Indexing method for assessment of pollution potential of leachate from non-engineered landfill sites and its effect on ground water quality

Using a combination of δ13CDIC-DOC-difference in dissolved inorganic and organic carbon, δ2H, and δ18O to localize leachate leaks at landfill sites in China

The investigation of leachate leakage at numerous landfill sites is urgently needed. This study presents an exploration of environmental tracing methods using δ2H and δ13C-difference in dissolved carbon (δ13CDIC-DOC) to localize leachate leak points at landfill sites. δ2H, δ13CDIC, δ13CDOC, δ18O, and an array of physicochemical indices (e.g., total dissolved solids, temperature, and oxidation reduction potential) were monitored in both leachate and groundwater from different zones of a landfill site in China during the year of 2021-2023. Moreover, data for these parameters (i.e., the isotopic composition and physicochemical indices) from twelve published landfill cases were also collected, and these groundwater/leachate data points were located within 1 km away from the landfill boundary. Then statistical analyses, such as Pearson correlation analysis and redundancy analysis (RDA), were performed using both the detected and collected parameters at landfill sites. Consequently, the intensity of interaction between leachate and background groundwater was found to significantly control the isotopic fractionation features of hydrogen and carbon, and both the content of major contamination indicators (total dissolved solids, chemical oxygen demand, and ammoniacal nitrogen) and the oxidation reduction potential were the key impact factors. Accordingly, the water type used to indicate leachate leakage points was determined to be leachate that significantly interacted with the background groundwater or precipitation (LBGP). δ2H showed a perfect linear correlation (0.81 ≤ r2 < 1.0) with δ13CDIC-DOC in leachate under highly anaerobic landfill conditions, and the δ2H & δ13CDIC-DOC combinations in the LBGP were significantly different from those in the other water types. For groundwater with total dissolved solids lower than 1400 mg/L at landfill sites, a strong positive linear correlation (r = 0.83) was revealed between δ13CDIC and δ13CDOC. Based on these insights, δ2H versus δ13CDIC-DOC plots and RDA using δ2H and δ13CDIC-DOC as response variables were proposed to localize leak points at both lined landfills and leachate facilities. These findings further understanding of the isotopic fractionation features of hydrogen, carbon, and oxygen and provide novel environmental tracer methods for investigating leachate leak points at MSW landfill sites.

Identification of prevalent leachate percolation of municipal solid waste landfill: a case study in India

Landfill leachate forms when waste-inherent water and percolated rainfall transfer are highly toxic, corrosive, acidic, and full of environmental pollutants. The release of leachate from municipal solid waste (MSW) landfill sites poses a severe hazard to human health and aquatic life. This study examined the impact of leachate from Delhi's Ghazipur landfill on the nearby groundwater quality. Analysis of leachate samples was done to determine various parameters such as total dissolved solids (TDS), hardness, alkalinity, electrical conductivity, pH, BOD5, COD, nitrate, sulphate, chloride and iron, and presence of coliform bacteria. Significant dissolved elements (22,690-34,525 mg/L) were observed in the samples, indicated by the high conductivity value (1156-1405 mho/cm). However, a stable pH range (6.90-7.80) of leachate samples was observed due to high alkalinity concentrations between 2123 and 3256 mg/L. The inverse distance weighing (IDW) interpolation tool from QGIS 3.22.7 developed spatial interpolated models for each parameter across the Ghazipur area. The IDW interpolated graphs of various parameters over the whole study area confirmed these contaminations. In addition, leachate and groundwater samples were physio-chemically analyzed, and temporal fluctuation in landfill waste has also been studied. The temporal fluctuation results showed that when heat is produced, transmitted, and lost throughout the waste system, the maximum temperature position fluctuates over time. The findings of this study highlight the critical importance of landfill management in reducing groundwater contamination from MSW leachate.

Effects of landfill age, climate, and size on leachate from urban waste landfills in Portugal: A statistics and machine learning analysis

The leachate generated by in urban waste landfills can cause environmental pollution if not controlled and treated. With different proportions of biodegradable waste, urban waste degrades over several phases in anaerobic conditions within a landfill. Using multivariate leachate data from 32 engineered landfills in Portugal, each with a similar waste composition, and all classified as non-hazardous waste landfills receiving urban waste, statistical inference was applied to categorise and deduce significant statistical differences in leachate volume and quality between landfill age, size, and climate, as well as the interactions and effects within these categories. The findings show that the effects of size and age on the leachate volume are prevalent over local, Mediterranean climate conditions; in larger landfills, waste may not be degrading as efficiently as in medium-sized landfills; hotter zones showed higher levels of COD and lower levels of BOD5 than warmer zones, indicating increased biological activity under higher temperature conditions; TN and NH4-N increase significantly with age and size; Cl- also significantly increases with age, showing higher levels, along with SO42-, in hotter zones as well as a concentration effect in the dry season, along with K+; heavy metals maintain levels as landfills age from intermediate to old, with only Cd2+ and Pb2+ showing significant reductions. High correlations between macro inorganics and between heavy metals were found. Cluster analysis showed two main branches, one representing the initial to intermediate stages of anaerobic degradation, and the other the interactions between leaching parameters in the later methanogenic phase of landfill stabilisation.

