Leachate Treatment Plant Research Articles

Pengaruh Waktu Aerasi terhadap Peningkatan Efisiensi Penghilangan Amonia di Air Lindi pada Sistem Ammonia Stripper

Talang Gulo Final Disposal Site (FDS) has a Leachate Treatment Plant (LTP) equipped with denitrification and nitrification facilities which function to reduce the concentration of ammonia (NH3) in leachate according to predetermined environmental quality standards. Research samples were taken in the form of leachate using the grab sampling method in accordance with SNI 6989.59:2008. The results of the research showed that the aeration time for the ammonia stripper of 3 hours, 6 hours and 12 hours both gave the highest value for the ammonia stripper efficiency percentage variable. The highest ammonia removal efficiency is aeration time of 12 hours. However, if we look at the operating efficiency of the ammonia stripper, the removal of ammonia by using an aeration time of 12 hours does not provide a significant improvement when compared to a treatment with an aeration time of 6 hours. This means that the operating time is 6 hours faster, the 6 hour variation can provide an ammonia removal efficiency of more than 90%

Pervasiveness and classification of microplastics in Landfill Leachate: Impacts, Risks, and Treatment Efficiency

Microplastics (MPs) in surface and groundwater in Bangladesh are a significant issue. The purpose of this research was to assess the possibility of landfill leachate acting as a potential origin of MPs and to determine if the surrounding surface water (SW) and groundwater (GW) act as recipients. Furthermore, this research assessed the leachate treatment plant MP removal efficacy and MP risk assessment. The findings show that discharge leachate from the Matuail landfill contributes 3.5 × 108 particles per hour to the surrounding aquatic environment, with an average of 350 ±10 MPs/L. MPs was found highly in SW and then in GW with an average of 1683 ± 70 and 614 ± 40 MPs/L, respectively, with 48.9% of MPs ranged from 0.1mm to 0.5mm. The dominant shapes were fibers and fragments. The Fourier transform infrared spectroscopy (FTIR) analysis revealed low density polyethylene (LDPE), high density polyethylene (HDPE), and Polypropylene (PP) was the most common, and Polyurethane (PUR), Polymethyl methacrylate (PMMA), and Polyacrylonitrile (PAN) posed the greatest threat to the environment. The inefficient treatment method resulted in the release of 83.33% of MPs, indicating a low removal efficiency in the leachate. The inefficient removal rate leads to the highest pollutant load index for surface water (2.18). Ultimately, the analysis of the nemerow pollution index (NPI), contamination factor (CF), pollution load index (PLI), polymer hazard index (PHI), and potential ecological risk (Ei), revealed a minimal to extremely high range of contaminations. A clear link was obsevered between the particles shape and size throught the principal component analysis (PCA). Moreover, it highlights the need for ongoing national surveillance of MPs considering the gravity of this contamination and indicates the importance of proactive management of landfill sites.

Microbial community dynamics in different floc size aggregates during nitrogen removal process upgrading in a full-scale landfill leachate treatment plant

Upgrading processes to reduce biodegradable organic substance addition is crucial for treating landfill leachate with high pollutant concentrations, aiding carbon emission reduction. Aggregate size in activated sludge processes impacts pollutant removal and sludge/water separation. This study investigated microbial community succession and driving mechanisms in different floc-size aggregates during nitrogen removal progress upgrade from conventional to partial nitrification–denitrification in a full-scale landfill leachate treatment plant (LLTP) using 16S rRNA gene sequencing. The upgrade and floc sizes significantly influenced microbial diversity and composition. After upgrading, ammonia-oxidizing bacteria were enriched while nitrite-oxidizing bacteria suppressed in small flocs with homogeneity and high mass transfer efficiency. Larger flocs enriched Defluviicoccus, Thauera, and Truepera, while smaller flocs enriched Nitrosomonas, suggesting their potential as biomarkers. Multi-network analyses revealed microbial interactions. A deep learning model with convolutional neural networks predicted nitrogen removal efficiency. These findings guide optimizing LLTP processes and understanding microbial community dynamics based on floc size.

