, dificultando sua separação por sedimentação, além de ter contribuído para a remoção de outros poluentes.<br>Advanced oxidation processes using Fenton's reagent (AOP/Fenton) are an attractive alternative for landfill leachate treatment. However, the implementation of the AOP/Fenton is limited by the generation of sludge in the process. The sludge has a high iron concentration, which needs its separation from the treated effluent. The aim of this study was to evaluate the microfiltration for sludge removal from an AOP/Fenton. The work was conducted in bench scale. The advanced oxidation process showed high efficiency in removing organic matter (75%) and true color (95%). The microfiltration was effective in separating the sludge, which showed low settling hindering their separation by sedimentation, and has contributed to the removal of other pollutants