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Adsorption capacity of manganese powder synthesized from spent battery waste solution was analyzed for simultaneous removal of congo red and hexavalent chromium. Manganese powder was synthesized by heat treatment followed by reaction with sodium borohydride to spent lithium-ion batteries. The removal conditions viz., pH, dosage of manganese and various concentrations of congo red and hexavalent chromium were optimized. The synthesized manganese powder was characterized by X-ray fluorescence spectrometer (XRF), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Further, FESEM was done to observe the difference in surface morphology of the particles with and without treatment. The adsorption performance was studied and the highest adsorption by the zero manganese was 475 mg/g and 125 mg/g for CR and Cr (VI), respectively when different concentrations of the contaminants (400 mg/L CR and 100 mg/L Cr (VI)) was used. Under the optimum conditions, simultaneous removal from 450 mg/L of CR to 250 mg/L and 125 mg/L of Cr (VI) to around 74 mg/L was achieved. Desorption study of the treated zero manganese exhibited that acid treatment (0.1 M HCl) for CR and alkali treatment (0.1 M NaOH) for Cr (VI) as the suitable reagent for desorption.

Groundwater samples were collected from the Brahmaputra Flood Plains (BFP) to study the effect of river proximity on the arsenic (As) and fluoride levels (F − ). Arsenic and F − contamination was found to be higher in the south bank. Higher carbonate weathering was found to elevate the alkalinity in the south bank which in turn appeared to influence the groundwater As and F − levels. Low NO 3 − levels in the groundwater indicated the existence of a predominantly reducing condition, which is confirmed by low ORP levels in majority of the groundwater samples. Positive correlation between As and Fe, along with close grouping in principal components analysis and hierarchical cluster analysis indicated the involvement of reductive hydrolysis of Fe (hydr)oxides. Principal components analysis showed that reductive hydrolysis was more common in the south bank, which could explain the higher As levels detected in that bank. Higher sedimentation rates on the south bank could also influence the elevated As levels in its groundwater. Co-occurrence of As and F − was also found to be more likely in the south bank as indicated by hierarchical cluster analysis, the process appeared to be influenced by dissolution of Fe (hydr)oxides. Distance from the river and groundwater As level appear to be related, newer sediments close to the river are more likely to have higher As compared to older sediments away from the river. Fluoride on the other hand appears to have an inverse relation with river proximity, as recharge interrupts rock-water interaction, which is the main pathway for F − release. Overall occurrence of groundwater As appears to be a more widespread problem in the floodplains, while F − in groundwater is localised and limited to isolated pockets which promote higher mineral and water interaction over long periods.

The present study, through a multi model assessment approach emphasizes the relevance of prior urban settlement planning with respect to the changing land use pattern. A coupled approach integrating satellite data products of Land Use and Land Cover (LULC) change along with chemical evaluation of As toxicity were modelled to evaluate the groundwater vulnerability. Change detection analysis was incorporated using the satellite images of 2013 and 2016 which shows 10 % increase in the buildings as compared to the total area of the study in given period. The LULC class that has been most compromised in this expansion and got reduced were the vegetation (∼6 %) and the barren areas (∼4 %) and the total surface water sources (0.5 %), all contributing in increased urban sprawl. As per the origin of As contamination in the area it seems that high sediment deposition along the braided Brahmaputra River stretch leads to As contamination which was associated with Fe-(oxy)-hydroxide dissolution. The vulnerability assessment using Artificial Neural Network technique in this region shows that As is present relatively in lesser concentration in the east direction. The continuous expansion of the urban habitation towards the greater As concentration zone will further make the situation critical for the people dependent on groundwater. The study suggests that prior settlement planning must be carried out in accordance to the presence of any toxic constituent in drinking water source to avoid future crisis for potable water.