Multi-omics illuminates the functional significance of previously unknown species in a full-scale landfill leachate treatment plant

Landfill leachate treatment plants (LLTPs) harbor a vast reservoir of uncultured microbes, yet limited studies have systematically unraveled their functional potentials within LLTPs. Combining 36 metagenomic and 18 metatranscriptomic datasets from a full-scale LLTP, we unveiled a double-edged sword role of unknown species in leachate biotreatment and environmental implication. We identified 655 species-level genome bins (SGBs) spanning 47 bacterial and 3 archaeal phyla, with 75.9 % unassigned to any known species. Over 90 % of up-regulated functional genes in biotreatment units, compared to the leachate influent, were carried by unknown species and actively participated in carbon, nitrogen, and sulfur cycles. Approximately 79 % of the 37,366 carbohydrate active enzymes (CAZymes), with ∼90 % novelty and high expression, were encoded by unknown species, exhibiting great potential in biodegrading carbohydrate compounds linked to human meat-rich diets. Unknown species offered a valuable genetic resource of thousands of versatile, abundant, and actively expressed metabolic gene clusters (MGCs) and biosynthetic gene clusters (BGCs) for enhancing leachate treatment. However, unknown species may contribute to the emission of hazardous N2O/H2S and represented significant reservoirs for antibiotic-resistant pathogens that posed environmental safety risks. This study highlighted the significance of considering both positive and adverse effects of LLTP microbes to optimize LLTP performance.

Analyzing performance and microbial mechanisms in an incineration leachate treatment after waste separation: Integrated metagenomic and metaproteomic analyses

The absence of food waste after separation poses a significant challenge to incineration leachate treatment, as it decreases the C/N ratio and COD of leachate, greatly impacting the biological treatment process. A one-year in-situ study was systematically conducted in an incineration leachate treatment plant that experienced waste separation, focusing on the variations in carbon and nitrogen removal performance as well as the involved microbial mechanism of the “anaerobic digestion (AD) + two-stage A/O” process. Results indicated that the biodegradability of leachate significantly decreased over time, with COD concentration decreasing by 10 times and the average C/N ratio decreasing from 12.3 to 1.4. The AD process was maintained stable, achieving a COD removal efficiency exceeding 92 %. The nitrification process also remained stable; while the denitrification process was significantly affected, and a nine-fold increase in external glucose addition was required to achieve a nitrogen removal efficiency of 85 %. Metagenomic analysis indicated that comammox Nitrospira (contributing 90 % to ammonia monooxygenase) occupied the dominant position over Nitrosomonas for nitrification due to the low NH4+-N concentration in A/O tanks (<35 mg/L), and Methanothrix was substituted by Methanosarcina for methanogenesis in AD unit. Metaproteomic results further elucidated that the expression of enzymes responsible for denitrification process, i.e., Nir, Nor, Nos (convert NO2− to N2), was decreased significantly, although the expression of enzymes related to glycolysis and TCA cycle were stimulated by glucose addition. The expression of Nar (convert NO3−-N to NO2−-N) remained stable, while the imbalance expression within denitrifying enzymes might have facilitated occurrence of partial denitrification, attributed to the low C/N ratio. The results prove that the function robustness and metabolic versatility were achieved in leachate treatment plant after waste separation but at the cost of the high external carbon resource addition, highlighting the urgent requirement for low-carbon nitrogen removal technologies.

Regular Tetrahedron Model for the Assessment of High-Resolution Mass Spectrometry Data of Four-Way Fractionated Dissolved Organic Matter.

