Semi-aerobic Landfill Research Articles

Evaluating the key success factors for low-carbon waste management of local administrative organizations: RDF production and semi-aerobic landfill in Thailand

Evaluating the key success factors for low-carbon waste management of local administrative organizations: RDF production and semi-aerobic landfill in Thailand

Numerical simulation to optimize passive aeration strategy for semi-aerobic landfill

Passive aeration has been proven to be efficient for oxygen supply in landfill. The combination of passive aeration and semi-aerobic landfill offers a cost-effective and energy-efficient approach to solid waste (SW) treatment. However, determining the optimal strategy for this combination has remained unclear. This study aimed to investigate the strategy of passive aeration in a semi-aerobic landfill using numerical simulation methods. A model coupled hydrodynamic model and compartment model for degradation of SW was implemented. The accuracy was well validated by comparing measured and simulated results in a pilot-scale landfill. Compared with natural convection, passive aeration by funnel caps could increase air input by 20 %. By simulating volumetric fraction distribution of CO2, CH4 and O2 in landfill, an orthogonal experiment including 4 factors was designed to identify that the diameter of tubes (DT), the spacing between tubes (ST) and the landfill depth (LD) have substantial impacts on aerobic zone ratio (AZR) of landfill. But the diameter of gas ports (DGP) has an indiscernible effect. The optimized factors were determined to be as follows: DT = 0.3 m, ST = 15.0 m, DGP = 0.05 m, and LD = 4.0 m, under which the semi-aerobic landfill could enhance SW degradation. Large diameter and spacing of tubes are favorable to improve the AZR at the top of the landfill, and the aerobic zone mainly exists near the ventilation tubes. These findings contribute to the development of more efficient and sustainable solid waste treatment strategies in semi-aerobic landfill.

Environmental Performance of Semi-Aerobic Landfill by Means of Life Cycle Assessment Modeling

The potential impacts and the environmental performance of the semi-aerobic landfill technology were assessed through the Life Cycle Assessment (LCA) methodology. Project data that referred to a hypothetical Italian plant design were used and ISO 14040/14044 standards were applied. All the life cycle phases were considered, from landfill construction to filling, aftercare, closure and conversion for future use. All the landfill processes and the inflow of materials, energy and rainwater, and the outflow of biogas and leachate, were included in the system boundaries. The results show that the overall environmental impacts associated to semi-aerobic landfill are primarily due to the filling and aftercare phases, but the impacts related to construction and closure phases are not negligible. The contribution analysis underlines the processes with major responsibility within the environmental profile, while the normalization of results demonstrates what are the environmental categories on which the landfill impacts fall most. Important lessons emerging from this research can support practitioners and scientists in optimizing semi-aerobic landfill design and management.

The Potential Use of Nephelium lappaceum Seed as Coagulant-Coagulant Aid in the Treatment of Semi-Aerobic Landfill Leachate.

Chemical-based coagulants and flocculants are commonly used in the coagulation–flocculation process. However, the drawbacks of using these chemical materials have triggered researchers to find natural materials to substitute or reduce the number of chemical-based coagulants and flocculants. This study examines the potential application of Nephelium lappaceum seeds as a natural coagulant–coagulant aid with Tin (IV) chloride (SnCl4) in eliminating suspended solids (SS), colour, and chemical oxygen demand (COD) from landfill leachate. Results showed that the efficiency of Nephelium lappaceum was low when used as the main coagulant in the standard jar test. When SnCl4 was applied as a single coagulant, as much as 98.4% of SS, 96.8% of colour and 82.0% of COD was eliminated at an optimal dose of 10.5 g/L and pH 7. The higher removal efficiency of colour (88.8%) was obtained when 8.40 g/L of SnCl4 was applied with a support of 3 g/L of Nephelium lappaceum. When SnCl4 was utilised as a coagulant, and Nephelium lappaceum seed was used as a flocculant, the removal of pollutants generally improved. Overall, this research showed that Nephelium lappaceum seed is a viable natural alternative for treating landfill leachate as a coagulant aid.

