Bangladesh is overly dependent on groundwater and the demand in the near future is expected to increase, as the country is experiencing rapid development and industrial growth. This study assesses the prospect and sustainability of groundwater in Mirsharai Upazila, Chattogram, where a large industrial area, namely ‘Bangabandhu Sheikh Mujib Shilpa Nagar (BSMSN)’, is taking shape. The physical aquifer system was characterized and groundwater quality was mapped. There is one thick aquifer in the northernmost part of the upazila, which splits into three separate aquifers in the south. Water quality indexing suggests that the deep (>130 m) groundwater throughout upazila is good (n = 5) to excellent (n = 18), while the shallow groundwater is mostly poor to unsuitable for both drinking and irrigation purposes. Because of the close proximity to the sea and the presence of thick clays above the deep freshwater aquifer in the BSMSN area, heavy industrial abstraction poses a threat to the lateral intrusion of seawater and land subsidence. Even a small subsidence in the project area at only a couple of meters above sea level would jeopardize the entire project. This study recommends limiting the use of the deep fresh groundwater for the current population of the upazila.

Bangladesh’s heavy minerals deposits in river systems remain largely unexplored with past research restricted to beach placer deposits along the south-eastern coastline of the country. In this study, 64 samples were collected from stable sand bars from the northern Brahmaputra River. The average total heavy minerals (THM) from all sample sites was 10.73 wt%, with the THM concentrations generally highest at the outermost edges of the river and lowest within the mid-channel regions. There was no variation in THM content from north (upstream) to south (downstream). Valuable heavy minerals (VHMs) magnetite, ilmenite, garnet and zircon made up around 25–30 wt% of the THM content, with other heavy minerals including amphibole, pyroxene, kyanite, sillimanite, monazite, apatite and xenotime making up the remaining 70–75 wt%. A VHM distribution map showed that the upstream division of the studied area appeared to be the most prospective for valuable heavy minerals. A bench scale heavy mineral sands beneficiation flowsheet involving unit processes employing gravity, magnetic and electrostatic properties was designed and based on a detailed characterisation and phase analysis of the resulting fractions, it was determined that VHMs made up ~2 wt% of the material recovered. Of these, garnet and ilmenite made up the bulk of the VHMs at levels of 0.88 and 0.51 wt%, respectively, with recoveries of >83%. Characterisation of the concentrates showed that further refinement of the processing conditions is required to generate concentrates that are potentially suitable for commercial applications.

Sand mining using dredging technology from channel bars is a common technique worldwide. To minimize adverse effects of dredging, geo-engineering nature of the soil should be evaluated before mining. Therefore, the present study deals with the potential risks associated with dredging for mineral sand extraction by analyzing the engineering geological properties of the soil from the Brahmaputra River bar and the surrounding areas, Bangladesh. A detailed engineering geological analysis was conducted using field and laboratory testing methods, including Standard Penetration Tests (SPT), mineralogy, grain size distribution (GSD), California Bearing Ratio (CBR), and direct shear tests. The findings divulge that the soil in the study area is light gray, unconsolidated, moderately sorted, poorly graded, and classified as fine-to-medium silty sand. SPT-based liquefaction potential assessments suggest that the soils are highly susceptible to liquefaction, particularly during dredging or seismic events. The study also identifies the risk of localized slumping and soil instability, which exacerbated by micaceous and quartz-rich sands. The CBR results further classify the subgrade as weak to medium-strong, indicating risks of slumping, erosion, and instability. The non-cohesive granular soil in the area may liquefy or be susceptible to erosion, wave attack, bank slope failures, and seepage development during and after dredging as indicated from GSD and direct shear test results. Thus, proper safety precautions, including soil stabilization techniques, controlled dredging, and slope reinforcement, should be taken before dredging on such river bar to minimize risk. This research offers practical guidance for dredging companies to minimize risks and improve soil stability, contributing to safer and more sustainable river bar dredging operations worldwide.