A regular tetrahedron model was established to pierce the fractionation of dissolved organic matter (DOM) among quaternary components by using high-resolution mass spectrometry. The model can stereoscopically visualize molecular formulas of DOM to show the preference to each component according to the position in a regular tetrahedron. A classification method was subsequently developed to divide molecular formulas into 15 categories related to fractionation ratios, the relative change of which was demonstrated to be convergent with the uncertainty of mass peak area. The practicality of the regular tetrahedron model was verified by seven kinds of sludge from waste leachate treatment and sewage wastewater treatment plants by using stratification of extracellular polymeric substances coupled with Orbitrap MS as an example, presenting the DOM chemodiversity in stratified sludge flocs. Sensitivity analysis proved that classification results were relatively stable with the perturbation of four model parameters. Multinomial logistic regression analysis could further help identify the effect of molecular properties on the fractionation of DOM based on the classification results of the regular tetrahedron model. This model offers a methodology for the assessment of specificity of sequential extraction on DOM from solid or semisolid components and simplifies the complex mathematical expression of fractionation coefficients for quaternary components.

Can on-site leachate treatment facilities effectively address the issue of perfluoroalkyl acids (PFAAs) in leachate?

In recent decades, the presence of perfluoroalkyl acids (PFAAs) in municipal solid waste leachate has emerged as a growing concern. Research has focused on PFAA release and occurrence characteristics in landfill and waste-to-energy leachate, highlighting their significant impact when released into wastewater treatment plants. Given the extremely high loading rate faced by current on-site leachate treatment plants (LTPs), the objective of this study is to assess whether the current “anaerobic/aerobic (A/O) + membrane bioreactor (MBR) + nanofiltration (NF) + reverse osmosis (RO)” configuration is effective in PFAAs removal. Concentrations of raw and treated leachate in 10 on-site LTPs with same treatment configuration and varying landfill ages were measured, and a comprehensive mass flow analysis of each treatment process was conducted. The results indicate that A/O treatment has limited capacity for PFAA removal, while NF and RO processes reached 77.44 % and 94.30 % removal rates of ∑PFAAs concentration, respectively. Short-chain PFAAs (> 80 % detected frequency) primarily influenced the distribution and variations of PFAAs in leachate and tend to disperse in the water phase. Correlation analysis revealed the current on-site LTPs exhibit a more efficient removal capacity for long-chain PFAAs.

Human and Ecological Risk Assessment of Soil and Plants Metal Contamination in a Tropical Municipal Solid Waste Dumping Site

ABSTRACT The growing open waste dumpsite contributes to heavy metal leaching, harming public health and ecosystem services. Hence, the study’s novelty lies in its integrated assessment of heavy metal concentration (Cd, Cr, Cu, Fe, Ni, Pb, and Zn) in soil and plants, incorporating risk assessment using both single and combined indexes in the largest active waste dumpsite in Kelantan, Malaysia. Heavy metal in soil samples Cu (164.896 ± 205.096), Pb (122.177 ± 93.309), and Cr (32.74 ± 26.569) were recorded to exceed the standards, while in the studied plants (castor bean, papaya, pea eggplant, and water spinach), Pb concentrations in all plant parts have surpassed the Malaysia Food Regulation (1985) and FAO/WHO guidelines (2016). Translocation factor (TF) in Cu, Cr, and Pb in water spinach and Cr, Cu, and Cd in pea eggplant have TF > 1. Bioconcentration factor (BCF) was < 1 in pea eggplant and water spinach except for Pb in pea eggplant. Correlation analysis revealed a strong correlation between heavy metals in the soil while contrasts in the plants. The potential ecological risk index (PERI) reveals that the soil waste dumpsite is contaminated with heavy metals. The hazard index (HI) and lifetime cancer risk (LCR) values of heavy metals on the soil surface had negligible non-cancer risks posed to adults and indicate that soil ingestion and dermal absorption were the two primary carcinogenic risk exposure routes. These findings implied that Beris Lalang waste dumpsite is a potential source of toxic pollutants to the environment and the local population. It is recommended to conduct a comprehensive feasibility study and design an implementation plan for leachate treatment plant. Additionally, a comprehensive assessment of the specific contaminants present in the leachate and their potential impacts on the environment should be conducted to inform targeted and effective treatment strategies.

