Abstract
To evaluate environmental impacts of solid waste landfilling, groundwater quality near the MSW landfill in a semi-arid climate of Iran (Hamedan) and its leachates were analyzed. To this aim, heavy metal concentrations, COD, BOD5, TOC, EC, NO3−, Cl−, TDS, and pH of two leachate ponds (active and closed sites) as the sources of contamination as well as the shallow groundwater of the area were measured. Monthly and seasonal monitoring program of 13 sampling points in the area were designed during the period of 2014–2016. Principal components analysis has been carried out using chemical data to deduce relationship between the samples. A special statistical approach including a main factor (age of leachate) and a subfactor (distance from the source of pollutant) was designed in order to identify the landfill role on the groundwater contamination. The physicochemical analysis of the leachate characteristics confirmed a high variation in the contaminants (i.e., organic compounds, salts, and heavy metals) related to leachate age. The BOD5/COD ratio of the active (0.73) and closed (0.77) sites ponds indicated that the leachates were in a biodegradable and unstabilized condition. The seasonal physicochemical analysis of the leachates showed that rainfall events increase the decomposition rate of the waste and affect pollutant concentration of the leachate. The proposed statistical analysis illustrated a direct relationship between the groundwater quality parameters and the leachates physicochemical characteristics.
Similar content being viewed by others
Explore related subjects
Discover the latest articles, news and stories from top researchers in related subjects.Avoid common mistakes on your manuscript.
Introduction
In Iran, such as other developing countries, approximately all produced solid waste is transported to the landfills sites. Open dumping solid wastes lead to environmental hazardous impacts. Penetrating precipitations into dumped solid waste and surface water passage through these areas result in chemical, organic, and inorganic compounds movement in the environment (Mor et al. 2006; Longe and Balogun 2010; Jhamnani and Singh 2009; Sabahi et al. 2009; Saarela 2003). Long-term impacts of landfills on the environment and human health linked to the knowledge of leachate composition (Mavakala et al. 2016). Moisture content of waste, rising water table, precipitation, and snowmelt are the principal components in leachate formation (Bhalla et al. 2013; Peng 2013). The solid waste liquid (leachate) generally spreads over surface ground and has an important environmental contamination potential (Bhalla et al. 2013).
One of the major causes of groundwater resources contamination is landfill (Fatta et al. 1999). Due to leachate percolation from landfill, the groundwater located near the landfills or dumpsites is highly polluted. Organic and inorganic constituents in leachate adversely affect the groundwater quality and make it unsuitable for domestic water supply and other uses. The leachate chemical constitution, its quantity and distance of contaminant from water sources can affect the scale of pollution (Slomczynska and Slomczynski 2004). A number of factors affect the leachate rate and its characteristics; these are inherent wastes water content and its composition, waste compaction degree, site hydrology condition, climate, and the waste age (Pantini et al. 2014). Landfill age and waste type may remarkably vary the leachate composition.
Tsarpali et al. (2012) analyzed temporal variations of the leachate composition and its toxic strength at a landfill site of Greece. The result showed the significant alterations between all of the physicochemical parameters with time. Further analysis also indicated that seasonal alterations of leachate composition were related to annual precipitation. Mavakala et al. (2016) studied leachate drained from MSW landfill in the Congo. The samples were collected during the wet and dry periods. The result demonstrated a significant temporal physicochemical variation in the leachate quality. Naveen et al. (2016) investigated the physical, chemical, and biological characteristics of a landfill leachate and water resources near the site in India. Their results indicated that the water quality was contaminated with the leachate and was not accepted for any use. Samadder et al. (2017) studied the physical and chemical parameters and heavy toxic metals of soil and groundwater in a waste dumping site of India. The result indicated the groundwater quality of the area was not suitable for potable water.
Depending on the landfill waste types (a combination of urban, industrial, and commercial waste) there are four types of pollutants in the leachate including: i) dissolved organic matters, ii) inorganic components, iii) heavy metals ions, and iv) xenobiotic organic compounds (Kjeldsen et al. 2002).
When the landfills are incorrectly secured and improperly operated, the leachate is free to flow directly from waste toward the groundwater. In these conditions, high concentrations of leachate leak into springs and wells. Hence, contaminants spread into the environment resulting in ecosystem pollution. However, this process does not stop in decommissioned landfills. Therefore, it is necessary to keep monitoring the surroundings of landfill sites.
There are very few studies on landfill leachate characteristics and its impact on groundwater quality in Iran. Thus, aim of the present study is the investigation of several physicochemical parameters along with the heavy metals in the solid waste dumping site leachate and nearby groundwater. In this study, impacts of the leachate on groundwater quality were explored at the Hamedan uncontrolled landfill site of Iran, using multivariate data analysis and an especial statistical testing. Therefore, various physicochemical parameters analyzed in the leachates (as the source of pollutant) and groundwater samples. The analysis focused on the leachate age (from active and closed sites of the landfill), distance from source of pollution and monthly meteorological condition.
Materials and methods
Study area
Hamedan municipal landfill is located in the Hamedan-Bahar plain, at a distance of 20 km from north of the city. Area of the landfill is about 2.3 km2 at latitude 34°58′17″N and longitude 48°35′50″E, located at an altitude of 1790 m from the sea level. Hamedan and its urban areas, with a population more than 0.6 million are estimated to produce about 300 ton of household garbage daily. Previous study conducted in the area shows a low thickness (in average about 5 m) of alluvial (sandy gravel with silt and clay) in the soil. The main clay minerals of the soil samples were found to be kaolinite (85%), illite (10%), and montmorillonite (5%). The alluvium deposit thickness increased (near to 30 m) toward west of the area. A shallow groundwater (about 2 m from the ground surface) with conglomerate–sandstone bedrock is located under the landfill area. In downstream of the landfill (northern and western sides), the Hamedan-Bahar aquifer depth varies from 20 to 50 m. The study area climate was semi-arid with an extremely dry condition associated with semi-hot summers and cold winters. The mean minimum and maximum air temperature are − 1.9 °C and 24.6 °C, respectively with an average rainfall of 330 mm.