Degradation of refractory organic matter in the effluent from a semi-aerobic aged refuse biofilter-treated landfill leachate by a nano-Fe3O4 enhanced ozonation process.

In this study, the transformation and degradation mechanisms of refractory organic matter in biologically treated leachate from a semi-aerobic aged refuse biofilter (SAARB) in a nano-Fe3O4 enhanced ozonation process (nFe3O4-O3) were investigated in batch experiments. A continuous experiment then confirmed the effectiveness of the process for SAARB effluent treatment. In a batch experiment, the effects of influencing factors, including nFe3O4 dosage, O3 dosage and initial pH on the treatment performance of nFe3O4-O3 process, were comprehensively investigated. The results showed that when the nFe3O4 dosage = 6 g L-1, O3 dosage = 0.15 L minute-1 and initial pH = 7, the total organic carbon, absorbance at 254 nm and colour number removal efficiencies were 40.58%, 62.55% and 89.80%, respectively. In addition, most of the humic- and fulvic-like substances in the SAARB effluent were removed, and the condensation degree, aromaticity and humification degree of the organics were substantially reduced. The morphology and elemental valence state analysis showed that the nFe3O4 in the process was relatively stable and could form an nFe3O4-organic complex. Therefore, the probability of organics reacting with hydroxyl radical increased and the oxidation efficiency was enhanced. In the continuous experiment, both the O3 dosage and hydraulic retention time (HRT) were the key influencing factors. The treatment efficiency of the nFe3O4-O3 process was enhanced at a higher O3 dosage and longer HRT. The electrical energy consumption of the continuous nFe3O3-O3 process was calculated to be 17.72 kW h m-3 in SAARB effluent treatment. This study proved the feasibility of biologically treated landfill leachate treatment by the nFe3O3-O3 process.

Stabilization of mechanically biologically treated waste in anaerobic, aerobic and semi-aerobic bioreactors.

The study aims to investigate the application of anaerobic (AN), aerobic (AER) and semi-aerobic (SA) laboratory scale landfill bioreactors for stabilization of mechanically and biologically treated (MBT) waste of Bangalore city. All major parameters pertaining to the waste, leachate and biogas are continuously monitored during the experiment. Carbon (C) and nitrogen (N) mass balance are carried out to understand the recovery/removal of C and N from the system. The biochemical oxygen demand, chemical oxygen demand and nitrogen removal efficiency of the bioreactors are in the range of 83%-87%, 81%-87% and 96%-99%, respectively. Total settlement observed in the AN, AER and SA bioreactors is 15.25%, 23.92% and 10.80%, respectively. The performance of the three bioreactors are compared, and their suitability in treating the MBT waste from Bangalore city is discussed. The study shows that the AER bioreactor landfills can be used for remediating the existing municipal solid waste dumpsites in Bangalore city.

Drivers and ecological consequences of arsenite detoxification in aged semi-aerobic landfill

Microbial populations responsible for arsenite [As(III)] detoxification were examined in aged refuse treated with 75 μM As(III) under semi-aerobic conditions. As(III) was rapidly oxidized to As(V) via microbial activity, and substantial As was fixed in the solid phase. The abundance of arsenite oxidase genes (aioA) was about four times higher in the moderate As(III) stressed treatment than in the untreated control. Network analysis of microbial community 16S rRNA genes based on MRT (random matrix theory) further illuminated details about microbe-microbe interactions, and showed six ecological clusters. A total of 166 “core” taxa were identified by within-module connectivity and among-module connectivity values. When compared with the control treatment without As(III), 12 putative keystone operational taxonomic units were positively correlated with As(III) oxidation, of which 10 of these were annotated to genera level. Eight genera were associated with As(III) detoxification: Pseudomonas, Paenalcaligenes, Proteiniphilum, Moheibacter, Mobilitalea, Anaerosporobacter, Syntrophomonas and Pusillimonas. Most of those putative keystone taxa were rare species in landfill, which suggests that low-abundance taxa might significantly contribute to As(III) oxidation.

