In developing countries, rapid economic growth and population increases have led to a surge in municipal plastic waste, intensifying environmental pollution and public health risks, and posing significant challenges to achieving sustainable development goals (SDGs). This study employs material flow analysis (MFA) to explore sustainable waste management solutions in the Chattogram City Corporation, Bangladesh. Using the waste wise cities tool (WaCT), a comprehensive survey was conducted across 150 representative households, 15 markets, 15 hotels and restaurants, 15 offices, and 15 streets. The region generates 204.99 tons of plastic waste daily, out of a total of 1630.91 tons of solid waste. Collection efficiency for plastic waste is approximately 24.49 %, achieved through both formal and informal sectors in two phases. However, about 154.79 tons of plastic waste remain mismanaged and are discarded into the open environment. This study suggests that implementing a comprehensive waste management strategy emphasizing the national 3Rs (Reduce, Reuse, Recycle) and an extended producer responsibility (EPR) model could support city officials and policymakers in developing a more sustainable urban waste management system, thereby reducing environmental impact and achieving long-term waste reduction goals. Overall, this research contributes new insights into plastic waste management at the regional level and highlights the urgent need for tailored waste management strategies in rapidly growing urban centers in developing countries like Bangladesh.

Sugar refinery industries are vital to the economy, but fire incidents at these facilities can cause severe environmental impacts. During a fire, firefighting water can mix with sugar processing residues, generating effluents that enter nearby rivers and deteriorate water quality. This study assesses the pollution status of the Karnaphuli River following a fire at a sugar refinery in Karnaphuli Upazila, Chattogram. Wastewater samples collected from multiple discharge points were analyzed for physicochemical parameters, nutrients, and heavy metals. Dissolved oxygen (DO) levels were far below the acceptable limit (0.45–2.34 mg/L), while biochemical oxygen demand (BOD5, 979–2557 mg/L) and chemical oxygen demand (COD, 1656–3810 mg/L) were substantially elevated, indicating severe organic pollution and oxygen depletion. Nutrient concentrations, particularly nitrate, were high, suggesting a risk of eutrophication. Heavy metals such as Fe and Mn exceeded permissible limits, posing threats to human health and aquatic ecosystems. Pollution indices further confirmed the severity of contamination: Metal Index (MI) ranged from 7.3 to 21.2, Heavy Metal Pollution Index (HPI) varied between 111 and 312, and River Pollution Index (RPI), Organic Pollution Index (OPI), and River Organic Pollution Index (ROPI) indicated moderate to severe pollution levels. These findings indicate river pollution extends downstream, ultimately affecting the Bay of Bengal, and underscore the urgent need for on-site effluent treatment, PFAS monitoring, and stricter firewater disposal policies to safeguard aquatic ecosystems from industrial fire events.

Single-use plastics are a major environmental concern in developing countries like Bangladesh due to their non-biodegradable nature. Finding sustainable alternatives is crucial to reduce reliance on these harmful plastics and mitigate pollution. This study aims to explore the public opinions on plastic pollution and investigate the challenges and potential for substituting plastics with jute. The study also provides essential recommendations for addressing these challenges and fostering the successful substitution of plastics with jute-based alternatives. A thorough social study was carried out in two major cities of Bangladesh, involving 212 participants through face-to-face questionnaire surveys. The selected participants represented diverse demographics in terms of age, gender, occupation, and education level. The findings reveal broad support for plastic recyclability, with many participants favoring jute and paper bags as alternatives to plastics. However, most individuals show little concern for reusing plastic products. Moreover, more than half of the total participants, spanning various demographics, have been exposed to plastic waste reduction campaigns. Furthermore, two-thirds of participants from diverse age groups, occupations, education levels, and genders support the introduction of higher pricing, such as additional tax, as measures to reduce plastic pollution. The correlation and Principal Component Analysis (PCA) plot reveal clustering patterns aligning plastic recycling, extra charges on plastic, and the availability of jute products with socio-demographic variables. Despite favorable views on jute, participants highlight high prices and limited availability as major barriers to adopting jute alternatives. Most of the participants call for additional support to the jute sector, with consensus favoring increased subsidies from the Government of Bangladesh and recognition of the significance of investing in research.

The chemical characteristics of rainwater in the south-eastern region of Bangladesh were investigated in this study in addition to identifying the potential sources of different precipitation constituents, which have often been unexplored or not well covered in the literature. Rainwater pH, major ions and trace metals were measured in samples collected from five different locations with different land-use patterns of the Chattogram Metropolitan area (CMA) during two rainy seasons. The results of this study showed variability in rainwater quality across the sites signifying site-specific influences. The mean concentration of all measured physicochemical parameters, ions and trace metals in rainwater samples was also found to be significantly lower compared with the drinking water quality standard of Bangladesh and WHO guidelines. The correlation matrix and principal component analysis (PCA) indicated that and originated from anthropogenic sources, while the average concentration of trace metals found in rainwater was exhibited in the following order: Zn>Cu>Fe>Cr>Mn>Pb>Cd. The findings of this study could be used as a reference to further investigate the influences of industrial, urban and agricultural emissions that regulate the chemical characteristics of the atmosphere in particular areas of study.