The landfill construction was started in 2000 and spread over an area of about 10 ha. In 2007, it was closed (decommissioned) and a new site (active) was started over an area of about 20 ha (Fig. 1). Distance between the closed and active sites is about 750 m. As shown in Fig. 1, the closed and active sites provide leachate ponds. Absence of an appropriate engineering design and/or manipulation brought about uncontrolled leachates in these sites. These leachates are sources of contaminants such as organic compounds, microorganisms, and heavy metals, which have a large potential pollution in the environment. Nine borewells (BW1–BW9) of distance from 300 to 700 m drilled for collection of groundwater samples and its quality analysis. According to standard methods (APHA 2012) one-litter sterilized sampling bottles were used. Before sampling, the bottles were firstly washed with a detergent liquid and rinsed with distilled water. Thereafter, it was rinsed with the water samples prior to collection, to avoid any interference that may arise from using contaminated sample containers. The sample preserved using 2 ml concentrated HNO3 acid to avoid metal precipitation and brought to the laboratory for further analysis.
a Location and geological units of the study area, b Locations of the active and closed sites, leachate ponds, borewells, and the springs
Groundwater and leachates monitoring program
A monitoring program of 13 sampling points of the groundwater and leachates was designed, including borewells (BW1–BW9), springs (S1 and S2), and leachates which were selected within an area about 12 km2. Distance between leachates and the sampling points ranged 0.3–1.7 km. Monthly water sampling was preceded in 2014–2016. June–October and January–May considered as dry and rainy seasons of the area in order to analyze a relatively long temporal variation of the contaminants.
Water table fluctuation was also observed using BW1–BW9 as well as the springs (S1–S2) during 2014 and 2016. Because of topographical condition of the area, borewells BW2 and BW3 and springs S1 and S2 were under subsurface flow of the active site leachate. BW4 and BW5 are also under influence of the closed site leachate flow. BW1 is located in the upstream area, out of the landfill influence. BW6, BW7, BW8, and BW9 are located in the downstream area of the landfill site. After each sampling, the samples were immediately transported to the laboratory and stored in cold room (4 °C). The methods used for the various determinations were based on the priority to analyze parameters as prescribed by APHA (2012). All the samples were analyzed according to the internationally accepted procedures and standard methods (APHA 2012).
Water quality parameters
The groundwater samples analyses included pH, electrical conductivity (EC), total dissolved solids (TDS), chemical oxygen demand (COD), biochemical oxygen demand (BOD5), potassium (K+), chloride (Cl−), nitrate (NO3−), total organic carbon (TOC), and heavy metals. K+ were estimated by flame photometric method. Al, As, Fe, Mn, Cu, Cr, Hg, Ni, Pb, and Zn concentrations were determined by atomic absorption spectrometry. NO3− analysis was performed by Brucine method using UV spectrophotometer. Cl− was determined by titration method (silver nitrate). COD was measured by reflux titrimetric method, while BOD5 was calculated by oxygen determination and Winkler titration method. TOC was measured with infrared spectrophotometry method. Based on the recorded water table level in the sampling points (BW1–BW9) and the springs (S1 and S2), the shallow groundwater flow of landfill area was evaluated using Surfer software (version 14) and a GIS-based map.
Water Quality Index
Water Quality Index (WQI) was used in order to get an overall idea of groundwater quality in the area. WQI is one of the most effective methods to evaluate the composite influence of water quality parameters on the overall quality of water. The WHO drinking water standard was used for the calculation of WQI. Its values are classified into five categories: excellent water (WQI < 50), good water (WQI = 50–100), poor water (WQI = 100–200), very poor water (WQI = 200–300), and water unsuitable for drinking (WQI > 300) (Batabyal and Chakraborty 2015).
The WQI was calculated through three steps: i) each chemical water quality parameters (pH, TDS, K+, Cl−, NO3−, TOC, Pb, Ni, Hg, Fe, Mn, and Zn) was weighted (wi) according to its relative importance in the overall quality of water for drinking purposes. ii) A relative weight (Wi) of each chemical parameter was calculated using Eq. 1. iii) For each chemical parameter, a quality rating scale (qi) calculated using Eq. 2.
where, Wi is the relative weight; wi is the weight of each parameter; and n is the number of parameters.
where, qi is the quality rating; Ci is the concentration of each chemical parameter in each water sample in mg/l; and Si is the WHO drinking water standard for each chemical parameter in mg/l.
A sub index (SI) also determined for each chemical parameter, using Eq. 3, and finally, the WQI calculated based on Eq. 4.
where, SIi is the sub index of ith parameter; Wi is relative weight of ith parameter; qi is the rating based on concentration of ith parameter; and n is the number of the chemical parameters.
Statistical analysis
In order to assess possible relationship between data, a multivariate data analysis including the correlation matrix (CM) and principal component analysis (PCA) applied using SPSS software (Vasanthavigar et al. 2013). The statistical test (nested designs) that composed of a main factor (age of leachate) and a subfactor (distance from contaminate source) designed in order to identify the role of landfill on groundwater contamination (Marofi et al. 2015). To this aim, leachates of the closed and active sites and borewells BW2, BW3, BW4, and BW5 were used. BW2–BW3 and BW4–BW5 were under effects of active and closed site leachates, respectively. BW2, BW4 and BW3, BW5 were considered as the points with short distance (≤ 300 m) and long distance (≥ 1000 m) from the leachate ponds locations (as the contaminate sources), respectively.
Results and discussion
The characteristics of the samples from leachate ponds of the closed and active sites are presented in Tables 1 and 2. The pH values of the active and closed sites leachate ponds were 7.73 and 8 respectively. It was higher in the samples of the closed site, due to alkalinity condition and suitability of the methanogenic bacteria in older leachate pond. Similar results were obtained by Samadder et al. (2017), Abd El-Salam and Abu-Zuid (2015), Tränkler et al. (2005), Al-Yaqout and Hamoda (2003). They found that leachate samples had a slightly high pH (from normal) and remained in the range of 7–8 during the operations which indicate the short acidic phase and early methanogenic phase. The relationship between pH and decomposition stages has been stated by several authors (Bahaa-eldin et al. 2010; Olaniya et al. 1998; USEPA 2003; Vasanthi et al. 2008; Salem et al. 2008).
