**1. Introduction**

With the rapid increase in population and urbanization, solid waste landfills are emerg‐ ing as a major problematic urban infrastructure. Urban solid waste can be stored both underground and aboveground, but each creates environmental and human health risks.

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Those involved in solid waste management continue to search for ways to reduce these risks. Landfills are required to use synthetic and/or soil liners of site-specific thickness and hydraulic conductivity as well as various other safeguards to isolate the waste from nearby groundwater, air and soil [1].

Waste landfill management is an important concern, as negative effects are often caused by discontinuation of traditional management practices. The adverse effects on flora and fauna resulting from changes inland use patterns have been described by landscape ecologists throughout Europe [2], and have been reported by several authors for Mediterranean land‐ scapes such as the montado and agro-silvopastoral systems in Portugal [3], the Tuscany region of Italy [4], the mountainous landscapes in northern Italy [5], and the shrub and woodland areas in Israel and other Mediterranean countries [6]. Aside from imparting aesthetic value, natural or planted vegetation on a landfill has an important role in erosion control and removal of contaminants, and may also be used in leaching treatment. Although phytoremediation of various contaminants has been investigated, the practical application of this technology to the remediation and rehabilitation of municipal solid waste landfill sites has not been sufficiently studied [7].

Areas of bare soil, where vegetation is not present, are open to erosion. The soil of landfills is not generally suitable for growing plants, and protective soil cover is needed. Additionally, planting will have no effect on erosion in the short term without the selection of optimal plants. In our previous study, we examined species best suited for this purpose and found that certain plants could be used for remediation of cover soil [7]. Other studies have found approximately 120 plant species, consisting of trees, shrubs, and grasses, that are appropriate for establishing plant cover in different types of vegetative amelioration [8, 9]. One of the most common plant mixtures used in rehabilitation is grasses and legumes. Grasses are regarded as most appro‐ priate for protection from soil erosion, while legumes grow rapidly, particularly in soils with a low concentration of nitrogen [8, 10, 11].

Leachate is a major issue in landfills and surrounding areas, as it is very harmful to the environment. Leachate interacts with soil and ground and surface waters, and contains high degrees of organic and inorganic pollutants. It is the longest-lasting emission from landfills [12], and therefore the liquid waste causes considerable pollution [13]. One of the most promising methods for mitigating these effects is the use of leachate water for irrigation of vegetation planted on landfills. Research has shown that this technique enables the reuse of polluted water as a result of the remediating effects of plants and microorganisms. The landfill cover soil was irrigated with leachate for maintaining appropriate moisture content for methane oxidation reaction. Municipal solid waste compost was found to be an effective landfill cover material for controlling landfill gas emissions, exhibiting the highest methane oxidation rate [14]. Soil is a habitat for a great number of organisms, but at the same time, it is perhaps the most endangered component of our environment, and can be altered by the different pollutants arising from human activity [15, 16]. Prevention of soil pollution and its harmful effects, however, requires some basic knowledge of the soil characteristics. Soil has a very complex structure and exhibits greatly different properties among various regions [17].

Trace elements such as metals in contaminated soil also have negative impacts on human health and the environment, and thus their removal is often required. Metals can be stabilized by soil amendments to increase metal adsorption or alter their chemical form [18]. There have been few experiments comparing different in situ remediation treatments under similar environmental conditions or investigating whether all soil components or properties (e.g., microbes, soil fauna, plants, soil retention and colloid stability) are similarly protected. As part of the EU FP7 Greenland project (reference number 266124), we compared the impact of novel soil amendments and their combinations with traditional materials with regard to metal solubility and the response of plants, soil organisms and microbial activity [19]. Soil metal bioavailability is often cited as a limiting factor in phytoextraction (or phytomining). Bacterial metabolites such as organic acids, siderophores, and bio surfactants have been shown to mobilize metals, and the use of microbial inoculants to improve metal extraction has been proposed by several authors [20].

Those involved in solid waste management continue to search for ways to reduce these risks. Landfills are required to use synthetic and/or soil liners of site-specific thickness and hydraulic conductivity as well as various other safeguards to isolate the waste from nearby

Waste landfill management is an important concern, as negative effects are often caused by discontinuation of traditional management practices. The adverse effects on flora and fauna resulting from changes inland use patterns have been described by landscape ecologists throughout Europe [2], and have been reported by several authors for Mediterranean land‐ scapes such as the montado and agro-silvopastoral systems in Portugal [3], the Tuscany region of Italy [4], the mountainous landscapes in northern Italy [5], and the shrub and woodland areas in Israel and other Mediterranean countries [6]. Aside from imparting aesthetic value, natural or planted vegetation on a landfill has an important role in erosion control and removal of contaminants, and may also be used in leaching treatment. Although phytoremediation of various contaminants has been investigated, the practical application of this technology to the remediation and rehabilitation of municipal solid waste landfill sites has not been sufficiently