Impact of internal conditions on the gas flow path in semi-aerobic landfill reactors

Despite the continuous development of waste disposal technology, landfill remains a significant means of municipal solid waste disposal around the world. Accelerating the process of waste stabilisation has become a pressing problem. In this study, four indoor landfill reactors were set up. Reactors A and C were semi-aerobic landfills, and in reactors B and D the gas vents were disconnected from the leachate collection pipes. Kitchen waste was the main ingredient of the sample waste (55.46%). The void fractions of reactors C and D were decreased by adding extra gravel. The void fractions were 32.82% and 33.27% in reactors A and B, respectively, whereas those in reactors C and D were about 6% lower. The temperatures of reactors A and B were higher than those of reactors C and D. The temperature peak in reactor A occurred earlier than that in Reactor B. The temperature and gas concentration measurements confirmed that not all the air was discharged directly through the gas vent, and some air passed horizontally through the waste layer of the reactor. It was finally showed that the void fraction and connections in the pipelines inside the landfill reactor affected the gas flow path.

Effect of air and water on the release of chlorine from semi-aerobic landfill

ABSTRACT Landfill leachate has a high chloride (Cl−) content. Because it is highly mobile, and cannot be sorbed or transformed bio-chemically, it is important to have detailed information about how it migrates in landfill sites. In this study, we set up four lab-scale simulated landfills, including an anaerobic landfill (AL), an anaerobic landfill with leachate recirculation (RAL), an anaerobic/semi-anaerobic landfill with leachate recirculation (RASL), and an anaerobic/semi-aerobic landfill (ASL), to explore how, when regulated, moisture and air affected the migration of chlorine. We found that water and air had a strong influence on the release of Cl−. Leachate obviously promoted Cl− dissolution in refuse when recirculated. When air was introduced into landfill, thereby changing it from anaerobic to semi-aerobic, the leachate Cl− concentration increased sharply from around 4–9 g L−1 (RASL) and 18 g L−1 (ASL), respectively. In principle, Cl− is released continuously when leachate is recirculated in landfills (RAL and RASL), but it can also be found a terminal when the leachate recirculation stops (AL and ASL). Cumulative amounts of 64, 66, 27, and 53 g of Cl− were released from the AL, RAL, RASL, and ASL, respectively. Lower COD/Cl and -N/Cl ratios in ASL and RASL after day 175 indicated that lower Cl− pollution risk than that in AL and RAL.

Effects of leachate recirculation quantity and aeration on leachate quality and municipal solid waste stabilization in semi-aerobic landfills

Although sanitary landfilling currently effectively treats municipal solid waste (MSW) semi-aerobic bioreactor landfills (SABLs) are designed to accelerate biological processes and shorten the landfill stabilization phase. In this study, the effects of SABLs with the joint treatment of leachate recirculation and preaeration on landfill stabilization were determined by four landfill reactors, one anaerobically as a control, and three semi-aerobically with different leachate recirculation treatments (reactor I, II and III: 300 mL leachate, 600 mL leachate, and 600 mL aerated leachate per week, respectively). Results showed that reactor III had the highest removal rates of chemical oxygen demand (COD) and ammonia-nitrogen (NH 4 + -N), reaching 97% and 88%, respectively. Degradation of the organic substances could be described using an exponential attenuation model; the rates of COD, NH 4 + -N and biochemical oxygen demand (BOD 5 ) in the SABLs increased from 0.019, 0.018, and 0.035 to 0.029, 0.025, and 0.053 day −1 , respectively, when leachate recirculation quantity was increased and preaeration was applied. Finally, classification index evaluation revealed that reactor III had the lowest I value of 312, indicating that the combination of increasing leachate recirculation quantity and preaeration could positively affect the MSW stabilization phase. This finding provides experimental evidence for improving landfill management for accelerating MSW stabilization in SABLs. • Different leachate quantity and preaeration were applied in semiaerobic landfills. • Higher pollutant removal rates were in semi-aerobic than in anaerobic reactor. • Greater recirculation quantities and preaeration accelerated waste stabilization. • The classification index method was used to evaluate landfill stabilization.