Evaluation of water from Lake Coatetelco in central-south Mexico and surrounding groundwater wells for drinking and irrigation, and the possible health risks

Due to an increasing reduction of hydrological resources across Mexico and their growing contamination from global warming and anthropogenic activities, this study evaluated water from the perennial Lake Coatetelco (Ca-Mg-HCO3) in tropical central-southern Mexico and groundwater (Ca-Mg-HCO3 and Na-HCO3-Cl) from the surrounding wells for drinking as well as irrigation qualities. Comparison with the WHO guidelines and the estimated water quality indices (DWQI and IWQI) grouped almost all the samples collected after the warm season rainfall in excellent and good categories (DWQI < 100) for drinking, even though fluoride remained > 1.5 mg/L in 50% samples. Except for one groundwater sample, all showed > 25% permeability (classes I and II) in Donnen classification indicating their suitability for irrigation. USSL and Wilcox classifications, however, catalogued some in the high-salinity hazard group and some as doubtful for irrigating regular plants. Samples from about 53% wells were also in high and severe restriction categories of IWQI for the irrigation. Total Hazard Quotient Index (THQI) for estimating the non-carcinogenic risk (HQfluoride > 1) showed that at least one lake water sample and 53% of groundwater might expose the adult and child population to dental and skeletal fluorosis. This water quality assessment data posterior to the rainfall season could be useful as a baseline for both the short- and long-term monitoring in attention to the United Nation's Sustainable Development Goal 6.

Characteristics and pollution potential of leachate from municipal solid waste landfills: Practical examples from Poland and the Czech Republic and a comprehensive evaluation in a global context

The formation of leachate is mainly due to the percolating of rainwater through the body of the landfill and the physical, chemical, and biological processes taking place inside the body of the landfill. The characteristics and pollution potential of leachate from the municipal solid waste (MSW) landfills in Poland (Łubna) and the Czech Republic (Zdounky) is presented. The objectives of this study are: 1) to evaluate and compare physicochemical characteristics of leachate, 2) to demonstrate the variability of leachate parameters in time, concerning stabilization phase of the landfill, 3) to present existing relationships between the characteristics of the leachate, 4) to indicate the factors determining the variability of the leachate composition. The Leachate Pollution Index (LPI) was applied to indicate temporal changes in leachate pollution, to assess polluting ability of leachate, and to compare the pollution potential of leachate. For the Łubna landfill, the minimum, maximum, and average values of LPI were: 6.10, 39.41, and 18.44, respectively. The LPI for the Łubna landfill tends to decrease in time due to stabilization of wastes. For the Zdounky landfill, temporal decreasing of LPI was not observed. The minimum, maximum, and average values of LPI were: 6.25, 14.25, and 10.11, respectively. Alkaline characteristics of leachate from both landfills indicate the mature stage of waste storage. This phenomenon was also evidenced by the Chemical Oxygen Demand (COD), ammonium (NH₄⁺), and cadmium (Cd). For both landfills, pH was negatively correlated with most of the leachate parameters. It is the task for environmental engineers to confront existing knowledge (supplemented by the results of this work) about the properties of leachate, its changes over time and its polluting potential with the possibilities of treating and managing it properly.

A machine learning-based approach for mapping leachate contamination using geoelectrical methods

Leachate is the main source of pollution in landfills and its negative impacts continue for several years even after landfill closure. In recent years, geophysical methods are recognized as effective tools for providing an imaging of the leachate plume. However, they produce subsurface cross-sections in terms of individual physical quantities, leaving room for ambiguities on interpretation of geophysical models and uncertainties in the definition of contaminated zones. In this work, we propose a machine learning-based approach for mapping leachate contamination through an effective integration of geoelectrical tomographic data. We apply the proposed approach for the characterization of two urban landfills. For both cases, we perform a multivariate analysis on datasets consisting of electrical resistivity, chargeability and normalized chargeability (chargeability-to-resistivity ratio) data extracted from previously inverted model sections. By executing a K-Means cluster analysis, we find that the best partition of the two datasets contains ten and eleven classes, respectively. From such classes and also introducing a distance-based colour code, we get updated cross-sections and provide an easy and less ambiguous identification of the leachate accumulation zones. The latter turn out to be characterized by coordinate values of cluster centroids<3 Ωm and >27 mV/V and 11 mS/m. Our findings, also supported by borehole data for one of the investigation sites, show that the combined use of geophysical imaging and unsupervised machine learning is promising and can yield new perspectives for the characterization of leachate distribution and pollution assessment in landfills.

