Impact of different schemes for treating landfill leachate

Investigating the partitioning behavior of per- and polyfluoroalkyl substances (PFAS) during thermal landfill leachate evaporation

Thermal landfill leachate evaporator systems can reduce the volume of leachate by up to 97%, while releasing water vapor and producing residuals (volume-reduced leachate and sludge) that are managed on-site. On-site thermal evaporators offer landfill operators leachate management autonomy without being subject to increasingly stringent wastewater treatment plant requirements. However, little is known about the partitioning of PFAS within these systems, nor the extent to which PFAS may be emitted into the environment via vapor. In this study, feed leachate, residual evaporated leachate, sludge, and condensed vapor were sampled at two active full-scale thermal landfill leachate evaporators and from a laboratory-scale leachate evaporation experiment. Samples were analyzed for 91 PFAS via ultra-high pressure liquid chromatography - tandem mass spectrometry (UHPLC-MS/MS). Similar trends were observed from Evaporator 1, Evaporator 2, and the laboratory-scale evaporator; ∑PFAS were concentrated in the residual evaporated leachate during evaporation by a factor of 5.3 to 20. All condensed vapors sampled (n = 5) contained PFAS, predominantly 5:3 fluorotelomer carboxylic acid (5:3FTCA), (full-scale vapors 729 - 4087 ng/L PFAS; lab-scale vapor 61.0 ng/L PFAS). For Evaporators 1 and 2, an estimated 9 - 24% and 10%, respectively, of the PFAS mass entering the evaporators in leachate was released with vapor during the days of sample collection. '.

Utilizing sludge-based activated carbon for targeted leachate mitigation in wastewater treatment

Activated carbon (AC) based adsorbents derived from waste sludge were utilized to remediate mixed contaminants in wastewater as an integrated waste-to-resource approach promoting a paradigm shift in management of refuse sludge and wastewater. This review specifically focuses on the remediation of constituents of landfill leachate by sludge-based activated carbon (SBAC). The adsorption effectiveness of SBAC for the exclusion of leachate characters including heavy metals, phenols, dyes, phosphates, and phosphorus were explored with regard to modifiers such as pH, temperature, properties of the adsorbent including functional groups, initial doses of absorbent and adsorbate, and duration of exposure to note the impact of each parameter on the efficiency of adsorption of the sludge adsorbent. Through the works of various researchers, it was noted that the properties of the adsorbent, pH and temperature impact the working of SBACs. The pH of the adsorbent by influencing the functional groups. Temperature was expected to have a paramount effect on the adsorption efficiency of the SBACs. The importance of the regeneration and recycling of the adsorbents as well as their leachability is highlighted. Sludge based activated carbon is recommended as a timely, resource-efficient, and sustainable approach for the remediation of wastewater.

Environmental pitfalls and associated human health risks and ecological impacts from landfill leachate contaminants: Current evidence, recommended interventions and future directions

The improper management of solid waste, particularly the dumping of untreated municipal solid waste, poses a growing global challenge in both developed and developing nations. The generation of leachate is one of the significant issues that arise from this practice, and it can have harmful impacts on both the environment and public health. This paper presents an overview of the primary waste types that generate landfill leachate and their characteristics. This includes examining the distribution of waste types in landfills globally and how they have changed over time, which can provide valuable insights into potential pollutants in a given area and their trends. With a lack of specific regulations and growing concerns regarding environmental and health impacts, the paper also focuses on emerging contaminants. Furthermore, the environmental and ecological impacts of leachate, along with associated health risks, are analyzed. The potential applications of landfill leachate, suggested interventions and future directions are also discussed in the manuscript. Finally, this work addresses future research directions in landfill leachate studies, with attention, for the first time to the potentialities that artificial intelligence can offer for landfill leachate management, studies, and applications.