Average values of BOD5 in active and closed site leachates were 8634 and 9217 mg/l, respectively; when COD values were 11,774 and 11,920 mg/l, respectively. The higher COD value of the closed site leachate could be related to the old waste compression and consolidation, which retarded the solid wastes degradation. The high BOD5 value indicated that the process of stabilization in the both sites was in the initial stage with a very slow rate of decomposition. These BOD5 and COD values clearly indicated severe contamination of the site. The BOD5/COD ratio showed that the leachate were in an unstabilized and biodegradable conditions, thus require more time and favorable situations for anaerobic biodegradation. Abd El-Salam and Abu-Zuid (2015) studied the leachate originating from sanitary landfills in Alexandria (Egypt). They concluded that the leachate had BOD5 value from 9620 to 11,700 mg/l with an average rate of 10,824 mg/l. The COD values also varied between 12,850 and 16,350 mg/l with a mean of 15,629 mg/l. The BOD5/COD ratio of about 0.69 showed the leachate had a high capacity for degradation through the anaerobic phase. These results are in agreement with the current study results. Al-Yaqout and Hamoda (2003) also focused on the leachate chemical characteristics from both active and old landfills in Kuwait. The results showed that BOD5 concentrations in active site leachate ranged from 30 to 600 mg/l and in closed site leachate ranged from 210 to 345 mg/l. The BOD5/COD ratio for active site leachate ranged from 0.004 to 0.38 and for closed site leachate ranged from 0.02 to 0.04. Regadío et al. (2015) studied a 14 years old landfill in Spain and indicated that the BOD5/COD ratio of their study was 0.1, indicating a relatively stabilized leachate condition. Chofqi et al. (2004) also investigated the leachate resulting from the El Jadida municipal landfill (Morocco). They reported the leachate had the mean values of COD and BOD5 of 1000 and 60 mg/l, respectively. The result showed that the leachate was stabilized and the landfill was in the methanic phase of anaerobic degradation, based on the BOD5/COD ratio that was about 0.06. Lower BOD5/COD ratio was recorded in another study in Colombia (Olivero-Verbel et al. 2008). Results of our study were in contradiction with Monje-Ramirez and Orta de Velasquez (2004) research that was reported about a well-stabilized Mexican sanitary landfill (BOD5/COD < 0.01, COD = 5000 mg/l and BOD5 = 20 mg/l). Hassan and Ramadan (2005) noted the higher values of BOD5 (28,833 mg/l), COD (45,240 mg/l), and BOD5/COD ratio (0.63), that are similar to our research results. Chen (1996) also researched on the effect of landfill age and rainfall on the landfill leachate value in Taiwan. Concentrations of BOD5 (296 mg/l) and COD (3340 mg/l) from the study were lower than the values of the present study, that indicate the maturity condition of the leachate.
Based on the study of Bashir et al. (2009), the young leachates can be more polluted than the mature ones where BOD5 of the young and mature samples reach up to 81,000 and 4200 mg/l, respectively. Chofqi et al. (2004) revealed that the BOD5/COD ratio of young leachate reaches to a value equal to 0.85, where biological activity corresponds to the acid phase of anaerobic degradation. On the basis of Bashir et al. (2009) study, stabilized leachate of old landfills produce a relatively low COD as well as a low BOD5/COD ratio (< 0.1).
In the present study, Cl− in the active site leachate ranged from 1640 to 4200 mg/l with a mean value of 3456 mg/l. In the closed site, it also widely ranged between 14,200 and 59,000 mg/l with an average value of 31,240 mg/l. Cl− values from the reports of Regadío et al. (2015), Monje-Ramirez and Orta de Velasquez (2004), Abd El-Salam and Abu-Zuid (2015), and Bahaa-eldin et al. (2010), were 7000, 11,378, 2050, and 5680 mg/l, respectively. This vast variation in the Cl− values may be resulting from the waste type and its characteristics.
NO3− in active site leachate pond ranged from 59.2 to 525 mg/l with a mean value of 289 mg/l. In closed site leachate, it ranged from 82.61 to 129 mg/l with a mean value of 109.06 mg/l. High nitrate values indicate oxidized condition of the environment. Hassan and Ramadan (2005) indicated that anaerobic condition of landfills could be affected by rainfall and the heterogeneous mixture of waste materials. Oxidizing conditions in the landfill may cause volatilization and nitrification reactions. Enriched free ammonia-NH3 (by volatilization of the wastes material) transformed to nitrate by nitrification process and therefore, increases concentrations of nitrate. They reported that the more prevalent-reducing conditions in the landfill, resulting in nitrate reduction to ammonia and N2.
In the active site leachate pond, EC extended from 26,520 to 42,400 μS/cm with a mean value of 34,491 μS/cm. In the leachate pond of the closed site, it ranged from 58,100 to 245,550 μS/cm with a mean value of 156,348 μS/cm. Al-Yaqout and Hamoda (2003) found that EC in active site ranged from 1200 to 16,900 μS/cm and in closed landfill ranged from 6210 to 21,900 μS/cm. The mean value of TDS in the active site was 23,050 mg/l and in the closed site was 109,572 mg/l. The result of the current study is in contradiction with Abu-Daabes et al. (2013) report that indicated the old landfill site shows less EC compared with the active sites.
