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Hydrological studies of glaciers in the Indian Himalaya are very important for understanding the melting processes and assessing the influences of climate change. The diurnal variation in the melt-runoff is controlled by the glacial drainage system. To understand the response of such systems continuous monitoring of hydrological and meteorological data is essential. In the present paper, we have studied the high-resolution data for the assessment of hydrological response of Dokriani Glacier in the upper Ganga basin of Garhwal Himalaya. The data were collected for a period of two years (2011–2012) by establishing an Automatic Weather Station (AWS) and discharge gauging site with the provision of automatic water level recorder (AWLR) near the snout of the glacier. A considerable amount of runoff has been observed at nighttime during the glacial ablation with maximum discharge in the evening and minimum in the morning. The depletion of snow from the glacier surface results into exposure of glacier surface ice and reduction in the holding capacity of water in the glacier. Such variations in the physical condition of a glacier attribute to the changes in the hydrological response of the glacier over time. The effect on the hydrological response has also been studied by analyzing diurnal hydrographs for each ablation month. The hydrological response of the glacier becomes faster with the advancement of the ablation season. Significant changes in the hydrological response of the Glacier are observed over a decade. [ABSTRACT FROM AUTHOR]

In the present study, we report the first operation of a pilot scale ion exchange membrane bioreactor (IEMB). It treated 1–2 m3/d of water contaminated with nitrate. IEMB was made up of anion exchange membrane spiral module integrated with a fixed bed bioreactor (FBBR), a novel configuration for an IEMB system. Nitrate elimination was accomplished through Donnan dialysis using chloride as counter ion followed by heterotrophic denitrification in an anoxic FBBR employing glycerol as electron donor and carbon source. The performance of IEMB revealed an excellent nitrate removal at the selected operating conditions, successfully eliminating a nitrate loading rate of 5.0 kg NO 3 −/m3/d and producing 30 ± 5 mg/L nitrate in the effluent at steady state. Anion exchange membrane being non-selective also transferred a significant concentration of sulphate from the feed-side to the bio-side leading to sulphate accumulation in FBBR. As a result, denitrification performance was affected due to the activation of sulphate reducing bacteria leading to the upset of FBBR. Batch experimental study aiming to screen the effect of nitrate to sulphate ratio on denitrification, demonstrated the possible occurrence of sulphate reduction at [nitrate]/[sulphate] < 0.2, exhibiting a highly negative oxidation reduction potential (ORP) value (−450 mV). This signifies that a minimum [nitrate]/[sulphate] > 0.2 is required as to suppress sulphate reduction phenomenon during denitrification. IEMB calibration for denitrification using glycerol as a carbon source revealed that 100 % stoichiometric donor/acceptor (C/N) ratio was suitable for producing sufficient nitrate biodegradation and acceptable ORP value (~−220 mV). Present work established promising application prospects of IEMB comprising nitrate selective membrane module for the treatment of high nitrate wastewater with a treatment capacity of 1.5 m3/d at optimized operating conditions. • Established IEMB treated high nitrate contaminated water with a capacity of 1.5 m3/d. • Exit nitrate from the IEMB satisfied legal limits of different countries. • ORP reflects the availability of electron donor for efficient denitrification. • Activity of coexisting bacterial communities depends on nitrate to sulphate ratios. • Improper [nitrate]/[sulphate] ratio impairs denitrification and initiate sulphate reduction. [ABSTRACT FROM AUTHOR]

