Seawater intrusion (SWI) is the most important hydrological problem in the highly populated coastal regions. SWI in the coastal aquifers is caused by the intense withdrawal of groundwater and reversal of the natural hydraulic gradient. The study focuses on geophysical and geochemical analysis to identify areas contaminated by saline water intrusion. Resistivity survey and groundwater analysis were conducted in 33 locations in the study area to identify the extent of SWI. Geochemical analysis indicated that the groundwater quality was not suitable for drinking and irrigation purposes in 64% and 85% of the study area, respectively. The areas with low resistivity and high values of water quality parameters, such as electrical conductivity, chloride, and low values of Na/Cl, indicate SWI. Resistivity study was verified by geochemical studies, and the results indicated high salinity prevailed up to 13.7 km, moderate salinity up to 16.5 km, and freshwater was present beyond 16.5 km from the coast. The study found that geophysical methods offer a valuable alternative to laborious geochemical approaches for estimating aquifer parameters and detecting saline water intrusion. The study indicated the need for proper management of coastal aquifers to control SWI.HIGHLIGHTSGeophysical survey and geochemical analysis can identify areas contaminated by saline water intrusion. GIS mapping is very efficient to assess the progression of seawater intrusion. Proper monitoring and management of coastal aquifers is needed to control seawater intrusion.

Groundwater recharge is a critical hydrologic component that determines groundwater availability and sustainability. Groundwater recharge estimation can be performed in a variety of ways, ranging from direct procedures to simulation models. The optimal strategy for recharge estimation depends on several factors, such as study objectives, climatic zones, hydrogeological conditions, data availability, methodology, and temporal and spatial constraints. Groundwater recharge is influenced by uncertainties in weather and hydrology. This study discusses conventional recharge estimation techniques and their application for optimal recharge calculation, and it also offers an overview of recent advances in recharge estimation methods. Most methods provide direct or indirect estimation of recharge across a small region on a point scale for a shorter time. With recent technological advancements and increased data availability, several advanced computational tools, including numerical, empirical, and artificial intelligence models, have been developed for efficient and reliable computation of groundwater recharge. This review article provides a thorough discussion of the techniques, assumptions, advantages, limitations, and selection procedures for estimating groundwater recharge.

India, as the world's largest consumer of groundwater, faces an alarming water crisis, particularly in southern regions like Upper Thurinjalar, Tamil Nadu. The relentless extraction of groundwater has severely depleted reserves, making it increasingly difficult to meet the water demands of households, agriculture, and industry. This unsustainable usage endangers the region's water security, emphasizing the urgent need for sustainable management practices. Immediate action is essential to safeguard these vital resources and secure a sustainable water future for the region. The present study addresses the critical need to identify optimal groundwater recharge areas to mitigate the adverse effects of groundwater depletion. Utilizing Remote Sensing (RS) and Geographic Information Systems (GIS), this research focuses on delineating suitable recharge zones in Upper Thurinjalar, Tamil Nadu, to promote sustainable water resource management. Through geospatial analysis, thematic maps were generated, incorporating variables such as geomorphology, geology, subsurface lithology, lineaments, land use, drainage density, soil types, and slope. Utilizing satellite data within the GIS framework, groundwater recharge zones were classified into three categories: highly suitable (61.06 km2), moderately suitable (214.18 km2), and least suitable (48.07 km2). Additionally, prioritized interventions for 18 rural reservoirs within the same catchment area included sediment removal, depth enhancement, and infrastructure upgrades. The application of artificial groundwater recharge in these targeted areas is anticipated to significantly alleviate irrigation water deficits, thereby advancing sustainable development and rehabilitating degraded land. The use of a weighted overlay technique within Geographic Information Systems (GIS) has proven to be a highly effective method for optimizing water resource management, facilitating the sustainable development of groundwater resources. The results emphasize the importance of promptly undertaking focused interventions, such as prioritizing tank improvements and deploying artificial recharge procedures, in order to guarantee the long-term availability of water. Implementing these proactive measures is essential for reducing water scarcity and promoting the development of unused land in the designated recharge areas.

