Stabilization Of Solid Waste Research Articles

Cold sintering of strontium-adsorbed titanate adsorbents for stabilization and immobilization of secondary solid nuclear waste

Cold sintering of strontium-adsorbed titanate adsorbents for stabilization and immobilization of secondary solid nuclear waste

Evaluation of the biodegradability of hazardous industrial solid waste: Study of key parameters.

The biological stability of solid waste is one of the main problems related to the environmental impact of landfills and their long-term emission potential. Current European legislation (European Landfill Directive, EC/99/31) introduced the need to reduce biodegradable organic compounds deposited in landfills; however, it set neither official parameters nor methods to define the stability of such a waste. In Spain, biodegradability is generally evaluated using the biological oxygen demand/chemical oxygen demand (BOD5/COD) ratio, measuring it on the leachate, thus not considering the non-soluble fraction and therefore creating false negatives. To solve this problem, the biodegradability of hazardous industrial waste has been determined by measuring its respirometric activity (AT4). Our results show that the measure of the AT4 is independent of the enrichment with a microbial inoculum, and a sample size no higher than 20g could be a reasonable value for a sensitive biodegradability determination. The highest respirometric index is obtained in waste with pH values between 6.5 and 10.5. Furthermore, respirometric biodegradability values are independent of traditional parameters of organic matter characterization such as BOD5/COD ratio, volatile content, and total and dissolved organic carbon. Consequently, the AT4 parameter provides new information on the composition and stability of organic matter in hazardous industrial waste. Its incorporation into pre-disposal waste characterization protocols allows to identify waste that exceeds recommended biodegradability thresholds. This approach ensures that only waste meeting specified biodegradability standards is deposited, avoiding landfill emissions and related environmental impacts, and thereby improving the overall effectiveness and sustainability of waste management practices.

Evaluation of bioplastics biodegradation under simulated landfill conditions.

Bioplastics that are generated from renewable sources have been regarded as an alternative to conventional plastics. Polylactic acid (PLA) is one of the mostly produced bioplastics because of its long shelf life for various applications. Even though bioplastics have drawn attention recently, their ultimate fate in landfills is still unknown. In this study, a standardized laboratory-scale lysimeter experiment was performed for the simulation of landfill conditions in order to evaluate the biodegradability of PLA during municipal solid waste stabilization. The reactors were loaded with municipal solid waste (MSW) taken from an operating landfill, certified PLA cups, and seed sludge. Various phases of landfill stabilization were simulated; hence, the reactors were operated under aerobic, semi-aerobic, and anaerobic conditions, respectively. Throughout the operation, both leachate and biogas generation in the reactors were regularly monitored. At the end of each phase, bioplastic cups were removed from the reactors, gently cleaned, weighed, and examined under a scanning electron microscope (SEM). The experimental results indicated that bioplastics did not undergo significant biodegradation during the first two stabilization phases (aerobic and semi-aerobic). On the other hand, it was observed that the cups were much softer and whiter at the end of the anaerobic phase. The weight of cups decreased by 12.8% on average, and their surfaces were prominently damaged after the completion of the last phase indicating the potential signs of biodegradation.

Lime sludge assisted anaerobic bioreactor landfilling of municipal solid waste for enhanced leachate stabilization and bioenergy yield

Bioreactor landfilling even being advanced technology for enhanced stabilization of municipal solid waste (MSW), often suffers with adverse acidogenic conditions. Such conditions reinforce poor leachate stabilization, and reduced biomethane yield. This work attempts to counter the challenges of adverse MSW landfilling conditions through incorporation of waste alkaline sludge from paper industry. The amendment in anaerobic bioreactor landfilling of MSW was practiced by adding lime sludge (LS) with MSW in three distinct proportions: 20 g LS/kg MSW (LS100), 50 g LS/kg MSW (LS250) and 100 g LS/kg MSW (LS500), keeping LS0 as control. Periodic leachate and biomethane analysis showed benefits of proportionate LS addition. The control reactor often experienced leachate ponding and inhibitory conditions for anaerobic digestion. However, reactor LS250 achieved highest decrease in leachate organic strength removal (76.47 %) and biomethane production (8.315 L) over the period of landfilling. The pH and volatile fatty acids (VFAs) were in coordination with LS proportions. The LS addition beyond 100 g LS/kg MSW (LS500) could decrease the leachate pollution removal and biomethane yield. Finally, the Gompertz growth model showed excellent fit (R2 >0.997) to recorded biomethane. The study expands the scope of utilizing similar sludges for amendment of existing landfilling practices for efficient bioconversion of organic fractions of MSW.