Assessing construction and demolition wood-derived biochar for in-situ per- and polyfluoroalkyl substance (PFAS) removal from landfill leachate

With regulations for per-and polyfluoroalkyl substances (PFAS) impending, the abundance of these chemicals of emerging concern in municipal solid waste (MSW) landfill leachate increasingly challenges landfill operators to seek on-site leachate pre-treatment options. This two-staged study explores the potential reuse of biochar derived from construction and demolition debris (CDD) wood as an in-situ PFAS sorbent for application within MSW landfill leachate collection systems. Batch leaching tests were first used to examine the feasibility of capturing PFAS from landfill leachate using two sources of CDD-wood-derived biochar. Then, columns were used to test the in-situ sorption capabilities of the same biochars under simulated landfill conditions. All leachates were characterized for pH, chemical oxygen demand, ammonia-nitrogen, and 92 PFAS. Seventeen PFAS were detected in the batch leaching experiment, and nine PFAS were detected in column leachates. In the batch leaching scenario, Biochar 1 achieved a maximum of 29% PFAS reduction compared to controls. Columns containing Biochar 1 generated leachates with PFAS concentrations 50% to 80% higher than those in control columns for the duration of the experiment. Columns containing Biochar 2 generated leachates with PFAS concentrations 44% less than controls in week 1 and similar concentrations in weeks 2, 3, and 4. In this study, PFAS removal from landfill leachate using biochar derived from CDD wood was not significant. Further research on biochar derived from CDD wood is needed before it can be recommended as an in-situ landfill leachate pre-treatment method.

Evaluating UV254 absorbance reductions in landfill leachate for municipal sewage co-treatment through timed UV/electrooxidation

Landfill leachate contains dissolved organic matter (DOM) exhibiting high ultraviolet absorbance at 254 nm (UVA₂₅₄). The UVA₂₅₄ limits leachate co-treatment with municipal sewage by hindering the downstream UV disinfection efficiency at wastewater treatment plants. Here, we alleviated the UVA₂₅₄ by timing the radiation in a UV/electrooxidation (UV/EO) process to accelerate reactive species formation. At 200 A·m^-2, the UV radiation was delayed by 10 min to accumulate 21 mg·L^-1 as Cl₂, which enhanced the initial radical formation rate by 5.25 times compared with a simultaneous UV/EO. The timed operation increased the steady-state concentrations of ClO^• by 700 times to 4.11 × 10^-14 M and reduced the leachate UVA₂₅₄ by 78.2% after 60 min. We identified that aromatic formulas with low oxygen content were susceptible to UV/EO from Fourier-transform ion cyclotron resonance mass spectrometry analysis. The toxicity of the treated leachate and generated byproducts was assessed through specific oxygen uptake rates (SOUR) and developmental assays with Platynereis dumerilii. After quenching the residual chlorine, leachate co-treatment at 3.5% v/v presented minimal toxicological risk. Our findings provide operational insights for applying UV/EO in high UVA₂₅₄ matrices such as landfill leachate.

A review on membrane concentrate management from landfill leachate treatment plants: The relevance of resource recovery to close the leachate treatment loop

Membrane filtration processes have been used to treat landfill leachate. On the other hand, closing the leachate treatment loop and finding a final destination for landfill leachate membrane concentrate (LLMC) - residual stream of membrane systems - is challenging for landfill operators. The re-introduction of LLMC into the landfill is typical; however, this approach is critical as concentrate pollutants may accumulate in the leachate treatment facility. From that, leachate concentrate management based on resource recovery rather than conventional treatment and disposal is recommended. This work comprehensively reviews the state-of-the-art of current research on LLMC management from leachate treatment plants towards a resource recovery approach. A general recovery train based on the main LLMC characteristics for implementing the best recovery scheme is presented in this context. LLMCs could be handled by producing clean water and add-value materials. This paper offers critical insights into LLMC management and highlights future research trends.