Abstract A large portion of the water environment is being contaminated and destroyed due to the direct liberation of industrial effluents, agricultural and municipal activities that are toxic to humans, animals, and plants. Among the several pollutants, heavy metals are considered to be a serious hazard and the presence arsenic in water will cause carcinogenic to humans. In this study, for sustainability easily available eco-friendly materials were used for the adsorption of heavy metal. An aqueous solution of zinc and arsenic metal was prepared and adsorption of heavy metal was performed by varying pH, initial concentration, time, and dosage. The metal productivity was optimized using Response Surface Methodology (RSM) with central composite design (CCD) by varying the obtained data. The model prediction result is in agreement with experimented result (R2=0.9706, 0.9799 adj R2=0.9432,0.9572 for and coconut shell carbon). ANOVA table shows that the adsorption of arsenic and zinc metal to carbon made from coconut shell. The optimization of carbon made from coconut shell pH, initial concentration, time, and dosage found to be the maximum adsorption capacity of both adsorbent pH (7,7), initial concentration (40,30), contact time (60,90), adsorbent dosage (0.3,0.3) was obtained. Characterization of activated coconut shell carbon was carried out by SEM.

Groundwater resources are increasingly strained by misuse and climate change, necessitating the identification of potential recharge zones for sustainable management. The study aimed to simulate potential recharge zones of a tropical river basin using two multi-criteria decision-making techniques: the Analytical Hierarchy Process (AHP) and Multi-Influencing Factor (MIF) methods. Thematic layers of key variables were integrated using a weighted overlay analysis in GIS environment to model recharge areas within a tropical river basin in Northern Kerala, India. Normalized weights and ranks were calculated to evaluate their influence on groundwater development. Five classes of groundwater recharge potential zones (GWRPZ) with their derived areas were identified for AHP and MIF, respectively: high (30.39% and 28.24%), low (21.55% and 21.60%), very high (19.20% and 18.45%), moderate (16.96% and 20.25%), and very low (11.90% and 11.45%). Validation with overall accuracy and Kappa coefficient confirmed the methods' comparability. The results guide water well site selection and improve managed aquifer recharge (MAR) strategies. Local bodies within the river basin were ranked utilizing the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) method to prioritize and implement recharge schemes, aiding sustainability goals in groundwater management.

Abstract Treating tannery wastewater poses a significant challenge due to its composition, comprising biogenic materials from hides and a diverse range of organic and inorganic chemicals. Experimental procedures were conducted using an electrochemical reactor employing sacrificial electrodes—mild steel as both anode and cathode—in a unceasing process. Numerous working parameters such as current density and electrolysis duration were examined to achieve optimal reduction in presence of turbidity, total solids, COD, BOD, TDS, and Chromium content. Enhanced reductions in COD, BOD, TDS, and chromium content were observed at higher flow rates. The applied current density also notably impacted the reduction efficiency of COD, BOD, TDS, and chromium content. Investigation into the electro coagulation method employing short cell current (1A) and solvable mild steel electrodes revealed their efficacy compared to aluminium electrodes, particularly in chromium removal, achieving over 90% removal efficiency. However, the use of mild steel electrodes resulted in the formation of a black precipitate characteristic of iron (II) sulphides during the treatment, although effectively reducing effluent coloration. The removal efficiency of chloride, however, remained lower, at less than 12%. A comprehensive discussion on the mechanisms involved in the removal of COD, chromium, total dissolved salts, total solids, chloride and coloration using soluble mild steel electrodes was presented. The predominant role of the electrode was highlighted by treating tannery wastewater with mild steel electrodes, followed by filtration, resulting in removal rates of 68.0% for chemical oxygen demand, 43.1% for chromium, 55.1% for total dissolved salts and 84.3% for coloration, considering initial concentrations of 2850 mg/L, 230 mg/L, 100 mg/L, 100 mg/L, and a 256- fold dilution, respectively.