In the Himalayas, most of the glaciers are covered by thick debris, especially in the ablation zone. Supraglacial debris cover might play an important role for sediment budget of the glaciated area or for the ablation of ice masses mantled in debris. During summer season, proglacial meltwater carries considerable amount of suspended sediment. The deglaciated area provides a ready source of sediment during Indian Summer Monsoon (ISM). The heavy sediment load from the glaciers affects the hydropower generation, irrigation and drinking water supply. Therefore, to understand the sediment delivery from glaciated basins, characteristics and variation of the suspended sediment concentrations in the proglacial meltwater stream, Dokriani Glacier, have been monitored during the ablation season (May-September). Suspended sediment samples were collected near the snout of Dokriani Glacier, Garhwal Himalaya, in 2010 and 2011. Results show that mean monthly suspended sediment concentrations (SSC) were 1499, 2303, 3845 and 1649 mg/l for the months June, July, August, and September, respectively, indicating highest concentration in August followed by July. Over the period of recording, daily mean suspended concentration in the melt stream varied from 13-9798.2 mg/l, which is very high, caused due to a flash flood event during the monitoring period. The mean daily suspended sediment concentration was computed to be 2196 mg/l. The suspended sediment concentration begins to increase with discharge from May and reduces in September. Present study provides TRMM (Tropical Rainfall Measuring Mission) derived and field based hydro-meteorological insight about severe rainstorms during the years 2010 and 2011 in the study area, which transported large amounts of sediment. [ABSTRACT FROM AUTHOR]

The present study focuses on the decolorization of real silk dyebath effluents using analytical-grade magnesium chloride (MCl) with and without guar gum (GG) as a coagulant aid and industrial-grade polyaluminium chloride (PACl) and aluminum chlorohydrate (ACH) as coagulants. A higher decolorization efficiency of 97% at a very high dosage of 1800 mg L–1 was observed for MCl. However, considering the purity, dosage, decolorization efficiency, and quantity and quality of sludge production, ACH was found to be the best coagulant, giving 91% decolorization efficiency at a dose of just 100 mg L–1. To achieve this high degree of decolorization efficiency, the dosage for PACl was found to be approximately 50% higher than that of ACH. Effective decolorization (>90%) at a very low dosage (100 mg L–1) and minimal quantity of sludge production by ACH demonstrate that ACH is an effective coagulant for decolorization of silk dyebath effluents. [ABSTRACT FROM AUTHOR]

Textile industry is one of the most chemically intensive industries on the earth and the major polluter of potable water. It generates huge quantities of complex chemical substances as a part of unused materials including dyes in the form of wastewater during various stages of textile processing. The direct discharge of this wastewater into environment affects its ecological status by causing various undesirable changes. As environmental protection becomes a global concern, industries are finding novel solutions for developing technologies that can diminish the environmental damage. However, colour removal from textile wastewater by means of cheaper and environmental friendly technologies is still a major challenge. In this manuscript, several options of decolourisation of textile wastewater by chemical means have been reviewed. Based on the present review, some novel pre-hydrolysed coagulants such as Polyaluminium chloride (PACl), Polyaluminium ferric chloride (PAFCl), Polyferrous sulphate (PFS) and Polyferric chloride (PFCl) have been found to be more effective and suggested for decolourisation of the textile wastewater. Moreover, use of natural coagulants for textile wastewater treatment has also been emphasised and encouraged as the viable alternative because of their eco-friendly nature. [Copyright &y& Elsevier]

The focus of this study is to evaluate electrocoagulation as a process for the remediation of phosphate contaminated synthetic aqueous solutions using scrap aluminium plate electrodes in monopolar-parallel mode. An attempt was made in modeling the phosphate removal as a function of the significant parameters as well as to optimize the process statistically with the help of Response Surface Methodology using Design Expert software Version 7.0.0. The full factorial central composite design was followed to obtain the required number of runs for batch study. Five parameters namely initial pH, inter-electrode distance (IED), the concentration of the supporting electrolyte (SEC), electrolysis-time and voltage were considered for the experimentations. A valid model to predict the removal efficiency was established and the removal efficiencies witnessed were as high as 98%. The techno-economic optimization yielded the following set of parameters as the most economical solution: pH = 7, Voltage = 11.23 V, IED = 3 cm, t = 14.03 min and SEC = 0.46 g/L exhibiting a 90% removal efficiency and an operating cost of 0.22 $/m3 of water treated or 2.52 $/Kg of phosphate removed. The study of crystallinity of the electrocoagulation byproduct was also conducted using XRD analysis, which showed the presence of amorphous or poorly crystalline phases. Image 1 • Statistical optimization of the electrocoagulation process for phosphate removal along with the techno-economic study. • Study of effect of parameters (individual and interactive) using 3D surface plots and contour. • Model validation using real wastewater at optimized condition. • Study of the floc-settling behavior and floc-crystallinity. • XRD, EDS and SEM study to validate the phosphate removal during the process. [ABSTRACT FROM AUTHOR]