Impact of Leachate Recirculation on the Stabilization of Municipal Solid Waste in Anaerobic Bioreactors of Different Compositions

The aim of the current study is to determine the impacts of leachate recirculation on the degradation of three compositions of municipal solid waste in anaerobic bioreactors. The study was completed by using six columns with equal volume (0.042m3) containing different densities and compositions of solid waste, in order to follow waste degradation over a limited time. Three compositions of waste were studied: simulated fresh waste of standard composition, simulated fresh waste of fermentable composition, and actual aged waste. Measurements of the significant parameters including pH, leachate conductivity, Chemical Oxygen Demand (COD), and waste settlement, were carried out. The quantity of oxidized organic matter was increased by the leachate recirculation, and the degradation period was reduced by using leachate recirculation. After 300, 150, and 480 days, waste stabilization seemed to be reached for fresh, aged, and fermentable waste, whereas the organic content decreased to 650, 480, and 4000mg COD/L, respectively.

Comprehensive Review of Hydrothermal Pretreatment Parameters Affecting Fermentation and Anaerobic Digestion of Municipal Sludge

Municipal solid waste treatment and disposal have become one of the major concerns in waste management due to the excessive production of waste and higher levels of pollution. To address these challenges and protect the environment in sustainable ways, the hydrothermal pretreatment (HTP) technique coupled with anaerobic digestion (AD) becomes a preferred alternative technology that can be used for municipal solid waste stabilization and the production of renewable energy. However, the impact of HTP parameters such as temperature, retention time, pH, and solid content on the fermentation of TWAS is yet to be well studied and analyzed. Hence this study was conducted to review the effect of hydrothermal pretreatment of thickened waste-activated sludge (TWAS) on fermentation and anaerobic digestion processes. Many studies reported that fermentation of TWAS at pretreatment temperature ranges from 160 °C to 180 °C resulted in a 50% increase in volatile fatty acid (VFA) yields compared to no pretreatment. However, for the AD process, HTP in the range of 175 °C to 200 °C with a 30–60 min retention time was considered the optimal condition for higher biogas production, with 30% increase in biodegradability and greater than 55% increase in biogas production. Even though there is a direct relationship between increased HTP temperature and the hydrolysis of TWAS, a pretreatment temperature range beyond 200 °C alters the biogas production. The solid content (SC) of sludge plays a crucial role in HTP, where in practice up to 16% SC has been utilized for HTP. Further, a combined alkaline-HTP enhances the process performance.

Effects of cellulose-based bio-plastics on the aerobic biological stabilization treatment of mixed municipal solid waste: A lab-scale assessment.

The aim of this work is to assess how the presence of cellulose-based bio-plastics influence the biological stabilization of mixed Municipal Solid Waste (MSW). For the scope, two cellulose acetate bio-plastics have been mixed with a synthetic mixed waste to create samples with and without bio-plastics. A self-induced biostabilization has been carried out for 7 and 14 days where temperature and off-gas have been monitored continuously. Results about temperature evolution, O2 consumption, CO2 production and respiratory quotient did not show a substantial difference regarding both the duration of the process and the presence of cellulose-based bio-plastics on the mixture. On the average, the temperature peak and the maximum daily O2 consumption and CO2 production were 52.2°C, 35.81g O2/kg DM *d and 48.95g CO2/kg DM *d respectively. Disintegration of bio-plastics samples after 7 and 14 days were comparable (on the average 23.13%). The self-induced biostabilization gave its main contribution after 4 days and resulted almost finished at the end of the day 7 of the process. Results showed that cellulose-based bio-plastics did not give a negative effect on mixed MSW biological stabilization and suggest a possible management, aiming at energy recovery of the outputs.

