Waste Biomass Valor DOI 10.1007/s12649-017-0015-x
ORIGINAL PAPER
Assessment and Evaluation of Heavy Metals Removal from Landfill Leachate by Pleurotus ostreatus Magdalena Daria Vaverková1 · Dana Adamcová1 · Maja Radziemska2 · Stanislava Voběrková3 · Zbigniew Mazur4 · Jan Zloch1
Received: 20 April 2017 / Accepted: 5 July 2017 © Springer Science+Business Media B.V. 2017
Abstract Landfilling is a common waste disposal method worldwide, especially for municipal solid waste. Landfill leachate is a potentially polluting liquid, which may cause toxic effects on the water near landfill sites. The present study explores the potential of Pleurotus ostreatus (a macro-fungus) to remove heavy metals from landfill leachate. The objective was also to study the change of leachate toxicity before and after P. ostreatus cultivation
using Sinapis alba L. growth inhibition test. Based on the results, it can be concluded that the P. ostreatus is efficient in landfill leachate water removal of heavy metals. In all the samples the enrichment coefficient values for tested heavy metal were higher than 1.0, confirming a high level of accumulation. P. ostreatus has a good potential in real applications to remove toxic heavy metals from landfill leachate.
* Magdalena Daria Vaverková
[email protected] 1
Department of Applied and Landscape Ecology, Faculty of AgriSciences, Mendel University in Brno, Zemědělská 1, 613 00 Brno, Czech Republic
2
Department of Environmental Improvement, Faculty of Civil and Environmental Engineering, Warsaw University of Life Sciences - SGGW, Nowoursynowska 159, 02 776 Warsaw, Poland
3
Department of Chemistry and Biochemistry, Faculty of AgriSciences, Mendel University in Brno, Zemědělská 1/1665, 613 00 Brno, Czech Republic
4
Department of Environmental Chemistry, Faculty of Environmental Management and Agriculture, University of Warmia and Mazury in Olsztyn, Pl. Łódzki 4, 10‑727 Olsztyn, Poland
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Vol.:(0123456789)
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Graphical Abstract
Keywords Waste treatment · Landfill leachate · Heavy metals · Pleurotus ostreatus · Bioconcentration · Growth inhibition test
Introduction Landfills are one of those humans’ activities that are changing the fate of the natural ecosystems [1–3]. Sanitary landfilling is a widely used large-scale waste disposal method worldwide, especially for municipal solid waste (MSW) [1, 4–7]. Landfill leachate is a potentially polluting liquid, which unless returned to the environment in a carefully controlled manner may cause harmful effects on the groundwater and surface water surrounding a landfill site [7–9]. The quality of a landfill leachate reflects the content of the landfill from which it originates; hence, the contamination patterns vary greatly between different types of leachates [7, 10, 11]. Additionally, the physicochemical characteristics of leachates may span over several orders of magnitudes. The main factors contributing to the landfill leachate toxicity are ammonia, pH, heavy metals and organic compounds [11, 12]. Heavy metals contamination has become a serious problem to the environment and to human life. The environmental problems with heavy metals such as Pb, Zn, Cu, Cd and Ni are serious because they are not biodegradable and they have toxic effects on living organisms when they exceed a certain concentration [13–16]. Furthermore, some heavy metals are subjected to bioaccumulation and may pose a risk to human health when transferred to the food chain [15, 17–20]. Bioremediation is a new and competing technology, offers a low cost, albeit slower alternative to physical and chemical treatment methods and is viable in mitigating
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contamination levels for a wide range of organic and inorganic contaminants [21]. Bioremediation is limited by a number of factors such as the long treatment time and site/ contaminant specificity etc. In addition, a key inhibiting factor for commercial implementation of phytoremediation is the disposal of large quantities of contaminated biomass material that accumulate throughout the process. When contaminant concentrations in the biomass exceed specific levels, the biomass material is regarded as potentially hazardous, therefore must be stored or disposed of appropriately [21–23]. However, this problem can be solved by incorporating a thermochemical conversion of biomass to renewable energy followed by a metal(loid) recovery stage to the process is proposed [24]. In recent years, research on phytoremediation has shown the overall environmental and economic benefits from remediation. Current research trends are focusing on maximizing the use of by-products from phytoremediation process. Researchers are also