Heavy metals concentrations in landfill leachates
Tables 3 and 4 shows heavy metal concentration of the closed and active site leachates. It is clear that Cr had a low concentration in the both sites while Fe and Zn had high concentrations. The elevated Zn concentrations can be due to disposal of large quantities of industrial wastes (such as synthetic paints, lighting bulbs, television screen, and electrical batteries) in the landfill. Abd El-Salam and Abu-Zuid (2015) founded similar results. Lower values were reported in another study in active landfill in Kuwait, where Zn values were 0.1–0.2 mg/l and in closed landfill ranged 0.2–4.8 mg/l. High Mg2+ levels was recorded in leachates of active and closed sites (Al-Yaqout and Hamoda 2003). Waste age role on leachate characteristic was also investigated in this study. Description of chemical reactions at landfills in arid and semi-arid countries such as Iran is difficult because of different decomposition stages of wastes. Based on this result, the chemical properties of the leachate indicated a various stage of decomposition of the waste sites. In this uncontrolled landfill, the dumping sites including several layers of different age, where the older layers buried with younger wastes. This condition resulted in continuous percolation flow of young leachate through the older wastes. Therefore, characteristics of the landfill leachate may be influenced by different stabilized stages. As such, age analysis of landfill sites may not be exactly obtained by the leachates characteristics. Al-Yaqout and Hamoda (2003) obtained similar results.
The characteristics of the leachate samples collected from the active and closed sites are presented in Fig. 2. Comparison of the leachates shows that the concentration of heavy metals (except for Al and Hg) in the closed site leachate was greater than the active site leachate. Concentrations of TDS, TOC, K+, and Cl− in the active site leachate were lower than the closed site leachate except for NO3−.
Comparison between active and closed sites leachates
Monthly rainfall distribution of the sampling period is presented in Fig. 3. The seasonal physicochemical variation of the leachates is also shown in Table 5. During dry season (June–October 2014), average values of pH in the leachate ponds of the active and closed sites were 7.6 and 7.88 while during rainy season (January–May 2015) it was 7.75 and 8.06, respectively. In the rainy seasons, specifically during the first rainy event, values of all the measured parameters in the leachates were higher than other periods that may be because of rainfall percolation into dumpsites of the landfill.
Monthly rainfall distribution in the study area
A few studies focused on seasonal variation of landfill leachate characteristics, especially on metal concentrations. During the rainy season, some metal concentrations were approximately from 10 to 40 times higher than the dry period (Mavakala et al. 2016; Tsarpali et al. 2012). Based on the research reports, percolating rainwater through the waste layers is a major factor in the landfill leachate generation (Kjeldsen et al. 2002). Therefore, landfill leachate characteristics vary according to waste composition, waste age, landfilling technology, and climatic conditions (temperature and precipitation) (Kjeldsen et al. 2002). Consequently, monitoring the landfill leachate requires several samplings program, according to seasonal variation.
The characteristic of landfill leachates that were reported by some studies is given in Table 6. A wide variation indicated in the leachate composition from different sanitary landfills. These data show that age of landfill and stability degree of solid waste have a significant effect on leachate characteristics. In the both leachates of the current study (active and closed site), several parameters (e.g., EC, TDS, Cl−, K+, As, Cu, Hg, and Ni) exhibited concentrations above those that reported in the literature.
Table 7 shows the correlations matrix (CM) for the two leachates sites and the shallow groundwater of the area. A strong correlation between two variables is indicated by correlation coefficients (r) greater than 0.7, while 0.5 < r < 0.7 indicates moderate correlation, and r < 0.5 show weak correlation between two variables (Kumar et al. 2006). The result shows 57% of correlation coefficients are strong correlation, 32% are moderate correlation, and 11% are weak correlation. The high correlation coefficients show that they originate from anthropogenic influences (Kumari et al. 2013).
Groundwater contamination
The results of physical, chemical, and heavy metals analyses of groundwater samples collected from the landfill are given in Tables 8 and 9. In the present study, pH at all groundwater samples (except in BW2 and BW7) was about the normal rate (7.19–7.78). Samadder et al. (2017) reported that pH value from groundwater samples which were under a landfill effects (in India) varied from 6.14 to 8.1. Abd El-Salam and Abu-Zuid (2015) also showed that pH rate of water table samples from the sanitary landfill of Alexandria (Egypt) varied between 7.4 and 8.8. In Italy, Rapti-Caputo and Vaccaro (2006) reported the chemical characteristics of an unconfined groundwater influenced by a landfill leachate. The pH values of the groundwater samples were 7.16–7.9.
The EC data of the shallow groundwater ranged from 1080.18 to 10,875.43 μS/cm. The result showed groundwater salinity of the landfill site. EC of water at BW4, BW5, BW2, S1, and S2 were recorded as the high rates. The lower values were also recorded in the border of the landfill, which is an important indicator of the landfill effect on the groundwater quality. EC of two monitored wells near sanitary landfill in Alexandria, Egypt investigated by Abd El-Salam and Abu-Zuid (2015). They reported high EC values with means of 10,354 and 12,745 μS/cm.
TDS that indicates the general nature of water quality was ranged between 705.45 and 7504 mg/l. Its concentration was found to be remarkably high at BW4, BW5, BW2, S1, and S2. Based on TDS classification (Rabinove et al. 1958), BW4 and BW5 were considered as the moderately saline sites and S1, S2, BW2, BW3, BW6, and BW8 were slightly saline sites. This high value may be due to the percolating leachate into the shallow water table of the area.
Samadder et al. (2017) revealed that TDS concentration of groundwater near the studied landfill varied from 2400 to 7000 mg/l, which are significantly high concentrations. The higher values of TDS (2855 to 16,276 mg/l) than of our study’s result were reported by Abd El-Salam and Abu-Zuid (2015). Improperly lined landfill may lead to increased TDS in groundwater.
COD as an important water quality (of organic pollution) index shows oxygen requirement to oxidize particulate organic matter in water. In this study, COD rate in the groundwater samples varied from 30.25 to 64.71 mg/l. According to the Abd El-Salam and Abu-Zuid (2015) results, the mean BOD5 and COD concentrations from monitoring wells of the area were about 45–60 and 68–80 mg/l, respectively. They concluded that the groundwater samples of the landfill site contained little organic matter. Hassan and Ramadan (2005) also reported similar results, although conversely, Samadder et al. (2017) observed very high concentration values of BOD5 (600–5400 mg/l) and COD (3640–6520 mg/l). In comparison with measured COD rates, the low BOD5 value confirms that the landfill groundwater samples contained relatively a large amount of non-biodegradable organic matter.