Effects of Environmental Factors on the Spatial Succession of the Bacterial Community in Municipal Solid-Waste Landfills

Secondary pollution control and rapid stabilization of municipal solid waste (MSW) landfills are closely associated with bacterial communities. The spatial variations in bacterial community structure and the environmental factors controlling it were studied by the 16S rRNA gene sequencing of MSW sampled at different depths in a large sanitary landfill (LSL) and a medium non-sanitary landfill (MNSL), respectively. The total nitrogen (TN) and total phosphorus (TP) content in the LSL and MNSL samples displayed a downward trend as the depth increased. However, the organic matter (OM) content followed the opposite trend. Diversity of microbes was highest in the middle layer of both the LSL and MNSL. Firmicutes and Proteobacteria were the dominant phylum both in the LSL and MNSL. In the LSL, the dominant bacteria genera succeeded from Psychrobacter, Pseudomonas to Clostridium, Savagea. However, in the MNSL, the genera succeeded from Uncultured, Pleomorphomonas to Hydrogenispora, Acetomicrobium. The type of landfill and the different environmental factors control the succession of the bacterial community in LSL and MNSL. The pH, OM, TN, and TP will change in the landfill as the landfill depth increased. The impact degree of landfill depth on pH, OM, TN, and TP content in the LSL was 15.3%, 16.1%, 4.9%, and 4.2%, respectively. These values were lower than those in the MNSL. In addition, depth and OM had the strongest correlations but no significance with the dominant bacteria both in the LSL (|Rdepth|average=0.48;|ROM|average=0.36) and MNSL (|Rdepth|average=0.51;|ROM|average=0.36). This indicated that bacterial community succession was mainly dependent on space, time, and MSW characteristics in different types of landfills.

Can the biological stage of a mechanical–biological treatment plant that is designed for mixed municipal solid waste be successfully utilized for effective composting of selectively collected biowaste?

Although the requirements for overall recycling rates can only be met when organic recycling is not overlooked, information is scarce regarding adaption to biowaste composting of existing mechanical–biological treatment (MBT) plants originally designed for stabilization of organic municipal solid waste (OFMSW). Thus, this study aimed to assess the suitability of the operational conditions in the biological part of a full-scale MBT plant now used for stabilization of OFMSW (working line: closed-module–covered-pile–open-pile) with a view to producing compost from biowaste. Temperatures above 75 °C were maintained in the closed module and reached again in the covered pile, indicating that intensive organic-matter mineralization occurred in both stages. In the covered pile, the temperature sharply decreased, indicating depletion of easily biodegradable organic matter. An aerobic 4-day respiration test (AT4) value below 10 mg O2/g dry matter, the cut-off for assessing compost stability, was obtained after 8 weeks. However, a high content of humic substances (HS), reflecting compost maturity, was obtained only after 120 days. The increase in HS content proceeded in two phases. In the first phase (45–84 day), the rate constant and the rate of HS formation were lower than in the second phase (84–120 day) (0.072 vs. 0.087 day−1, 1.97 vs. 3.06 mg C/(g organic matter·d)). All the above-mentioned indicators and the nutrient content (N, P, K, Mg, Ca) in the compost indicates that the biological stage of an MBT plant can successfully treat biowaste. This is in accordance with a circular economy and will contribute to increasing recycling rates.

Stabilization of organic municipal solid waste by composting

The article examines the process of vermicomposting of municipal organic waste. To determine the optimal composition of bio humus, various options and proportions of mixingorganic waste with soil are considered. In the course of the study, three different variations of organic waste were developed, mixed with manure: 1 — soil, paper, vegetables, fruits, wood waste, cow manure (1:0.5:1); 2 — soil, vegetables and fruits, wood waste (1:1); 3 — soil, cow manure (1:1). The results of the experiment showed that all substrates have high germination of tomato seeds. However, a mixture of soil, paper, vegetables,fruits, wood waste, cow manure increases the yield of tomatoes by 11 % compared to other experimental substrates. Vermicomposting E. was performed using E. fetida worms. This kind of worms is characterized by high yield. For vermic content, the moisture content must be at the level of 60 %. Bacteria also play an important role in vermicompost. With air humidity below 40 %, their activity decreases and stops at temperatures below 10 %.In this experiment, solid organic waste processing technology reduces the shortage of cheap organic fertilizers in the market and offers new opportunities for profit for small enterprises. The results obtained can be usedfor processing organic waste of the city on an industrial scale and applied as fertilizer in agriculture.