Recycling of wet grinding industry effluent using effective Microorganisms™ (EM)

A considerable volume of effluent released from the food processing industries, after the extensive use in the products manufacturing and industrial process. Effluents, either without treatment or with improper treatment, released out from the industries would severely damage the environment and human health. An investigation was done by recycling the effluent samples, collected from the wet grinding industry, Madurai, India, which was determined with an acidic pH (5.93), high turbidity (160.78 NTU), high BOD (62.4 mg/l) and COD (274.38 mg/l) and a significantly higher quantity of starch (115.81 mg/l). Biological wastewater treatment method was chosen in this experiment on the basis of the biodegradability index of effluent (3.21-10.75). The main goal of this study was to evaluate the effectiveness of wastewater treatment in a prototype STP utilizing the Effective Micro-organisms™ Consortium application. The US EPA International Water Quality Standards and the Water Quality Index were used to compare the water quality of the recycled effluent with and without the EM application. The effluent from the EM consortium treatment was found to have acceptable levels of pH (7.38), salinity (1.94 ppt) and Conductivity (4.05 mS); and a declining trend found in TDS (1.81 ppt), BOD (24.4 mg/l) and COD (148.83 mg/l) level when the effluent treated using EM. Removal effectiveness of EM significant reduce in the treated effluents starch (85.15%), sulphate (78.42), phosphate (79.60), nitrogen (65.54%), and turbidity (82.73%) level were observed. Which was shown to be comparatively better than employing without EM treatment. This research substantially intends to the best practices, towards sustainable industries through Cleaner Production Mechanism.

Investigation of groundwater vulnerability to open dumpsites and its potential risk using electrical resistivity and water analysis

Understanding the impacts of open dumpsites and its implication on groundwater systems is a critical component of water security for sound long-term environmental management strategies. However, predicting the impacts of dynamic dumpsites on environmental systems is a difficult task that requires a technical approach. This paper applies electrical resistivity and physicochemical water analysis techniques to investigate the groundwater vulnerability to open dumpsite leachates and its potential environmental risk. A total of twenty-nine (29) vertical electrical sounding (VES) were acquired within and around the dumpsites. A physicochemical properties analysis of water from seven hand-dug wells (HDWs) within a 200 m radius of the dumpsite was performed. The subsoil resistivity values encountered within the dumpsite and off-dumpsite vary from 2.4 Ωm to 17 Ωm and 68 Ωm - 611 Ωm respectively. The study links up the subsurface geo-electrical properties (resistivities) with the physiochemical water analysis, which affirmed the electrical resistivity technique efficiency in dumpsite investigation. The geophysical and water analysis results indicate that the groundwater systems within and around the dumpsite are highly susceptible to dumpsite leachates and require urgent evacuation to avoid the impending risks posed to both human health and the environment. While the geophysical analysis indicates high leachates infiltrating index in the subsoil, which invariably affects the groundwater resources, the physicochemical analysis indicates a high concentration of heavy metals, COD, BOD, TDS and high electrical conductivity (EC), affirming the geophysical results. The leachate plumes of the dumpsite suggest to have masterminded the groundwater pollution, the high heavy metals dominating the 7 HDWs have significantly influenced the chemistry of the groundwater quality within the area. Thus, dumpsite is the major cause of groundwater pollution. Indications show that the impacts of dumpsite leachates decreased with depth and source distance. More also, groundwater systems within a 200 m radius of the dumpsite are at risk of a high vulnerability index. Besides the study indications, some influential regional factors such as climatic conditions, hydrology and geology of the dumpsites have further amplified the impending major environmental crisis. Consequently, the study suggests future environmental preservation for the future direction.

Development of fuzzy leachate pollution index for treatability-based classification of solid waste landfills

The fuzzy leachate pollution index (FLPI) was established to classify the landfill sites on the basis of their leachate pollution potential by considering the limitations of traditional methods. The FLPI was developed adopting 9 critical input parameters, i.e., TDS, pH, Cl, Cu, Pb, Cr, Zn, BOD, and COD, from 22 major landfill sites across India. Using these critical parameters, 3 groups, i.e., inorganic leachate strength (INLS), organic leachate strength (ORLS), and heavy metal leachate strength (HMLS), were generated to estimate the FLPI. The regression analysis, ANOVA, and sensitivity analysis were also performed to determine the significance and uncertainty of the index. The results showed that among all MFs, the triangular with overlapping open ends (TOO) MF was best fitted (R = 0.90) for FLPI estimation. Accordingly, 41% of the landfill sites showed less treatment while the others (59%) required moderate degree of treatment. The regression (R² = 0.92) and ANOVA (F value = 15.003, p = 0.000031) analyses described that the developed tool was significant (p < 0.05). The sensitivity analysis showed that Zn (R = 0.99) was the most influencing factor followed by BOD > COD > pH > Cr > Cu > Cl > Pb > TDS. The study provides an important tool that can also be used by researchers and scientists for investigating and evaluating various environmental problems.