Because of the existence of the cellulosic materials (paper) and vegetables in municipal solid waste, there is a high source of K+ concentration in the leachate. Hence, it can be used as an indicator of groundwater pollution caused by leachate (Ellis 1980). Based on our results, the K+ concentration in the groundwater samples varied from 2 to 233.3 mg/l. The high value recorded at BW4.
Cl− is a mobile element of landfill leachate which affects groundwater quality. Each increase in its concentration rate generally consider as groundwater contamination. Therefore, Cl− concentration used as an important tracer to verify groundwater pollution by the researchers (Loizidou and Kapetanios 1993). It ranged between 56.2 and 2730.2 mg/l in the groundwater samples. At BW4, BW5, BW2, and S1, its concentration was observed to be higher than the acceptable upper limits for potable water as proposed by WHO (250 mg/l for chloride).
The concentration of NO3− in the groundwater samples varied from 28.89 to 66.25 mg/l. At BW2, BW3, S1, S2, and BW4, it exceeds the permissible limit of human health that shows a moderately high concentration. In Malaysia, Bahaa-Eldin et al. (2010) studied the effect of a MSW landfill leachate on groundwater quality. Their results showed that the concentration of chloride (355.48 mg/l) and nitrate (10.40 mg/l) indicate that the groundwater quality was extremely affected by the migrated leachate from the landfill site.
TOC is also used as a pollution indicator of groundwater under leachate effect in the saturated or unsaturated porous media (Jones-Lee and Lee 1993). Its origin is decomposed materials that include the following: i) natural organic matter such as humic and fulvic acids, amines, and urea, ii) synthetic materials such as detergents, pesticides, fertilizers, and herbicides (Hendricks 2007). In this study, the TOC concentration ranges from 0.2 to 26.9 mg/l. In BW4 and BW5, its concentration was recorded as the highest values, respectively. In BW2 and S1 which are under the active site leachate effect, TOC concentration in groundwater ranked as the lower rates. In the downstream area, TOC was decreased significantly. Due to this result, sampling location not only is an important factor, but the landfill age also plays a considerable role on the TOC rate.
In the present study, all heavy metals concentrations of the groundwater samples showed low values as shown in Table 9 and were below the allowable limits for drinking described by WHO (2011) except for Mn in BW4 and BW2 and Fe (0.331–1.041 mg/l) which exceeded the limits (0.1 for Mn and 0.3 mg/l for Fe). Abd El-Salam and Abu-Zuid (2015) obtained similar results. The physicochemical composition of the groundwater collected during the dry and wet seasons are shown in Table 10. These data are compared with drinking water quality standard (WHO 2011).
WQI results
The WQI value and water type of the individual samples are presented in Table 11. The WQI ranges from 53.8 to 597.8 and 64.2 to 720.3 for dry and rainy seasons, respectively. The dissolved ions in groundwater affected WQI values, particularly K+, Cl−, NO3−, Zn, Fe, Ni, and Mn. High iron and chloride concentrations in the groundwater caused a high WQI value, especially during the rainy seasons. The rainy season samples reveal a higher contaminate rates (more poor quality), compared with the dry season (Table 10). This may explained by a higher contaminate concentrations such as iron, chloride, nitrate, and TDS in the rainy season samples compared with the dry season samples. The WQI values show that the quality of groundwater at some locations (BW2, BW3, S1, and S2) deteriorated in the rainy season. According to the WQI values, groundwater at BW4 in the dry and rainy seasons was found unsuitable for drinking (WQI > 300).
Treatment of the leachates
The characteristics of landfill leachate play a major role to select appropriate methods to treat before discharging to the environment. As mentioned before, disposed waste composition and its age affect the leachate composition and the contaminants concentration. Treatment of the leachate should be initiated along with the landfill operation, because in the young landfills, the biological treatment has a high efficiency on removal of biodegradable organic matter. However, while getting older, it becomes harder to remove recalcitrant compounds and consequently, a higher treatment cost is necessary (Castilhos Junior et al. 2009; Kawahigashi et al. 2014). In the case of the leachates containing a high organic material (COD > 10,000 mg/l, 0.4 < BOD5/COD < 0.8) as well a low nitrogen ammonia concentrations, the most appropriate approach is biological treatment (anaerobic and aerobic processes). However, for leachates with a high concentration of ammoniacal nitrogen and a low biodegradability, the most suitable approach is a physical–chemical process, linked with biological treatment (Pasalari et al. 2018).
In Iran, four methods that commonly used for landfill leachate treatment are: i) physicochemical methods ii) combined physical, physicochemical, and biological methods, iii) biological method, and iv) physical methods. Because of the rigorous environmental limits and existence of bio-recalcitrant elements in old leachate, most treatment methods have concentrated on physicochemical process, having ability to degrade refractory materials, and biodegradability increasing. The treatment cost data is highly variable due to differences in pretreatment technics employed prior to discharge and relevant strategies.
Factors that affect these costs include transport distance, treatment plant capacity, contaminant concentrations, pH and leachate quality characteristics, and environmental standards. Leachate treatment costs (capital and operational) may constitute between 5 and 15% of the total landfilling costs before its end of operation (closure). Aftercare period of landfill, the leachate treatment costs (capital and operational) can constitute over 50% of the total landfilling costs (Johannessen 1999).