Greenhouse gas emission analysis of upgrading from an open dump to a semi-aerobic landfill in Mozambique – the case of Hulene dumpsite

Halting the unsustainable solid waste disposal practices has been a concerning issue due to the severe implications to public safety, health and the adverse impacts on the environment.As such, in lower-income nations where dumpsites are the leading waste disposal structures, there is an ongoing effort to upgrade to more sustainable options. In Mozambique, a semi-aerobic landfill, also known as the Fukuoka method, was selected to replace the key dumpsite located in the capital. Nevertheless, limited information is available on the prospective environmental impacts resulting from the planned upgrade. This study aims to assess the greenhouse gas emissions from Hulene dumpsite in Maputo City, Mozambique, operating under anaerobic conditions and the changes after the upgrade to a semi-aerobic landfill, employing the Intergovernmental Panel on Climate Change (IPCC) methodologies. The emissions from 1980 to 2030 in the dumpsite totaled 2,455 Gg CO2-eq, which 568 Gg CO2-eq corresponds to the contribution from open-burning activities. On the other hand, emissions for the semi-aerobic landfill from 2020 to 2030 were 685 Gg CO2-eq, 40% less than the total emissions from open dumping in the same period. The findings suggest that transitioning to a semi-aerobic landfill can significantly reduce GHG emissions, improve the local environment, and protect human health.

Simulating the impact of heavy rain on leaching behavior of municipal solid waste incineration bottom ash (MSWI BA) in semi-aerobic landfill

In Japan, approximately 64% of municipal solid waste incineration bottom ash (MSWI BA) is landfilled. Because landfills in Japan are operated without capping, the landfill body is directly exposed to climatic events. Increased frequency of heavy rain is predicted to affect the chemical stabilization of bottom ash (BA) landfill, as rainwater seeps into and interacts with landfill components. This study examined the effect of normal rainfall (15 mm/h) and heavy rainfall (25, 50, and 100 mm/h) events on the leaching behavior of ions (Cl−, Na+, K+, and Ca2+) and total organic carbon (TOC) in BA (<10 mm particle size) using a percolation column test. The results showed the decreased leaching of leachate components after heavy rainfall and increased leaching after normal rainfall. In addition, the pH fluctuated around 11–12 after heavy rainfall but decreased to 7–9 after normal rainfall. The carbonation of the leachate and BA layers appears to be the main factor in lowering the pH value. Changes in the TOC and ion concentrations can be explained by dissolution, dilution, and the contact time of water molecules and BA particles. The data showed that the cumulative TOC and ion release rates were not affected by heavy rain intensities. The release rate of leachate components during normal rainfall was higher than that in heavy rainfall in all the scenarios. Significant correlations were found between the leachate components (TOC, Cl−, Na+, K+, and Ca2+ concentrations) and rainfall variation.

THE ELEVATED TEMPERATURE AND GAS COMPONENT WITHIN AN OPERATING SEMI-AEROBIC LANDFILL

The semi-aerobic landfill concept, which is based on passive aeration, is the compulsory standard for planning new landfill projects in Japan. The semi-aerobic landfill concept is also applied in several other countries because of its low construction and operating costs. The landfill gas (LFG) component and the LFG temperature are the main indicators of the aerobization of semi-aerobic landfills. Analysis of LFG, its concentration, and its temperature can be easily carried out on-site to evaluate the passive aeration of an operating semi-aerobic landfill. Therefore, this study observed LFG temperatures and LFG components to assess the partial aerobization within an operating semi-aerobic landfill. The observational data revealed that the methane (CH4) gas concentration of most of the main LFG venting pipes (VPs) was below 15%. The aerobic condition happened effectively surrounding the main LFGVP M2 because over the observation period, the ratio of CH4 to CO2 was less than 1.0. The highest gas temperature was above 60°C within the main LFGVP M2, and there was a trend of high temperatures above 40°C for more than 5 years before the temperature declined to 20°C in the most recent observation. The high LFG temperatures were recorded in the winter months due to the buoyancy effect. High temperature and the CH4/CO2 ratio less than 1.0 potentially representing good indicators showed that aerobic decomposition is becoming dominant. The study showed clearly that the aerobic biodegradation performance in this semi-aerobic landfill is extremely good.