Rainwater is considered as a dependable potable and non-potable water source, used for domestic purposes as well as for human consumption in many cases. While it is usually believed that rainwater is safe for drinking purposes, many studies have explored the existence of trace metals in harvested rainwater, which can impose a serious health risk to human beings when present in relatively high concentrations. The concentration of trace elements in atmospheric precipitation including rainwater also provides a good indication of the environmental pollution caused by anthropogenic activities.Chattogram, located in the south-eastern side of Bangladesh, is the busiest port city and the second-largest city in the country with a population of around 4.5 million people. With the presence of high salinity and arsenic in groundwater and poor quality of surface water in the region, rainwater harvesting is the most sustainable solution to be considered in the water system management for the area, particularly given annual mean precipitation of 2488 mm during the rainy season. In recent years, extensive studies have been carried out on the potential application of different rainwater harvesting systems across the region, but there have been very few studies devoted to the identification of the composition of trace elements in rainwater considering site-specific influences in the trace metal distribution in the rainwater.The purpose of this study was to investigate the composition and source appointment of trace metals (Fe, Cu, Zn, Pb, Mn, Cr, and Cd) in rainwater in the south-eastern region of Bangladesh. To determine their sources and relative contributions in rainwater, a total of ninety-five rainwater samples were collected in this study from five different locations representing different land-use patterns (industrial, commercial, urban, and sub-urban) within the study area, from June 2018 to October 2019. The collected water samples were analyzed for Fe, Cu, Zn, Pb, Mn, Cr, and Cd using Atomic Absorption Spectrophotometer maintaining standard protocols. The measured trace elements from the collected rainwater samples were then compared with the WHO and Bangladesh drinking water standards.The resulting concentration of trace metals in this study was found within the allowable limits in accordance with WHO and Bangladesh drinking water standards, confirming the suitability of rainwater as a potable water source for human consumption. The average concentration of trace metals in rainwater was found in the order of Zn ˃ Cu ˃ Fe ˃ Cr ˃ Mn ˃ Pb ˃ Cd for the tested samples. Overall, the trace metal concentrations of Cu and Zn were predominantly observed in rainwater samples collected from the industrial area, indicating the influence of anthropogenic activities on atmospheric pollution. The concentrations of the trace elements in this work were found to be overall higher when compared to those reported in other investigations around the world. The measurements of this study would provide an indication of atmospheric pollution in rainwater caused by the anthropogenic origins of trace metals as well as provide a database of trace metals in rainwater for further relevant research studies across the country.

•Heavy metal pollution and subsequent health risk is estimated for BCM area.•Metal uptake in roots, stems and grains for three varieties of rice are investigated.•Fe and Zn are found the highest concentration in all three varieties of rice grain.•Cr is found with lowest concentration but higher than USEPA reference oral dose.•People at the area are exposed to heavy metal pollution hazard particularly for Cr.

The present study portrayed a better understanding of the chemical characteristics of rainwater in South-Eastern region of Bangladesh (e.g. Chattogram) as well as to identify the potential sources of different precipitation constituents in the study region that were often unexplored and not well understood. Rainwater pH, major ions, and trace metals were measured in samples collected from five different locations with different land use patterns of Chattogram Metropolitan area (CMA) during the two rainy seasons. The samples were tested following standard protocols. The results of this study exhibit variability in rainwater quality across the sites signifying site-specific influences. The mean concentration of all measured physicochemical parameters, ions and trace metals in rainwater samples were found significantly lower compared to the drinking water quality standard of Bangladesh. In context of ionic constituents, the higher concentrations of nitrate (NO 3 - ) and sulphate (SO 4 2- ) were generally in commercial area. The correlation matrix and principal component analysis (PCA) indicated that NO 3 - and SO 4 2- were from anthropogenic sources, e.g. automobile exhaust, incomplete fuel combustions, and industrial emissions. The average concentration of trace metals in rainwater was followed a decreasing order: Zn ˃ Cu ˃ Fe ˃ Cr ˃ Mn ˃ Pb ˃ Cd. Trace metals concentration, especially copper (Cu) and zinc (Zn) were found maximum in the industrial catchment area. The resulting outcomes of this study could be useful to investigate the influences of industrial, urban, and agricultural emissions that elaborate the physical processes regulating the chemical characteristic of the atmosphere in the investigated area.