In this research, the leachate treatment costs were compared with total investment and operation costs for the active and the closed sites leachates. It assumes that the landfill has a natural clay lining and the aerobic biological process with ammonia stripping is the relevant treatment method. Leachate treatment costs for the landfill are shown in Table 12 and Fig. 4. as shown, the leachate treatment costs in the active and closed sites constitute 15 and 58% of total landfilling costs, respectively.
leachate treatment costs compared with total landfilling costs
In order to clarify the relationship between the samples and whether there were defined groups among them, the chemical data including TDS, K+, Cl−, BOD5, TOC, NO3−, Fe, Ni, Mn of the leachate, and groundwater samples were applied to PCA. As shown in Fig. 5, first two principal components could be explained 90% of the variation in the data set and are sufficient for interpretation of the landfill. The loading graph identifies which variables have the largest effect on the PCs. The score graph shows the data structure and detects clusters, outliers, and trends. In this study, all samples are placed in the positive value of the PC1. It is observed that samples that are placed in the positive values of the PC2 are influenced by concentrations of Cl−, Ni, and Mn while samples with negative values on the PC2 are influenced by the concentration of NO3−, (Fig. 5 a, b).The results revealed the two groups are distinguished. The first group consists of closed site leachate (P2) and the borewells BW4 and BW5 and the second group composed of active site leachate (P1) and the borewells BW2 and BW3.
Multivariate analysis graphs of the data (leachate ponds and groundwater) a PCA loading graph b PCA Scores graph
Effect of leachate age and sampling distance on the water quality parameters
Result of ANOVA test for the leachates of active and closed sites and the sampling distances (borewells) is presented in Table 13. The result shows that the groundwater quality parameters were influenced by the leachate ages and the interaction of leachate ages and the sampling distances (p < 0.01).
Comparison of the means water quality parameters related to the leachate ages
Comparison of the means groundwater quality parameters (observed in BW2, BW3 and BW4, BW5) related to the leachates ages is shown in Table 14. According to these results, the maximum value of Cl−, Fe, TOC, COD, TDS, and EC was obtained in BW4 and BW5, where they were under the closed site leachate. The maximum NO3− was also obtained in BW2 and BW3, where they were under the active site leachate. However, the differences of all water quality parameters between BW2, BW3 and BW4, BW5 were not significant (p < 0.05).
Groundwater quality parameters related to the sampling distance
According to Table 15, the maximum value of the all water quality parameters was obtained in a short distance. The differences on the water quality parameters rates (except to Fe and COD) between the short and long distances were not significant (p < 0.05). However, the differences of Fe and COD between the short and long distances were significant (p < 0.05).
Groundwater quality parameters related to interaction of the leachate age effects and the sampling distances
Comparison of the means water quality parameters related to the interaction of the leachates ages effect and the sampling distance is shown in Table 16. According to these results, maximum and minimum Cl−, TOC, TDS, and EC were obtained in P2L1 and P1L2, respectively. The maximum (0.96) and minimum (0.62 mg/l) value of Fe was obtained in P2L1 and P1L2, respectively. Also, the maximum (65.93) and minimum (43.8 mg/l) value of NO3− was obtained in P1L1 and P2L2, respectively. The maximum (64.71) and minimum (30.25 mg/l) value of COD was obtained in P2L1 and P2L2, respectively. Differences of all the water quality parameters between all treatments were significant (p < 0.05).
Conclusions
This study focused on an uncontrolled landfill in a semi-arid climate of Iran. The landfill composed of a closed and active sites. The results indicated that the pollutants concentration in the leachate pond of the closed site (with older solid wastes) was more than one of the active site. This is probably due to climatic conditions (low annual precipitation and extreme dryness) of the study area that resulted in slow waste decomposition. Therefore, chemical characteristics of the leachates in semi-arid climatic region such as our study site differ significantly from those in wet climatic regions, as reported by researchers. Comparison of the average water quality parameters concentrations related to the age of waste leachates and sampling distance (using ANOVA test) shows a direct relationship between physicochemical characteristics of groundwater and the leachate ponds. Therefore a statistical testing including a main factor (age of leachate) and a subfactor (distance from the source of pollutant) was proposed to illustrate the landfill role on the groundwater quality.
References
Abd El-Salam, M. M., & Abu-Zuid, G. I. (2015). Impact of landfill leachate on the groundwater quality: a case study in Egypt. Journal of Advanced Research, 6(4), 579–586.
Abu-Daabes, M., Abu-Qdais, H., & Alsyouri, H. (2013). Assessment of heavy metals and organics in municipal solid waste leachates from landfills with different ages in Jordan. Journal of Environmental Protection, 4, 344–352.
Al-Yaqout, A. F., & Hamoda, M. F. (2003). Evaluation of landfill leachate in arid climate_a case study. Environment International, 29, 593–600.
Amirian, P., Bazrafshan, E., & Payandeh, A. (2017). Optimisation of chemical oxygen demand removal from landfill leachate by sonocatalytic degradation in the presence of cupric oxide nanoparticles. Waste Management & Research, 35, 636–646.
APHA. (2012). Standards for examination of water and waste water. American Public Health Association, America Water Works Association (22nd ed.). Washington DC: Water Environment Federation.
Bagheri, M., Bazvand, A., & Ehteshami, M. (2017). Application of artificial intelligence for the management of landfill leachate penetration into groundwater, and assessment of its environmental impacts. Journal of Cleaner Production, 149, 784–796.
Bahaa-eldin, E. A. R., Yusoff, I., Samsudin, A. R., Yaacob, W. Z. W., & Rafek, A. G. M. (2010). Deterioration of groundwater quality in the vicinity of an active open-tipping site in West Malaysia. Hydrogeology Journal, 18, 997–1006.
Bashir, M. J. K., Isa, M. H., Kutty, S. R. M., Awang, Z. B., Abdul Aziz, H., Mohajeri, S., & Farooqi, I. H. (2009). Landfill leachate treatment by electrochemical oxidation. Waste Management, 29, 2534–2541.
Batabyal, A., & Chakraborty, S. (2015). Hydrogeochemistry and water quality index in the assessment of groundwater quality for drinking uses. Water Environment Research, 87, 607–617.
Baun, D. L., & Christensen, T. H. (2004). Speciation of heavy metals in landfill leachate: a review. Waste Management & Research, 22(1), 3–23.
Bhalla, B., Saini, M., & Jha, M. (2013). Effect of age and seasonal variations on leachate characteristics of municipal solid waste landfill. International Journal of Research in Engineering & Technology, 2, 223–232.