Impact of leachate on quality of ground water around Chunga Landfill, Lusaka, Zambia and possible health risks

We report the characteristics and possible impact of leachate on quality of groundwater in the Chunga Landfill area of Lusaka, Zambia. Water and leachate samples were collected within and around the landfill for analysis. The pH, biological oxygen demand (BOD), chemical oxygen demand (COD), nitrates, sulphates, chlorides for the leachate and groundwater samples were (6.6 ± 0.1 to 8.7 ± 0.0), (1.7 ± 0.3 to 1,569.6 ± 4.9 mg/L), (4.0 ± 0.0 to 10,378.5 ± 59.2 mg/L), (8.0 ± 0.0 to 37.7 ± 0.4 mg/L), (11.7 ± 0.0 to 273.1 ± 1.7 mg/L), (43.0 ± 1.2 to 974.2 ± 0.8 mg/L) respectively. Heavy metal concentration ranges were cadmium (0.004 ± 0.000 to 1.149 ± 0.021 mg/L, chromium (0.007 ± 0.000 to 2.699 ± 0.039 mg/L), copper (0.013 ± 0.002 to 0.246 ± 0.005 mg/L), lead (0.062 ± 0.005 to 2.591 ± 0.065 mg/L) and zinc (0.008 ± 0.001 to 2.032 ± 0.017 mg/L). The pH of the leachate (8.5 ± 0.0 to 8.7 ± 0.0) meant the landfill was in the methane fermentation phase. An indexing approach was used with the leachate pollution index (LPI) of 30.173, heavy metal pollution index (HPI) of 3,938.92. The heavy metal index (HMI) for copper, lead, chromium, cadmium and zinc were found to be 0.92, 1,124.19, 47.20, 994.17 and 1.48 respectively. Principal component analysis (PCA) showed that anthropogenic activities contributed to pollution with high loading values. Ash from continuous burning of the waste may provide alkalinity which reduces leachate BOD and COD. Results showed that the landfill has outgrown the designed cells capacity as not all leachate was collected by the under-drainage. Results also showed that lack of adequate landfill cover significantly increases rainfall infiltration thereby increasing volumes of leachate produced with a, hence potential for underground water contamination and a human health and environmental problem.

Quality assessment and prediction of municipal drinking water using water quality index and artificial neural network: A case study of Wuhan, central China, from 2013 to 2019

The sanitary security of drinking water is closely related to human health, but its quality assessment mainly focused on limited types of indicators and relatively restricted time span. The current study was aimed to evaluate the long-term spatial-temporal distribution of municipal drinking water quality and explore the origin of water contamination based on multiple water indicators of 137 finished water samples and 863 tap water samples from Wuhan city, China. Water quality indexes (WQIs) were calculated to integrate the measured indicators. WQIs of the finished water samples ranged from 0.24 to 0.92, with the qualification rate and excellent rate of 100 % and 96.4 %, respectively, while those of the tap water samples ranged from 0.09 to 3.20, with the qualification rate of 99.9 %, and excellent rate of 95.5 %. Artificial neural network model was constructed based on the time series of WQIs from 2013 to 2019 to predict the water quality thereafter. The predicted WQIs of finished and tap water in 2020 and 2021 qualified on the whole, with the excellent rate of 87.5 % and 92.9 %, respectively. Except for three samples exceeding the limits of free chlorine residual, chloroform and fluoride, respectively, the majority of indicators reached the threshold values for drinking. Our study suggested that municipal drinking water quality in Wuhan was generally stable and in line with the national hygiene standards. Moreover, principal component analysis illustrated that the main potential sources of drinking water contamination were inorganic salts and organic matters, followed by pollution from distribution systems, the use of aluminum-containing coagulants and turbidity involved in water treatment, which need more attention.

Insights into the Titania (TiO2) Photocatalysis on the Removal of Phthalic Acid Esters (PAEs) in Water

In this era of globalization, plastic is regarded as one of the most versatile innovations, finding its uses ranging from packaging, automotive, agriculture, and construction to the medical and pharmaceutical industries. Unfortunately, the single-use nature of plastics leads to ecological and environmental problems. Among conventional disposal management of plastic waste are landfilling dumping, incineration, and recycling. However, not all plastic waste goes into disposal management and ends up accumulating in lakes, rivers, and seas. In the aquatic environment, the action of photochemical weathering plastics has resulted in the release of chemical additives such as phthalic acid esters (PAEs), an important plasticizer added to plastic products to improve their softness, flexibility, and durability. Nowadays, PAEs have been ubiquitously detected in our environment and numerous organisms are exposed to PAEs to some extent. As PAEs carry endocrine disruptive and carcinogenicity properties, an urgent search for the development of an efficient and effective method to remove PAEs from the environment is needed. As a viable option, titania (TiO2) photocatalysis is a promising tool to combat the PAEs contamination in our environment owing to its high photocatalytic activity, cost-effectiveness, and its ability to totally mineralize PAEs into carbon dioxide and water. Hence, this paper aims to highlight the concerning issue of the contamination of PAEs in our aquatic environments and the summary of the removal of PAEs by TiO2 photocatalysis. This review concerning the significance of knowledge on environmental PAEs would hopefully spark huge interest and future development to tackle this plastic-associated pollutant. Copyright © 2022 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