Nowadays low calcium fly ash-based geopolymer concrete can be replaced with cement-based concrete to avoid the adverse effect of manufacturing cement on the environment. Utilization of geopolymer concrete instead of traditional concrete using low calcium fly ash and nano silica reduces a significant amount of CO­ 2 emission towards the atmosphere. However, the performance of geopolymer concrete is less than that of Portland cement concrete. To improve the performance of geopolymer concrete nano silica was used in the present study. In this work, geopolymer concrete was made utilizing fly ash, ground granular blast furnace slag (GGBS), and sugarcane bagasse ash. In the first instance, binary combinations i.e. fly ash and GGBS were employed as cementitious materials for the production of geopolymer concrete. In the second instance, a ternary mixture of pozzolanic material was prepared by taking 25% GGBS, 65% Fly ash, and 10% bagasse ash. In the third instance, varying percentages of nanoparticles were used for the above ternary mixture. The mechanical and durability properties of the geopolymer composite that was made earlier were tested. The compressive strength and split tensile strength of geopolymer composites were assessed for mechanical properties and a rapid chloride permeability test, water absorption test, and acid attack test were done to know about the porosity of concrete. Results showed that, with a dose of 4% nanoparticles, the durability and strength properties of the concrete had improved the most. The GCBA-N4 mixture had the highest split tensile and compressive strength was measured to be 2.91 MPa and 41.33 MPa and the rapid chloride permeability test, water absorption rate, and percentage of mass loss due to sulfate attack were found as a minimum for GCBA-N4 specimen.

The present investigation was aimed to explore the cadmium removal efficiency, mechanism and characterization of Chitosan biopolymers from cephalopods waste. The extracted chitosan has showed good yield of 32% and with high minerals, ash and moisture content. In the Fourier-transform infrared spectroscopy (FT-IR) analysis multiple active functional groups of Amine, Amine, Hydroxyl were found between 612 and 3424 cm-1 and the sugar signals such as N-acetyl glucosamine (GlcNAc) and H-1 [GlcN (H-1D), GlcNAc (H-1A)] were identified in Chitosan by 1H Nuclear Magnetic Resonance (NMR). The Crystalline, rough surface, micropores characters were observed in Chitosan surface by Scanning Electron Microscope (SEM) analysis and the pores played a key role in adsorption process. The Cd ions removal was performed by batch experiment and the results were revealed that the pH, temperature, time and dosage highly influenced the process and the optimum condition was discovered through RSM for pH 7, temperature 42.5 °C, time 220 min and dosage of sorbent 1 g/L respectively. The kinetics models of the Cd removal were carried out and the results revealed that the Pseudo-second order is more suitable and fit for removal than Pseudo-first order model. Chitosan surface characters and functional groups played a big role in adsorption process and Chitosan can be alternative eco-friendly, low cost and highly efficient sorbent for heavy metal removal in effluent treatment plants.

The Penman-Monteith evapotranspiration (ET) model has superior predictive ability than the other methods, but it is challenging to apply for several Indian stations, owing to the need for a large number of climatic variables. The study investigated an artificial neural network (ANN) model for calculating ET for various agro-climatic regions of India. Sensitivity analysis showed that the overall average change in ET0 values for 25% change in the climatic variables were 18, 16, 14, 7, 5, and 4%, respectively, for T-max, RHmean, R-n, wind speed, T-min, and sunshine hours. The dominant climatic variables were identified from the principal component analysis (PCA) and ET0 was computed using an ANN with dominant climatic variables. The ANN architecture with backpropagation technique had one hidden layer and neurons ranging from 10 to 30 for all climatic variables and from 5 to 10 for PCA variables. The new ET models were statistically compared with Penman-Monteith ET estimate, and found reliable. PCA variables guaranteed an estimate of ET0 accounting for 98% of the variability. The average values of coefficient of determination, standard error of estimate, and percentage efficiency were observed as 0.96, 0.24, and 94%, respectively.

In this study, the phytoremediation technology from marine source Dunaliella salina was chosen to eliminate fluoride ions from aqueous solution by Adsorption isotherm, Kinetics and RSM optimization methods. Marine microalgae were collected, identified and mass cultured then its physical characteristics, functional groups and surface microstructure was examined by FT-IR, NMR, XRD and SEM analysis also the same was performed on post treated bioadsorbent. Fluoride removal was optimized by different conditions through response surface methodology and kinetics modelling also performed. Several active functional groups were noticed in IR spectra and NMR of pre and post treated microalgal biosorbent. Many micropores, crystalline structure, voids were observed in pre-treated and lesser in post treated bioadsorbent, removal process was optimized by temperature, pH, dose and time and its showed high influence of removal process. The fluoride removal process was optimized by response surface methodology, Langmuir Isotherm, Freundlich Isotherm, Temkin isotherm, Pseudo I order, Pseudo II order and Intra particle diffusion and revealed that the F ions removal mechanism clearly. Microalgae are novel, low-cost and effective bio based innovative methods which are sustainable for the bioremediation of fluoride from water bodies and industrial wastewaters.

