Hydrologic Evaluation Of Landfill Performance Research Articles

Landfill cap models under simulated climate change precipitation: assessing long-term infiltration using the HELP model

The Hydrologic Evaluation of Landfill Performance (HELP) model (v 3.04) was used to assess the hydrological performance of two large-scale (~ 80 × 80 × 90 cm) laboratory-based landfill cap models. Desiccation cracking under simulated climate change precipitation (CCP) events was modelled to predict the performance of landfill caps over a 50-year period in Cumbria England, UK. Cumulative infiltration values under different climate conditions were highly sensitive to macro-pore development in the clay liner which is represented by the changing hydraulic conductivity in HELP simulations. Simulation results of cap design 1 (a clay barrier layer only) show that cumulative annual infiltration under normal precipitation (NP) and CCP events, with the initial hydraulic conductivity, ranged between 1 and 2% of the annual precipitation; however, cumulative annual infiltration was 10 to 68% when maximum (degraded) hydraulic conductivity values were used in simulations. A geosynthetic clay liner (GCL) included in cap design 2 significantly reduce cumulative infiltration.

Theory, framework, and methodology for physical lifespan prediction of hazardous waste landfills

Landfill is a predominant method for hazardous waste disposal in both developed and emerging economies due to simple disposal technology and wide applicability. The prediction of landfill lifespan during the design stage provides support for environmental management of hazardous waste landfill (HWL) and technical support for the implementation of national standards. It also provides guidance for necessary responses after the lifespan expires. At present, research on the degradation of main components or materials of HWLs has been paid much attention, however, how to predict the lifespan of HWLs is a big issue for researchers. In this study, the HWL was selected as research subject, and literature research, theoretical analysis, and model calculation, were used to establish a HWL lifespan prediction framework for the first time. Firstly, the HWL life was defined based on the functional characteristics; secondly, according to comprehensively analyzing the functional requirements, system composition, and structural characteristics of HWLs, the indicators of life termination and the thresholds were confirmed. Then, according to Failure Mode, Mechanism, and Effect Analysis (FMMEA), the failure modes of the core components affecting the lifespan of the HWLs were identified. Finally, a process simulation method (Hydrologic Evaluation of Landfill Performance, HELP) was proposed to simulate the performance degradation of the HWL, combined with the core performance parameters variation caused by the deterioration of the main functional unit. The life prediction framework was developed to increase the prediction accuracy of the performance degradation of HWLs and to provide a methodology for further research on HWL life prediction.

Modeling leachate generation: practical scenarios for municipal solid waste landfills in Poland

The idea of water balance calculations within the landfill is to determine the distribution of water input and output, and finally the volume of leachate generated. The scope of this data is essential for rational planning of water and wastewater management, and designing leachate drainage network and leachate treatment systems. The aim of this study was to assess the possible amounts of leachate generation regarding ten different scenarios of landfill sealing systems. The calculations were performed using the Hydrologic Evaluation of Landfill Performance (HELP) model. It was revealed that the greatest share among the components of water balance in the landfill has precipitation (on average 509 mm in the 5-year period of simulation), together with evapotranspiration (on average 391 mm in the 5-year period of simulation). The study shows that the minimum amount of leachate (797–803 m3/year) occurs when the best placement quality (=5) is regarded for the geomembrane installed in the bottom of the landfill. The maximum leachate generation (830 m3/year) was found for those scenarios in which only three layers of bottom sealing systems were adopted, with the worst placement quality (=1) assigned to geomembranes. The results of this study confirm that the application of multilayer sealing systems has visible impact on the reduction of leachate generation of around 33 m3/year.