A mixed blessing of influent leachate microbes in downstream biotreatment systems of a full-scale landfill leachate treatment plant

In landfill leachate treatment plants (LLTPs), the microbiome plays a pivotal role in the decomposition of organic compounds, reduction in nutrient levels, and elimination of toxins. However, the effects of microbes in landfill leachate influents on downstream treatment systems remain poorly understood. To address this knowledge gap, we collected 23 metagenomic and 12 metatranscriptomic samples from landfill leachate and activated sludge from various treatment units in a full-scale LLTP. We successfully recovered 1,152 non-redundant metagenome-assembled genomes (MAGs), encompassing a wide taxonomic range, including 48 phyla, 95 classes, 166 orders, 247 families, 238 genera, and 1,152 species. More diverse microbes were observed in the influent leachate than in the downstream biotreatment systems, among which, an unprecedented ∼30 % of microbes with transcriptional expression migrated from the influent to the biological treatment units. Network analysis revealed that 399 shared MAGs across the four units exhibited high node centrality and degree, thus supporting enhanced interactions and increased stability of microbial communities. Functional reconstruction and genome characterization of MAGs indicated that these shared MAGs possessed greater capabilities for carbon, nitrogen, sulfur, and arsenic metabolism compared to non-shared MAGs. We further identified a novel species of Zixibacteria in the leachate influent with discrete lineages from those in other environments that accounted for up to 17 % of the abundance of the shared microbial community and exhibited notable metabolic versatility. Meanwhile, we presented groundbreaking evidence of the involvement of Zixibacteria-encoded genes in the production of harmful gas emissions, such as N2O and H2S, at the transcriptional level, thus suggesting that influent microbes may pose safety risks to downstream treatment systems. In summary, this study revealed the complex impact of the influent microbiome on LLTP and emphasizes the need to consider these microbial characteristics when designing treatment technologies and strategies for landfill leachate management.

The Environmental Impact of Leachate Processing Installations: Life Cycle Assessment (LCA) Study

This study aims to analyze waste management in the face of population growth and increasing human activity. As the population continues to grow and human activities intensify, the proper management of waste becomes crucial to safeguarding the environment. In this context, leachate treatment through the Leachate Treatment Plant (LTP) emerges as a key element in protecting the environment from the negative impacts of leachate. The Life Cycle Assessment (LCA) method serves as a valuable tool for analyzing the environmental implications of LTPs and aiding in sustainable decision-making. The research process commences with gathering essential data and constructing an inventory related to energy use, greenhouse gas emissions, water pollution loads, and the utilization of natural resources. Through the gate-to-gate approach using the SimaPro application with the CML-IA Baseline method, the environmental impacts are quantified. The study reveals the significant impacts of Global warming (3.03E-08 Pt), Photochemical Oxidation (3.70E-09 Pt), Human toxicity (2.09E-09 Pt), and Eutrophication (1.87E-06 Pt). Eutrophication stands out as the most prominent impact of wastewater treatment. The resultant eutrophication impact predominantly originates from the Biological Oxygen Demand (BOD) pollutant component, mainly generated from the equalization tub unit and constructed wetland. Furthermore, the control tank emerges as the primary source of the dominant pollutant.

Impact of waste separation on the biological nitrogen removal in a MSW incineration leachate treatment plant: Performance and microbial community shift