exploring the use phytoremediation biomass as a renewable energy source [21, 25, 26]. In addition, the concept of moving from ‘phytoremediation’ to ‘phytomining’ to reclaim potentially valuable elements for further economic benefits is underway [21]. In order to protect the natural environment from leachates, each landfill must be properly secured [27] and the most common practice to avoid environmental risks is to pump and discharge leachate into conventional wastewater treatment plants [28, 29]. Although, new technologies and new treatment combinations are required to reach the target discharge limits [29, 30]. Among other things, metal uptake (bioaccumulation) has been proposed as an alternative method for leachate treatment. Attention has been focused on the microbial biomasses (dead or living), which can bind the heavy metals even from dilute solutions [31,
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32]. In the past few years, “macromycetes” have appeared as potential materials for the remediation of wastewater containing toxic metal ions. Macromycetes are macro-fungi that belong in the division “basidiomycota” and are characterized by the formation of visible fruiting bodies. Various basidiomycetes have shown good potential for removal of heavy metals from wastewater [32–34]. Among the groups of fungi, basidiomycetes (macromycetes) are a useful source of mycelial biomass for bioaccumulation of metal ions because of ease of cultivation, high yield and non-hazardous nature [32]. The genus Pleurotus includes 40 species [32, 35, 36], which are commonly referred to as “oyster mushrooms”. They are found both in temperate and tropical climates, and are now the second most important cultivated Table 1 Characteristic of raw landfill leachate used in experiment Parameter
Unit
Mean*
pH N–NO2− N–NO3− N P Cd Hg As Zn Cr Pb Ni EC COD Mn AOX PAU
mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mS/m mg/l µg/l µg/l
8.303 ± 2.33 0.318 ± 0.61 5.546 ± 9.70 507.417 ± 156.65 4.908 ± 1.20 0.018 ± 0.02 0.001 ± 0.00 0.043 ± 0.02 0.289 ± 0.26 0.940 ± 0.43 0.036 ± 0.03 0.343 ± 0.25 1073 ± 150.93 370 ± 95.25 1027 ± 201.29 0.411 ± 0.21
*Results are the mean of values for the years 2008–2015 and ±indicate standard deviation
mushrooms in the world [32, 37]. White-rot fungi are characterized by their unique ability to degrade and convert lignocellulosic compounds into protein-rich biomass. In addition to lignin degradation, white-rot fungi are also able to degrade a variety of structurally similar organic compounds [38]. Moreover, fungi are able to extend extracellular enzymes production through hyphal growth, thus being able to grow under stressful conditions in their environment [39]. Pleurotus ostreatus has been studied as a novel bioaccumulation of heavy metals under laboratory conditions. In a study done by Kapoor et al. (1999), P. ostreatus was chosen based on its simple growth requirements using common fermentation techniques and inexpensive medium [40, 41]. However, P. ostreatus is not yet being applied in the treatment of landfill leachate. The uptake of heavy metal ions from leachate by P. ostreatus may offer another alternative method with great efficiency [41]. An experimental investigation was conducted to explore the bioaccumulation potential of P. ostreatus as a heavy metal removal from the leachate. The objective was also to study the change of leachate toxicity before and after P. ostreatus cultivation using the Sinapis alba L. growth inhibition test.
Materials and Methods Landfill Site Description The Kuchyňky landfill is classified in the S-category for ‘other waste’, sub-category S-OO3. The area of the landfill is 70,700 m2 in five stages, with a total volume of 907,000 m3, i.e. around 1,000,000 × 103 kg of waste. The planned service life of the facility is up to 2018. The facility receives waste (in the category of ‘other waste’) from a catchment area with a population of around 75,000 residents. The annually deposited amount of waste is around 40,000 × 103 kg, of which 50% is from the communal
Fig. 1 Containers with samples of P. ostreatus before and after cultivation