Spatiotemporal evaluation of future groundwater recharge in arid and semi-arid regions under climate change scenarios

ABSTRACT In this study, the Hydrologic Evaluation of Landfill Performance (HELP3.8D) model was developed to evaluate the spatiotemporal distribution of potential groundwater recharge (GWR) in Tasuj aquifer, northwestern Iran. High-resolution future climatic data from second-generation Canadian Earth System Model (CanESM2) general circulation models (GCMs) was produced under different scenarios of Representative Concentration Pathways (RCP2.6, RCP4.5, and RCP8.5). The analysis of climate parameters demonstrated that under RCP2.6, climatic variation will be substantially similar to that of the observed period (1961–2005), while moderate and severe droughts are anticipated under scenarios RCP4.5 and RCP8.5, respectively, over 2017–2030. The projection results showed that GWR will be altered by climate change, on average, from 31 mm/year at baseline to 32 (+3%), 28.5 (−8%) and 11.5 (−63%) mm/year under the RCP2.6, RCP4.5 and RCP8.5 scenarios, respectively. This approach can be easily replicated by other researchers and could be beneficial for monitoring water security and managing groundwater resources in other catchment areas.

Comparison between prediction models and monitored data on leachate generation from a sanitary landfill in the metropolitan region of rio de janeiro, Brazil

Estimating leachate generation during a landfill lifespan is a key issue in reducing its potential risk. Hence, a useful tool is represented by empirical and computational models. In order to ratify the applicability of the Swiss Method, most applied tool in Brazil, and the Hydrologic Evaluation of Landfill Performance (HELP), most utilized in USA, the present article carried out a case study in the São Gonçalo Waste Treatment Center (CTR-SG), located in a humid subtropical climate. Firstly, climate data were collected with Brazil’s National Institute of Meteorology, and landfill structural and operational data were assembled with the company responsible for CTR-SG’ management, Foxx-Haztec, from 2014 to 2018. Subsequently, simulations were conducted on both tools, which indicated that: Swiss Method and HELP do not consider relevant variables for leachate prediction, such as: waste composition and moisture content, organic matter decomposition and dumping methods; thus, these techniques results vary mainly according to annual precipitation, landfill surface area and, for HELP, covering layer thickness. In addition, it was verified that the models forecasted approximately half of the actual volume of generated leachate. In this bias, despite the requirement of few and generally known parameters, these are not reliable tools for assertive prediction. Furthermore, it was found that the Swiss Method employs an imprecise variable, the compaction coefficient, which made pertinent the proposal of a new coefficient, suitable to tropical regions, which should be validated in other landfill scenarios.

Comparison of landfill leachate generation and pollution potentials in humid and semi-arid climates

Climate conditions e.g., rainfall water are highly affecting landfill leachate generation and characteristics. This article aims to assess leachate generation and pollution potentials from landfills in different climate conditions, e.g., humid and semi-arid regions. Leachate volumes have been estimated by hydrologic evaluation of landfill performance (HELP) model, and the main water quality parameters and heavy metals were in-situ and laboratory analysed. Results of annual leachate generation rates per one ton of waste in humid and semi-arid landfill were 0.148 and 0.079 m3 respectively. However, leachate pollutants from humid landfill showed lower concentrations comparing with semi-arid landfill. This was reflected in LPI results of 25.1 and 29.5 for both landfills, respectively. These results concluded that semi-arid leachate gave lower generation rates and higher pollution potential than humid leachate, which can be revealed to the dilution effect of high rainfall levels in humid climates.

Variability assessment of simulated recharge resulted from precipitation using different GCMs, case study: west shore of Lake Urmia, Iran

Variations associated with recharge rate prediction are studied by a comparison between the simulated recharge based on weather data generated by Long Ashton Research Station Weather Generator (LARS-WG), which is a downscaling model with spectra of global circulation models (GCMs). The study area included aquifer of Urmia Plain (West Shore of Lake Urmia) located in Iran, Middle East. The aquifer area was classified based on soil composition gradation. Hydrologic Evaluation of Landfill Performance (HELP) model and percolation into vertical column were used for 1-dimensional modelling (pseudo-2-D modelling) of the recharge of various zones of Urmia Plain. The data required for modelling of weather parameter and recharge include average daily temperature, daily rainfall, and solar radiation. The recharge modelling was performed for time periods of 2020–2040, 2041–2060, 2061–2080, and 2081–2100 and five GCMs based on the 5th report issued by Intergovernmental Panel on Climate Change (IPCC), namely, EC-EARTH, GFDL-CM3, HadGEM2, MIROC5, and MPI-ESM-MR, under RCP 8.5 and RCP 4.5 scenarios. The recharge results of periods were compared between the GCMs. This variability in recharge prediction indicated that GCMs are highly important tools for water management planning.