Environmental and energy performances of the Italian municipal solid waste incineration system in a life cycle perspective

The environmental and energy performances of the Italian municipal solid waste incineration (MSWI) system was investigated by a life cycle assessment approach. On average the 39 MSWIs operating in Italy in 2018 treated about 6,000,000 Mg of residual municipal solid waste (RMSW) recovering on average from 448 kWh Mg^-1 RMSW to 762 kWh Mg^-1 RMSW of electricity and from 732 kWh Mg^-1 RMSW to 1102 kWh Mg^-1 RMSW of heat. The average quantity of CO₂eq Mg^-1 RMSW emitted ranged from about 800 up to about 1000 depending on the size and on the energy recovery scheme of the facility. Avoided impacts (i.e., negative values) were detected for the kg PM_2,5eq Mg^-1 RMSW and for human health (disability-adjusted life year Mg^-1 RMSW). The determination of the hybrid primary energy index (MJ Mg^-1 RMSW) indicated that mainly large size facilities and those operating according to a power and heat energy recovery scheme are effectively able to replace other primary energies by the exploitation of the lower heating values of the RMSW.

Evaluating the impacts of leachate co-treatment on a full-scale municipal wastewater treatment plant in Canada

The objective of this study was to evaluate the impacts of leachate co-treatment on a full-scale municipal WWTPby comparing plant performance at varying levels of leachate contributions and hydraulic loadings.Leachate BOD:COD ratio was 0.08 ± 0.07 and indicated a stabilized, old matrix and concentrations of zinc, iron, aluminum, chloride and sulfate were 0.174, 38, 1.47, 1803 and 119.1 mg/L, respectively. The average volumetric leachate ratio (VLR%) was approximately 0.01% corresponding to a daily volume of 30 m³ but reaching a maximum of 270 m³(VLR% = 0.1%) and fluctuating on a daily-basis. A cluster analysis revealed 5 VLR% groupings that were used for subsequent analyses:no leachate, 0 < Low ≤ 0.001, 0.001 < Medium ≤ 0.02, 0.02 < High ≤ 0.05, 0.05 < Very high ≤ 0.2. Treated effluent concentrations of TKN, ammonia, fecal coliforms (FC),E. coli(EC), TSS and TP experienced atrend where effluent quality was improved at low and medium VLR%compared to no leachate addition, but deteriorated in high and very high VLR%.Treated effluent UVT% and EC were not statistically significantly different at varying VLR%, but FC was.Plant hydraulic had a significant impact on removal rates.Ammonia removals and nitrite concentrations improved inhigh flow conditions, whileTP, BOD and cBODremovals deteriorated. Finally,VLR%, leachate COD, TKN ammonia, chloride and arsenic had significant relationships with plant performance. Thus,for leachate with comparable age and strength, VLR% should not exceedlow to medium contributions(0 and 0.02%)during co-treatment at this WWTP.

Life Cycle Assessment of Leachate Treatment Strategies

Increasingly stringent regulations for leachate discharge call for leachate treatment plants (LTPs) to increase their treatment capacity by adopting membrane treatment processes to remove nitrogen and organics beyond conventional biological treatment processes. This study developed four common treatment strategies based on the existing operation and construction conditions of seven representative LTPs in China. We evaluated the LTPs' environmental impacts using life cycle assessment (LCA) following the International Organization for Standardization (ISO 14040 and ISO 14044). Compared with conventional secondary treatment processes, implementing high-level technologies to meet the strict standards could reduce an average of 59% of the eutrophication potential while increasing other environmental impacts resulting from both direct and indirect emissions by an average of 146%. We propose advanced technologies that integrate both midpoint and endpoint LCA results to meet stringent standards in areas sensitive to eutrophication.

Decreasing environmental impact of landfill leachate treatment by MBR, RO and EDR hybrid treatment

A prototype pilot plant testing for a novel complete treatment strategy for landfill leachate aimed to decrease its environmental impact was studied. Pre-treatment of leachate was performed by means of a membrane biore-actor (MBR) decreasing inorganic carbon concentration by 92 ± 8% and achieving N removals of 85%. Suspended solids removal in the MBR >99.9% conditioned leachate for the next membrane step. Spiral-would reverse osmosis (RO) regenerated membranes were used to treat the MBR effluent. This RO unit achieved a global recovery of 84% along with operation and rejections of >95% for most of the analyzed compounds. Since RO permeate did not meet discharge standards, promising results were obtained after a second RO pass was applied. The RO brine produced was further concentrated by an electrodialysis reversal (EDR) unit, achieving an averaged recovery of 67% throughout the operation. The average recovery of the whole pilot plant system was >90%. The reduction of global brine volume together with the use of regenerated membranes are key to the environmental impact of the process and contribute to closing the loop of the circular economy. Life Cycle Assessment (LCA), performed according to ILCD Handbook guidelines, demonstrated that proposed new treatment had lower environmental impact than conventional treatments currently used in landfill facilities. Concretely, for the nine impact categories evaluated, the proposed treatment presented an average impact reduction of 93% compared to an advanced oxidation system and an average reduction of 26% when compared to a conventional RO treatment.