Eutrophication, driven by excessive nutrient concentrations in water bodies, is a critical global environmental issue affecting water quality, ecosystems, and human health. Discharging nutrient-rich secondary effluents from municipal wastewater treatment plants exacerbates this problem. This study aimed to assess the effectiveness of a pilot-scale Ion Exchange Membrane Bioreactor (IEMB) in removing nitrate from secondary treated effluent. The process involved Donnan dialysis (DD) followed by heterotrophic denitrification in an anoxic fixed bed bioreactor (FBBR). DD process demonstrated an efficiency of over 75 % when nitrate was externally spiked in the secondary treated effluent and over 90 % without spiking, reaching final concentrations below 5.65 mg NO 3 –N/L and 1.1 mg NO 3 –N/L, respectively. Furthermore, denitrification in FBBR was greater than 95 % at C/N ratio of 1.8–2 provided in the form of glycerol at an HRT of 2 h when nitrate was not spiked externally. Though sulphate accumulation occurred in the receiver (bio-side) during DD, denitrification outperformed sulphate reduction, as confirmed by the favourable oxidation-reduction potential (ORP) readings (−50 to −200 mV) in the FBBR reactor. Optimal conditions for nitrate removal, considering chemical and energy consumption, resulted in a cost of $0.237 per cubic meter of treated secondary effluent during continuous operation. A life cycle assessment (LCA) was also conducted to understand the environmental impacts of the IEMB. In light of these findings, IEMB showed a promising potential for tertiary wastewater treatment, providing an economical and sustainable solution for nutrient removal and indirect potable reuse of treated wastewater. [Display omitted] • Pilot scale IEMB treated high nitrate secondary effluent at a capacity of 2.88 m3/d. • Transport in DD was influenced by initial concentration, driving ion, feed composition. • Sulphate had minimal effect on denitrification as denitrifiers dominated FBBR. • Operational cost of treating 1 m3 of secondary effluent for nitrate was $0.237. • LCA showed IEMB has lesser environmental impacts than RO. [ABSTRACT FROM AUTHOR]

Disturbingly high rates of consumption of surfactants in household and industries have led to mark them as emerging contaminants in the environment. In the present work, removal of sodium dodecyl sulfate (SDS), an anionic surfactant, using an industrial waste (dolochar) was explored. The adsorbent material was characterized with the help of Fourier transform infrared spectroscopy (FTIR) and X‐ray diffraction (XRD). Kinetic evaluation was performed using first, pseudo‐first, second, and pseudo‐second order models. Adsorption of SDS over dolochar was expressed best by pseudo‐second order kinetic model with regression coefficient (R2) of.99. Three input parameters including adsorbent dose (20–10 g/L), initial concentration (30–100 mg/L) of the surfactant, and contact time (2–60 min) were chosen for optimization using response surface methodology based on Box–Behnken design (BBD) approach. A total of 15 experiments were run to examine the effect of these variables on removal of SDS by dolochar in a multivariate system. A regression analysis indicated the experimental data fitted well to a quadratic polynomial model with coefficient of regression (R2) as.99. ANOVA and lack‐of‐fit test depicted the precision and efficiency of the model. The optimized conditions for SDS removal were found to be adsorbent dose 16.62 g/L, contact time 40 min, and initial concentration 47 mg/L with removal efficiency as 98.91%. Practitioner points: Daily ablutions and use of personal care products introduce a number of surfactants and recalcitrant compounds into the environment.Adsorption is a handy and easy to operate treatment technique to remove graywater pollutants.Kinetic and statistical modeling may be recommended as one of the most prominent tools to understand the removal mechanism.Decentralized treatment of graywater using industrial wastes is recommended as sustainable solution in the developing nations. [ABSTRACT FROM AUTHOR]

