Browsing by Author "Sultana, Mst Sufia"

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    A reflectance-based water quality index and its application to examine degradation of river water quality in a rapidly urbanising megacity
    (Elsevier, 2021-08-14) Sultana, Mst Sufia; Dewan, Ashraf
    The water quality in rivers around Dhaka is deteriorating very fast given extensive sources of pollutants associated with rapid urbanisation and industrialisation. This paper introduced a water quality index (WQI) utilising Landsat bands 1 to 3 (0.45 to 0.67 µm) against band 5 (1.55 to 1.75 µm). The value of the proposed index varies from – 1 to + 1, whereby around 0 (small positive and negative) indicated probable contamination, if the water depth is around 2 m or above. This approach was developed using Landsat data to study long-term water quality change in the rivers surrounding Dhaka megacity, Bangladesh. The values were converted to total suspended solids (TSS) by utilising observed in-situ data, which showed a clear seasonal influence of water pollution, suggesting it reduces to the background level with the onset of high monsoonal river flows. However, long-term analysis showed that the rivers remain polluted throughout the year, particularly since 2011. The main reason for increasing river water pollution may be linked to the contaminant load which has increased extensively in recent years. The approach developed in this study may be used in other urban rivers, particularly in Asia.
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    Spatial representation of faecal pollution in unsewered urban catchments
    (Cranfield University, 2023-12) Sultana, Mst Sufia; Tyrrel, Sean; Waine, Toby
    In many secondary cities in Bangladesh and other economically developing regions in Asia, Africa and Latin America, urban sanitation is dependent on individually constructed and maintained decentralised sanitation technologies, e.g., septic tanks operating in the absence of a city-wide support system. In such urban areas, wastewater is transported through a network of storm drains which were not designed for this purpose. The release of wastewater runs the risk of imperfect containment and high risk of exposure to faecal pathogens. Effective methods to identify the sources and movement pathways of faecal matter within cities are currently lacking. Here, a Sanitation Infrastructure and Faecal Flow (SanIFFlow) approach is introduced, representing a novel methodology that utilises open-source data to map the sanitation infrastructure and the faecal matter sources and movement pathways. This approach is first demonstrated through a prototype sub-catchment model within Rajshahi city, Northwest Bangladesh. The sub-catchment model identifies and characterises the sources, pathways, and movement of faecal matter. To refine and validate the method, an uncertainty analysis was conducted, supplemented by a field study, to assess the reliability of the approach. Sensitivity analysis identified five key factors influencing the spatial pattern of faecal flow: septic tank emptying, soak pit use, sludge removal from drains, variations in faecal matter production, and the absence of toilets in some buildings. While each factor might have a negligible impact individually, in combination the factors showed almost 50% faecal matter cannot reach the outlet point. Further insights from the uncertainty analysis and fieldwork suggest that, although the sub-catchment model has potential for individual building level sanitation management, the existing ward-level management system, being the smallest administrative unit in the case study city, calls for a model at that spatial scale as a more practical approach. Building upon this, the SanIFFlow approach has been deployed to develop a city-scale model built from ward-level subunits, tailored for practical application in unsewered cities like Rajshahi. This approach holds promise for global applicability, given the widespread availability of open-source data.
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    ItemOpen Access
    Towards a new spatial representation of faecal sources and pathways in unsewered urban catchments using open-source data
    (IWA Publishing, 2023-03-14) Sultana, Mst Sufia; Waine, Toby; Bari, Niamul; Tyrrel, Sean
    Spatial representation of sanitation infrastructure and service coverage is essential for management planning and prioritising services. The provision of sanitation services in developing countries is inherently unequal because the sanitation infrastructure is lacking, and onsite sanitation is managed individually. Here, we developed a prototype method for creating a spatial representation of faecal sources and movement in a small area in Rajshahi city in northwest Bangladesh, which is representative of 60 other such secondary cities. We demonstrate an approach to estimate spatial variability in faecal production at the building scale by combining widely accessible buildings, ground elevation, and population data. We also demonstrate an approach to attribute potential faecal movement pathways by integrating drainage data, and faecal production at the building scale. We made use of free and open-source data and provide answers to the broader topic of spatial representation of faecal mobility in unsewered urban settings which has implications in a similar setting in developing countries.