After waste separation program was launched in China in 2019, incineration leachate treatment plants are facing a challenge of effective removal of nitrogen from leachate due to lack of sufficient carbon source. In this study, the performance of a biological incineration leachate treatment process (anaerobic digestion (AD) - two-stage anoxic/aerobic (A/O) process) was evaluated after adopting the waste separation program, and the changes in the microbial community and function was analyzed using 16S rRNA amplicon sequencing technology. Results showed that after the waste separation, the influent chemical oxygen demand (COD) concentration reduced by 90% (from 19,300 to 1780 mg L−1) with the COD/N ratio decreased from 12.3 to 1.4, which led to a decreased nitrogen removal efficiency (NRE) of <65% and a high effluent NO3− accumulation (445.8–986.5 mg N·L−1). By bypassing approximately 60% of the influent to the two-stage A/O process and adding external carbon source (glucose), the mean NRE increased to 86.3 ± 7.4%. Spearman's analysis revealed that refractory compounds in the bypassed leachate were closely related to the variations in bacterial community composition and nitrogen removal function in the two-stage A/O, leading to a weakened correlation of microbial network. KEGG functional pathway predictions based on Tax4Fun also confirmed that the bypassed leachate induced xenobiotic compounds to the two-stage A/O process, the relative abundance of nitrogen metabolism was reduced by 32%, and more external carbon source was required to ensure the satisfactory nitrogen removal of >80%. The findings provide a good guide for regulation of incineration leachate treatment processes after the waste separation.

Insights into the adsorption of perfluoroalkyl substances (PFASs) on excess sludge from an on-site leachate treatment plant

The disposal and reduction of excess sludge is one of the most challenging aspects of wastewater treatment. Recycling excess sludge as functional materials is an innovative approach that has garnered broad attention, as it can address environmental concerns and reduce the consumption of valuable materials. However, this approach is still challenging due to the low mixed liquor suspended solids in sewage treatment plants and the high synthesis costs involved. In this study, we proposed the application of excess sludge from an on-site leachate treatment plant for the efficient removal of perfluoroalkyl substances (PFASs) from wastewater. A simple thermal treatment was conducted and the obtained sludge-based adsorbents enable effective PFASs removal. Through the use of low field nuclear magnetic resonance and structural characterizations, results demonstrated that denitrifying sludge had higher hydrophobicity and specific surface area (30.85 m2/g) than nitrifying sludge, resulting in enhanced PFASs adsorption capacity and initial adsorption rates. Kinetic and isotherm simulations indicated that the adsorption was efficient and controlled by surface and intraparticle diffusion. Characterization and regulation results showed that the adsorption was dominated by hydrophobic and electrostatic interactions. These findings suggest a promising recycling approach of excess sludge while elucidating the dominant mechanisms involved.

Assessment of Denitrification and Nitrification Processes during Landfill Leachate Treatment

Landfill leachate is generated from waste degradation in landfill sites, and its treatment includes biological or combined treatment with physico-chemical methods. A frequently applied technology in the biological stage of landfill leachate treatment plants is based on denitrification and nitrification. Nevertheless, with the availability of a huge number of scientific reports, the management of denitrification and nitrification (D/N) processes in the frame of real wastewater treatment plants (WWTPs) is rather difficult and always remains a critical technological problem. This study aims to perform a comparative assessment between denitrification and nitrification processes during landfill leachate treatment in three different situations in the WWTP of the Municipal Enterprise for Waste Treatment in Sofia City, Bulgaria. The comparative assessment is based on the biotransformation effectiveness of ammonium ions in the course of nitrification and of nitrates in the course of denitrification. Mixed samples (wastewater and activated sludge) were taken from the sequencing batch reactors operating in the mode of denitrification and nitrification. All physico-chemical (pH, dissolved oxygen, organics concentration, BOD5:COD, nitrogen and phosphorous) and biological (sludge volume index, sludge biotic index, quantity of aerobic heterotrophs, denitrifiers and nitrifiers, total dehydrogenase activity) indicators were investigated in the samples from the biobasins in the mode of denitrification and nitrification. The conditions for the implementation of the two processes were compared, along with the state of the activated sludge in the different reactors. The obtained results showed that denitrification was the critical process in the technology on the base of D/N. A major factor that managed the denitrification was the lower concentration of biodegradable organic matter which led to a deformation of the activated sludge structure, a decrease in the count of heterotrophic microorganisms, a decrease in the total activity of the activated sludge and an inhibition of the nitrate reductase activity. The nitrification processes were accomplished with high intensity. The results confirmed that D/N could be optimized and controlled using specific wastewater treatment technology parameters and purposely applied indicators.