On 7 February 2021 at 10:30 am, a huge amount of slurry material flooded the Rishiganga catchment, resulting in excessive flow along the valley. The main cause of this flood was the dislocation of a huge rock mass approximately 540 m wide and 720 m long from the main rock body, which slipped down towards the Raunthi Gadera valley floor, causing massive devastation in the areas such as Raini, Tapovan, and Vishnuprayag. This event was not expected and was the first event in history when a flash flood occurred in winter. In this study, we tried to answer two major questions which are not been explained so far that are related to this disaster. These questions are (i) why did this event occur in winters? (ii) where did so much debris and water come from?. This study clearly answers these questions based on field observations. [ABSTRACT FROM AUTHOR]

In the present study, a phenol degrading actinomycetes strain was isolated from paper pulp wastewater. The isolated strain was identified as Rhodococcus pyridinivorans PDB9T N-1 using 16S rRNA gene sequencing technique, which yielded the complete degradation of 1600 mg l−1 of phenol within 56 h. Moreover, the Rhodococcus species could remove over 97.5% of total organic carbon (TOC) at an initial phenol concentration of 1000 mg l−1. The metabolic profile of phenol biodegradation by the actinomycetes species has been investigated using liquid chromatography–mass spectrometry (LC-MS) and Fourier-transform infrared spectroscopy (FT-IR). The key intermediate products detected in the actinomycetes culture were hydroquinone, protocatechuic acid, beta-carboxycis-cismuconate, maleyl acetate, 4–oxalocrotonic acid and 3-fumarylpyruvic acid. Further, a tentative oxalocrotonic acid pathway has been proposed on the basis of the detected intermediate products. The culture medium constituents are highly indispensable for the microbial growth, enzyme and other cellular metabolic activities associated with phenol biodegradation. Therefore, the effect of media components were modelled with the help of response surface methodology (RSM) and central composite design (CCD). A reliable quadratic model was established which predicted the degradation efficiency as high as 99.5% with an appreciable correlation coefficient (R2) of 0.98. Moreover, phenol degradation efficiency was improved with concentrations beyond the central values for all media components except K 2 HPO 4 and NaCl. • An indigenous Rhodococcus pyridinivorans strain PDB9T N- 1 has been isolated. • A new 4–oxalocrotonic acid metabolic pathway is proposed. • All media components except K 2 HPO 4 and NaCl showed strong positive effect on phenol biodegradation. • 1600 mg l−1 phenol degraded in 56 h. [ABSTRACT FROM AUTHOR]

A ground-based and heliborne survey was conducted immediately after the disaster that took place on 7th February, 2021 in the Chamoli district of Uttarakhand. Based on these observations and freely available Google Earth imagery, we have arrived at plausible causes of this catastrophe as detachment of a sizeable rock mass and overlying hanging glacier in the Raunthi catchment that dammed the Rishiganga River and led to the devastation of roads, bridges and hydropower projects in downstream. [ABSTRACT FROM AUTHOR]

