Assessing seasonal fluctuations in leachate chemical properties and leachate pollution index as contamination indicators

Municipal solid waste (MSW) management practices that lack scientific rigor and use impromptu methods have produced massive leachate in urban complexes. Nowadays, the management of leachate has become an utmost concern worldwide. The MSW landfill site was a low-lying, open dump that operated in a non-engineered way. In this context, the physicochemical characterization of leachate has been carried out. Leachate sampling was done at the Bhandewadi dumpsite, Nagpur, for three seasons (summer, rainy, and winter). During analysis, parameters such as COD, BOD5, pH, TKN, TSS, sulfates, and chlorides were analyzed, and the obtained data was compared with the standard EPA 2003 and CPHEEO 2016 methods. Values of COD, BOD5, TKN, sulfates, and chlorides were in the range of 2500-16,000 mg/L, 495-2500 mg/L, 167-1900 mg/L, 240-900 mg/L, and 1400-5900 mg/L with respect to all three seasons, respectively. In conjunction with physicochemical analysis, the landfill leachate's leachate pollutant index (LPI) was assessed. The highest LPI values were observed for summer (14.323) as compared to rainy (12.301) and winter (11.348) data. This index reflects the hazardous character of MSW leachate and the total potential for leachate contamination. The results of this study showed seasonal variations in the observed data. Age and seasonal fluctuations therefore substantially influence the composition of the leachate.

Physical and chemical characterization and pollution index applied in the assessment of the polluting potential of leachate from urban landfills

During the operation of the landfills, leachate should be managed with caution to avoid possible negative environmental impacts. Considering this, the present study aims to evaluate the relationship between different variables in the leachate composition and elucidate the transformation processes through which this effluent passes during the landfill's period of operation. The study was conducted with eight sanitary landfills from the state of Minas Gerais, in southeastern Brazil, and used descriptive statistical analysis, principal component analysis (PCA), correlation analysis, and calculation of the leachate pollution index (LPI). The biochemical oxygen demand (BOD5)/chemical oxygen demand (COD) ratio was between 0.20 and 0.60. We also observed a significant correlation of 0.45 between Cl- and N-NH4+, which reflects the biological degradation processes that contribute to the presence of both variables. The PCA showed that inorganic variables and organic matter dominated the first component, with coefficients above 0.65, indicating the importance of those variables in determining the general data variability. The LPI values were between 15.26 and 25.97, with BOD5, COD, and N-NH4+ having sub-indexes above 35, being the main variables that increase the pollution potential of the leachate. On the other hand, trace metals present sub-indexes below 7 due to precipitation caused by increased pH and the characteristics of the waste discarded in landfills. The study provides essential information regarding the landfill leachate characteristics and its variation over time, which can contribute to the definition of treatment technologies for this affluent in different scenarios.

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.

Application of multi-criteria decision-making techniques to develop modify-leachate pollution index

The modify-leachate pollution index (m-LPI) was developed with the help of multi-criteria decision-making (MCDM) technique based on the landfill leachate pollution potential by considering the limitations of traditional methodologies. Across India, twenty major landfill sites (LS) were selected for which m-LPI was assessed. Twenty-five experts' opinions were taken for the determination of nine input criteria weights, such as pH, COD, TDS, Cl, Zn, Pb, Cu, annual rainfall, and landfill age with the help of a questionnaire-based survey. In this context, six MCDM techniques were investigated to develop m-LPI. Among different MCDM techniques selected, weighted aggregated sum product assessment (WASPAS) proved to be an effective one with an R² value of 0.828 and IA value of 0.813. WASPAS gave first and last rank to Kadapa, Andhra Pradesh LS (1.677) and Turbhe, Maharashtra LS (2.193), respectively. The investigation revealed that around 90% of LS considered in the present study require leachate treatment. WASPAS sensitivity analysis showed that the least sensitive criteria were pH, followed by Cl and Zn. The m-LPI can be used by researchers and scientists to investigate and evaluate various challenges involved with solid waste management in LS.