The spread of nitrogen compounds in an active groundwater exchange zone within a valuable natural ecosystem

The aim of the paper is to present a methodical approach for developing a hydrodynamic model of groundwater flow and transport of nitrogen compounds in the area covered by the precision farming system. The study area covers the part of the Vistula River floodplain terrace near Warsaw (Poland), in the vicinity of nature reserves: Wyspy Zawadowskie, Wyspy Świderskie and Łęgi Oborskie. The components of the water balance in the analysed area were determined using the HELP (Hydrologic Evaluation of Landfill Performance) model. In reference to the doses of mineral nitrogen used during precise fertilisation, the scenarios of the spread of nitrogen ions in the soil-water environment were detailed. The results were presented graphically in the form of hydroisohypses and isolines of nitrate and ammonium concentrations. The activity of overbank flows and the effect of the geological settings on the course of aquifer layers in the active exchange zone were taken into consideration when describing groundwater flow. This allowed us to indicate potential paths of intense nitrate migration resulting from the evolution of the fluvial environment. Moreover, “hydrogeological windows” have been identified, where contaminants can freely migrate to usable aquifer in the major groundwater basin.

Hydrological aspects of an industrial landfill

A water balance for a landfill in the South-West of Sweden has been performed. The waterbalance is based on measured values of leachate and calculated values of potentialevaporation using Penman's equation. The calculations include a period of 6 years (1995-200 I). During this period, the yearly precipitation was 6 I 0-1180 mm in the Halmstad area. Itwas concluded that the total storage of leachate in the landfill and in the ponds increased withtime. If increasing tendency will proceed then the amount of leachate generated might behigher during the next years and similar to results found in the literature. There is a need forthe more physical based model, the Hydrologic Evaluation of Landfill Performance (HELP)model, for calculation in order to take into account the top cover soils and vegetationinfluence.

Two Scenarios for Landfills Design in Special Conditions Using the HELP Model: A Case Study in Babylon Governorate, Iraq

The sound design of landfills is essential in order to protect human health and the environment (air, water, and soil). The study area, Babylon Governorate, is situated in the middle of Iraq, and is distinguished by a hot climate and shallow groundwater. The governorate did not have landfill sites that meet international criteria; in addition, the groundwater depth in Babylon Governorate is commonly shallow. Previously, the most important criteria for the study area and GIS software were used to select the best sites for locating landfills in the major cities of the governorate. In this study, the Hydrologic Evaluation of Landfill Performance (HELP 3.95D) model was applied in order to ensure that there was no leakage of the leachate that results from the waste in the selected landfill sites. It is the most commonly utilized model for landfill design, and it is used to estimate water inflow through the soil layers. For the present study, to avoid groundwater pollution by leachate from a landfill site due to the shallow groundwater depth, compacted waste was placed on the surface using two height scenarios (2 m and 4 m). This design was developed using the soil properties of the selected sites coupled with the weather parameters in Babylon Governorate (precipitation, temperature, solar, and evapotranspiration) for a 12-year period covering 2005 to 2016. The results from both of the suggested landfill designs showed an absence of leachate from the bottom liner.

COST-EFFECTIVENESS ANALYSIS OF DIFFERENT LANDFILL COVERS IN SEMIARID ZONES

In order to reduce the production of pollutants, it is most important that landfills are adapted to the climatic conditions of the area where they are located. In this sense, there are very few studies focused on how to reduce leachates from landfills in semiarid regions, which are especially sensitive to the impacts that this type of activity potentially has on water resources. The aim of this study is to identify the best type of landfill cover that reduces leachate production in semiarid regions by means of a Cost-Effectiveness Analysis (CEA). Three types of covers are evaluated: conventional multilayer, monolithic and mixed monolithic. The evaluation of the effectiveness of each alternative has been carried out with the HELP model (Hydrologic Evaluation of Landfill Performance), which allows for the estimation of the reduction of leachates. Results show that mixed monolithic cover is the most cost-effective alternative. In contrast, monolithic cover is an even worse alternative than the status quo, so its implementation may be not recommended in semiarid regions.