In 2017–2019 a surge of Shispare Glacier, a former tributary of the once larger Hasanabad Glacier (Hunza region), dammed the proglacial river of Muchuhar Glacier, which formed an ice-dammed lake and generated a small Glacial Lake Outburst Flood (GLOF). Surge movement produced the highest recorded Karakoram glacier surface flow rate using feature tracking (~18 ± 0.5 m d−1) and resulted in a glacier frontal advance of 1495 ± 47 m. The surge speed was less than reports of earlier Hasanabad advances during 1892/93 (9.3 km) and 1903 (9.7 km). Surges also occurred in 1973 and 2000–2001. Recent surges and lake evolution are examined using feature tracking in satellite images (1990–2019), DEM differencing (1973–2019), and thermal satellite data (2000–2019). The recent active phase of Shispare surge began in April 2018, showed two surface flow maxima in June 2018 and May 2019, and terminated following a GLOF on 22–23 June 2019. The surge likely had hydrological controls influenced in winter by compromised subglacial flow and low meltwater production. It terminated during summer probably because increased meltwater restored efficient channelized flow. We also identify considerable heterogeneity of movement, including spring/summer accelerations. [ABSTRACT FROM AUTHOR]

The paper concerns ice dams and glacial lake outburst floods (GLOFs) in the Karakoram. Some 146 events are identified, including 30 major disasters. Large downstream populations and major infrastructure are threatened. Risk factors differ from recent reports of other Himalayan GLOFs associated with glacier recession and global warming. Ice dams are largely or entirely active ice, put in place by advancing glaciers. Climate change is a factor, but the ice cover in the Karakoram has been sustained, and even some increase in mass. Surge-type glaciers comprise or affect~70% of our inventory. The most frequent, large GLOFs come from local clusters of glaciers in five sub-basins, given special attention here. In four there were new ice dams formed since 2008 and two generated dangerous GLOFs. An urgent need arises to track short-term ice and lake behavior and how surge dynamics may be involved. Satellite images and DEMs are employed in cross-correlation feature tracking and elevation change respectively. The glaciers of interest all exhibit irregular movement, including recent advances, but with great variability and no clear relation to climatic fluctuations. • Study updates inventory of ice dams and related GLOFs in the Karakoram. • Study reports recent evidence of surface displacement and elevation changes of glaciers involved in ice dam generation. • Surge-type glaciers comprise or affect ~70% of inventory of ice dams and related GLOFs. • Four glaciers formed new ice dams since 2008, two (Kyagar, Khurdopin) generating dangerous GLOFs. • The studied glaciers exhibit irregular movement, but with great variability and no clear relation to climatic fluctuations. [ABSTRACT FROM AUTHOR]

Abstract A debris flow occurred in the foreland of Gangotri Glacier by its former tributary, Meru (Bamak) Glacier between 16 and 19 July 2017. We investigated the debris flow using pre- and post-event field observations; hydro-meteorological data along with remote sensing assessments to understand the mechanism and evolution of the debris flow. A large volume of sediments (−7.9 × 106 m3 ± 0.1 × 106 m3) moved from the Meru Bamak and adjoining Neela Taal (4380 m a.s.l) during the debris flow, depositing 6.5 × 106 m3 ± 0.1 × 106 m3 of sediments in the frontal region (4050 m a.s.l) of the Gangotri Glacier. This event transported sediments up to 1.5 km downstream, as a debris flow fan-type feature. During the event, ~18% of the sediments were transferred by the meltwater stream. The stream of the Meru Bamak completely dissected and exposed the ice-cored left lateral moraine of the Gangotri Glacier. This event comprehensively reworked the morainic material and entirely changed the morphology of the pro-glacial area. A small pro-glacial lake (area: 5075 m2) is also observed at the snout of Gangotri Glacier because of the blockage by morainic material and sediments. A sharp increase in the concentration of suspended sediments (SSC), reaching 11,370 and 10,605 mg/l on July 18 and 19, respectively was recorded at Bhojwasa (~3 km downstream). Multiple factors such as recession of Gangotri Glacier, degraded ice-cored moraine, loose sediments at the front of the Meru Bamak, and continuous rainfall created favourable conditions for the debris flow. Therefore, geomorphic hazards associated with glacial retreat need to be investigated intensively in the Himalaya especially, in areas where significant glacial retreat is observed, lateral moraines are exposed, and the unstable slopes are occupied by the tributary glaciers. [ABSTRACT FROM AUTHOR]

