Leachate Quality Research Articles

Agricultural waste-based biochars for sustainable removal of heavy metals from stabilized landfill leachate.

In this work, biochars were used as adsorbents to remove Cu, Cd, and Zn ions in a real stabilized leachate from a controlled landfill. Oak fruit shells biochar (OFSBC) and date palm fibers biochar (DPFBC) were obtained by pyrolysis of oak fruit shells and date palm fibers at 700°C and 400°C, respectively. OFSBC and DPFBC showed well-developed structures and high specific surface areas (520.16 m2/g and 470.46 m2/g, respectively). Equilibrium adsorption of heavy metal ions on DPFBC and OFSBC occurred after 4h and 2h of stirring. The removal efficiencies of Cu, Cd, and Zn ions were 97.01%, 94.40%, and 80.59% with DPFBC and 90.10%, 88.33%, and 76.16% using OFSBC, respectively. The Avrami fractional order model was appropriate for describing kinetic adsorption. Increasing the dose of adsorbent improves heavy metal ion retention. Thermodynamic tests have proven the spontaneous and endothermic adsorption of these heavy metals. The electrostatic attraction, ion exchange, complexation, metal-π bending, and surface precipitation and pore filling were regarded as the most predominant heavy metal retention mechanisms from the landfill leachate onto the biochar surface. Separately, the DPFBC showed the best performance than OFSBC regarding the improvement of leachate quality. Chemical oxygen demand (COD), biological oxygen demand (BOD5), ammoniacal nitrogen (NH3-N), and phosphorus (P) were respectively removed at an efficiency of 53.57%, 29.17%, 36.07%, and 37.5%, respectively. Thus, the results allow highlighting that the adsorption on DPFBC and OFSBC can be an effective alternative in the practice of landfill leachate treatment.

A Novel Technosol Formulation for Sustainable Landfill Top Covers Using Non-Hazardous Wastes

This study explores the potential of non-hazardous wastes for crafting an engineered soil-like material (Technosol) suitable for landfill capping applications. Three distinct materials—waste foundry sand (WFS), washing aggregate sludge (WAS), and composted biosolids (CBS)—were strategically combined to develop this innovative Technosol. The formulation process involved a comprehensive analysis of their physical–chemical properties, mineral composition, leachate quality, and a series of geotechnical assessments to ensure compliance with landfill top cover construction standards. The blend 90WFS/10WAS showed optimal geotechnical properties for constructing a protective layer, including maximum dry density (1.77 g cm−3), void ratio (0.4), CBR index (23.2), cohesive strength (40 kPa), internal friction (ϕ = 30°), and permeability coefficient (k = 1.48 × 10−6 cm s−1). Further enhancement was achieved by adding 10% CBS, resulting in the development of a functional organo-mineral topsoil horizon (81WFS/9WAS/10CBS). Importantly, leachate analysis confirmed the negligible environmental footprint of this Technosol. Moreover, a pot-based experiment with Brassica juncea planting validated its capacity to support plant growth and establish a vegetative cover on the landfill surface.

Investigations into the landfill behaviour of raw and treated wastes

Bioreactor landfills (BLFs) basically involve recirculation of leachate in controlled quantities back into the bioreactor landfill to boost biodegradation of municipal solid wastes thereby improving its efficiency. This augmented biodegradation leading to faster and improved stabilization of landfill waste is being showcased by a study on two anaerobic bioreactors. One bioreactor is being loaded with raw wastes having high organic content causing an impediment in the biogas production and biodegradation and on the other hand, there is a bioreactor of same configuration loaded with windrow compost as treated waste having lower polluting potential. An attempt is made to showcase a comparative analysis to investigate the impact of treatment on biodegradation in both raw and treated MSWs. Over a 9–10 month study period which is currently under progress, data from the first 3 months (13 weeks) is presented. Treated wastes have given better results as compared to raw MSW due to lower polluting potential in terms of both leachate quality as well as biogas production. Speculations are being made that treated wastes will give better results for the whole study period in terms of environmental sustainability.