Spatio-temporal dynamics of water quality in river sources of drinking water in Uttarakhand with reference to human health

Any contamination in potable water leads to high risk on human health. Hence, it is inevitable to characterize water quality and assess temporal change with reference to human health. In this paper, nineteen water quality parameters from 50 sources of drinking water supply operated by state agency Uttarakhand Jal Sansthan (UJS) were analysed. The water samples were collected for pre-monsoon (May) and post-monsoon (November) seasons for the year 2010, 2011, 2018 and 2019. Multivariate analysis such as Pearson's correlation coefficient (r), K-mean, hierarchical clustering and principle component analysis (PCA) were applied to examine the drinking water quality at source sites. The strength of correlation among the parameters is reduced over the time. Cluster analysis provides six major hydro-chemical clusters in the study region. Clusters were compact during 2010-2011 and converted to overlapping structure in later period. The size of clusters was change from two clusters to six clusters during 2018-2019. These hydro-chemical clusters were examined through PCA and established six major hydro-chemical components of water quality. The physico-chemical parameters, namely, pH, alkalinity, TH, TDS, Na, K, Ca, Mg, Cl and SO₄, were in PC-1, the heavy metals in PC-3, turbidity in PC-4, TC in PC-5 and PC-6 is combination of turbidity, NO₃ and TC, whereas PC-2 was a mix of pH and Na and K salts. Study highlighted that the water quality has changed over the time due to runoff of plant debris, erosion, agricultural fertilizer, development activities and local geology hosts. Each PCs was mapped with associated human health issues. Result reveals that structures and pattern of PCs indicate several human health diseases over the later period with seasonal effects.

Microbial Treatment of Raw and Primary Treated Sanitary Landfill Leachate by Indigenous Strain Brevibacillus agri

Landfill leachate is a potential environmental threat. Sanitary landfills are model sites which contains a leachate collection pool and a processing facility to treat it up to environmental standards before discharge. The present study is the very first endeavor to establish leachate treatment efficiency of indigenous microbial strain Brevibacillus agri. Leachate samples were inoculated with isolated strain and incubated for 41 days in an orbital shaker. Percent reduction in major water quality parameters was assessed after 0, 7, 21, and 41 days of incubation, for understanding the degradation kinetics. Results of the study demonstrate that Brevibacillus agri was effective in improving the wastewater quality of both raw and primary treated leachate. Overall reduction for different water quality parameters was found to be 50% higher for primary treated leachate than that for raw leachate within 21 days of incubation. Microbial degradation followed first-order kinetics with rate constants in the range of 0.0047-0.03 and 0.0061-0.074 day^-1 for raw and primary treated leachate respectively. Calculated half-life of each pollutant parameter was significantly higher in the raw sample (23-147 days) as compared to the primary treated one (27-112 days). The leachate pollution index (LPI) value of the raw leachate was also found to be > 25% higher than primary treated leachate sample after microbial treatment. Hence, it can be concluded that on site application of primary treatment technology followed by secondary microbial degradation by indigenous microflora, viz., Brevibacillus sp., may prove effective to achieve desirable water quality for safe environmental discharge.

Water quality assessment in two lakes of Panchkula, Haryana, using GIS: case study on seasonal and depth wise variations

Water is the most important commodity available on earth and exists as both surface and sub-surface sources, but increased water pollution has reduced its potability. In this context, it has become imperative to regularly monitor the water quality. In situ and laboratory experimental procedures involve point wise collection of samples for quality determination which are too elaborative and time consuming. As such, the use of methods like Geographic Information System (GIS) modelling if used in collaboration with the traditional methods can prove to be a great tool as they are less expensive and gives a complete spatial resolution of the study site. Therefore, the present study focuses on the determination of water quality using traditional methods in collaboration with GIS modelling system using the inverse distance weighing (IDW) method for two natural lakes in Haryana. The IDW technique was used to interpolate parameters like temperature, dissolved oxygen (DO), nitrates (NO₃) and total phosphorous (TP) as they represent the effects of recent and old pollution in lake waters at different depths. These parameters were interpolated for determining the overall water quality status for the lakes. The collaboration can prove to be of great practical significance in today's time by giving an elaborative view of the present water quality status, easing daily telemetric monitoring of the sites as well as give an opportunity for futuristic modelling. The technique can work for almost all the sites around the globe which have either not been evaluated from quality aspect or are inaccessible for monitoring. Parameters like temperature and DO show significant depth wise and seasonal variations for both the lakes with highest values observed at the surface levels, whereas the NO₃ and TP represented effects of point pollution sources to a smaller extent. The maximum value of temperature was determined to be of 30.7 °C and 9 mg/l for DO and was recorded at the surface of lakes 2 and 1, respectively. Further, nitrate and phosphorous concentrations were observed to have maximum values of 0.99 and 0.5 mg/l at the centre of the lake 1 for monsoon season due to influx of pollutants and settlements in the bed. The primary reason for the variation of water quality may be attributed to increased sedimentation at the bottom of lake due to agricultural activities in the vicinity which creates impacts on different hydrodynamic processes leading to increased levels of TP and NO₃ concentrations. Further, increased recreational activities lead to induced variations in the water quality as well.