This study aimed to investigate the phytochemical profile, the antibacterial and antioxidant activities of mass cultured Spirulina platensis and the structural characterization of the methanolic extracts. S. platensis was isolated from estuary and mass cultured in the laboratory, methanol was used for extraction, and the yield was calculated as 16

In this research, the activated carbon was prepared using burnt Coconut (Cocos Nucifera) shell and was used as an adsorbent in the removal of toxic heavy metal ions of lead (Pb) and cadmium (Cd) from the aqueous solution using batch adsorption study. Cocos Nucifera was initially collected in the forming shell and then it was crushed in the form of granular. The carbon shell's surface has been modified with an oxidizing agent such as sulphuric acid or nitric acid to increase the shell's adsorption capacity. The effect contact time, pH, temperature, initial concentration, and adsorbent dosage level were analyzed. The result shows that the optimum pH was 6, and the capacity of adsorption was affected by the temperature. The efficiency of the adsorption rises with an increment in temperature. In addition, the characteristics of the adsorbents were studied by making use of SEM, FT-IR, and Energy Dispersive X-ray Analysis (EDX). The adsorption isotherm study was carried out using Langmuir and Freundlich isotherm model, and it shows the charcoal/carbon shell adsorption followed the Langmuir isotherm model. The modeling result of the kinetic model study indicates that the adsorption mechanism of lead (Pb) and cadmium (Cd) process of adsorption were fitted with a pseudo-second-order equation.

The study was aimed to remove the fluoride from aqueous solution by plant materials through batch experiment. The bio-adsorbents (Manilkara zapota and peels of Solanum tuberosum) were thermally activated and converted into ash. The batch study was performed in a laboratory and optimized by dose and time. The maximum removal of fluoride was observed in 0.8 g/100 ml for 77.6

This study was undertaken to investigate the biosorption of lead (Pb) by marine microalgae D. salina through batch model. The D. salina was isolated and identified by standard method and mass cultured in outdoor condition with optimum condition. The sorbent was prepared and analysed through FT-IR spectroscopy, and observed active functional groups such as alkyl halide (C-I and C–Cl), alcohol (C-O), aromatic (C = C), alkene (C = C), C≡N, alkyl (C-H) and amine (N–H) with different stretching were observed at the wavelength between 501.71 and 2897.19 cm −1 . The batch experiment was conducted with several factors such as pH, contact time and sorbent dosage. In the pH experiment, the results were shown pH dependent, and the maximum Pb absorption was noticed for 4.5 mg/L at the pH of 7–8, and the lowest Pb absorption was recorded 1.1 mg/L at the pH of 12. In time duration set, the absorption was noticed time dependent, and maximum of Pb removal by contact time was noticed higher in 120 min of 3.9 mg/L and lower absorption in initial time of 30 min. The influence of sorbent dosage on Pb removal was displayed concentration dependent, the maximum removal of lead 6.1 mg/L was noticed in 10 g L −1 , and the lowest removal was observed in initial dosage of 2 g L −1 . In conclusion, D. salina has more metal binding functional groups and sites on surface, and also it is a cheap cost additional biosorbent for removal of metal from industrial effluents.

The present study reports the novel approach to remove the excess fluoride in water using nano sized zinc oxide (ZnO) particles extracted from the plant leaf Solanum nigrum and Eclipta prostrate. The thermal behavior of the fabricated ZnO particles were characterized by XRD, the porosity and microstructure were studied by the SEM. The measurement of FTIR was carried out to find the probable biomolecules in both plant leaves. These leaves contain high amount of proteins, amino acids and rich in polyphenols. The batch experiment was carried out to study the removal of Fluoride under several factors like the effects of initial concentration, adsorbent dosage and various time intervals. It is revealed at optimum dosage of Eclipta and Solanum is 0.8g/100ml and the capacity of adsorption was creating to be 1.984mg/g and 1.943 mg/g and its efficiency is 98% and 55% respectively. Thus, the optimum dosage of the adsorbents can be used to lowering the fluoride concentration. The synthesized ZnO Nanoparticles in this work are highly capable material for removal of Fluoride ion. Thus, it is proven that the leaf of Solanum nigrum and Eclipta prostrata produce higher efficiency in reduction of Fluoride.