Sustainable Leachate Treatment Plant System at Landfill Site: A Multicriteria Analysis Approach

Leachate generated from Municipal Solid Waste (MSW) landfill may cause various negative impacts, therefore it should be treated properly in a Leachate Treatment Plant (LTP). The paper aims to select a more sustainable LTP system in Indonesia by applying Analytic Network Process (ANP) as multicriteria analysis approach. 5 alternative LTP systems were analyzed using 5 criteria namely economic, environmental, social, technical, and institutional capacity with a total of 25 sub-criteria. Total 36 respondents from municipality staffs, academics, professionals, and LTP operators were interviewed by adopting pair wise comparison. The results from Driving Dependence Power Analysis (DDPA) showed that sub-criteria for operating costs (E2), maintenance costs (E3), processing effectiveness (T1) and monitoring needs (T3) have the highest dependence power value. Sub-criteria of the operational cost (E2) and the availability of regulations (K2) have the highest driving power value. Main considerations for selecting LTP system at a final disposal site by respondents were economic criteria (weight 0.3219) and water protection sub-criteria (L2, weight 0.17). Top priority of the technology chosen by respondents were Alternative#1 consist of Anaerobic, Facultative and Maturation ponds and Biofilter.

Metagenomic analysis unveils the underexplored roles of prokaryotic viruses in a full-scale landfill leachate treatment plant

Enormous viral populations have been identified in activated sludge systems, but their ecological and biochemical roles in landfill leachate treatment plants remain poorly understood. To address this knowledge gap, we conducted an in-depth analysis using 36 metagenomic datasets that we collected and sequenced during a half-year time-series sampling campaign at six sites in a full-scale landfill leachate treatment plant (LLTP), elucidating viral distribution, virus‒host dynamics, virus-encoded auxiliary metabolic genes (AMGs), and viral contributions to the spread of virulence and antibiotic resistance genes. Our findings demonstrated that viral and prokaryotic communities differed widely among different treatment units, with stability over time. LLTP viruses were linked to various prokaryotic hosts, spanning 35 bacterial phyla and one archaeal phylum, which included the core microbes involved in biological treatments, as well as some of the less well-characterized microbial dark matter phyla. By encoding 2364 auxiliary metabolic genes (AMGs), viruses harbored the potential to regulate microbial nucleotide metabolism, facilitate the biodegradation of complex organic matter, and enhance flocculation and settling in biological treatment plants. The abundance distribution of AMGs varied considerably across treatment units and showed a lifestyle-dependent pattern with temperate virus-associated AMGs exhibiting a higher average abundance in downstream biological treatment units and effluent water. Meanwhile, temperate viruses tended to carry a higher load of virulence factor genes (VFGs), antibiotic resistance genes (ARGs), and biotic and metal resistance genes (BMRGs), and engaged in more frequent gene exchanges with prokaryotes than lytic viruses, thus acting as a pivotal contributor to the dissemination of pathogenicity and resistance genes in downstream LLTP units. This study provided a comprehensive profile of viral and prokaryotic communities in the LLTP and unveiled the varying roles of different-lifestyle viruses in biochemical processes and water quality safety.