Castilhos Junior, A. B., Fernandes, F., Lange, L. C., Lopes, D. D., Costa, R. H. R., Silva, S. M., Martins, C. L., Ferreira, C. F. A., & Moravia, W. G. (2009). Treatment of landfill leachate in lagoon systems. In L. P. Gomes (Ed.), Characterization and treatability of landfill leachates for Brazilian conditions. Rio de Janeiro: ABES (In Portuguese).
Chen, P. H. (1996). Assessment of leachates from sanitary landfills: Impact of age, rainfall, and treatment. Environment International, 22, 225–237.
Chofqi, A., Younsi, A., Lhadi, E., Mania, J., Mudry, J., & Veron, A. (2004). Environmental impact of an urban landfill on a coastal aquifer (El Jadida, Morocco). Journal of African Earth Sciences, 39, 509–516.
Ellis, J. A. (1980). Convenient parameter for tracing leachate from sanitary landfills. Water Research, 14, 1283–1287.
Fatta, D., Papadopoulos, A., & Hoizidoi, M. A. (1999). A study on the landfill leachate and its impact on the ground water quality on the greater area. Environmental Geochemistry and Health, 21, 175–190.
Grisey, E., & Aleya, L. (2016). Prolonged aerobic degradation of shredded and pre-composted municipal solid waste: report from a 21-year study of leachate quality characteristics. Environmental Science and Pollution Research, 23, 800–815.
Hajipour, A., Moghadam, N., Nosrati, M., & Shojaosadati, S. A. (2011). Aerobic thermophilic treatment of landfill leachate in a moving-bed biofilm bioreactor. Iranian Journal of Environmental Health Science & Engineering, 8, 3–14.
Hassan, A. H., & Ramadan, M. H. (2005). Assessment of sanitary landfill leachate characterizations and its impacts on groundwater at Alexandria. Journal of the Egyptian Public Health Association, 80, 27–49.
Hendricks, D. W. (2007). Water treatment unit processes: physical and chemical. Boca Raton: CRC Press.
Jhamnani, B., & Singh, S. K. (2009). Ground water contamination due to Bhalaswa landfill site in New Delhi. International Journal of Civil & Environmental Engineering, 1, 121–125.
Johannessen, L. M. (1999). Guidance note on leachate management for municipal solid waste landfills (English). Urban and local government working paper series; no. UWP 5. Washington, D.C.: The World Bank.
Jones-Lee, A., Lee, G. F. (1993) Groundwater pollution by municipal landfills: Leachate composition, detection and water quality significance. Proc. Sardinia ‘93 IV International Landfill Symposium (pp. 109–1103). Italy: Sardinia.
Kawahigashi, F., Mendes, M. B., Júnior, V. G. A., Gomes, V. H., Fernandes, F., Hirooka, E. Y., & Kuroda, E. K. (2014). Post-treatment of landfill leachate with activated carbon. Engenharia Sanitaria e Ambiental, 19, 235–244 (In Portuguese).
Kheradmand, S., Karimi-Jashni, A., & Sartaj, M. (2010). Treatment of municipal landfill leachate using a combined anaerobic digester and activated sludge system. Waste Management, 30, 1025–1031.
Kjeldsen, P., Barlaz, M. A., Rooker, A. P., Baun, A., Ledin, A., & Christensen, T. H. (2002). Present and long-term composition of MSW landfill leachate: A review. Critical Reviews in Environmental Science & Technology, 32, 297–336.
Kumar, M., Ramanathan, A., Rao, M. S., & Kumar, B. (2006). Identification and evaluation of hydrogeochemical processes in the groundwater environment of Delhi, India. Environmental Geology, 50, 1025–1039.
Kumari, M., Tripathi, S., Pathak, V., & Tripathi, B. D. (2013). Chemometric characterization of river water quality. Environmental Monitoring and Assessment, 185, 3081–3092.
Loizidou, M., & Kapetanios, E. (1993). Effect of leachate from landfills on underground water quality. Science of the Total Environment, 128, 69–81.
Longe, E. O., & Balogun, M. R. (2010). Groundwater quality assessment near a municipal landfill, Lagos, Nigeria. Research Journal of Applied Sciences, Engineering and Technology, 2, 39–44.
Marofi, S., Shakarami, M., Rahimi, G., & Ershadfath, F. (2015). Effect of wastewater and compost on leaching nutrients of soil column under basil cultivation. Agricultural Water Management, 158, 266–276.
Mavakala, B. K., le Faucheur, S., Mulaji, C. K., Laffite, A., Devarajan, N., Biey, E. M., Giuliani, G., Otamonga, J. P., Kabatusuila, P., Mpiana, P. T., & Poté, J. (2016). Leachates draining from controlled municipal solid waste landfill: detailed geochemical characterization and toxicity tests. Waste Management, 55, 238–248.
Monje-Ramirez, I., & Orta de Velasquez, M. T. (2004). Removal and transformation of recalcitrant organic matter from stabilized saline landfill leachates by coagulation–ozonation coupling processes. Water Research, 38, 2359–2367.
Mor, S., Ravindra, K., Dahiya, R. P., & Chandra, A. (2006). Leachate characterization and assessment of groundwater pollution near municipal solid waste landfill site. Environmental Monitoring and Assessment, 118, 435–456.
Naveen, B. P., Mahapatra, D. M., Sitharam, T. G., Sivapullaiah, P. V., & Ramachandra, T. V. (2016). Physico-chemical and biological characterization of urban municipal landfill leachate. Environmental Pollution, 220, 1–12.
Olaniya, M. S., Sur, M. S., Bhide, A. D., & Swarnakar, S. N. (1998). Heavy metal pollution of agricultural soil and vegetation due to application of municipal solid waste: a case study. Indian Journal of Environmental Health, 40(2), 160–168.
Olivero-Verbel, J., Padilla-Bottet, C., & De la Rosa, O. (2008). Relationships between physicochemical parameters and the toxicity of leachates from a municipal solid waste landfill. Ecotoxicology and Environmental Safety, 70, 294–299.
Pantini, S., Verginelli, I., & Lombardi, F. (2014). A new screening model for leachate production assessment at landfill sites. International journal of Environmental Science and Technology, 11(6), 1503–1516.