Reliability Based Approach for the Prediction of Leachate Head in MSW Landfills

The paper presents the reliability-based approach to assess the performance of landfill considering uncertainties associated with the hydraulic properties of various components of the system. A model domain having final cover system and municipal solid waste (MSW) layer is considered as an integrated system for the analysis. Water balance is computed using the Hydrologic Evaluation of Landfill Performance (HELP) model to construct response surfaces for the reliability analysis. The probability of accumulation of leachate head \(({{h}_{ac}})\) at the bottom of the MSW layer above an allowable head \(({{h}_{al}})\) is considered as the criterion for reliability estimates in this study. The results of the analysis are discussed in terms of the reliability index, \(\beta\). The impact of variations in (a) hydraulic characteristics of the various layers (b) defects and placement conditions of geomembrane (GM) on the system performance have been studied. The results reveal that the hydraulic conductivity of compacted clay layer (CCL) of the cover component along with the porosity and saturated hydraulic conductivity of MSW layer are the significant parameters, which influence the reliability. Further, impact of model uncertainty and parametric analysis of significant variables are conducted and the results are discussed.

Characterizing of a capillary barrier evapotranspirative cover under high precipitation conditions

Capillary barrier covers are a type of evapotranspirative (ET) cover in which the water storage capacity of an overlying finer textured soil layer is enhanced by the presence of an underlying coarser textured soil layer. The capillary barrier will fail when the overlying finer textured layer becomes sufficiently saturated, so capillary barriers generally are considered for use in arid or semi-arid areas. As a result, there have been few tests or practical applications of capillary barrier covers in humid regions. In this study, a column test was conducted at a humid site where 2361 mm precipitation occurred during a 541-day monitoring period. Water content, percolation, surface runoff and meteorological data were recorded. The water balance of the column and a breakthrough characterization of the capillary barrier were investigated. Numerical predictions using the Hydrologic Evaluation of Landfill Performance (HELP) model and the VADOSE/W model were performed. Test results showed that surface runoff during the monitoring period was 88 mm, which corresponded to 3.7 % of precipitation. Percolation was 67 mm, which equated to 2.8 % of precipitation. The majority of the precipitation (93.5 %) was evaporated back to the atmosphere. Failure of the capillary barrier occurred only when the critical volumetric water content of the overlying clay layer was exceeded. The breakthrough was caused by consecutive intense rainfall events. VADOSE/W predicted the behavior more accurately than HELP, because VADOSE/W can model the unsaturated flow behavior associated with the capillary barrier covers.

On the current state of the Hydrologic Evaluation of Landfill Performance (HELP) model

The Hydrologic Evaluation of Landfill Performance (HELP) model is the most widely applied model to calculate the water balance of cover and bottom liner systems for landfills. The paper summarizes the 30year history of the model from HELP version 1 to HELP 3.95 D and includes references to the three current and simultaneously available versions (HELP 3.07, Visual HELP 2.2, and HELP 3.95 D). A sufficient validation is an essential precondition for the use of any model in planning. The paper summarizes validation approaches for HELP 3 focused on cover systems in the literature. Furthermore, measurement results are compared to simulation results of HELP 3.95 D for (1) a test field with a compacted clay liner in the final cover of the landfill Hamburg-Georgswerder from 1988 to 1995 and (2) a test field with a 2.3m thick so-called water balance layer on the landfill Deetz near Berlin from 2004 to 2011. On the Georgswerder site actual evapotranspiration was well reproduced by HELP on the yearly average as well as in the seasonal course if precipitation data with 10% systematic measurement errors were used. However, the increase of liner leakage due to the deterioration of the clayey soil liner was not considered by the model. On the landfill Deetz HELP overestimated largely the percolation through the water balance layer resulting from an extremely wet summer due to an underestimation of the water storage in the layer and presumably also due to an underestimation of the actual evapotranspiration. Finally based on validation results and requests from the practice, plans for improving the model to a future version HELP 4 D are described.