Characteristics of leachate from refuse transfer stations in rural China

The properties of leachate from refuse transfer stations (RTSs) in rural China were indefinite. In this study, a total of 14 leachate samples from RTSs in nine provinces of China were characterized for their pH, electric conductivity, chromaticity, concentration of organic substances, nitrogen distribution, volatile organic compounds (VOCs), organic phosphorous pesticide, and heavy metals. The structural composition of fluorescent dissolved organic matter (FDOM) was also determined. To evaluate the leachate pollution potential in this study, a leachate pollution index was derived and used. Chromium (Cr) was the most polluting heavy metal present in rural leachate. Ethanol and ethyl acetate were the most frequently detected VOCs at high concentrations. Three-dimensional fluorescence excitation-emission matrix spectra were used to characterize the FDOM. Three components, tryptophan (C₁), tyrosine-like (C₂), and humic acid- and fulvic acid-like (C₃) substances, were identified from all 14 samples. Tryptophan was the major component of FDOM and present in 45.7% of the samples by calculating the fluorescence intensity percentage, on average. Pearson correlations revealed that the fluorescence intensity of C₁ and C₃ was strongly related to soluble chemical oxygen demand and dissolved oxygen carbon, while C₂ had significant positive correlations with ammonia nitrogen and total phosphorus of the solid waste. This study provided detailed data and findings that could serve as a preliminary basis for broadening options for the treatment and management of leachate from rural RTSs in China.

Determination of risk of spontaneous waste ignition and leachate quality for open municipal solid waste dumpsite

The waste receiving capacity of most municipal solid waste (MSW) landfill sites in India is exhausted, resulting in the formation of larger waste heaps. In the majority of Indian cities, these old waste heaps are prone to frequent smoldering and ignition resulting into fires. In this study, the potential risk of spontaneous ignition of landfilled waste at landfill surface was analyzed based on the physico-chemical characteristics of waste, carbon monoxide (CO) levels, landfill surface temperature (LST). The leachate pollution index was also determined to analyze the leachate quality for three different seasons (monsoon, pre-monsoon and post-monsoon). The regression analysis was carried out to understand the thermal properties (smoldering temperature, smoldering time, ignition temperature etc.) of MSW. The results showed that old waste has a higher tendency to undergo ignition compared to fresh waste. It has also been observed that the lower MC of old waste samples in the range of 3.4% and 18.2% is the most likely cause of early smoldering (106.6-109.5 °C) and ignition (198.6-208.4 °C) of old waste. In pre-monsoon season, CO concentrations for sub-surface (10-30 cm depth) smoldering events (SSE) were observed to be between ∼ 150 to 200 ppm. This CO level substantially dropped to 10 ± 1 ppm in the post-monsoon season. The estimation of the leachate pollution index (LPI) showed an index score of 27.35, 30.47 and 10.71 for pre-monsoon, monsoon and post-monsoon seasons, respectively. The determination of CO levels, increased LST and physico-chemical properties of landfilled waste will greatly assist in the abatement of environmental pollution arising from landfill fires.

A comprehensive investigation of toxicity and pollution potential of municipal solid waste landfill leachate