Pasalari, H., Farzadkia, M., Gholami, M., et al. (2018). Management of landfill leachate in Iran: valorization, characteristics, and environmental approaches. Environmental Chemistry Letters, 1–14.
Peng, Y. (2013). Perspectives on technology for landfill leachate treatment. Arabian Journal of Chemistry, 10, S2567–S2574.
Pirsaheb, M., Azizi, E., Almasi, A., et al. (2015). Evaluation of the efficiency of the electrochemical process in removal of COD and NH4–N from landfill leachate. Desalination and Water Treatment, 57, 1–8.
Rabinove, C. J., LongFord, R. H., & BrookHart, J. W. (1958). Saline water resources of North Dakota. United States Geological Survey, Water Supply, 1428, 72p.
Rapti-Caputo, D., & Vaccaro, C. (2006). Geochemical evidences of landfill leachate in groundwater. Engineering Geology, 85, 111–121.
Rasool, M. A., Tavakoli, B., Chaibakhsh, N., Pendashteh, A. R., & Mirroshandel, A. S. (2016). Use of a plant based coagulant in coagulation–ozonation combined treatment of leachate from a waste dumping site. Ecological Engineering, 90, 431–437.
Regadío, M., Ana, I. R., Rodríguez-Rastrero, M., & Cuevas, J. (2015). Containment and attenuating layers: an affordable strategy that preserves soil and water from landfill pollution. Waste Management, 46, 408–419.
Robinson, H., & Maris, P. (1985). The treatment of leachates from domestic waste in landfill sites. Water Pollution Control Federation, 57(1), 30–38.
Saarela, J. (2003). Pilot investigations of surface parts of three closed landfills and factors affecting them. Environmental Monitoring and Assessment, 84, 183–192.
Sabahi, E. A., Rahim, A., Wan Zuhairi, W. Y., Nozaily, F. A., & Alshaebi, F. (2009). The characteristics of leachate and ground water pollution at municipal waste solid landfill of Ibb city, Yemen. American Journal of Environmental Sciences, 5, 256–266.
Safari, E., & Bidhendi, G. N. (2007). Removal of manganese and zinc from Kahrizak landfill leachate using daily cover soil and lime. Waste Management, 27, 1551–1556.
Salem, Z., Hamouri, K., Djemaa, R., & Allia, K. (2008). Evaluation of landfill leachate pollution and treatment. Desalination, 220(1), 108–114.
Samadder, S. R., Prabhakar, R., Khana, D., Kishan, D., & Chauhan, M. S. (2017). Analysis of the contaminants released from municipal solid waste landfill site: A case study. Science of the Total Environment, 580, 593–601.
Slomczynska, B., & Slomczynski, T. (2004). Physico-chemical and toxicological characteristics of leachates from MSW landfills. Polish Journal of Environmental Studies, 13, 627–637.
Tahiri, A. A., Laziri, F., Yachaoui, Y., El Allaoui, A., & Tahiri, A. H. (2017). Heavy metals leached from the waste from the landfill in the city of Meknes, and their impact on groundwater. Journal of Materials and Environmental Sciences, 8, 1004–1014.
Tränkler, J., Visvanathan, C., Kuruparan, P., & Tubtimthai, O. (2005). Influence of tropical seasonal variations on landfill leachate characteristics-results from lysimeter studies. Waste Management, 25, 1013–1020.
Tsarpali, V., Kamilari, M., & Dailianis, S. (2012). Seasonal alterations of landfill leachate composition and toxic potency in semi-arid regions. Journal of Hazardous Materials, 233–234, 163–171.
USEPA. (2003). Drinking water quality standards. Waterford: Edstrom Industries.
Vasanthavigar, M., Srinivasamoorthy, K., & Prasanna, M. V. (2013). Identification of groundwater contamination zones and its sources by using multivariate statistical approach in Thirumanimuthar subbasin, Tamil Nadu, India. Environmental Earth Science, 68, 1783–1795.
Vasanthi, P., Kaliappan, S., & Srinivasaraghavan, R. (2008). Impact of poor solid waste management on ground water. Environmental Monitoring and Assessment, 143, 227–238.
Vilar, V. J. P., Rocha, E. M. R., Mota, F. S., Fonseca, A., Saraiva, I., & Boaventura, R. A. R. (2011). Treatment of a sanitary landfill leachate using combined solar photo-Fenton and biological immobilized biomass reactor at a pilot scale. Water Research, 45, 2647–2658.
Weng, H.-X., Zhang, F., Zhu, Y.-M., Qin, Y.-C., Ji, Z.-Q., & Cheng, C. (2010). Treatment of leachate from domestic landfills with three-stage physicochemical and biochemical technology. Environmental Earth Sciences, 64, 1675–1681.
WHO. (2011). Guidelines for drinking-water quality, 4th edition. Geneva 27. In Switzerland.
Xiaoli, C., Shimaoka, T., Xianyan, C., Qiang, G., & Youcai, Z. (2007). Characteristics and mobility of heavy metals in an MSW landfill: implications in risk assessment and reclamation. Journal of Hazardous Materials, 144, 485–491.
Zloch, J., Vaverková, M. D., Adamcová, D., Radziemska, M., Vyhnánek, T., Trojan, V., Đorđević, B., & Brtnický, M. (2018). Seasonal changes and toxic potency of landfill leachate for white mustard (Sinapis alba L.). Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis, 66, 235–242.
Acknowledgements
This study was partially supported by Hamedan Regional Water Authority. The authors wish to express their gratitude for their assistance.
Author information
Authors and Affiliations
Corresponding author
Additional information
Publisher’s note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
About this article
Cite this article
Vahabian, M., Hassanzadeh, Y. & Marofi, S. Assessment of landfill leachate in semi-arid climate and its impact on the groundwater quality case study: Hamedan, Iran. Environ Monit Assess 191, 109 (2019). https://doi.org/10.1007/s10661-019-7215-8
Received:
Accepted:
Published:
DOI: https://doi.org/10.1007/s10661-019-7215-8