A watershed-scale study of climate change impacts on groundwater recharge (Annapolis Valley, Nova Scotia, Canada)

The potential impacts of future climate change on the evolution of groundwater recharge are examined at a local scale for a 546-km2 watershed in eastern Canada. Recharge is estimated using the infiltration model Hydrologic Evaluation of Landfill Performance (HELP), with inputs derived from five climate runs generated by a regional climate model in combination with the A2 greenhouse gas emissions scenario. The model runs project an increase in annual recharge over the 2041–2070 period. On a seasonal basis, however, a marked decrease in recharge during the summer and a marked increase during the winter are observed. The results suggest that increased evapotranspiration resulting from higher temperatures does not offset the large increase in winter infiltration. In terms of individual water budget components, clear differences are obtained for the different climate change scenarios. Monthly recharge values are also found to be quite variable, even for a given climate scenario. These findings are compared with results from two regional-scale studies.Editor D. Koutsoyiannis; Associate editor M. BesbesCitation Rivard, C., Paniconi, C., Vigneault, H., and Chaumont, D., 2014. A watershed-scale study of climate change impacts on groundwater recharge (Annapolis Valley, Nova Scotia, Canada). Hydrological Sciences Journal, 59 (8), 1437–1456. http://dx.doi.org/10.1080/02626667.2014.887203

Transient, spatially varied groundwater recharge modeling

The objective of this work is to integrate field data and modeling tools in producing temporally and spatially varying groundwater recharge in a pilot watershed in North Okanagan, Canada. The recharge modeling is undertaken by using the Richards equation based finite element code (HYDRUS‐1D), ArcGIS™, ROSETTA, in situ observations of soil temperature and soil moisture, and a long‐term gridded climate data. The public version of HYDUS‐1D and another version with detailed freezing and thawing module are first used to simulate soil temperature, snow pack, and soil moisture over a one year experimental period. Statistical analysis of the results show both versions of HYDRUS‐1D reproduce observed variables to the same degree. After evaluating model performance using field data and ROSETTA derived soil hydraulic parameters, the HYDRUS‐1D code is coupled with ArcGIS™ to produce spatially and temporally varying recharge maps throughout the Deep Creek watershed. Temporal and spatial analysis of 25 years daily recharge results at various representative points across the study watershed reveal significant temporal and spatial variations; average recharge estimated at 77.8 ± 50.8 mm/year. Previous studies in the Okanagan Basin used Hydrologic Evaluation of Landfill Performance without any attempt of model performance evaluation, notwithstanding its inherent limitations. Thus, climate change impact results from this previous study and similar others, such as Jyrkama and Sykes (2007), need to be interpreted with caution.

Estimation of leachate from a pilot scale lysimeter

The most important component of solid waste management is long-term safe and reliable disposal of solid waste in sanitary landfills. Leachate formed in landfills needs proper management. The biodegradable portion of waste is largely responsible for the production of leachate and landfill gas. This paper presents the outcome of the research on the water management of landfill in Nepal using a designed and built pilot scale field lysimeter model. The leachate production from the lysimeter as an effect of climatological factors is assessed. The Hydrologic Evaluation of Landfill Performance (HELP) model is used to compute estimates of water balances. Simulation of the model indicates that the evapotranspiration (ET) is nearly constant and do not follow the precipitation and percolation trend. Also the evapotranspiration component in this case, is not high. This may be due to the small surface area of lysimeter and larger portion of the leachate percolated before evaporation could take place. The model has been calibrated for the local situation with the limited observed data of leachate generation from the lysimeter. However the trend of leachate generation on HELP simulation and Actual Data seem to be similar during month of October to December season, but during June to September, the trend shows higher actual percolation rate compared to the model output. This may be due to the higher value of permeability of barrier soil (in the range of 10-5 cm/s), which should be generally in the range of 10-7 cm/s or lower. The rainy season during June to September may be another reason, when soil is wet most of the time. The annual data shows that percolation is about 81-84% of precipitation amount, whereas evapotranspiration is about 15-19%. The application of the model may be a valuable tool to determine strengths and weaknesses of designing and operating of landfills in developing countries like Nepal. Kathmandu University Journal of Science, Engineering and Technology Vol. 8, No. II, December, 2012, 93-100 DOI: http://dx.doi.org/10.3126/kuset.v8i2.7331

