Biosorption of fluoride by water lettuce (<Emphasis Type="Italic">Pistia stratiotes</Emphasis>) from contaminated water

Phytoremediation is a proven low-cost and sustainable method for the removal of toxic pollutants from water. This green technology has been practiced for the past several years all over the world. In the present study, the interaction of fluoride on the surface of the floating aquatic plant water lettuce (Pistia stratiotes) during fluoride removal was investigated. Batch kinetic studies were performed to examine the fluoride uptake capacity of the plant with different initial fluoride concentrations such as 3, 5, 10, and 20 mg/L. The effects of various process parameters on fluoride uptake dynamics such as pH, plant biomass, initial fluoride concentration, and time were examined. Freundlich’s isotherm model was found to (R ² = 0.957) fit well to the experimental data. The nature of reaction order followed pseudo-first-order kinetics, when the initial fluoride level in the solution was 5 mg/L. The experimental findings showed that the removal mechanism was driven by biosorption phenomenon. High fluoride concentration in the solution reduced the growth ratio of P. stratiotes. The lowest growth ratio of this aquatic macrophyte was found to be 76.80 ± 3.73% at 20 mg/L fluoride concentration. At lower fluoride concentrations such as 3 and 5 mg/L, the growth ratio of the plant was not reduced significantly.     

Arsenic distribution along different hydrogeomorphic zones in parts of the Brahmaputra River Valley,Assam (India)

The spatial distribution of arsenic (As) concentrations along three classified hydrogeomorphological zones in the Brahmaputra River Valley in Assam (India) have been investigated: zone I, comprising the piedmont and alluvial fans; zone II, comprising the runoff areas; and zone III, comprising the discharge zones. Groundwater (150 samples) from shallow hand-pumped and public water supply wells (2–60 m in depth) was analysed for chemical composition to examine the geochemical processes controlling As mobilization. As concentrations up to 0.134 mg/L were recorded, with concentrations below the World Health Organization and the Bureau of Indian Standards drinking-water limits of 0.01 mg/L being found mainly in the proximal recharge areas. Eh and other redox indicators (i.e., dissolved oxygen, Fe, Mn and As) indicate that, except for samples taken in the recharge zone, groundwater is reducing and exhibits a systematic decrease in redox conditions along the runoff and discharge zones. Hydrogeochemical evaluation indicated that zone I, located along the proximal recharge areas, is characterized by low As concentration, while zones II and III are areas with high and moderate concentrations, respectively. Systematic changes in As concentrations along the three zones support the view that areas of active recharge with high hydraulic gradient are potential areas hosting low-As aquifers.     

Solid waste management through multi-criteria decision making: using analytic hierarchy process as an assessment framework for the Hooghly district,West Bengal

Solid waste management (SWM) is a crucial service governed by urban local bodies (ULB). Hence, it is essential to identify challenges and opportunities in the SWM procedures and practices towards improved delivery of services. In this study, analytic hierarchy process (AHP) has been applied in the three sub-divisional towns of the Hooghly district, West Bengal (India), namely Chandannagar, Hooghly-Chinsurah and Serampore to analyze the existing SWM scenario. As AHP is a Multi-Criteria Decision Making tool, hence, it has been deployed by experts to come up with SWM performance index, clearly demonstrating the strengths and weaknesses of management strategies in selected study sites. This article further advances the significance of the AHP method by carving out multi-layered realities through the quantification of qualitative insights across various segments of waste management in the three towns. While interviews with waste management officials led to the formulation of key performance indicators and sub-indicators matrix, the obtained normalized weights brought to the fore the real engagement and actions executed by each of these towns in managing solid wastes. The application of this innovative AHP method ensured accuracy in the ranking system across performance of the specified ULBs. This AHP-induced situational analysis of SWM is not only significant in terms of policy formulation in the ULBs of the Hooghly district but has potentials to work at scales.

Graphical abstract