Comprehensive analysis and modeling of landfill leachate

Landfill leachate data compiled from 220 different landfills from 46 countries in Europe, Middle East, Asia, Africa, and America was analysed by multivariate statistical approaches. Data pre-treatment procedure such as handling of outliers, completion of missing data, and standardization of data was applied to prepare the raw data matrix for the complex statistical analyses including cluster and principal component analyses (PCA). Regression modeling was conducted to estimate leachate parameter values. Results show that usually inorganic parameters, if included in the PCA, dominated the first components indicating the highest correlations as well as accounting for majority of the variation in the data. Those highly correlated parameters in landfill leachate could be important in evaluation of their pathways into leachate in terms of transport and biodegradation mechanisms as well as their elimination potential from sampling and analytical procedures during monitoring activities at landfills. Some leachate parameters having significantly high concentrations, such as organics, salts, and some inorganics, impacted the formation of components in PCA. This in turn provides important information about the specific characteristics of leachate samples and the landfills to which they belong.

Progress and prospects in mitigation of landfill leachate pollution: Risk, pollution potential, treatment and challenges

The escalating loads of municipal solid waste (MSW) end up in open dumps and landfills, producing continuous flows of landfill leachate. The risk of incorporating highly toxic landfill leachate into environment is important to be evaluated and measured in order to facilitate decision making for landfill leachate management and treatment. Leachate pollution index (LPI) provides quantitative measures of the potential environmental pollution by landfill leachate and information about the environmental quality adjacent to a particular landfill. According to LPI values, most developing countries show high pollution potentials from leachate, mainly due to high organic waste composition and low level of waste management techniques. A special focus on leachate characterization studies with LPI and its integration to treatment, which has not been focused in previous reviews on landfill leachate, is given here. Further, the current review provides a summary related to leachate generation, composition, characterization, risk assessment and treatment together with challenges and perspectives in the sector with its focus to developing nations. Potential commercial and industrial applications of landfill leachate is discussed in the study to provide insights into its sustainable management which is original for the study.

Groundwater pollution index (GPI) and GIS-based appraisal of groundwater quality for drinking and irrigation in coastal aquifers of Tiruchendur, South India

We assessed groundwater pollution index (GPI) and groundwater quality of coastal aquifers from Tiruchendur in South India for drinking and irrigation by evaluating the physico-chemical parameters of 35 samples of mainly Na-Cl type in an area of 470 km² with respect to the World Health Organization (WHO) standard as well as by estimating different indices such as total hardness (TH), sodium percentage (Na%), magnesium ratio (MR), Kelley's ratio index (KR), potential salinity (PS), Langelier saturation index (LSI), residual sodium carbonate (RSC), sodium adsorption rate (SAR), permeability index (PI), and the irrigation water quality index (IWQI). Minimal influence of aquifer lithology and the dominant influence of evaporation on groundwater chemistry reflected the semi-arid climate of the study area. Electrical conductivity (EC) of about 89% of the samples across 418 km² exceeded the permissible limit and Ca values of 74% of samples, however, remained within the allowable limit for drinking. More chloride was caused by influx of seawater and salt leaching and higher K was due to excessive fertilizer usage for agriculture. The spatial distribution map created using inverse distance weighting (IDW) method shows that the suitable groundwater is present close to the river basin. GPI values between 0.40 and 4.7, with an average of 1.5, classify insignificant pollution in 43% of the study region and the groundwater suitable for drinking purposes. In addition, 17% of the groundwater samples are also marginally suitable for drinking. The irrigation water quality indices provided contradictory assessments. Indices of TH, Na%, MR, PS, and LSI suggested 32-95% of the samples as unsuitable for irrigation, whereas the indices of RSC, SAR, and PI grouped 72-100% samples as permissible for irrigation. The IWQI map, however, indicated that the groundwater from more than half of the study area are not apt for irrigation and the groundwater of about one-third of the area could only be applied to salt-resistant plants.