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sphere [42]. The landfill contains non-hazardous waste including MSW. Leachate Sampling In the study raw and untreated leachate was collected from the pond in the sanitary landfill in Kuchyňky. Two samples (0.5 L sample) of landfill leachate were collected in sterile collection containers. The samples were packed in cool boxes (8–15 °C) and were transported to the laboratory for analysis. The Leachate was kept refrigerated at 4 °C in the dark in order to keep its characteristics constant. Leachate samples were analyzed for pH, electrical conductivity (EC), chemical oxygen demand (COD) and a series of metals (Cd, Cr, Ni, Pb, Zn, Hg). Mean values for landfill leachate (years 2008–2015) are listed in Table 1. Fungal Growth on the Leachate The pure culture of the P. ostreatus was a strain obtained from the Culture Collection of the Faculty of Forestry and Wood Technology of the Mendel University in Brno (CZ) [42]. The substrates used were: wheat straw (100 g) mixed with distilled water (200 ml) (control) and wheat straw (100 g) mixed with landfill leachate (200 ml). According to the methodology used by da Silva (2012) the straw was boiled in water for 2 h, in order to reduce some compounds, which could inhibit fungal growth and contaminants and centrifuged at 1800 rpm for 5 min to remove excess water. At the end of the procedure, once the straw reached room temperature, the inoculation with fungus spawn was performed [43]. Samples were poured into sterilized containers of high-density polyethylene (Fig. 1). Afterwards, the bags were transferred to an Ecocell incubator at 24 °C ± 2
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with complete darkness during the first 3 weeks until the substrate was entirely colonized with mycelium. The containers were closed during the process after the incubation period, holes (4 per container) of about 3 cm diameter were made (using clean knife) in the sides of the containers. During the fruiting process the temperature was about 22 °C ± 2. After the first fruiting, the containers were kept open until the appearance of new primordia. Mushrooms were harvest from the substrate when the caps got fully mature. Mushrooms were separated on mycelium and fruit and dried in an Ecocell incubator at 45 °C ± 1 for 24 h until they reached a constant weight and then homogenized in a blender to break into smaller fragments of 0.5–1 mm diameter. Separated samples were brought to the laboratory for analyses. Phytotoxicity Test of Leachate To assess the toxicity of landfill leachate before and after P. ostreatus cultivation a test organism white mustard (S. alba L.) was used. Phytotoxicity of the leachate was determined by calculating the germination index. Germination index is widely used for the assessment of phytotoxicity [4]. As well as in the study design by Ribé (2009) each leachate sample was diluted to give final leachate concentrations of 25, 50, 75 and 90%. Each concentration of the dilution series was tested with two replicate samples. The test organisms were exposed to the leachate solutions for a total of 72 h [44]. The seeds of S. alba L. were germinated in Petri dishes (Fig. 2) with a 14 cm diameter on filter paper on the bottom. The hydroponic solution (distilled water with the following chemical ingredients (mg/l): Ca(NO3)2 0.8, KH2PO4 0.2, KNO3 0.2, MgSO4·7H2O 0.2, KCl 0.2, FeSO4 0.01, pH = 5.2) with tested liquid was added into each dish, and 15 healthy looking seeds of similar size were evenly spread onto the surface of the filter paper. The Petri dishes were covered by a glass cap to prevent loss due to evaporation and were located in the dark of an Ecocell incubator (t = 24 °C). After 72 h the root length was measured [45]. Analytical Methods
Fig. 2 Petri dish with the seeds of Sinapis alba L.
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The P. ostreatus samples were analyzed for the content of heavy metals. Concentration of Cd, Cr, Ni, Pb and Zn were analyzed according to ČSN EN ISO 17294 and Hg according to AAS 06–07: ČSN 757,440. For the determination of the contents of trace elements, the samples were mineralized in nitric acid (HNO3 p.a.) with a concentration of 1.40 g/cm and 30% H 2O2 using a microwave oven (Milestone Start D, Italy). After filtration, the digested products were adjusted to 100 ml volume with deionized water. Extracts were analyzed for total metal concentrations, using flame atomic absorption spectroscopy (AAS)
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on a SpecrtAA 240FS atomic absorption spectrophotometer (VARIAN, Australia), using a Sample Introduction Pump System (SIPS). Five-point calibration was performed with standard solutions. Triplicates were carried out for each sample. Leachate samples were analyzed for pH, electrical conductivity, dissolved oxygen by multi-parameter (Model HQ30d, Hach, USA) and a series of metals (Cd, Cr, Ni, Pb, Zn, Hg). All trace metals were analyzed by SpecrtAA 240FS spectrophotometer (VARIAN, Australia). All reagents were of analytical reagent grade unless otherwise stated. Stock solutions of metals (1000 mg/L) were prepared from their nitrate salts. Ultra-pure water (Millipore System, USA) of 0.055 µS/cm resistivity was used for preparing the solutions and dilutions. All glass and polyethylene flask ware had been previously treated for 24 h in 5 mol/l HNO3 and then rinsed with ultrapure water.