Stabilization of available arsenic in arsenic-calcium residue (ACR) using a developed cost-effective composite Fe-based stabilizer

In this study, FeSO4·H2O, zero valent iron (ZVI), and MnO2 were combined to develop a composite Fe-based stabilizer (CFS) for the stabilization of arsenic-calcium residue (ACR). The simplex-centroid mixture design (SCMD) method was used to model and optimize the mixture proportion. The study was concluded that the optimum combination for high As stabilization performance and low cost of stabilizer was the mixture of 65.05, 10.00 and 24.95 wt% FeSO4·H2O, ZVI and MnO2 (optimum CFS). Further stabilization tests indicated that addition of 25% optimum CFS led to a pronounced decrease in the As leaching concentration from 162 to 0.645 mg/L, lower than the Chinese regulatory limit (1.2 mg/L). XRD, SEM-EDS, FTIR and XPS were applied to reveal the stabilization mechanism of As in ACR. Overall, CFS combined with H2SO4 achieved excellent As stabilization performance through a “release-oxidation-stabilization” process. The released H+ from H2SO4 ionization and Fe(Ⅱ) hydrolysis facilitated the available As release. FeSO4·H2O and Fe0 as the sources provided Fe(Ⅱ), which activated molecular O2 to generate reactive oxygen species (ROSs). Then ROSs and MnO2 act as oxidants to drive the oxidation of As(Ⅲ) synergistically. The available As was stabilized by Fe/Mn (hydr)oxides and Fe(Ⅲ) by adsorption complexation and precipitation, and form stable amorphous Fe/Mn-As species. This study provided important insights into the design of multi-component composite stabilizer for achieving the effective stabilization of As-bearing solid wastes.

Effect of geometry and material of municipal solid waste landfills on seismic response

The stability of municipal solid waste (MSW) landfills is a significant environmental concern. The performance of landfills during earthquakes should be evaluated to ensure their stability. The geometry and material types of MSW landfills are the main factors affecting their seismic response. In this study, the individual and coupled impact of these factors is investigated using numerical analyses. Amplification factors (AFs = Accsurface/Accbase) are investigated for six common MSW landfill types, namely canyon type, hill type, side-hill types 1 and 2 and stepped-base types 1 and 2. The results show that landfill types have significantly different behaviours due to their geometry and waste material properties. For low stiffness contrasts, the stepped-base landfill type has the minimum and the hill type experiences the maximum AF, 1.74 and 3.53, respectively. However, for high stiffness contrasts, the canyon type has the minimum AF (0.46) due to the effect of damping and thickness of the waste. Therefore, the proper geometry of the MSW landfills should be designed for specific waste material properties according to the seismic response.

Influence of moisture content and leachate recirculation on oxygen consumption and waste stabilization in post aeration phase of landfill operation

Sustainable completion of municipal solid waste landfills requires post-closure care after a time when utilization of landfill gas produced from biodecomposition of organic waste be not possible/or economically feasible. Research proved that in-situ aeration is a promising approach employed for landfill aftercare. The application of post aeration operation is targeted to achieve accelerated waste stabilization to avoid long term environmental and public health impacts from landfills. In in-situ aeration operation, consumption of supplied oxygen has significant influence on biological stabilization of solid waste placed in the landfills. The consumption of oxygen is regulated by operation parameters of landfill – one of the important is presence of moisture in landfill ecosystem. This research aims to assess the influence of moisture content and leachate recirculation on the oxygen consumption during post aeration phase of landfill operation. The effect of oxygen consumption on the extent of waste stabilization achieved after experiment was also assessed. Three lab-scale landfill simulation reactors (LSRs) were used – in two of three reactors (LSR-1 and LSR-3) operation was carried out in two phases: Anaerobic and post-aeration. One reactor (LSR-2) was operated under anaerobic condition throughout the experiment and used as control. To compare the oxygen consumption, conventional landfill (CLF) conditions without excess water addition and leachate recirculation were simulated in LSR-1 and the bioreactor landfill conditions (BRLF) with excess water injection and leachate recirculation were simulated in LSR-3. In CLF 46.4% of supplied oxygen was consumed during post aeration phase while in BRLF only 0.96% of oxygen consumption was noticed. In result of higher oxygen consumption, biostabilization rate of waste in CLF was 7% higher than BRLF at the end of experiment. This study demonstrated that, in presence of low moisture in landfill ecosystem optimal air distribution can be realized which results in enhanced waste oxidization and stabilization.

Minimization and stabilization of smelting arsenic-containing hazardous wastewater and solid waste using strategy for stepwise phase-controlled and thermal-doped copper slags.