VFS-based OFSP model for groundwater pollution study of domestic waste landfill

The groundwater quality is essential for high quality of life and social development. Thus, the importance and necessity of the accurate and rigorous requirements for contaminated groundwater assessment has increasingly attracted engineers' and researchers' attentions. In order to improve the precision and robustness of the groundwater quality evaluation of domestic waste landfills, based on the variable fuzzy set (VFS) pair and the optimized N.L. Nemerow index, we develop an optimized fuzzy set pair (OFSP) model for groundwater quality assessment. Then, we devise the OFSP model by five key elements of optimized synthesis operator "C", relative difference[Formula: see text], connection degree"ui", optimized N.L. Nemerow index "Pi," and pollution load ratio "Ji", which can achieve the reasonable groundwater quality assessment model, the stable groundwater quality evaluation process, and the convincing evaluation results. Finally, a case study on groundwater quality assessment of various domestic landfills in China is conducted to explore the comprehensive impacts of domestic landfills in different regions and types on groundwater pollution from multiple perspectives, and demonstrate the effectiveness of the proposed OFSP model. The groundwater quality assessment results of various domestic landfills indicate that the pollution level of groundwater under unregulated domestic landfills in eastern and southern China is the worst. Based on the assessment results of groundwater quality, we compare the groundwater quality levels obtained by various mainstream methods. In line with precision (0.985), correlation (0.934), robustness (0.953), and rationality (0.946), our designed OFSP model has the best performance. In addition, according to the indexes of discrimination (0.217) and versatility (0.837), the designed OFSP model also has a good ability. Results of experiments well prove that the proposed OFSP model could play a good performance on groundwater quality evaluation in domestic landfills, compared with other mainstream models.

Eco-restoration of river water quality during COVID-19 lockdown in the industrial belt of eastern India

The sudden lockdown recovers the health of the total environment particularly air and water while the country's economic growth and socio-cultural tempo of people have been completely hampered due to the COVID-19 pandemic. Most of the industries within the catchment area of river Damodar have been closed; as a result, significant changes have been reflected throughout the stretch of river Damodar. The main objective of the study is to analyze the impact of lockdown on the water quality of river Damodar. A total of 55 samples was collected from eleven different confluence sites of nallas with the main river channel during and pre-lockdown period. The relevant methods like WQI, TSI, Pearson's correlation coefficient, and "t" test have been applied to evaluate the physical, chemical, and biological status of river water. The result of "t" test indicated that there are significant differences (α = 0.05) of each parameter between pre and during lockdown. Water quality index (WQI) is used for analysis of drinking water quality suitability followed by BIS. The values of WQI showed "very poor" (S1, S2, S3, S6, S7, and S11) to "unfit for drinking" (S4, S5, S8, S9, and S10) of river water during pre-monsoon season. The nutrient enrichment status of the river was analyzed by Trophic State Index (TSI) method and it shows the "High" eutrophic condition with a heavy concentration of algal blooms in almost an entire stretch. During lockdown, nutrient supplies like TN and TP have been reduced and is designated as "Low" (S1, S2) to "Moderate" (S3 to S11) eutrophic condition of middle stretch of Damodar. This research output of river Damodar will definitely assist to policy makers for sustainable environmental management despite the dilemma between development and conservation.

Novel consortia of enterobacter and pseudomonas formulated from cow dung exhibited enhanced biodegradation of polyethylene and polypropylene

This study prioritizes the biodegradation potential of novel bacterial consortia formulated from cow dung samples towards low-density polyethylene (LDPE) and polypropylene (PP) in comparison with our previous studies. Ten possible consortia were formulated using 10 selected isolates with >10% weight reduction of LDPE and PP, these were pre-treated under UV for 1 h, and their biodegradation potential was studied for 160 days. The isolates present in prioritized consortia were characterized by standard microbiology and 16SrRNA gene sequencing methods. Out of 10 bacterial consortia formulated, potential consortium-CB3 showed greater percentage degradation (weight reduction) of 64.25 ± 2% and 63.00 ± 2% towards LDPE and PP films, respectively (p < 0.05) at 37 °C compared to other consortia. Significant structural variations due to the formation of bacterial biofilm were observed in CB3 treated LDPE and PP films. The three bacteria-IS1, IS2, and IS3-that constituted CB3 were found to be novel strains and designated to be Enterobacter sp nov. bt DSCE01, Enterobacter cloacae nov. bt DSCE02, and Pseudomonas aeruginosa nov. bt DSCE-CD03, respectively. This novel consortium can be scaled up for enhanced degradation of plastic polymers and probably design cost-effective bio-digester for industrial applications using CB3 as potential inoculum.

Long-term redox conditions in a landfill-leachate-contaminated groundwater

Indicators of redox conditions; oxygen, sulphate, nitrate, ammonium, iron and manganese, and in addition, bicarbonate and total organic carbon were studied in groundwater samples contaminated by leachate emanating from Revdalen Landfill (Norway). Based on these variables, the study aimed to deduce the redox conditions in the aquifer. Literature on landfill leachate contamination of confined aquifers is scarce and to the best of our knowledge, this study, which describes long-term analysis of redox chemistry, is the first of its kind in such an environment. Groundwater samples were monitored for a period of 24 years, enabling us to describe redox conditions on both short-term and long-term bases. Levels of measured parameters in the contaminated aquifer varied spatially and with time, but were generally elevated except oxygen; pH (4.9-8.8), oxygen (0-11.3 mg/L), sulphate (0-28 mg/L), nitrate (0-16 mg N/L), ammonium (0.02-40 mg/L), iron (0-99 mg/L), manganese (0.06-16 mg/L), bicarbonate (22-616 mg/L) and total organic carbon (1.3-47 mg/L). From the result, levels of iron, manganese, nitrate and ammonium violated the Norwegian drinking water norms. However, iron, ammonium, total organic carbon and bicarbonate showed strong attenuation along the groundwater flow path. By contrast, oxygen, nitrate and sulphate increased farther out in the plume. The redox conditions that developed in the aquifer were similar to those previously reported for phreatic aquifers, structuring by proximity to the landfill as sulphate-reducing, iron-reducing, manganese-reducing, nitrate-reducing, and finally aerobic condition. Eventually, there was an apparent breakdown of this system due to ecosystem shift in the landfill when leachable reduced ions were depleted and the landfill became aerobic. Overall, the redox framework provided remarkable attenuation to contaminants, and thus prevented potential degradation of ecological health due to the landfill leachate.