It is evident from the literature that research on the treatment of leachate generated from municipal solid waste (MSW) landfills has been a focus area of environmental management. However, the available information is discrete because most studies have reported only one or a couple of aspects of either closed or active MSW landfill leachate treatment. Hence, this investigation has focused on comprehensive attributes of both closed landfill leachate (CLL) and active landfill leachate (ALL), including generation, characterisation, and toxicity assessment to quantify and establish their pollution potential. The results indicated that CLL generation is higher (188.59 m³/d) than ALL (49.53 m³/d). The concentrations of principal physical, chemical, and biological constituents and concomitant leachate pollution index were higher in CLL (33.20) than in ALL (26.65). Furthermore, the germination indices of CLL (57.48) and ALL (79.14) and tail DNA damage of CLL (56.49%) and ALL (23.8%) ratified greater phytotoxicity and genotoxicity potential, respectively of CLL over ALL. The reasons for the variations in the generation, characteristics, and toxicity of CLL and ALL were discussed in detail. Evaluation of the commonly used landfill leachate treatment methods through the analytical hierarchy process confirmed that the activated sludge process and Fenton oxidation process are the most and least preferred treatment methods. The comprehensive investigation of CLL and ALL have established their pollution potential and the inevitable necessity for their treatment. The findings of this investigation will serve as a ready reference for researchers from academia and industry who work on the monitoring, treatment, and management of landfill leachate.

Pollution potential of dumping sites on surface water quality in Ethiopia using leachate and comprehensive pollution indices

Municipal solid waste disposed of in illegal dumpsites pollutes the surface and groundwater. However, accurately determining these pollution levels is typically challenging for practitioners and decision-makers in developing countries. The purpose of this study is to use the leachate pollution index (LPI) to assess the contamination potential of uncontrolled dumping sites along the course of the Kulfo River in Arba Minch, Ethiopia. The comprehensive pollution index (CPI) approach was also utilized to assess the suitability of Kulfo River water quality for aquatic species. Leachate samples were collected from four uncontrolled dumping sites along the Kulfo River's course and analyzed for fifteen leachate characteristics necessary to quantify the LPI sub-indices. Water samples were taken from three monitoring stations along the river and examined for aquatic species suitability. When the leachate parameters were compared to the Indian limit for discharge of treated leachate, it was found that dumping sites posed a considerable risk of pollution to adjacent water resources. The overall LPI ranged from 23.34 to 27.35, which is higher than the discharge standard LPI of 5.69, indicating that dumping sites can threaten the surrounding water resources and human health. Based on the rating scale of CPI, at all monitoring stations, the river resulted severely polluted. Finally, appropriate strategies to reduce the pollution and the related mismanagement of solid waste were discussed. Combining LPI and CPI methods can represent a crucial tool for experts and decision-makers in developing countries to evaluate the pollution potential of dumping sites and water resource monitoring.

Temporal variation of leachate pollution index of Indian landfill sites and associated human health risk

The present study investigated the variation in leachate pollution index (LPI) of four municipal solid waste (MSW) dumping sites: non-engineered (Okhla, Ghazipur, Bhalswa) and engineered (Narela-Bawana) of Delhi, India. A review of 142 screened studies from Google Scholar database was done for synthesis of information on LPI parameters. Further, the rate constant determination and human health risk assessment for various leachate parameters was done. Results showed the following LPI trends: Okhla landfill: irregular with exceedance to threshold value; Bhalswa landfill: exponential increase; and Narela-Bawana landfill: linear increase. Parameters such as pH, dissolved solids, copper, nickel, zinc, and chromium of Bhalswa landfill, exhibited an exponential decay with LPI variation. Whereas, for Narela-Bawana's leachate BOD and COD parameters, an exponential decay in LPI vs zinc and linear increase for LPI vs lead was observed. For all dumping sites, a positive correlation was observed between heavy metals and LPI. In case of human health risk assessment, order of oral risk posed by Okhla's metals was cadmium > chromium > nickel > lead, with maximum hazard quotient (HQ) of 1.61 for cadmium. For Ghazipur and Bhalswa landfills, cancer risk values for both adult and child sub-populations were observed to be maximum for cadmium followed by nickel, chromium, and minimum for lead. For Narela-Bawana landfill, the order of cancer risk was as follows: chromium > nickel > lead. HQ for Pb-contaminated groundwater exceeded the threshold limit in Ghazipur and Bhalswa landfills. For dermal groundwater exposure, cadmium for Okhla (adult 2.3 × 10^-4 and child 1.4 × 10^-4), Ghazipur (adult 9 × 10^-5 and child 5.2 × 10^-5), and Bhalswa (adult 1.5 × 10^-4 and child 8.6 × 10^-5) was observed to have maximum cancer risk. The analyzed year-wise LPI trend, calculated rate constants, and human health risk values from present study provide a basis to waste managers and regulators for understanding various waste sources.