The effects of water content on mineralogical and drainage quality dynamics in weathering mine waste rock

Water content plays a critical yet ambivalent role in the physical and geochemical stability of mine tailings and waste rock, but its effects on individual chemical weathering reactions (dissolution and precipitation) and bulk water quality remain poorly understood. We experimented with synthetic waste rock to quantitatively reconcile modal and textural mineralogical parameters (mineral size, association, and liberation) with leachate quality at different water saturation levels (5–100%). Leachate pH consistently decreased from a 13-week average of 6.14 at 100% saturation to 5.37 at 5% saturation. Simultaneously, mineralogical analyses revealed a reduction in the size of carbonate phases over the course of weathering, decreasing from 200 µm to 145 µm as water saturation increased from 5% to 100%, which could be a contributing factor to more alkaline pH in samples with higher water saturation. Total concentrations of iron (Fe) and copper (Cu) in solution increased with lower moisture, with Cu concentrations increasing 24-fold in samples at 5% saturation compared to full saturation. In contrast, arsenic (As) concentration increased with higher moisture levels, which we attribute to reduced galvanic protection of As-bearing pyrite from oxidation. Multivariate statistical evaluation allowed us to uncover correlations between water chemistry and mineralogical data (i.e., sulfide associations or phase perimeters) and to explain chemical differences between samples, particularly those at 100% and 5% water saturation. Our findings underscore the importance of conducting quantitative mineralogical investigations on mine waste materials and considering their stored water content in the formulation of mine waste management strategies.

Soil profile distribution of nutrients in contrasting soils amended with struvite and other conventional phosphorus fertilizers

AbstractPhosphorus (P) can be recovered from wastewater and used as an alternative fertilizer, namely, struvite [MgNH4PO4·6(H2O)]. However, the soil mobility of wastewater‐derived P and other nutrients needs to be evaluated. The objective of this study was to compare the vertical distribution of water‐soluble (WS) soil P and other nutrients from a synthetic‐wastewater‐derived electrochemically precipitated struvite (ECST) to that from a chemically precipitated struvite (CPST), triple superphosphate (TSP), monoammonium phosphate (MAP), and a control in six soils from Arkansas (AR; loam [L] and silt loam [SiL]), Missouri (MO; SiL 1 and SiL 2), and Nebraska (NE; sandy loam [SL] and SiL). A column‐leaching experiment was conducted with the six soils and five fertilizer‐P treatments. Water‐soluble (WS) P from the two struvite materials generally did not differ (p > 0.05) and was similar to that of MAP in the depths of 0–3, 3–6, and 6–10 cm, but was greater than that of TSP in the top 6 cm in four of the six soils. WS P from CPST in the MO‐SiL 2 and NE‐SL soils (6.6 and 12.7 mg kg−1, respectively) was larger than that from ECST, MAP, and TSP. In the AR‐L and MO‐SiL 1 soils, TSP was the only fertilizer‐P source that had increased WS P concentrations in the top 6 cm relative to the other fertilizer‐P sources. Results showed that ECST‐derived, WS P had similar soil profile distributions in the top 10 cm, suggesting that ECST will be equally protective of environmental health and leachate quality across multiple soil textures as other common fertilizer‐P sources.

Activated carbon amendment of sand in the base of a permeable pavement reduces total nitrogen and nitrate leaching

Urban runoff from impermeable surfaces contains various pollutants. Stormwater samples were collected for one year from car parks on the campus of Newcastle University, located in northeast England, to monitor seasonal variation in stormwater properties and leachate quality following stormwater percolation through pilot-scale, outdoor permeable pavements. The pilot study compared an innovative ‘pollution munching’ permeable pavement with 2 % activated carbon (AC) amendment in the sand base with a conventional, un-amended sand base permeable pavement. Faecal coliforms were detected in stormwater at an average value of 3.75 ± 0.79 log10 CFUs per 100 mL. The permeable pavements without and with AC had mean log removal values of 0.81 ± 0.35 and 0.70 ± 0.35 for these faecal bacteria. The absence of genetic markers for human host associated Bacteroides (HF183) in eleven out of twelve stormwater samples showed that the faecal bacteria were mainly from animal sources. 16S rRNA gene sequencing results confirmed the presence of nitrifying bacteria from the genera Nitrosomonas, Nitrobacter, Nitrosococcus, Nitrospira, and Nitrosospira in stormwater. Nitrification and nitrate leaching was more notable for the conventional permeable pavement and may pose a groundwater pollution risk. Two percent AC amendment of the sand base reduced nitrate and total nitrogen leaching significantly compared with the conventional permeable pavement, by 57 ± 15 % and 40 ± 20 %, respectively. The AC amendment also resulted in significantly reduced Cu and DOC leaching, and lesser accumulation of PAHs by passive samplers embedded in the permeable pavement base. Hydraulic tests showed that the AC amended base layer still met the design specifications for permeable pavements, making it a promising proposition for pollution reduction in Sustainable Drainage Systems (SuDS).

