Contamination of arsenic (As) in water, especially groundwater, has been recognized as a major problem across the world. The presence of arsenic in groundwater has become a global problem in the past decades. Health risks have also been reported for many years. Different areas of the world are affected by arsenic contamination of groundwater, the largest population at risk in Bangladesh, followed by West Bengal in India. Arsenic concentrations in drinking water cause severe health effects on human, more than 150 million people worldwide. The current drinking water standard regulation has become strict and requires a reduction in arsenic content. Therefore, the treatment of arsenic contaminants can be the only effective option to reduce health risks. This review paper briefly describes arsenic sources, arsenic chemistry, arsenic contamination in groundwater, its impact on human health and many conventional as well as advanced techniques that are used to remove arsenic from water.

Currently, there is increasing interest on low cost and commercially available materials for the adsorption of heavy metals. The vital benefits of adsorption technologies are its potential in reducing the concentration of heavy metal ions using low-cost adsorbent materials. Fruit peel wastes (FPW) are readily available in abundance. Furthermore, it has a high potential as a sustainable adsorbent due to its large quantity of lignocellulosic materials. Realizing this potential, there are many studies on various fruit peels waste adsorbents used in the removal of Pb (II), Cu (II) and Cd (II) ions from wastewater. However, there is no comprehensive review of these adsorbents, especially on the factors that influenced the adsorption capacity. Hence, this review aims to study on the various fruit peels waste adsorbents and the factors by comparing the metal binding capacities, metal removal performances, sorbent dosage, optimum pH, temperature, initial concentration and contact time. Finally, the adsorption mechanisms were also discussed.

Pentachlorophenol (PCP) has been used extensively in the wood preservation industry. It is highly persistent in the environment and toxic to living organisms. The present study investigated the effectiveness of an oil palm empty fruit bunch biochar (EFBB) pyrolyzed at 350, 550 and 650°C in adsorbing PCP as compared to a commercial activated carbon (AC). The ash content, surface area and aromaticity increased while the pore volume, cation exchange capacity, O/C and (O+N)/C molar ratios decreased as the pyrolysis temperature increased. Only the EFBB pyrolyzed at 350°C and the AC adsorbed the PCP while no PCP adsorption was observed on the EFBBs pyrolyzed at 550°C and 650°C. The Langmuir maximum adsorption capacity (Q_max) values was 6.035 mg g⁻¹, and 126.582 mg g⁻¹ for the 350°C EFBB and the AC, respectively. The higher porosity and more oxygenated functional groups of the EFBB pyrolyzed at 350°C EFBB could be the reason for its ability to adsorb the PCP compared to the other EFBBs. The high PCP sorption by the AC on the other hand, could be attributed to its high surface area and microporous structure.

Present study assessed the pathogenic prevalence in municipal water from 10 supply point and deep tube-well water from 10 deep tube-well point delivered across the Kashipur zone of Narayanganj city, Bangladesh along with their drug resistant pattern through conventional, biochemical and disk diffusion methods. The physico-chemical properties of the deep tube-well water were in satisfactory level, only the samples from location 1, 3, 5 and 9 were exceed the marginal limit for dissolved oxygen however most of the samples of supplied water cross the marginal limit of all parameter (dissolved oxygen ,temperature, pH, electrical conductivity, total dissolve solid and turbidity). Pathogenic bacteria including Escherichia coli and Staphylococcus spp. were found in both supplied water and sewerage authority water (10²–10⁶ cfu/ml) and deep tube-well water (10²–10⁴ cfu/ml). Additionally, fecal coliforms, Klebsiella spp., Salmonella spp., Shigella spp., Vibrio spp. and Pseudomonas spp. was monitored only among the supplied water. Both of the samples were found to be contaminated with heterotrophic bacteria up to 10⁸ cfu/ml. Most of the bacteria were found to be resistant against more than one drug. Hence, the municipal water of the study area was microbiologically unsafe. The propagation of drug resistant strains was assumed to escalate the public health threat. A survey on public opinions were also conducted to know their daily life style and their concern on water treatment and diseases outbreaks caused by contaminated water.

Fluvial Acoustic Tomography System (FATS) as an advanced technology acquires continuous streamflow data in rivers and estuaries even during floods. However, the acoustic signals are dramatically attenuated by suspending sediments which this problem is a new field of study. In this study, we propose a new equation to estimate the maximum applicable measurement distances (MAMDs). It is based on the cross-sectional suspended sediment concentration (<SSC>) and the particle sizes on the 30-kHz FATS. Our study results show that MAMD might be 2,380 m in the clear water. Moreover, the streamflow monitoring can be perfectly done while <SSC> is less than 12.67 kg/m³ with the particle radii of 3 μm, when the horizontal distance between two acoustic stations is 100 m. Also, the acoustic signals are not decayed if the particle radii equal to 20 mm and the maximum <SSC> is 6.6 kg/m³. This study highlights the performance of FATS in the presence of high <SSC> and provides a better perspective of applying FATS in different rivers with high variability of <SSC>.