In this present investigation, sixteen sampling locations were selected around the Chrompet area, Chennai, which serves as a hub of a large number of tanning industries. The water in this location was contaminated as a result of these industrial operations. Solid waste as of industrial units is being dumped near the factories. This reacts with percolating rainwater and reaches the groundwater. A large number of Heavy Metals (HMs) have been picked up by the percolating water, which reaches the aquifer system and the groundwater gets contaminated. The water quality evaluation of sixteen samples was executed for various toxic HMs like chromium, cadmium, nickel, iron, lead, and manganese. From the outcomes, the HM's concentration followed the order of Cd > Pb > Cr > Ni > Mn > Fe. The outcomes of the analysis were also utilized for computing the Heavy Metal Pollution Index (HPI) along with the metal Index (MI) of the study area. The HPI and MI are useful instruments for evaluating water quality regarding HM contamination. An index value of more than 100 has been considered the critical value. The critical state of the pollution index was observed in sample 10 and the calculated index was 586.68. This value shows that in the study region, the quality of water was seriously affected, and overall, 75% of the water sample was under this category. The average MI of the collected samples is 20.67, which is also higher than the crucial limit of 1. The result of the investigation shows that the industrial activities in the study region had an important impact on the water in the area. As a result, adequate control measures must be implemented to avoid the water in this area from deteriorating further.

Sustainable groundwater management necessitates evaluation of the performance of recharge structures to replenish the aquifer without sacrificing quality. Different recharge arrangements were constructed independently in different locations, and also in combination in Cuddalore aquifer in the Tamil Nadu, India, to assess artificial recharge. The individual and combined effectiveness of these structures were studied using water level fluctuation, water balance, and numerical models. It was found that a check dam, a check dam with one recharge well, and a percolation pond with percolation wells had monthly recharge rates 0.30 m3/m2, 0.54 m3/m2 and 0.69 m3/m2 of ponding area respectively. Computational approach based on finite difference method was also used to find the effectiveness of recharge structures. MODFLOW was used to create a finite-difference model and the same was applied to Cuddalore aquifer and the simulated head contours for different scenarios for individual and combined structures were compared to the condition without recharge structures. The study was carried out for three years: one year preceding, and two years following the construction of recharge structures. Maximum water level increase was obtained as 2.54 m, 3.46 m, and 4.7 m for the percolation pond, check dam, and combination structure arrangement, respectively. The developed flow model can be used for groundwater management in the area.

The primary objective of this research is to assess the hydrogeochemical features and water quality of the Thamirabarani river stretch, located in southern India. Thirty-five water samples from the Thamirabarani river stretch were obtained from the districts of Tirunelveli and Thoothukudi. Twelve water quality parameters were measured during the pre-monsoon and post-monsoon periods of 2020 and 2021. The analytical results were verified with BIS and WHO standards to evaluate the water for drinking purposes. A Geographic Information system (GIS) was applied to know the spatial variation of the hydrogeochemical properties over the research area. Moreover, the Water Quality Index was calculated and it was revealed that 15% of the water samples used are outstanding, 35% are fit for potable use, 25% are poor, 15% water are very poor, and 10% unfit for consumption. Principal Component analysis (PCA) was performed to find out the dominant factors and their variance coverage for the overall water quality. The PCA results indicate that a water sample in Zone 1 is known for its alkalinity. The water qualities in Zone 2 and Zone 3 were affected by anthropogenic factors and industry wastes. More sea water intrusion was observed in Zone 4 in the water quality of the Thamirabarani river basin.

The application of system dynamics techniques is gaining significance and is much needed for an effective management of the depleting water resources in a dynamically complex region and considers it as the feedback from the system. The present study deals with the application of a system dynamic approach to simulate a chain of four tanks in the Guduvanchery watershed, Tamil Nadu, India. Standard data-driven models cannot be effectively used due to a lack of quality data for ungauged basins. VENSIM was used for the system dynamic simulation to assess water availability for the sustainable management of water resources. Inflow into the four tanks, net losses in each tank, and crop water requirement were given as inputs into VENSIM. Along with different models, an extensive field survey was carried out to quantify each input component. Based on system dynamics simulation, only 28% of the total available water is used for irrigation and the rest is wasted due to evaporation, transition loss, and spill from the tanks. It was found that there was approximately 5.46 MCM of surface water available in the watershed, and it will be able to supply the domestic demand of the watershed of 0.672 MCM in addition to the irrigation requirement.