Areas of bare soil, where vegetation is not present, are open to erosion. The soil of landfills is not generally suitable for growing plants, and protective soil cover is needed. Additionally, planting will have no effect on erosion in the short term without the selection of optimal plants. In our previous study, we examined species best suited for this purpose and found that certain plants could be used for remediation of cover soil [7]. Other studies have found approximately 120 plant species, consisting of trees, shrubs, and grasses, that are appropriate for establishing plant cover in different types of vegetative amelioration [8, 9]. One of the most common plant mixtures used in rehabilitation is grasses and legumes. Grasses are regarded as most appro‐ priate for protection from soil erosion, while legumes grow rapidly, particularly in soils with

Leachate is a major issue in landfills and surrounding areas, as it is very harmful to the environment. Leachate interacts with soil and ground and surface waters, and contains high degrees of organic and inorganic pollutants. It is the longest-lasting emission from landfills [12], and therefore the liquid waste causes considerable pollution [13]. One of the most promising methods for mitigating these effects is the use of leachate water for irrigation of vegetation planted on landfills. Research has shown that this technique enables the reuse of polluted water as a result of the remediating effects of plants and microorganisms. The landfill cover soil was irrigated with leachate for maintaining appropriate moisture content for methane oxidation reaction. Municipal solid waste compost was found to be an effective landfill cover material for controlling landfill gas emissions, exhibiting the highest methane oxidation rate [14]. Soil is a habitat for a great number of organisms, but at the same time, it is perhaps the most endangered component of our environment, and can be altered by the different pollutants arising from human activity [15, 16]. Prevention of soil pollution and its harmful effects, however, requires some basic knowledge of the soil characteristics. Soil has a very complex structure and exhibits greatly different properties among various regions [17].

groundwater, air and soil [1].

228 Advances in Bioremediation of Wastewater and Polluted Soil

a low concentration of nitrogen [8, 10, 11].

studied [7].

Plants, in combination with their associated micro flora, have a prominent role in remediating soils contaminated with organic pollutants such as petroleum hydrocarbons. Several plantassociated bacteria have the capacity to degrade hydrocarbons, promote plant growth and alleviate plant stress. In many cases, this is due to the fact that inoculant strains may not adequately interact with or colonize plants used for phytoremediation and/or cannot compete with the resident micro flora under certain environmental conditions. However, colonization and the competitive ability of inoculants trains is generally rarely addressed, despite the fact that an understanding of the efficiency of inoculation is essential [21].

In cases when phytoremediation is successfully performed, target pollutants play roles such as enhancing bioavailability by altering the flora or microbial community structure, either through stimulation of existing microbial degraders or through the introduction and estab‐ lishment of new organisms [22]. For example, surface flow wetlands have proved to be successful in removing selenium (Se) from wastewater. Researchers also reported that constructed wetlands can remove up to 90 % of Se contained in the inflow of oil refinery waste water and up to 80 % from agricultural irrigation drainage [23].

As a result of manmade activities, large areas of soil are contaminated with multiple pollutants, and these high concentrations of pollutants have toxic effects on the environment. Plant microorganism-based technologies can supply a strategy for soil remediation and for the restoration of soil functionality after treatment [24].Soil conditions such as pH, the composition of organic matter and vegetation, and supplements influence soil micronutrient dynamics [25]. Soils may become polluted with high concentrations of heavy metals that are naturally produced by the melting of ore or artificially produced by industrial activities [26, 27].Among pollutants, heavy metals exceeding specific thresholds have been the subject of particular attention because of their long-standing toxicity. Their mobility in the ecosystem and transition through food chains are key issues in environment research [28–33]. Organic amendments may influence soil properties for years after application, as only a fraction of the organic material may be initially degraded or become available to plants and soil microorganisms [34, 35].

Issues with heavy metal contamination at landfill sites have recently been noted. Landfill remediation is generally performed by restoration of the site through the creation of a low hill planted with plants indigenous to the area. The aim of the current study was to search for ways to use leachate water from solid waste landfill sites for irrigation of plant species that grow wild under normal climate conditions. The study focuses on the plant species *Alcea rosea* (hollyhock)*, Cynodon dactylon* (Bermuda grass) and *Melilotus officinalis* (yellow melilot). During the 2 years of the study, plants were irrigated with tap and leachate water under drought conditions. The wild plant species were determined in the hollyhock, Bermuda grass and yellow melilot parcels. After the experiment, populations of *E. coli*, total coliforms and fecal coliform bacteria in the soil samples were analyzed. Results showed that using leachate water to cultivate various types of plants affected total and fecal coliform populations in the soil.