Case Study on Transfer Technology by Semi-aerobic Landfill Concept in African Region

昨今，地球温暖化の下で，多くの国々において大規模な災害が発生し大きな社会問題となっている。特に，近年急激な都市化と人口増加の著しいアフリカ地域において廃棄物問題が深刻化し，廃棄物の埋立地への技術対応が求められている。 しかし，高度成長期の下では，廃棄物対策への政策の優位性は低く，依然として Lack of 6Ms (金・物・人・維持・管理・やる気の不足) の状況で，多くの埋立地はオープンダンピングが一般的で，このような埋立地は，異常気象の豪雨によって環境汚染や崩落事故が多発し，社会問題となっている。 こうした中で，筆者らは UN-HABITAT 福岡事務所から，「福岡方式による埋立地の技術支援」の要請を受け，現在アフリカ地域で複数の埋立地の改善事業を行っている。本稿では，ケニアにおける「福岡方式による埋立処分施設建設事業」とエチオピアにおける「崩落事故現場における廃棄物埋立地緊急改善事業」の技術移転事例を紹介する。

Comparative assessment of waste disposal systems and technologies with regard to greenhouse gas emissions: A case study of municipal solid waste treatment options in China

Municipal solid waste (MSW) management has shifted to include multiple functions, especially energy recovery and reduction of greenhouse gas emissions, other than sanitary treatment of waste. In China, two main MSW treatment options exist: landfill and incineration. The objective of this study was to evaluate the landfill and incineration methods in terms of two important indicators, energy balance and greenhouse gas (GHG) emissions, and to discuss the advantages as they relate to decarbonization policy. We set up two landfill cases: LF-Anaero, which adopted an anaerobic landfill structure, and LF-SAero, which adopted a semi-aerobic landfill structure. Two incineration cases were also established: INC-Non, where the MSW was not subjected to separated collection of non-burnable waste, and INC-Sep, where separated collection was conducted. Two conditions were also established. In the one-year condition, waste was assumed to entirely decompose in one year, whereas in the variable decomposition condition, the rate varied. Under the one-year condition, INC-Sep gave the best results for both energy balance and GHG emission reduction. When the decomposition rate of landfilled waste was considered, LF-SAero and INC-Sep had very similar cumulative amounts of GHG emissions after 50 years. However, in INC-Sep, the emissions all occurred in the first 20 years. In LF-SAero, about one-third of the emissions were accounted for in the last 30 years (after the landfill was out of service). Thus, this landfill method must be considered as a GHG emission source for a longer period when considering the total global warming impact. We concluded that INC-Sep is the superior technological option.

OPTIMISED MANAGEMENT OF SEMI-AEROBIC LANDFILLING UNDER TROPICAL WET-DRY CONDITIONS

The processes involved in semi-aerobic landfills are heavily influenced by local climate conditions and waste composition. In particular, when considering rainfall seasonality in a tropical climate, the lack of moisture during the dry season and heavy rainfalls during the wet season may negatively affect biodegradation processes and landfill emissions. The aim of the present study was to investigate the performance of semi-aerobic landfill under tropical dry-wet climate conditions and to assess the potential benefits afforded by appropriate management of water input when operating the landfill by overlaying a new layer of waste in each climate season. Six lab-scale lysimeters were operated in two phases to reproduce, on two subsequent waste layers, a sequence of dry and wet tropical seasons: two with an initial dry phase, two with an initial dry phase under controlled watering and two with an initial wet phase, during which leachate was stored to allow recirculation during the subsequent dry phase. In each pair of lysimeters one was filled with low putrescible content waste and the other with high putrescible content waste. Although appropriate management of water input significantly improved landfill performance under dry climate conditions, the overlaying of a new layer of waste in each climate season played a fundamental role in ensuring good stabilisation over the one year simulation period; following stabilisation, the landfill bottom layer acts as an internal attenuating biological filter. In particular, under initial dry conditions, final BOD COD and ammonia values detected were below 20mgO2/L, 200mgO2/L, and 30mgN/L, respectively.