Microbiology of post-fermentation leachate

Using post-fermentation leachate as fertilizer is a good alternative and solution to the problem of waste at wastewater treatment plants and contains the principles of sustainable development. Leachate from anaerobic treatment of sewage sludge contains valuable elements such as phosphorus, nitrogen and potassium, which can improve soil properties. The production of liquid fertilizer minimizes the negative impact of leachate on the main biological stream in the WWTP and improves the energy efficiency of the entire wastewater treatment system. This transfers into the operating costs of the facility. When thinking about the agricultural use of digestion leachate and its introduction into the environment, a very important issue is its microbiological contamination. The purpose of the conducted research was to determine the microbiological quality of digestion leachates from municipal wastewater treatment plants and to determine the parameters of their hygienization. The number of bacteria in raw leachate is indicative of a sanitary risk in the case they are used in agriculture as fertiliser. Heating the leachate at 60°C for 15 minutes produces an effect comparable to that achieved by heating the leachate to 70°C. The sonication process itself did not affect the better temperature effect. Heating the leachate for 20 minutes after prior sonication for 20 minutes does not result in the complete elimination of microflora.

Evaluating the landfill leachate quality using leachate pollution index (LPI) and technique for order preference by similarity to an ideal solution (TOPSIS)

Variability and diversity of landfill leachate cause difficulties in assessing the actual degree of threat to the environment and selecting an appropriate method of disposal or treatment. Therefore, quantifying leachate contamination potential is essential in landfill management and could be used to assess the accuracy of landfill operation and its impact on surrounding areas. The aim of this paper was to evaluate the performance of the Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) method and its suitability in determining leachate pollution potential in comparison to the Leachate Pollution Index (LPI) method. For this purpose, the quality of leachate from the landfill, collected four times a year from 2004 to 2021, was analysed. The following parameters were monitored: pH, EC, Pb, Cu, Zn, Cr, and Hg. On the basis of the measured parameters, the LPI and TOPSIS indexes were calculated. The obtained results indicated that the TOPSIS method is more sensitive and accurate in observing changes in leachate quality. It can be applied to any number of contaminant parameters without restrictions on scope, quantity, or their relative importance. It can also be used to compare the variations in leachate quality over time or to analyse differences in leachate quality among various landfill sites.

Hydrological and geochemical properties of bottom ash landfills

In Switzerland, municipal solid waste incineration bottom ash is deposited in open landfills, which leads to its interaction with rainwater and thus the formation of a polluted leachate. This study attempts to provide a better understanding of the hydraulic and geochemical properties of bottom ash landfills by combining field and laboratory investigations. The results show that a bottom ash landfill can be described as a generally unsaturated body with several layers of different grain sizes. Three different water domains with variable hydraulic and geochemical properties were identified in the landfill: (1) zones of preferential flow, (2) a reservoir of mobile porewater, and (3) an immobile porewater reservoir. Preferential flow systems account for approximately 5–10 vol.%. The landfill layering is primarily responsible for the formation of various flow systems during heavy rainfall events. The domains and reservoirs provide variable volumetric contribution to the leachate, depending on precipitation rates and duration of dry periods. Sampling of leachate during heavy rainfall events revealed dilution effects for Na (− 59–61% compared to concentrations prior to the event), Ca (− 44–47%), Cl (− 57–77%), and SO4 (− 35–47%), while pH (+ 7–8%) and concentrations of Al (+ 368–1416%), Cu (+ 7–58%), Cr (+ 29–48%), V (+ 100–118%), and Zn (+ 289%) increased significantly. The findings of this study serve as a basis for the development of a hydrogeochemical model of a bottom ash landfill, which allows better prediction of the future evolution of leachate quality.