Minimization and stabilization of arsenic-containing smelting wastewater and residue is of crucial issue to resolve the arsenic contamination. Calcium arsenate is a typical precipitate produced from disposal of smelting acid wastewater. However, it suffers from poor stability and large quantity in the aqueous environment. Copper slags, as for rich-iron species materials, are disposed of in landfills or open-air tailing ponds, which are another waste material that have not been effectively utilized for reuse application. In this study, strategy for sequence of phase-controlled and thermal-doped copper slag technique was used as the efficient means of minimization and stabilization of arsenic-bearing resides. Detailed results were showed that stepwise phase precipitation significantly reduced the formation of hazardous solid waste; the total solid waste was reduced 47.0 wt% because the gypsum was separated from arsenic calcium residues through two-step methods. Subsequently, solid waste stabilization was achieved by using thermal-doped slag, and the high yield of magnetite (75.6 wt%) and fayalite (22.7 wt%) was produced from copper slags. It was proved that these iron-rich species displayed the remarkable performance to stabilize arsenic due to the formation of Fe-As-Ca-O complex; compared with the raw solid waste, the arsenic leachability was decreased from 280.75 to 1.05 mg/L via copper slag stabilization process. The immobilized arsenic content was 25.0 wt%. Overall, the proposed strategy for stepwise phase-controlled and thermal-doped copper slags was a potentially effective strategy for reducing emissions and pollution of arsenic-containing wastewater and residue.

Greenhouse gas emissions from semi-aerobic bioreactor landfills with different vent-pipe diameters.

The emission patterns of three greenhouse gasses (GHGs), viz. CH4, CO2, and N2O from landfills, were examined on a lab scale. Three simulated semi-aerobic bioreactor landfills (SABL1, SABL2, SABL3), with respective vent-pipe inner diameters (φ) of 25, 50, and 75mm, were used to investigate their effect on the greenhouse effect (GHE) during the municipal solid waste (MSW) stabilization process. We found that the vent-pipe φ influenced both MSW degradation and GHG emissions, increasing the vent-pipe φ which improved the removal of carbon and nitrogen-based pollutants. The GHG emissions were 364, 356, and 309kg CO2 equivalents per ton of MSW from the SABL2, SABL1, and SABL3, respectively, during the operation of 465days. Of the three GHGs, CH4 influenced the GHE the most, contributing 72.53%, 79.17%, and 71.42% in SABL1, SABL2, and SABL3, respectively. In the same sequence, CO2 (14.87%, 14.06%, and 21.9%) and N2O (12.6%, 6.77%, and 6.69%) were the second and third contributors to the GHE, respectively. Considering the rapidly MSW stabilization and the mitigation of GHG emissions, a vent pipe with φ of 75mm in the SABL column (φ of 800mm) was suggested. Moreover, the GHG mitigation in the SABL should be implemented by prioritizing CH4 collection and oxidation. The results provided a technical guidance for GHG mitigation in MSW management.

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.

Characterization of Variability of Unit Weight and Shear Parameters of Municipal Solid Waste

The safety and stability of municipal solid waste (MSW) slopes are governed by unit weight (γ), cohesion (c), and friction angle (ϕ) of the MSW. Variability associated with the unit weight, cohesion, and friction angle of MSW is a major problem in the design of landfills because it negatively affects the performance of the slope. Variability associated with these properties may trigger catastrophic slope failures. The reported studies on the reliability-based design of MSW landfills adopted either Gaussian or lognormal distributions based on a reasonable approximation. The limitations are apparent when a coefficient of variation (COV) is higher. The accuracy of reliability-based designs depends on the selection of best-fit continuous and extreme value distributions (such as Gumbel and Weibull) that can model a high degree of variability precisely. The present study has undertaken to propose a suitable statistical model that gives a better representation of variability by optimizing the statistical parameters. A high degree of variability associated with the unit weight, cohesion, and friction angle of MSW is also investigated. A novel approach is proposed to determine reliable continuous probability density functions (PDFs) that can be fitted to the database consisting of 184 sample points collected from the most comprehensive experimental studies reported in the literature. The best-fit PDFs are recommended by optimizing the mean and standard deviation such that errors associated with quantiles (Q­­–Q), percentiles (P–P), and cumulative distribution functions (CDFs) are as minimum as possible. This study signifies the selection of optimized PDFs for the representation of parameter variability, and it is proved that the probability of failure is either underestimated or overestimated considerably when other conventional PDFs are chosen. The recommended mean, COV, and PDF can be useful in the reliability-based design of engineered MSW landfills and for judging the performance of existing MSW slopes.