4E analysis and tri-objective optimization of a landfill plant integrated with power-to-gas and leachate treatment

Management of waste is essential since waste production has increased drastically. Landfilling is prevalent in controlling and managing wastes, particularly municipal solid wastes. Tackling the environmental problems of landfill is the goal of this work. The outputs of the landfill are biogas and leachate, which are hazardous to the environment. This problem can be solved by using the power-to-gas system and leachate treatment plant. The leachate has the potential to produce biogas, and the CO2 in biogas can be converted to methane in the methanation unit of power to gas. For this, power-to-gas needs the electricity in the electrolyzer, which can be provided from the surplus electricity of available renewables (here solar photovoltaics and wind turbine). Energy, exergy, economic and environmental analyses are applied to the system, and tri-objective optimization by the genetic algorithm is performed to gain optimum results. The obtained exergy efficiency from the given data is 19.03%. Also, the energy efficiency, net electricity generation, methane production rate, total annual cost, and CO2 conversion are 19.51%, 4.24 MW, 176.63 kg/h, €1.8 million, and 82.42%, respectively. In the ideal point of tri-objective optimization, the exergy efficiency, total annual cost, and CO2 conversion become 26.16%, €1.31 million, and 96.57%, respectively.

Effect of the association of coagulation/flocculation, hydrodynamic cavitation, ozonation and activated carbon in landfill leachate treatment system

Mature landfill wastewater is a complex effluent due to its low biodegradability and high organic matter content. Currently, mature leachate is treated on-site or transported to wastewater treatment plants (WWTPs). Many WWTPs do not have the capacity to receive mature leachate due to its high organic load leading to an increase in the cost of transportation to treatment plants more adapted to this type of wastewater and the possibility of environmental impacts. Many techniques are used in the treatment of mature leachates, such as coagulation/flocculation, biological reactors, membranes, and advanced oxidative processes. However, the isolated application of these techniques does not achieve efficiency to meet environmental standards. In this regard, this work developed a compact system that combines coagulation and flocculation (1st Stage), hydrodynamic cavitation and ozonation (2nd Stage), and activated carbon polishing (3rd Stage) for the treatment of mature landfill leachate. The synergetic combination of physicochemical and advanced oxidative processes showed a chemical oxygen demand (COD) removal efficiency of over 90% in less than three hours of treatment using the bioflocculant PGα21Ca. Also, the almost absolute removal of apparent color and turbidity was achieved. The remaining CODs of the treated mature leachate were lower when compared to typical domestic sewage of large capitals (COD ~ 600 mg L−1), which allows the interconnection of the sanitary landfill to the urban sewage collection network after treatment in this proposed system. The results obtained with the compact system can help in the design of landfill leachate treatment plants, as well as in the treatment of urban and industrial effluents which contains different compounds of emerging concern and persistence in the environment.

Mitigation of N2O emissions via enhanced denitrification in a biological landfill leachate treatment using external carbon from fermented sludge

The effects of an external carbon source (C-source) on the mitigation of N2O gas (N2O(g)) emissions from landfill leachate were investigated via enhanced denitrification using anaerobically fermented sewage sludge. Anaerobic fermentation of sewage sludge was conducted under thermophilic conditions with progressively increasing organic loading rates (OLR). Optimal conditions for fermentation were determined based on the efficiency of hydrolysis and the concentrations of sCOD and volatile fatty acids (VFAs) as follows: at an OLR of 40.48 ± 0.77 g COD/L·d with 1.5 days of solid retention time (SRT), 14.68 ± 0.59% of efficiency of hydrolysis, 14.42 ± 0.30 g sCOD/L and 7.85 ± 0.18 g COD/L of VFAs. Analysis of the microbial community in the anaerobic fermentation reactor revealed that degradation of sewage sludge might be potentially affected by proteolytic microorganisms producing VFAs from proteinaceous materials. Sludge-fermentate (SF) retrieved from the anaerobic fermentation reactor was used as the external C-source for denitrification testing. The specific nitrate removal rate (KNR) of the SF-added condition was 7.54 mg NO3−N/g VSS·hr, which was 5.42 and 2.43 times higher than that of raw landfill leachate (LL) and a methanol-added condition, respectively. In the N2O(g) emission test, the liquid phase N2O (N2O–N(l)) of 20.15 mg N/L was emitted as N2O(g) of 19.64 ppmv under only LL-added condition. On the other hand, SF led to the specific N2O(l) reduction rate (KN2O) of 6.70 mg N/g VSS hr, resulting in mitigation of 1.72 times the N2O(g) emission compared to under the only-LL-added condition. The present study revealed that N2O(g) emissions from biological landfill leachate treatment plants can be attenuated by simultaneous reduction of NO3−N and N2O(l) during enhanced denitrification via a stable supply of an external C-source retrieved from anaerobically fermented organic waste.