Unveiling a Technosol-based remediation approach for enhancing plant growth in an iron-rich acidic mine soil from the Rio Tinto Mars analog site

This paper explores the potential of Technosols made from non-hazardous industrial wastes as a sustainable solution for highly acidic iron-rich soils at the Rio Tinto mining site (Spain), a terrestrial Mars analog. These mine soils exhibit extreme acidity (pHH2O = 2.1–3.0), low nutrient availability (non-acid cation saturation < 20 %), and high levels of Pb (3420 mg kg−1), Cu (504 mg kg−1), Zn (415 mg kg−1), and As (319 mg kg−1), hindering plant growth and ecosystem restoration. To address these challenges, the study systematically analyzed selected waste materials, formulated them into Technosols, and conducted a four-month pot trial to evaluate the growth of Brassica juncea under greenhouse conditions. Technosols were tailored by adding varying weight percentages of waste amendments into the mine Technosol, specifically 10 %, 25 %, and 50 %. The waste amendments comprised a blend of organic waste (water clarification sludge, WCS) and inorganic wastes (white steel slag, WSS; and furnace iron slag, FIS). The formulations included: (T0) exclusively mine Technosol (control); (T1) 60 % WCS + 40 % WSS; (T2) 60 % WCS + 40 % FIS; and (T3) 50 % WCS + 16.66 % WSS + 33.33 % FIS. The analyses covered leachate quality, soil pore water chemistry, and plant response (germination and survival rates, plant height, and leaf number). Results revealed a significant reduction in leachable contaminant concentrations, with Pb (26.16 mg kg−1), Zn (4.94 mg kg−1), and Cu (2.29 mg kg−1) dropping to negligible levels and shifting towards less toxic species. These changes improved soil conditions, promoting seed germination and seedling growth. Among the formulations tested, Technosol T1 showed promise in overcoming mine soil limitations, enhancing plant adaptation, buffering against acidification, and stabilizing contaminants through precipitation and adsorption mechanisms. The paper stresses the importance of tailoring waste amendments to specific soil conditions, and highlights the broader implications of the Technosol approach, such as waste valorization, soil stabilization, and insights for Brassica juncea growth in extreme environments, including Martian soil simulants.

Quality variations of leachate resulting from cigarette filter recycling as a challenge for its management

Recycling is known as a solution for cigarette filter management, but this may cause the release of trapped pollutants in it. Cigarette smoke toxins and chemicals that trapped in the cigarette filter can accumulate in the recycling leachate. In this study, littered cigarette filters and freshly smoked cigarette filters were recycled and the resulting leachate was analyzed. The results showed that the minimum and maximum Chemical Oxygen Demand (COD) of the studied leachates were 2100 mg/L and 11,300 mg/L, respectively. The maximum temporal variation in the studied leachate quality was 74.28%, but the maximum spatial variation was 314.2%. COD in the freshly smoked sample was 2600–9200 mg/L more than the littered samples. The average concentration of chromium, lead, nickel, and cadmium in littered samples was 0.023, 0.024, 0.045, and 0.019 mg/L, respectively. Environmental conditions such as humidity, the efficiency of the urban cleaning system in reducing the resistance of littered filters, the difference in the quality of the filter and tobacco, and the difference in smoking behaviors were effective in this variation. Reducing the toxicity of cigarette smoke and improving the efficiency of the urban cleaning system can lead to the same quality, but leachate treatment is necessary to reduce the environmental risk.

Complex electrical measurements of waste rock during acid mine drainage generation and release: Kinetic column tests

Acid mine drainage (AMD) emanating from waste rock piles (WRPs) at mining sites is a global concern. Successful rehabilitation of these sites requires effective characterization and monitoring of the waste rock during AMD generation/release. Traditional approaches involve ex-situ analysis of waste rock and porewater samples collected via corings and monitoring wells; however, this is highly disruptive, costly, and provides sparsely distributed point information across enormous volumes typical of WRPs. Geoelectrical techniques are a promising approach for non-invasive continuous imaging; however, their application has been limited to ‘one-off’ imaging with few studies on monitoring waste rock evolution. The objective of this study is to assess the geoelectrical signatures of changing waste rock during AMD generation/release. Field waste rock samples were extracted from three mine WRPs and first characterized for mineralogy and acid generation potential. Kinetic tests were then performed on each sample using leaching columns and humidity cells, with simultaneous measurements of effluent quality and complex electrical conductivity (real and imaginary components measure conduction and polarization, respectively). Results show that real conductivity was highly sensitive to changes associated with AMD leachate quality (e.g., 28,800 to 68 mg/L acidity) and surface of the waste material. Imaginary conductivity measurements identified changes in the waste mineralogy over time, though these signatures were not very distinct, which is likely due to low sulfide contents and limited oxidation (e.g., 0.59 wt% sulfide and 33% air saturation). This study improves our understanding of geoelectrical signatures associated with real waste rock, demonstrating the potential application of the electrical resistivity tomography and induced polarization techniques for mine waste investigations.