The Karakoram has a large concentration of surge-type glaciers, including 69 tributary glaciers, compared to 152 surge-type main or trunk glaciers. The paper addresses the interactions between tributary and trunk glaciers using digital elevation models (DEMs), surface displacement, field and archival reports. In particular, it explores the behavior and impacts of 13 tributary glacier surges on three trunk glaciers, namely the Hispar, Braldu and Panmah. Observations include five surge tributaries of Panmah, five of Braldu, and three of Hispar. We observed ASTER DEMs can help in some cases to detect surge signature where automated surface displacement does not detect the surge. We also observed substantial differences in surge dimensions, timing and histories of the main trunk glacier and their tributaries. East Braldu III tributary surged between 2000 and 2003, whereas East Braldu IV surged from 2003 to 2006, but in these periods, no other tributary shows surge signature. Between 2013 and 2016, Braldu trunk Glacier surged along with four tributaries out of five except West Braldu I. Volumes and geometry of ice transferred from tributary to trunk glaciers are unique to each case, but the surging ice melted rapidly in about 2 to 4 years for some cases such as Little Skamri and Drenmang. The tributary ice modified all studied trunk glacier dynamics, morphology, distribution of debris and hypsography. The ice transferred from tributaries such as Little Skamri and Drenmang blocked the flow of trunk Nobande Sobonde Glacier from 2004 to 2006. Such ice transfer by surge tributaries to the main trunk glacier is referred here as surge-modified ice. It introduces indirect and post-surge effects and complicates or delay in tracking glacier responses to climate change. Also, mass balance in surge-type and surge-modified glaciers differ from systematic direct responses to climate in non-surge-type glaciers. Therefore, more research and monitoring are required to address the distinct responses of such glaciers and individual tributaries to better understand the heterogeneity of surging glaciers in Karakoram. [ABSTRACT FROM AUTHOR]

• Topography and climate control the distribution of seasonal snow cover. • TLRs for Chorabari Glacier are lower than the environmental lapse rate. • ELA of Chorabari Glacier lies within the elevation zone of 5000–5500 m. • Study of UHB can be useful for policymakers and researchers working in the region. Himalayan glaciers exert considerable influence on basin hydrology and its response to climate change. Melt-runoff generated from ungauged Himalayan basins (UHB) requires an understanding of snow and ice cover extent along with prevailing meteorological conditions. Therefore, an estimation of seasonal snow cover distribution, topographic (elevation, aspect, and slope) and climatic variability was carried out using satellite data and meteorological observations from three automatic weather stations (AWSs) located at different elevations in an UHB (Chorabari Glacier). Results suggest that the topography and the meteorological conditions of the basin influence the dynamics of snow cover and the corresponding processes responsible for the melt-runoff generation. The snow cover area (SCA) has high variability in the elevation range of 3799–5000 m, indicating that as glacier ablation begins, SCA below this elevation primarily contributes to the melt-runoff. Likewise, the eastern aspect and the slopes (0–10° and 70–80°) show higher variability. Further, the annual distribution of air temperature gradients (dT/dZ) or temperature lapse rates (TLRs) exhibits a bimodal pattern. The mean annual TLR for the basin is 6.0 °C km−1, which is lower than the traditionally used adiabatic or environmental lapse rate (6.5 °C km−1). We also established the role of TLRs in the dynamics of SCA, which is an important parameter used for the computation of melt-runoff. The 0 °C isotherm established indicates that the elevation zone above 5000–5500 m has persistent snow cover throughout the year and snow cover below this zone contributes to the melt-runoff during the ablation season. Therefore, validating the equilibrium line altitude (ELA) of Chorabari Glacier lies within this zone. Since the TLR and SCA vary with space and time, our study in an ungauged glacierized basin of river Ganga could be useful for policymakers as well as other researchers working on the regional hydrology. [ABSTRACT FROM AUTHOR]