This paper aims to re-examine the current urban water use system in the urban areas of developing country discuss a better way for resilience investigation. The study proposes that analysis of data on the available amount of chemical and biological contamination in water is the first pressing requirement for this approach. In addition, climate change is causing an uneven pattern of rainfall and severe drought conditions and thus need a substantial attention to delineate the preventive ways for its mitigation in the water-scarce area as well as areas with high groundwater depletion or area contributing to the recharge. Most of the Indian rivers are polluted, and hence the removal of pollutants is an additional task for making a watershed resilient. There is a necessity to evaluate urban water for its better definition and develop the Water Quality Information Platform (WQIP) for layman understanding. The contemporary need for an approach for sustainable water supply must be developed with an understanding of the expected climate change scenario. The idea of “your experience, my learning opportunity” was found very relevant in implementing the developed world experience to a developing nation scenario. Study concludes that without a strong will power and action mantra of “Targeting the target: Bull's eye approach”, the resilience system will not be evolved. This study will have an impact on the critical scientific knowledge of deterioration of water quality, posing a threat to potable water availability, and also on the development of sustainable water management.

The problem of salinization in the Delhi aquifer, that currently exhibits rapid landuse change, is conspicuous and severe. Salinization may be caused either by a single process, or a combination of different processes; including anthropogenic related activities, water logging and evaporative concentration of salts, influx of natural saline water, upconing of brines from the deeper parts of the aquifer, and airborne salts depositions. However, there is a lack of well-proven theory that can explain the salinity of the order of 5000 μS/cm in the deeper aquifers of Delhi. This work identifies inconclusiveness in the previous theories of marine ingression, evaporation enrichment and subsequent leaching of salt. Further, the study depicts a conceptual understanding of the origin of salinity in groundwater based on the integrated investigations of groundwater quality, age and stable isotopic fingerprinting as well as GIS based mapping of geomorphic features. In order to explain the salinity observed in groundwater of NCT Delhi, a phenomenological scenario is illustrated and supported by additional evidences. The highest average EC value was for the shallow aquifer and is strongly symptomatic of anthropogenic influences on groundwater chemistry. Piper diagram showed heterogeneous water type and sufficient recharge/mixing of the groundwater from different aquifers. The relationship between Cl − /Br − ratios vs. Cl − indicated dissolution of salt deposits containing evaporative fraction present in the unsaturated zones or in the sediments of deeper aquifers and leaching of evaporative minerals from dunes of the adjacent Thar Desert. Cl − /SO 4 2− ratio suggested the presence of connate seawater, halite dissolution and concentration of dissolved salts by evapo-transpiration of river water diverted for irrigation. The results show, that the closed inland marine conditions developed and buried with the active sedimentation in the geological past in this region, and further intensive exploitation of groundwater, and enhanced evaporation have together resulted in saline playa condition in some part of the region. The scenario was further verified by matching the required condition for the formation of salt pan or playa with the existing geo-morphological conditions of the area. Isotopic results indicate that salinity flushing is possible and proceeds in the areas of freshwater recharge.

Despite its limited aerial extent, the National Capital Territory (NCT) Delhi, India, has diversified geological and topographical setup. A geochemical assessment of prevailing conditions of aquifer underlying the NCT was attempted and further classified into different hydrogeochemical zones on the basis of statistical and analyses and its correlation with land use, geological and climatic setting. Mineral phase study and isotopic analyses were used for the verification of performed clustering. Saturation indices (SI) calculated using the geochemical modelling code PHREEQC were used to distinguish the characteristics of four zones, as saturation states of the water does not change abruptly. Four different hydrogeochemical zones were statistically identified in the area: (1) intermediate (land-use-change-impacted) recharge zone, (2) discharge (agriculture-impacted) zone, (3) recharge (ridge) zone, and (4) recharge floodplain (untreated-discharge-impacted) zone. The distinctiveness of hydro-geochemical zones was further verified using stable isotopic (H-2 and O-18) signature of these waters. GIS-based flow regime in association with long-term geochemical evidences implied that these zones are being affected by different problems; thus, it necessitates separate environmental measures for their management and conservation. The study suggested that in a diversified urban setup where the complex interactions between anthropogenic activities and normal geochemical processes are functioning, hydrogeochmical zoning based on the integration of various techniques could be the first step towards sketching out the groundwater management plan.