Evidence of microplastics in leachate of Randegan landfill, Mojokerto City, Indonesia, and its potential to pollute surface water

About 80–90 tons municipal solid waste (MSW) in Mojokerto City, Indonesia, is disposed of into Randegan landfill daily. The landfill was facilitated with a conventional leachate treatment plant (LTP). The plastic waste component in the MSW, which is 13.22 % weight, possibly contaminates leachate with microplastics (MPs). This research aims to determine the presence of MPs in leachate of the landfill, its characteristics, and the removal efficiency of the LTP. The potential of leachate as MP pollutant source to surface water was also discussed. Raw leachate samples were collected from the LTP inlet channel. Leachate samples were also taken from each LTP's sub-units. Leachate collection was performed two times using a 2.5 L glass bottle during March 2022. The MPs were treated using Wet Peroxide Oxidation method, and filtered using PTFE membrane. MP size and shape were determined using a dissecting microscope with 40–60 x magnifications. The polymer types in the samples were identified using Thermo Scientific™ Nicolet™ iS™ 10 FTIR Spectrometer. The average MP abundance in raw leachate was 9.00 ± 0.85 particles/L. MP shape in the raw leachate was dominated by fiber (64.44 %), followed by fragment (28.89 %), and film (6.67 %). The majority of the MPs were of black color (53.33 %). Abundance of 350 - <1000 μm sized MPs was the highest (64.44 %) in the raw leachate, followed by those of 100–350 μm (31.11 %), and 1000–5000 μm (4.45 %). MP removal efficiency of the LTP was 75.6 %, leaving <100 μm fiber shaped MP residuals of 2.20 ± 0.28 p/L in the effluent. Based on these results, effluent of the LTP is considered potential as MP contamination source to surface water.

Retrofitting a full-scale multistage landfill leachate treatment plant by introducing coagulation/flocculation/sedimentation and ultrafiltration process steps.

Considering that landfilling still remains among the most commonly used methods for the confrontation of solid wastes, effective methods should be applied to treat the leachate generated, due to its recalcitrant nature. In this work, a full-scale system consisting of two SBRs operating in parallel (350 m3 each) and two activated carbon (AC) columns operating in series (3 m3 each) was retrofitted by introducing a coagulation/flocculation/sedimentation (C/F/S) unit of 7.8 m3 and an ultrafiltration (UF) membrane of 100 m2 to effectively treat landfill leachate. The raw leachate was characterized by high COD and NH4+-N concentration, i.e., 3095 ± 706mg/L and 1054 ± 141mg/L respectively, a BOD/COD ratio of 0.22, and high concentrations of certain heavy metals. Leachate processing in this retrofitted multistage treatment system resulted in total COD removal efficiency of 89.84%, with biological treatment, C/F, UF, and AC contributing 46.31%, 4.68%, 15.98%, and 22.87% to the overall organic content removal. The retrofitted scheme achieved an overall NH4+-N and TKN removal of 92.03% and 91.75% respectively, attributed mostly to the activity of an effective nitrifying community. Color number (CN) was reduced by 26.96%, 10.29%, 15.94%, and 5.39% after the activated sludge, the C/F, the UF, and the AC adsorption process respectively, corresponding to a 58.91% overall decrease. Regarding heavy metal removal, all elements examined, apart from Ni, i.e., effluent As, Cd, Co, Cr, Cu, Hg, Mg, Mn, and Pb, were below the legislative limits set by the national authorities for restricted or unrestricted irrigation. Lastly, total operating expenses (OPEX) were estimated as equal to 72,687 €/year or 6.64 €/m3.