Solar still is a simple device that utilizes the evaporation–condensation technique to convert impure saline water into the distilled water by eliminating dissolved salts as well as other dissolved impurities and suspended solids. This study aims to produce fresh drinking water from saline water with solar still in the context of Bangladesh. For this study, a pilot-scale solar still with an effective surface area of 0.214 m 2 is fabricated with mild steel sheet. At first, solar still productivity is evaluated by varying basin water amount by 3 L, 3.5 L, 4 L and 4.5 L synthetic water. Experimental investigations show a decrease in water production with an increase in basin water amount. The optimum basin water amount is found to be 3.5 L at which distillate production is maximized. Then, the effect of salt concentration is assessed by synthetic solutions with 2000 ppm, 5000 ppm and 8000 ppm total dissolved solids (TDS). An inverse relation is found between salt concentration and freshwater production. Lastly, real seawater is fed to the basin and an average freshwater production of 2.38 L/m 2 -day is obtained with a removal efficiency of 99.87%, 99.83%, 99.78% and 99.81% for turbidity, chloride, TDS and electrical conductivity respectively.

A new approach for the analysis of polysaccharides in membrane bioreactor (MBR) is proposed in this study. Enrichment of polysaccharides by glyco-blotting, in which polysaccharides are specifically collected via interactions between the aldehydes in the polysaccharides and aminooxy groups on glycoblotting beads, enabled MALDI-TOF/MS analysis at a high resolution. Structures of polysaccharides extracted from fouled membranes used in a pilot-scale MBR treating municipal wastewater and those in the supernatant of the mixed liquor suspension in the MBR were investigated. It was found that the overlap between polysaccharides found in the supernatants and those extracted from the fouled membrane was rather limited, suggesting that polysaccharides that dominate in supernatants may not be important in membrane fouling in MBRs. Analysis using a bacterial carbohydrate database suggested that capsular polysaccharides (CPS) and/or lipo-polysaccharides (LPS) produced by gram-negative bacteria are key players in the evolution of membrane fouling in MBRs.

DNA microarray-based transcriptome analysis with human hepatoma HepG2 cells was applied to evaluate the impacts of whole wastewater effluents from the membrane bioreactors (MBRs) and the activated sludge process (AS). In addition, the conventional bioassays (i.e., cytotoxicity tests and bioluminescence inhibition test), which were well-established for the evaluation of the overall effluent toxicity, were also performed for the same samples. Transcriptome analysis revealed that 2 to 926 genes, which were categorized to 0 to 225 biological processes, were differentially expressed after exposure to the effluents and the raw wastewater. Among the tested effluents, the effluent from a MBR operated at a relatively long solid retention time (i.e., 40 days) and small membrane pore size (i.e., 0.03 μm) showed the least impacts on the HepG2 even at the level comparable to tap water. The observed gene expression responses were in good agreement with the results of cytotoxicity tests, and provided additional molecular mechanistic information on adverse effects occurred in the sublethal region. Furthermore, the genes related to "lipid metabolism", "response to endogenous stimulus", and "response to inorganic substance" were selected as potential genetic markers, and their expression levels were quantified to evaluate the cellular impacts and treatability of wastewater effluents. Although the harmful impacts and innocuous impacts could not be distinguished at present, the results demonstrated that the DNA microarray-based transcriptome analysis with human HepG2 cells was a powerful tool to rapidly and comprehensively evaluate impacts of whole wastewater effluents.

Membrane bioreactors (MBRs) have become very attractive during the past decade owing to their advantages, although MBR operation has not been optimized yet. Recently, air-sparged side-stream MBRs (ASMBRs) have received much attention because they can overcome the drawbacks of submerged MBRs such as the difficulty of cleaning membrane modules. Widespread application of MBRs has been limited by problems associated with membrane fouling, and ASMBRs are not exceptions. Hydraulic conditions on the membrane surface used in an ASMBR are different from those in a submerged MBR, and this difference affects the characteristics of foulants. The aim of this study was to determine foulant characteristics in a pilot-scale ASMBR operated at an existing municipal wastewater treatment plant. Cylindrical membrane modules holding about 100 membrane tubes each were installed vertically in the ASMBR. Differences of foulants depending on tube positions in the horizontal cross section were investigated in the first experiment. There were no significant differences in the foulant characteristics regardless of the tube positions in the membrane module. This first experiment also showed that humic substances were dominant in the foulants extracted from the tubular membranes used in the ASMBR, whereas hydrophilic substances such as polysaccharides/proteins were reportedly dominant in foulants in the case of submerged MBRs. In the following experiment, a tiny hollow-fiber membrane module was submerged in the ASMBR's reaction tank to filter the shared biomass suspension and enable direct comparison of foulant characteristics in different MBR configurations (i.e., air-sparged side-stream versus submerged). Humic substances were again found to be dominant in foulants extracted from the ASMBR's tubular membranes, whereas hydrophilic organic matter was dominant in foulants extracted from the submerged hollow-fiber membranes. We hypothesize that different hydraulic conditions in the two configurations brought about the difference in foulants. The results obtained in this study suggest that effective measures to address membrane fouling will differ depending on the MBR configuration. (C) 2012 Elsevier B.V. All rights reserved.