Environmental, human health, and economic implications of landfill leachate treatment for per- and polyfluoroalkyl substance removal

Landfill leachate is commonly treated offsite with municipal wastewater. This offsite leachate treatment may be limited or no longer applicable due to the increasingly stringent regulations and concerns related to per- and polyfluoroalkyl substance (PFAS) discharge into the environment, resulting in development of full-scale, onsite leachate treatment facilities. To help landfills prepare for the potential shift from offsite to onsite leachate treatment for PFAS compliance, this study analyzed and compared the environmental, human health, and economic performances of a typical onsite and a typical offsite leachate treatment alternative through life cycle assessment (LCA) and life cycle cost assessment (LCCA) using a landfill site located in Zhuzhou, China as a testbed. Two distinct functional units (FUs) were investigated: 1 m³ of leachate treated and 1 g of PFAS removed. Our results show that the onsite scenario offered benefits from human health and economic perspectives, while the offsite scenario generally performed better from the environmental perspective when a leachate PFAS concentration of 150,704 ng/L was assumed. The extent of this tradeoff varied when different functional units were adopted. The onsite scenario will not be competitive from all three perspectives when PFAS concentration in the raw leachate is less than 1666 ng/L.

Factors affecting aerobic granule sludge formation in leachate treatment - a systematic review

The biological treatment of landfill leachate due to high concentration of Chemical Oxygen Demand (COD), ammonia, and other toxic compounds is so difficult. One of the leachate treatment technology is the sludge biogranulation, that containing the two aerobic and anaerobic process. The aim of this study was conducted for determining the main factors affecting aerobic granule sludge formation in leachate treatment. In this study, all related papers in international databases were evaluated including Google Scholar, Science Direct, and PubMed, Also Open Access Journal Directory from 1990 until 2020 were investigated. The keywords used included Aerobic Granule Sludge (AGS), leachate treatment, Wastewater treatment, Granular Sequential Batch Reactors (GSBR), Formation Extracellular polymeric substance (EPS). Overall, 2,658 articles were retrieved of which 71 were selected after revising the titles and abstracts. Aerobic granulation has been only lately studied and a limited number of studies have been devoted to identification aspects of the process such as the organic source, and other factor affecting on formation granules. Some factors as shear stress, settling time, and the effluent discharge site have direct effect on the efficiency of aerobic granules reactor and other factors such as divalent metal ions, dissolved oxygen concentration, the ratio of height to diameter of the reactor, temperature affecting on the granulation process. If suitable conditions provide, the aerobic granule sludge process can be useful for leachate treatment.

Cost estimation of landfill leachate treatment by reverse osmosis in a Brazilian landfill

The reverse osmosis (RO) process has been increasingly applied to landfill leachate treatment. The published literature reports several studies that investigated the technical feasibility of RO. However, information about process costs is scarce. Also, companies that run leachate treatment plants do not provide actual costs. To fill this gap, this study aimed to evaluate the treatment costs of a full-scale RO for the treatment of landfill leachate located in Rio de Janeiro State, Brazil. A procedure was proposed to estimate the capital expenses (CAPEX), operational expenses (OPEX), and specific total treatment cost, the total cost per m³ of treated leachate, of the leachate treatment by membrane process, and the results obtained are discussed. The CAPEX for this full-scale RO was estimated at MUS$ 1.413, and OPEX ranged from US$ 0.132 to US$ 0.265 m^-3 per year. The cost of leachate treatment has been estimated at US$ 8.58 m^-3 considering the operation of the RO-unit for 20 years after landfill closure.