Quantification of leachate discharged to groundwater using the water balance method and the Hydrologic Evaluation of Landfill Performance (HELP) model

Landfills are a source of groundwater pollution in Gaza Strip. This study focused on Deir Al Balah landfill, which is a unique sanitary landfill site in Gaza Strip (i.e., it has a lining system and a leachate recirculation system). The objective of this article is to assess the generated leachate quantity and percolation to the groundwater aquifer at a specific site, using the approaches of (i) the hydrologic evaluation of landfill performance model (HELP) and (ii) the water balance method (WBM). The results show that when using the HELP model, the average volume of leachate discharged from Deir Al Balah landfill during the period 1997 to 2007 was around, 6800 m3/year. Meanwhile, the average volume of leachate percolated through the clay layer was 550 m3/year, which represents around 8% of the generated leachate. Meanwhile, the WBM indicated that the average volume of leachate discharged from Deir Al Balah landfill during the same period was around 7660 m3/year--about half of which comes from the moisture content of the waste, while the remainder comes from the infiltration of precipitation and re-circulated leachate. Therefore, the estimated quantity of leachate to groundwater by these two methods was very close. However, compared with the measured leachate quantity, these results were overestimated and indicated a dangerous threat to the groundwater aquifer, as there was no separation between municipal, hazardous and industrial wastes, in the area.

Hydrologic evaluation of landfill performance (HELP) modeling in bioreactor landfill design and permitting

The practice of operating municipal solid waste landfills as bioreactor landfills has become more common over the past decade. Because simulating moisture balance and flow is more critical in such landfills than in dry landfills, researchers have developed methods to address this problem using the hydrologic evaluation of landfill performance (HELP) model. This paper discusses three methods of applying the HELP model to simulate the percolation of liquids added to landfill waste: the leachate recirculation feature (LRF), the subsurface inflow (SSI) feature, and additional rainfall to mimic liquids addition. The LRF is simple to use but may not be able to bring the landfill to bioreactor conditions. The SSI feature provides a convenient user interface for modeling liquids addition to each layer. The additional rainfall feature provides flexibility to the model, allowing users to estimate the leachate generation rate and the leachate head on bottom liner associated with daily variation in the liquids addition rate. Additionally, this paper discusses several issues that may affect the HELP model, such as the time of model simulation, layers of liquids addition, and the limitations of the HELP model itself. Based on the simulation results, it is suggested that the HELP model should be run over an extended period of time after the cessation of liquids addition in order to capture the peak leachate generation rate and the head on the liner (HOL). From the perspectives of leachate generation and the HOL, there are few differences between single-layer injection and multiple-layer injection. This paper also discusses the limitations of using the HELP model for designing and permitting bioreactor landfills.

Pumping dry: an increasing groundwater budget deficit induced by urbanization, industrialization, and climate change in an over-exploited volcanic aquifer

A methodology is proposed to improve the groundwater budget model by determining the past, present, and future recharge and discharge rates. The model is applied to an increasingly urbanized and industrialized region with drying tendencies: the Toluca Valley, Mexico. This study includes spatially variable recharge determined from the historical climate data, the climate change predictions, and the multiple parameters used in the Hydrologic Evaluation of Landfill Performance (HELP3) model. Using HELP3 a spatial discretization for the average recharge is obtained and estimated at 376 million cubic meters per year (Mm3/year). When considering climate change predictions, by 2050 the average scenario projects recharge to decrease by 15 Mm3/year (from 376 to 361 Mm3/year), and in a worst case scenario up to a maximum decrease of 88 Mm3/year (from 376 to 288 Mm3/year). Groundwater pumping has increased steadily since 1970 and is estimated at 495 Mm3/year for 2010. The current average deficit estimated for 2010 is 172 Mm3/year with average projections increasing to over 292 Mm3/year by 2050. This study of two of the most important components of the water cycle (recharge and discharge) clearly shows that the decreasing water availability in the Toluca basin is due mainly to groundwater pumping and that the current pumping rates are not sustainable. The current deficit can be considered problematic and projections based on expected water consumption and climate change reinforce the need for management of the water resources to be addressed.