Impact of landfill leachate contamination on surface and groundwater of Bangladesh: a systematic review and possible public health risks assessment

Dumping of solid waste in the non-engineered landfill is very common in the developing countries. Among the different disadvantages of this kind of landfilling, leachate is the major concern to public health, which is a toxic byproduct generated from the landfill; and can percolate to the ground water and consequently migrate in surface water. Using systematic review on published data, the present study endeavors to compare the leachate contamination potential of four major landfills of Bangladesh, named Amin Bazar, Matuail, Mogla Bazar and Rowfabad; which are situated in 3 of the 6 big mega cities of Bangladesh and assessed the effects of leachate leakage on surrounding water body as well as on human health. This study, for the first time calculated the leachate pollution index (LPI) for the landfill sites of Bangladesh and found that the LPI of Matuail landfill site (19.81) is much higher which is comparable to some polluted landfill sites of India and Malaysia. The concentrations of several potentially toxic metals found in the surface and ground water in the vicinity of the landfill sites were above the maximum permissible limit values of department of Environment, Bangladesh and World Health Organization (WHO). The human health risk index for toxic heavy metals in different vegetables and rice grain showed high health risk potential for Pb, Cd, Ni, and Mn. The total carcinogenic risk for Ni and Pb are found very high in the edible plants near those landfill sites, suggesting the risk of Ni and Pb induced carcinogenesis by the consumption of those plants. The present conditions of surface, ground water and agriculture products near the landfill sites of Bangladesh are much frightening to the biota and local inhabitants.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13201-021-01431-3.

Treatment of urban municipal landfill leachate utilizing garbage enzyme

In the present study, an attempt has been made to extend the application of garbage enzyme (GE) (fermented mixture of jaggery, organic waste, and water in the ratio 1:3:10) from the domestic wastewater to the urban municipal landfill leachate of Ghazipur, Okhla and Bhalswa landfill sites of Delhi (India). The Leachate Pollution Index (LPI) has been found to be 27.6, 25.4 and 29.2, respectively. The competence of GE was assessed by comparing the initial and final LPIs. The GE was added to the leachate for the contact period of 7-28 days under different mix proportions of 5%, 10%, 15%, and 20%. The maximum final LPI reduction of 74.75% was observed in the Okhla landfill leachate for mixing the proportion of 20% GE after 28 days. However, the mixing ratio of 5% GE showed significant reduction of 60.61% and 55.12% in the final LPI of Ghazipur and Bhalswa landfill leachate, respectively.

Rural solid waste-characteristics and leachate pollution assessment for different precipitation levels, China

Open dumping adversely affects the environment and remains the most widely used method for waste disposal in many developing rural areas in China. Information regarding the impact of rural solid waste (RSW) on the environment remains limited. The objectives of this study are to investigate the characteristics of RSW and the impact of different precipitation rates, and to evaluate the contamination potential of RSW using a leachate pollution index (LPI). The study showed that leachate concentration was significantly influenced by precipitation rates at the initial precipitation stages. Precipitation rates of 42.00 mm/day appeared to have the largest dilution effects. In contrast, the concentrations of leachate at rainfall rates of 24.00 mm/day and soaking were steady, and no similar trends were observed. The highest amounts of pollutants in leachate were the result of soaking. In the first week of our experiment, the LPI value for each rural area waste sample rapidly increased with rising precipitation rates from soaking to 42.00 mm/day. However, no significant change in LPI was observed thereafter (after 5 weeks) even with increasing precipitation rates. The values of chemical oxygen demand, biochemical oxygen demand, total nitrogen, and NH₃-N in the leachate after 10 weeks were 4.00, 7.34, 1.87, and 2.21 times higher, respectively, than those of the prescribed leachate quality standards in China. The results of our study suggest the following course of action for the three dump sites investigated: in Banqiao, given the size of the population and the size of the waste amount, landfill might be a suitable way for disposing of RSW. In Machen, building a standardized waste collection site would be an economical solution for reducing potential pollution risks. In Jiuduhe, increasing the transportation rate of solid waste might be an effective solution. The results of this study can help to improve the understanding of leachate pollution in Chinese rural areas.