Nanofiltration applied to the landfill leachate treatment and preliminary cost estimation

The leachate treatment by nanofiltration (NF) process has received much attention over the last two decades. Previous studies focused on the investigation of the technical feasibility of NF. However, there are a limited number of works that examined leachate treatment costs. On the other hand, in a landfill management system, the economic component is an imperative factor for the decisions of all operations. Thereby, this work aimed to investigate the technical feasibility and economic parameters involved in a full-scale NF plant for the treatment of leachate previously treated by the physicochemical process. The average quality of the pre-treated leachate was 2258 ± 230 mg L^-1 chemical oxygen demand (COD) and 821 ± 86 mg L^-1 humic substances (HS). NF was performed using a bench-scale filtration module with commercial polymeric membranes SR100 and NP030. At the end of each filtration, a cleaning protocol was applied to recover the initial membrane permeability. The concentration of recalcitrant compounds, expressed as HS, was reduced to 84 ± 8 mg L^-1 in the permeate, and COD complies with the wastewater discharge standards imposed by local legislation. The capital costs for a full-scale NF was estimated at MUS$ 0.772, and specific total cost, treated leachate per volume unit, has been estimated at US$ 8.26 m^-3.

Benchmarking leachate co-treatment strategies in municipal wastewater treatment plants under dynamic conditions and energy prices

Combined leachate treatment at municipal wastewater treatment plants (WWTPs) is applicable to a certain extent depending on the leachate composition, treatment plant configuration and its capacity. Co-treatment of leachate at WWTPs has several advantages, but due to increasingly stringent discharge standards applied in WWTPs, it has become more problematic. This study was undertaken to investigate the impact of leachate feeding strategies on effluent quality and the aeration energy costs of WWTPs. A modified version of Benchmark Simulation Model No.1 was used to develop, test and compare several leachate feeding and WWTP control strategies in the context of dynamic pollutant loads and energy prices. The results highlighted that combined leachate treatment led to a deterioration in the quality of discharged wastewater, as indicated by a 12-20% increase in effluent quality index. Additionally, it adversely affected aeration energy demand and cost of the plant by increasing them 1.7-2.3% and 0.8-2.5%, respectively. The impacts could be mitigated by adjusting leachate flow based on effluent ammonium concentrations and by using advanced process control, i.e. feedback ammonium control for dissolved oxygen regulation in aerobic reactors. The study demonstrates that modeling can be used as a valuable tool to assess the potential impacts of leachate co-treatment and develop better management strategies.

Is the policy of the European Union in waste management sustainable? An assessment of the Italian context

The sustainability of the waste management system imposed by EU legislation was assessed using the Italian context as a case study by analysing the period from the year 2007 to the year 2016. An integrated sustainability indicator (ISI) based on environmental, social and economic life cycle approach was used. Since the earlier directives the EU waste management policy was strongly oriented to the implementation of the higher levels of the hierarchy, i.e. preparation for reuse and recycling, and a contemporary ban of disposal activities and in particular of landfill. All this was stated in legal quantitative targets to be achieved within a given scheduled time, demonstrated by continuous implementation of a reliable economic, legal and political framework including, among others, penalties, economic support and extended producer responsibility. Noticeable increase of the amount of waste moved to recycling led to a decrease of main environmental burden due to kgCO₂eq and kgPeq. The same activity led to avoided impacts detected for both kgPMeq and human health (DALY). A relevant role related to these benefits was also played by the waste to energy sector. Opposite trend was found for the whole average management costs that change from about 146 €/inhabitant in 2007 to about 218 €/inhabitant in 2016. A general decrease of the ISI of about 10% was also detected indicating an increase of the overall sustainability of the system.

Stabilisation/solidification of landfill leachate concentrate and its residue obtained by partial evaporation

Landfilling of waste is inseparably linked to the production of landfill leachate, which is treated and processed by different procedures. One of the options according to technical and economic development is the application of pressure-driven membrane processes, where landfill leachate concentrate (LLC) is produced. This may be further subjected to a stabilisation/solidification process (S/S) as one of its possible processing methods that leads to limited re-introduction of undesirable substances into the landfill body. This paper presents the research of the S/S of LLC, investigates the effect of the waste/binder ratio, the influence of Portland cement substitution, the influence of the additional concentration of the concentrate by evaporation at different levels from the original LLC, and the use of an innovative special highly absorbing binder based on specifically treated fly ash for selected leachate characteristics and compressive strength of the test specimen. The S/S process in most cases met the legislative requirements for water leachate characteristics for non-hazardous waste. Additionally, the comparison of indicative expense for selected solidificate compositions and scenarios is involved. The results of the study serve as necessary basement for further development of treatment of LLC.