Study of the Effect of Adding Eco-Enzyme to the Process of Decomposing Organic Waste on the Quality of Compost, Leachate, and Methane Gas Production

Waste generation is increasing along with the increase in population and human living needs. The most dominant waste composition in Indonesia is organic waste, which accounts for 53.97% of the total waste. Eco-enzyme is one of the waste utilization products that has the potential to become an activator for the decomposition process and reduce the environmental effects of waste decomposition. The aim of this research is to analyse the micronutrient content of compost, reduce leachate toxicity, and accelerate the production of methane gas resulting from decomposition using eco-enzymes. The method used was an experimental method (trial) to obtain primary data from laboratory test results during 28 days of research. The research results show that, in general, there is a significant difference in the quality of compost in organic waste that uses eco-enzyme compared to that that does not use eco-enzyme. The results of measuring the quality of the leachate resulting from decomposition show that the quality of the leachate that uses eco-enzyme is better and has lower toxicity than without using eco-enzyme (control). In the production of methane gas, the results show that methane gas production in decomposition using eco-enzymes reaches the methanogenesis process more quickly.

Assessing the physicochemical parameters of leachate from biowaste fractions in a laboratory setting, using the elusion method

Leachate emissions, which are regarded as one of the primary polluters of groundwater and the environment, are unavoidable side effect of landfill operation. The leachate includes hazardous chemicals, heavy metals, suspended particles, and soluble organic molecules. The objective of this study was to simulate the leachate quality from the biowaste and assess its impact on groundwater pollution in a laboratory setting. For laboratory analysis, a variety of waste fractions that make up the waste composition of household bins in Windhoek were collected and mimicked in the laboratory for analysis. The aim of modeling these scenarios in the laboratory was to examine the quality of the leachate in the eluate when substantial volumes of biowaste were added to the residual samples. The analysis was carried out in accordance with the German Institute for Standardization's (DIN 12457) with respect to the process for sampling strategy and sample preparation. From the laboratory analyses, the values of pH decreased from 6.9 to 4.4 as the biowaste was increasing from 0 to 100 %, while EC was increasing with the increase in biowaste input from 0.6 to 4.99 mS/cm; equally, the concentrations of COD were increasing with the increase of biowaste input from 643 to 24,616 mg/l. These parameters had the strongest influence on the properties of leachate, as the high level of COD indicates the presence of high level of organic strength and a sign of organic pollution. The low or acidic pH values were also as a result of the production of volatile organic acids, which can cause the landfill leachate of such a nature to enhance pH of drinking water and contribute in trihalomethane formation which is a toxic substance for human health. High values of EC on the other hand indicate the discharge or other sources of pollution that has lowered the water body’s relative quality. From the findings, it can be concluded that leachate in this study is biodegradable and un-stabilized, as shown by the low pH levels and high COD concentrations. It also alluded that a change in physicochemical parameters, regardless of how little the concentration is, has the ability to change the quality of groundwater. According to this study, leachate was highly contaminated with organic matters. This has proven that the more biowaste inputs, the higher the concentrations of the physicochemical metrics, which can then alter the quality of groundwater. Hence, a recommendation for organic waste to be diverted from landfill sites or treated before landfilled. The findings from the leachate and groundwater samples of the Kupferberg showed that the landfill is mature methanogenic and stabilized stage, when compared to the pH of the laboratory results. COD values in the leachate samples are way higher than the permissible limit of the Namibian standard guidelines for drinking water, as well as the WHO guidelines. As alluded to by many researchers, high COD concentrations indicate high organic strength and pollution. Just as observed in the laboratory, conductivity is equally high in the leachate samples of the Kupferberg landfill, indicating high salts or dissolved inorganic components. This study can conclusively say that there is a relationship between the observed laboratory results and the actual field results, because of the similar trends they portray, noting that the filed values are always higher than the laboratory values. Hence, a proper correlation method is recommended.