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

Dumping of solid waste in a non-engineered landfill site often leads to contamination of ground water due to leachate percolation into ground water. The present paper assesses the pollution potential of leachate generated from three non-engineered landfill sites located in the Tricity region (one each in cities of Chandigarh, Mohali and Panchkula) of Northern India and its possible effects of contamination of groundwater. Analysis of physico-chemical properties of leachate from all the three landfill sites and the surrounding groundwater samples from five different downwind distances from each of the landfill sites were collected and tested to determine the leachate pollution index (LPI) and the water quality index (WQI). The Leachate Pollution Index values of 26.1, 27 and 27.8 respectively for landfill sites of Chandigarh (CHD), Mohali (MOH) and Panchkula (PKL) cities showed that the leachate generated are contaminated. The average pH values of the leachate samples over the sampling period (9.2 for CHD, 8.97 for MOH and 8.9 for PKL) show an alkaline nature indicating that all the three landfill sites could be classified as mature to old stage. The WQI calculated over the different downwind distances from the contamination sites showed that the quality of the groundwater improved with an increase in the downwind distance. Principal component analysis (PCA) carried out established major components mainly from natural and anthropogenic sources with cumulative variance of 88% for Chandigarh, 87.1% for Mohali and 87.8% for Panchkula. Hierarchical cluster analysis (HCA) identifies three distinct cluster types for the groundwater samples. These clusters corresponds to a relatively low pollution, moderate pollution and high pollution regions. It is suggested that all the three non-engineered landfill sites be converted to engineered landfill sites to prevent groundwater contamination and also new sites be considered for construction of these engineered landfill sites as the present dumpsites are nearing the end of their lifespan capacity.

A framework for assessment and characterisation of municipal solid waste landfill leachate: an application to the Turbhe landfill, Navi Mumbai, India

Rapid industrialisation, growing population and changing lifestyles are the root causes for the generation of huge amounts of solid waste in developing countries. In India, disposal of municipal solid waste (MSW) through open dumping is the most common waste disposal method. Unfortunately, leachate generation from landfill is high due to the prolonged and prominent monsoon season in India. As leachate generation rate is high in most of the tropical countries, long-term and extensive monitoring efforts are expected to evaluate actual environmental pollution potential due to leachate contamination. However, the leachate characterisation involves a comprehensive process, which has numerous shortcomings and uncertainties possibly due to the complex nature of landfilling process, heterogeneous waste characteristics, widely varying hydrologic conditions and selection of analytes. In order to develop a sustainable MSW management strategy for protecting the surface and ground water resources, particularly from MSW landfill leachate contamination, assessment and characterisation of leachate are necessary. Numerous studies have been conducted in the past to characterise leachate quality from various municipal landfills; unfortunately, none of these propose a framework or protocol. The present study proposes a generic framework for municipal landfill leachate assessment and characterisation. The proposed framework can be applied to design any type of landfill leachate quality monitoring programme and also to facilitate improved leachate treatment activities. A landfill site located at Turbhe, Navi Mumbai, India, which had not been investigated earlier, has been selected as a case study. The proposed framework has been demonstrated on the Turbhe landfill site which is a comparatively new and the only sanitary landfill in Navi Mumbai.