Using advanced statistical tools to assess the impact of a small landfill site on the aquatic environment

The aim of the study was to assess the impact of a small municipal landfill on the aquatic environment over 9 years, using advanced statistical tools. The results of the study of surface, ground- and leachate waters from 2008 to 2016 were subjected to detailed statistical analysis based on 15 physicochemical indicators. Factor analysis accounted for the requirements of the WHO, the European Union and the nation of Poland using 8 statistical analytical methods. The analysis of leachate contamination from the landfill site with the use of advanced statistical tools revealed its interaction with groundwater. The assessment was based on increased and statistically significant values and correlations of temperature, Zn and N-NO₃ between leachate and groundwater, factors demonstrating the negative impact of the landfill. In the case of Zn, there was also a correlation between the tested waters below the landfill. The increased PAH values in the examined surface and ground waters were not a consequence of waste disposal. However, the deterioration of the chemical state of groundwater in the vicinity of the landfill could result from a certain dysfunction of the facility's infrastructure after operating for more than 20 years.

Assessment of spatio-temporal variations in lake water body using indexing method

The study assesses the characteristics of two lakes located in close vicinity to each other in identifying the status of the lakes based on Designated Best Use (DBU) criteria for optimum utilization and use. Further, the study reports the characteristic assessment of the lakes for two seasons with sampling carried out in August and October months of 2019 and samples collected at different depths and locations to present the comprehensive existing water quality conditions of the lake. The study utilized about twenty parameters evaluated experimentally for determination of Water Quality Indices. In this context, different water quality indices including National Sanitation Foundation Method (NSFWQI) and BIS 10500 (BISWQI) were utilized in determining the indices. The WQI were determined depth wise and a weighted average method was utilized in presenting the overall WQI of the lakes which represents the true water quality based on depth wise evaluation. Hence, the study represents both spatial and temporal variations in the lake water quality. The overall classification of water quality for both the lakes using the NSFWQI methodology was good for both the sampling periods. Similarly, the overall water quality was categorized to be excellent for both the sampling periods using the BISWQI. Further, a new approach in determining water quality indexing is presented through introduction of a Modified Water Quality Index (MWQI) which utilizes the maximum number of parameters and thereby provides a means to reduce ambiguity and eclipsing problems of WQI. Using this newly developed MWQI, the water quality was categorized to be excellent and good for samples collected in August and October respectively for both the lakes. However, conservative estimation considering spillover effects may lead to classification of good category using MWQI. The Heavy Metal Pollution Index (HMI) were classified to be good for both the lakes and sampling periods. Spectral characterization of water samples revealed the presence of oxygen (O), tantalum (Ta), sodium (Na) and Zinc (Zn). However, further monitoring studies are being carried out to cover a period of 1 year to observe if there is a change in water quality due or any seasonal variations.

Investigating the drinking and surface water quality and associated health risks in a semi-arid multi-industrial metropolis (Faisalabad), Pakistan

Urban areas under the influence of multi-industrial activities with arid and semi-arid environments witness the significant increase in environmental pollution especially in the water sector. The present study evaluated the water quality and associated health risk assessment through heavy metal pollution. Drinking (n = 48) and surface (n = 37) water samples were collected from semi-arid multi-industrial metropolis, Faisalabad, Pakistan. Physio-chemical and biological parameters and different metals (Al, As, Ba, Cd, Cr, Cu, Fe, Pb, Ni and Zn) were investigated using standard procedures and multivariate water quality assessments. Many physio-chemical and biological parameters and metals especially arsenic were exceeding the permissible limit of Punjab environmental quality standards and the World Health Organization. The results from water quality index showed that < 56% samples have poor, < 8% have very poor and < 6% have unsuitable water quality for drinking purposes. Water quality for the Gugera Branch Canal was found suitable with medium sodium (alkalinity) and salinity hazards, while it was found poor with magnesium absorption ratio. Hazard quotient (HQ) values for arsenic were found at the threshold level (HQ > 1) and carcinogenicity was found in case of arsenic and chromium (1 × 10^-4) in adults and children. Semi-arid weather combined with different anthropogenic activities and unusual water features provoked metal contamination. Results of the present study can deliver basic information for effective management of water in the most populous and industrial areas.