KAJIAN SISTEM PENGELOLAAN SAMPAH DI KOTA PALANGKA RAYA DAN PENGARUHNYA TERHADAP KUALITAS AIR LINDI

Waste management in Palangka Raya City is in the Km Landfill. 14. The landfill is divided into 2 activities, namely waste management and leachate management installation. The waste management system is a method applied at the end point of waste processing. Waste collected at the landfill arrives at the landfill. The purpose of this study is to analyze waste generation, waste composition, and waste sources, analyze whether the waste management method affects the quality of leachate water and groundwater of the surrounding residents, and analyze the pollution index in the groundwater of the surrounding residents. This study uses a quantitative descriptive method by analyzing leachate and groundwater samples examined at the regional health laboratory. The results of these samples will be compared with leachate water quality standards, groundwater quality standards for sanitary hygiene purposes, and groundwater pollution index tests. The quality of leachate is unaffected by the operational method of waste processing. All leachate water samples for the parameters TSS and Cadmium are below the quality standard for final waste processing, except for the TSS value at station St2, this is because the wastewater is still in the waste pile area and has not yet entered the leachate management installation pond. The results of groundwater sample tests in several residents' homes for the pH parameter are below the quality standard. The pollution index results show that the water used daily is categorized as lightly polluted.

Landfill leachate treatment in Malaysia: Continuous circulation motion using mixed agricultural wastes with an open grid-like Luffa's configuration

In this study, adsorbent materials from agriculture waste such as luffa, coconut husk, pineapple leaf and activated charcoal (AC) from coconut shell were synthesized and characterized. The material is termed as COLUFNAS/AC. The adsorbent material then was used to treat landfill leachate with ammonia as Total Kjeldahl Nitrogen (TKN), ammoniacal nitrogen (NH3−N), total suspended solid (TSS), turbidity, biochemical oxygen demand @5 days (BOD5), chemical oxygen demand (COD) and heavy metals with values of 2,279.2 ADMI, 417.2 mg/L, 1,0220 mg/L, 2,388 mg/L, 9,092 mg/L, 45,164 mg/L and <0.08 mg/L, respectively. The experiments were conducted at the laboratory and pilot scale. For laboratory scale, 8 PVC pipes with COLUFNAS/AC were used to treat 30 L of landfill leachate. Under 6 h operating conditions, COLUFNAS/AC was significantly reduced the TKN (44.84 %), turbidity (45.90 %), and COD (31.88 %). Therefore, the potential removal efficiency of COLUFNAS/AC at laboratory scale was further applied at pilot scale in pH adjustment and coagulation tanks for 15 days. The complex composition of leachate at pilot scale (30,605.5 m3) significantly improved the leachate quality by 11.11 %, 17.03 %, 12.92 %, 52.25 % and 55 % reduction of NH3–N, TSS, turbidity, BOD5 and COD. The pH of leachate was also changed to less acidic. Implementing COLUFNAS/AC in both tanks not only effectively saved treatment costs to 3,955.22 USD/month but also achieved the lowest operational treatment cost at just 0.22 USD/m3.

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.

Physicochemical properties and heavy metals distribution of waste fine particles and soil around urban and peri-urban dumpsites

In developing countries like Ghana, the use of open dumpsites and landfills without proper waste management technique has resulted in environmental pollution with long-term adverse effects on soil, groundwater, human health and environmental sustainability. This study assessed the contaminants in fine particles of dumpsite waste and soil around urban and peri‑urban dumpsites at different depths of excavation and different age of deposited waste. Specifically, the study: (i) assessed physiochemical properties of fine particles of dumpsite waste and the surrounding soil, (ii) assessed heavy metals distribution from waste fine particles and surrounding soil at different depths and different ages of deposition, (iii) also determined soil quality indices (pollution index, geo-accumulation, and the potential ecological risk), and the hazards associated with the dumpsites on the residents living near the dumpsites. About 50 kg of waste was taken from surface, 0.5, 1.0 and 1.5 m depths. The samples were dried, segregated and sieved to obtain fine particles. Again, 1 kg soil was excavated form 0.5, 1.0 and 1.5 m depths at different age zones around each dumpsite. The fine particles and soil were analysed for physiochemical parameters using standard methods, and heavy metals using microwave plasma spectroscopy. The results showed that, the concentrations (electrical conductivity, potassium, cadmium, iron, copper and zinc) of waste fine particles and soil samples observed statistically significant different between them (p < 0.05). Waste particles recorded high cadmium and iron concentrations (41.7 mg/kg) and (4355 mg/kg) respectively at urban dumpsite. Similarly, there is statistically significant difference between calcium concentrations (p = 0.0221), potassium concentrations (p = 0.0227) and cadmium concentrations (p = 0.019) in the three age zones of urban dumpsite. The fine particles were heavily polluted with cadmium (PI > 6). High potential ecological risk of Hg (RI = 514.29), and (RI = 571.43) was observed at (SMZC1) and (NZA1) respectively; and high potential ecological risk of Cd (1000 ≤ RI ≤ 320), at (SMZA1-SMCA4. The study shows that both dumpsites have caused environmental hazards and this can cause surface and groundwater pollution and adverse effect on public health. But the study could not assess the impacts of dumpsite on leachate and water quality. The findings can be used as benchmark for developing appropriate technology for dumpsite mining, reclamation or decommission project; and exploit valorization potentials of the fine particles of the waste as composite and construction materials.