Leachate after aerobic stabilization of municipal solid waste supplemented by waste glycerine from saponification to improve biogas production during co-digestion

Co-digestion of leachate from aerobic stabilization of OFMSW (leachateOFMSW) with waste glycerine (WG) from saponification is a promising approach for municipal waste and wastewater treatment. The effect of feedstock composition on co-digestion efficiency was examined. Two feedstocks with different contents of WG (6%, 13%) were used, which affected the COD:TKN ratios in those feedstocks (60, 100). LeachateOFMSW provided nitrogen and the micro- and macroelements. In both feedstocks, the N–NH4:TKN ratio was low (0.08), indicating that the dominant form of nitrogen was organic nitrogen (Norg). Co-digestion was carried out in upflow anaerobic-sludge blanket reactors (37 ± 2 °C; OLR, 4 kg COD m−3 d−1).This process ensured highly effective COD removal (over 97%). At a feedstock COD:TKN ratio of 60, specific biogas production (SBP) was ca. 0.22 m3 kg−1 COD, and methane content, 61.6%. Increasing the COD:TKN ratio to 100 significantly increased SBP to ca. 0.36 m3 kg−1 COD, but reduced biogas quality (54.2% CH4). Although Norg had to be ammonified to ammonium because of the low N–NH4:TKN ratio in the feedstocks, the ammonium concentration in the post-processing wastewater remained low. Moreover, the low ammonium concentrations meant that the pH (8.8) did not have a toxic effect on anaerobic co-digestion (free ammonia concentrations were merely ca. 28 and 5.5 mg L−1, respectively). However, at higher feedstock COD:TKN ratios than those tested, ammonium could be exhausted, which would impede methane production. These results indicate that WG is an effective co-substrate for leachateOFMSW if an appropriate amount of WG is added to the feedstock.

Municipal solid waste management and landfilling technologies: a review

The USA, China and India are the top three producers of municipal solid waste. The composition of solid wastes varies with income: low-to-middle-income population generates mainly organic wastes, whereas high-income population produces more waste paper, metals and glasses. Management of municipal solid waste includes recycling, incineration, waste-to-energy conversion, composting or landfilling. Landfilling for solid waste disposal is preferred in many municipalities globally. Landfill sites act as ecological reactors where wastes undergo physical, chemical and biological transformations. Hence, critical factors for sustainable landfilling are landfill liners, the thickness of the soil cover, leachate collection, landfill gas recovery and flaring facilities. Here, we review the impact of landfill conditions such as construction, geometry, weather, temperature, moisture, pH, biodegradable matter and hydrogeological parameters on the generation of landfill gases and leachate. Bioreactor landfills appear as the next-generation sanitary landfills, because they augment solid waste stabilization in a time-efficient manner, as a result of controlled recirculation of leachate and gases. We discuss volume reduction, resource recovery, valorization of dumped wastes, environmental protection and site reclamation toward urban development. We present the classifications and engineered iterations of landfills, operations, mechanisms and mining.

Biological treatment of leachate from stabilization of biodegradable municipal solid waste in a sequencing batch biofilm reactor

The aim of this study was to determine the effectiveness of pollutant removal in sequencing batch biofilm reactors (with floating or submerged carriers) when treating nitrogen- and organic-rich real leachate generated during aerobic stabilization of the biodegradable municipal solid waste. A control reactor contained suspended activated sludge. The share of leachate in synthetic wastewater was 10%, which resulted in ratios of chemical oxygen demand and biochemical oxygen demand to total Kjeldahl nitrogen in the influent of ca. 11 and ca. 8.5, respectively. Regardless of whether the reactors contained carriers or not, the effectiveness of nitrification (84.2–84.3%) and of the removal of chemical oxygen demand (86.5–87.0%), biochemical oxygen demand (95.5–98.0%) and ammonium (88.9–89.3%) did not differ. However, the presence of carriers and their type determined in which phase of the cycle denitrification occurred. In the control reactor, denitrification took place during mixing phase with the effectiveness of ca. 43.2% (57.7% of the total nitrogen removal). During aeration, the oxygen content increased rapidly, thus reduced the possibility of simultaneous denitrification. In reactors with carriers, in the aeration phase, not only nitrification but also denitrification occurred. The increase in oxygen content in wastewater was slower, which could have caused dissolved oxygen gradients and anoxic zones in deeper layers of the biofilm and flocks. In the reactor with floating carriers, the effectiveness of denitrification and total nitrogen removal increased 1.23- and 1.10-times, respectively, as compared to the control reactor. The highest efficiencies (67.7% and 73.0%, respectively) were observed in the reactor with submerged carriers.