Calculations and Data Analysis The analyses and the length measurements were performed using the Image Too l3.0 for Windows (UTHSCSA, San Antonio, USA). The bioassays were performed in two replicates. The percent inhibition of seed germination and root growth inhibition were calculated with the formula (Eq. 1) [46, 47]:
SG(RI) =
A−B ×1 A
(1)
where A means seed germination and root length in the control; B means seed germination and root length in the tested leachate sample [46–48]. The enrichment coefficient (EC) was calculated to assess the accumulations of metals from hydroponic solution with tested liquid (leachate) to fungus/mycelium, and it is described as the following formula [49, 50] (Eqs. 2, 3):
Table 2 Results for samples mycelium and fungus Parameter
Unit
Mycelium control
Mycelium 1
Mycelium 2
Cd Cr Ni Pb Zn Hg
mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg
0.37 0.61 1.77 0.50 22.6 0.03
0.15 3.68 1.50 3.42 28.1 0.09
0.16 2.98 6.11 1.85 9.94 0.01
Parameter
Unit
Fungus control
Fungus 1
Fungus 2
Cd Cr Ni Pb Zn Hg
mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg
2.77 0.30 1.50 0.50 97.1 0.13
0.91 0.88 1.50 0.50 111 0.13
0.28 1.27 0.93 0.46 61.9 0.07
Fig. 3 Contents of heavy metals (Cd, Cr, Ni, Pb, Hg and Zn) in the samples fungus and mycelium (mg/kg DM) (n = 3)
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Fig. 4 Results of the EC for mycelium 1–2 and fungus 1–2 (n = 3)
Fig. 5 Growth inhibition of Sinapis alba L. before (a) and after (b) P. ostreatus cultivation
EC =
EC =
Mfungus Mleachate water Mmycelium Mleachate water
(2)
(3)
where EC is the enrichment coefficient for mycelium, fungus/tested liquid system; Mfungus—is the concentration of a metal in the tissue of the fungus, mg/kg, in dry matter; Mmycelium—is the concentration of a metal in the tissue of mycelium, mg/kg, in dry matter; Mleachate water—is the total
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concentrations of a metal in leachate water where this fungus (mycelium) is grown, mg/l, in dry matter [51].
Results and Discussion Landfill leachate contaminated with heavy metals is a world-wide concern and efficient and inexpensive remediation methods are needed. Conventional methods for the removal of heavy metals include chemical precipitation and sludge separation, chemical oxidation or reduction, ion exchange, reverse osmosis, filtration, adsorption using
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activated charcoal, electrochemical treatment and evaporative recovery. However, physico-chemical techniques can be very costly, consume a lot of energy, and may cause secondary pollution [52, 53]. The present study describes the efficiency of P. ostreatus as a bioaccumulator for the removal of heavy metals from leachate water from the landfill. Laboratory experiments with P. ostreatus conducted by Baldrian (2003) showed that it was possible to adapt the fungi to higher heavy metal concentrations [38]. The fungus and mycelium samples were analyzed for their metal contents. It appears that metal concentration in different samples varies to a great extent from sample to sample. Table 2 presents the results of the analysis of heavy metals in samples of fungus and mycelium. The bioaccumulation of heavy metals in mushroom are affected by specified environmental factors i.e. metal concentration, pH, humus, age of the fruiting body and mycelia, type of enzymes and proteins produced by the mushrooms [54]. The metals necessary for fungal growth include Cu, Mn, Fe, Mo, Zn and Ni while nonessential metals include Cr, Hg, Pb, and Cd [38, 55]. White rot fungi are a major mushroom group that is known to possess tolerance to metal [56]. Results for the contents of heavy metals in the samples mycelium and fungus are presented in Figs. 3 and 4. Based on the measured values, the results of all examined samples (two samples of fungus and two samples of mycelium) were subjected to a mutual comparison. Figure 5 shows the comparison of samples of mycelium according to the parameter of heavy metals (Cd, Cr, Ni, Pb, Hg and Zn). There are differences among some of the sample values. The highest values in samples mycelium 1 and 2 reached Zn (9.94–28.1 mg/ kg DM), the second highest values were recorded for Ni (1.5–6.11 mg/kg DM) and third was Cr (2.98–3.68 mg/ kg DM). Damodaran et al. (2014) have reported that mushrooms can absorb larger concentrations of heavy metals such as Cd, Pb and Hg [57]. In addition, studies by Baldrian (2003) prove that the white rot fungi growing on wood have been found to accumulate several heavy metals Cd, Fe, Zn, and Cu from the wood into their fruit bodies [38]. Figure 4 shows the comparison of samples of fungus according to the parameter of heavy metals (Cd, Cr, Ni, Pb, Hg and Zn). The highest values in samples Fungus 1 and Fungus 2 reached Zn (61.9–111 mg/kg DM), the second highest values were recorded for Ni (0.93–1.5 mg/kg DM) and the third was Cr (0.88–1.27 mg/kg DM). The results of EC for fungus (mycelium)/leachate water are shown in Fig. 3. Malayeri et al. (2008) grouped species according to their heavy metal uptake capacities and sensitivity to metal pollution: EC