Leachate indicators of an elevated temperature landfill

Elevated temperature landfills (ETLFs) are municipal solid waste (MSW) landfills that have been impacted by subsurface exothermic reactions (SERs) and display unusual gas and leachate composition. Leachate quantity and quality data were analyzed to identify indicators of a SER at an ETLF in Ohio, USA. ETLF leachate generation increased from 2.04 to 14.4 m3/hectare-day (218 to 1,539 gallons/acre-day), peaking 16 months after the reaction was first noticed. The leachate generation rate for this ETLF remains about two times greater than the average Ohio MSW landfill. Several general parameters such as pH, electrical conductivity (EC), and total dissolved solids (TDS) remain impacted 5 years later. Similarly, metals such as arsenic, iron, calcium, potassium, and magnesium have increased in concentration. Volatile organic compounds (VOCs) behavior was less consistent as a group of chemicals. Increases of VOCs such as acetone, benzene, and methyl ethyl ketone (MEK) also increased. Importantly, in one year, benzene exceeded its toxicity characteristic threshold meaning the leachate was a hazardous waste, substantially increasing treatment and disposal costs. It is not clear if the VOCs are produced directly by the SER or if they are an indicator that microbial processes -which would otherwise consume them- have been disrupted. ETLFs likely do not all undergo the same exothermic reaction(s) and, unlike the analysis of landfill gas composition, temporal changes in leachate constituents’ concentrations may be more important than comparing to absolute values.

Investigating Landfill Leachate and Groundwater Quality Prediction Using a Robust Integrated Artificial Intelligence Model: Grey Wolf Metaheuristic Optimization Algorithm and Extreme Learning Machine

The likelihood of surface water and groundwater contamination is higher in regions close to landfills due to the possibility of leachate percolation, which is a potential source of pollution. Therefore, proposing a reliable framework for monitoring leachate and groundwater parameters is an essential task for the managers and authorities of water quality control. For this purpose, an efficient hybrid artificial intelligence model based on grey wolf metaheuristic optimization algorithm and extreme learning machine (ELM-GWO) is used for predicting landfill leachate quality (COD and BOD5) and groundwater quality (turbidity and EC) at the Saravan landfill, Rasht, Iran. In this study, leachate and groundwater samples were collected from the Saravan landfill and monitoring wells. Moreover, the concentration of different physico-chemical parameters and heavy metal concentration in leachate (Cd, Cr, Cu, Fe, Ni, Pb, Mn, Zn, turbidity, Ca, Na, NO3, Cl, K, COD, and BOD5) and in groundwater (Cd, Cr, Cu, Fe, Ni, Pb, Mn, Zn, turbidity, EC, TDS, pH, Cl, Na, NO3, and K). The results obtained from ELM-GWO were compared with four different artificial intelligence models: multivariate adaptive regression splines (MARS), extreme learning machine (ELM), multilayer perceptron artificial neural network (MLPANN), and multilayer perceptron artificial neural network integrated with grey wolf metaheuristic optimization algorithm (MLPANN-GWO). The results of this study confirm that ELM-GWO considerably enhanced the predictive performance of the MLPANN-GWO, ELM, MLPANN, and MARS models in terms of the root-mean-square error, respectively, by 43.07%, 73.88%, 74.5%, and 88.55% for COD; 23.91%, 59.31%, 62.85%, and 77.71% for BOD5; 14.08%, 47.86%, 53.43%, and 57.04% for turbidity; and 38.57%, 59.64%, 67.94%, and 74.76% for EC. Therefore, ELM-GWO can be applied as a robust approach for investigating leachate and groundwater quality parameters in different landfill sites.