Effects of Different Additives and Ambient Conditions on Acceleration of Sludge Stabilization: Laboratory-Scale Simulated Landfill Study

AbstractFresh cow dung and iron scraps were added to municipal sewage sludge under laboratory-simulated anaerobic landfill conditions. Simulated anaerobic and semiaerobic landfilling of sludge with...

Lab tests on semi-aerobic landfilling of MSW under varying conditions of water availability and putrescible waste content

Semi-aerobic landfilling is applied increasingly as a sustainable technology worldwide, although frequently controversial results are achieved. The authors suggest that differences in water availability (climate, moisture content, etc.) and putrescible waste content are the key factors involved in controlling performance and efficiencies. The aim of the present study was to investigate the effect of inverse conditions (high/low) of these two factors. Six lab-scale lysimeters were specifically set up to correspond to three different conditions of water availability (wet conditions, dry conditions and artificially controlled watering under dry conditions) and two different waste types (high and low putrescible content). Lysimeters were operated for four months under thermal-insulated conditions and the quality and quantity of emissions monitored regularly. Concentrations of mobile ammonia and total organic carbon (TOC) in landfilled waste were modelled by means of first-order kinetics, and carbon and nitrogen mass balances were calculated. The best performance for the semi-aerobic process was achieved at a water availability of approximately 1.5–2.4 kgH2O/kgTS using the following two combinations: a) Waste with high putrescible content and no addition of external water due to the presence of sufficient endogenous water in the waste (moisture) to promote biological stabilisation of waste (Respiration index in 4 days, RI4 = 12.87 mgO2/gTS, BOD/COD < 0.05); b) Waste with low putrescible content and controlled watering (RI4 = 12.25 mgO2/gTS, BOD/COD < 0.04). The study highlighted how semi-aerobic landfilling operations should be carefully adjusted case by case according to waste quality and climate conditions.

Assessment and prioritisation of low-carbon technology for the waste sector in Vietnam

This paper presents a multi-criteria assessment approach for the prioritisation of low-carbon technologies for the waste sector in order to enable the implementation of Vietnam’s nationally determined contributions (NDCs) in terms of the Paris Agreement. A four-step approach is developed for assessing and prioritising low-carbon technologies for the waste sector using this approach. A set of five criteria and indicators are defined for multi-criteria assessment. Based on mitigation options defined in the NDCs, a shortlist of 26 technological options are defined. The multi-criteria assessment and prioritisation is conducted based on the shortlist. The assessment results in eight prioritised low-carbon technologies. Of the eight technologies prioritised, semi-aerobic landfill, which is a low cost and relatively simpler technology than the other technologies evaluated and can contribute to greenhouse gas emission reduction, is given the highest priority. The technical, financial, and social and environmental feasibility of each of the technologies evaluated is presented.

Influence of the void fraction and vertical gas vents on the waste decomposition in semi-aerobic landfill: Lab-scale tests

The waste classification has not been carried out worldwide, especially in developing countries. The high content of water in the kitchen waste will definitely affect the amount of air flowing into waste layer from leachate collection pipe. In this experiment, three lab-scale landfill simulation reactors were established. Reactor A and B are semi-aerobic landfill modes, while reactor C has no vertical gas vent. The void fraction in the waste of reactor B was increased by adding gravel serve as part of the waste. The waste sample used in landfill reactor mainly included kitchen waste (58%). The waste decomposition conditions in the landfill were investigated using temperature sensors embedded in the waste, by determining the velocity and gas flow direction and by measuring the volume and composition of leachate produced. The results showed that the void fraction of waste in reactor A and C was 29.79% and 30.86% respectively, and that of waste in reactor B 34.96%. Compared with reactor A, reactor B had its temperature increase earlier. In addition, the temperature distribution in vertical gas vent of the reactor A and B is higher than in the leachate collection pipe. The gas flux of vertical gas vent increased with the temperature of gas vent. Reactor A and B had significantly lower concentration of chemical oxygen demand (COD) and ammonia nitrogen (NH3+-N) than that of reactor C. It was concluded that landfill decomposition can be accelerated by increasing the void fraction in the waste and keeping a vertical gas vent open.