A sustainability assessment for use on land or wastewater treatment of the digestate from bio-waste

The sustainability of use on land or by processing in a wastewater treatment plant of the digestate from bio-waste was investigated. Sustainability was assessed following a triple bottom line approach entailing environmental, social and economic consequences. A methodology for developing an integrated sustainability indicator was also defined. Global warming and acidification were about 40 kgCO_2eq/m³ and 0.7 molcH⁺_eq/m³ and 90 kgCO_2eq/m³ and 1.1 molcH⁺_eq/m³ for wastewater treatment and use on land, respectively. The impact on human health for use on land was about 3.5 × 10^-4 (DALY), six times higher than wastewater treatment but quite negligible when compared to the DALY associated with other diseases in the same area. Costs calculated for wastewater treatment ranged from about 18 €/m³ up to 35 €/m³, about ten times higher than those related to use on land. The integrated sustainability indicator that was developed indicated higher sustainability for use on land and the relevant influence of such finding with respect to the environmental consequences.

Assessment of the ecotoxicity of phytotreatment substrate soil as landfill cover material for in-situ leachate management

Phytotreatment capping in closed landfills is a promising, cost-effective, in situ option for sustainable leachate treatment and might be synergistically coupled with energy crops to produce renewable energy (e.g.: biodiesel or bioethanol). This study proposes to use 0.30 m of soil as growing substrate for plants cultivated on the temporary cover of closed landfills. Once the leachate phytotreatment process is no longer required, 0.70 m of the same soil would be added to attain the final top cover configuration. This solution would entail saving the costs of excavation and backfilling. However, worsening of the initial soil quality due to potential contaminant transfer from the liquid to the solid matrix must be avoided because EU legislation (such as that in Italy) fixes concentration limits for contaminants in soil. In this research, samples of soil used as substrate in a lab-scale leachate phytotreatment test with sunflowers were analysed to provide chemical characterization before, during, and at the end of the experiment. The results showed that the phytotreatment activity did not increase initial contaminant concentrations. These results are reinforced by those from ecotoxicological bioassays in which Eisenia fetida (earthworms), Lepidium sativum (cress), Folsomia candida (collembola), and Caenorhabditis elegans and Steinernema carpocapsae (nematodes) were used. It was observed that, by the end of the experiment, the substrate soil did not affect the earthworms, collembola and nematode behaviour, or the growth of cress.

Effectiveness of municipal solid waste incinerators in replacing other fuels. A primary energy balance approach for the EU28

The latest European Union legislation introduced the possibility of considering high efficiency incineration of waste as a recovery operation, that is, to use waste as a means of producing energy and hence able to replace other fuels. This possibility has been further investigated by expanding the boundaries for the mass and energy balance of municipal solid waste incinerators operating in the EU28. An energetic analysis based on a hybrid primary energy (MJ Mg^-1) approach was performed also using the cumulative energy demand index. Average results showed a net hybrid primary energy >0 for those municipal solid waste incinerators recovering only electricity, indicating that no primary energies can be replaced. For those operating in combined heat and power mode, an average hybrid primary energy ranging from about -200 MJ Mg^-1 to about -4800 MJ Mg^-1 was detected for large-size municipal solid waste incineration facilities (>200,000 Mg y^-1). The value of hybrid primary energy for medium and small facilities ranged from about +3000 MJ Mg^-1 to -4000 MJ Mg^-1. Furthermore, in some operating conditions landfill had a lower hybrid primary energy than those of small-size municipal solid waste incinerators. To some degree, these results are not in agreement with the classification of municipal solid waste incinerators based on the energy efficiency formula, particularly for those recovering only electrical energy.