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M. Darwish et al.
9.1 Introduction
Nitrogen is considered as a key nutrient that is necessary for all forms of life. It is
a basic element for many vital industries such as foods and fertilizers. On the other
hand, N is one of the most harmful pollutants for humans and aquatic environment.
Disposal of high N loads to natural water bodies promotes eutrophication, which
results in oxygen depletion and toxicity to aquatic life. Ammonium nitrogen represents more than 80% of total nitrogen in wastewater (Gunay et al. 2008a; Zhang
et al. 2012), which means that recovery of NH 4 −N should be highly considered.
Landfilling is the most widely applied method for solid wastes disposal. Globally,
about 60% of generated solid wastes are disposed in landfills. Corresponding to pollutants migration into the environment, landfills produce two main hazardous wastes:
the biogas (formed by the fermentation of organic matter), a source of air pollution;
and the leachate (generated by the contact of percolated water with the decomposing wastes), a source of groundwater and soil contamination. Landfill leachate is
one of the hazardous wastewaters that contains high concentrations of NH 4 −N (Li
et al. 1999). In their study, Alslaibi et al. (2011) revealed that NH 4 −N concentration
(>8 mg/L) was higher than natural concentration (0.2 mg/L) in groundwater, near
landfill sites in Gaza Strip, Palestine. In Malaysia as well, it has been found that
LL pollutes some rivers and increases the concentration of NH 4 −N to above the
Interim National Water Quality Standard (INWQS) Class IIA/IIB river for Malaysia
(>0.3 mg/L) (Yusof et al. 2009). These studies showed obviously the high risk of
disposing LL without a proper treatment of NH 4 −N. For these reasons, recovery of
NH 4 −N from LL is crucial for environmental protection.
9.2 Characteristics of Landfill Leachate
Fundamentally, physical and chemical characteristics of LL are strongly influenced
by the composition of wastes, climate conditions and landfill age. Age of landfill is
the driving factor, and accordingly, LL can be classified into three main types: young,
medium-aged and old (mature). Besides, LL is usually characterized by the basic
parameters, which are pH, COD, BOD, NH 4 −N, total Kjeldahl nitrogen (TKN),
heavy metals and SS.
Table 9.1 presents the main characteristics of LL in some literatures. It can be
noticed that the age of landfill, and hence the degree of wastes stabilization, has a
significant effect on LL characteristics. It is also important to mention that NH 4 −N
constitutes nearly 90% of total nitrogen in old LL (Gunay et al. 2008a; Siciliano et al.
2013), which indicates that the organic content is almost completely stabilized. The
ratio of BOD 5 /COD is much lower in stabilized LL due to the release of recalcitrant
organics from the solid wastes. Therefore, old LL can be characterized by the low ratio
of BOD 5 /COD and the high concentration of NH 4 −N, while young and medium-aged
leachates often have higher BOD 5 /COD ratios.
M. Darwish et al.
9.1 Introduction
Nitrogen is considered as a key nutrient that is necessary for all forms of life. It is
a basic element for many vital industries such as foods and fertilizers. On the other
hand, N is one of the most harmful pollutants for humans and aquatic environment.
Disposal of high N loads to natural water bodies promotes eutrophication, which
results in oxygen depletion and toxicity to aquatic life. Ammonium nitrogen represents more than 80% of total nitrogen in wastewater (Gunay et al. 2008a; Zhang
et al. 2012), which means that recovery of NH 4 −N should be highly considered.
Landfilling is the most widely applied method for solid wastes disposal. Globally,
about 60% of generated solid wastes are disposed in landfills. Corresponding to pollutants migration into the environment, landfills produce two main hazardous wastes:
the biogas (formed by the fermentation of organic matter), a source of air pollution;
and the leachate (generated by the contact of percolated water with the decomposing wastes), a source of groundwater and soil contamination. Landfill leachate is
one of the hazardous wastewaters that contains high concentrations of NH 4 −N (Li
et al. 1999). In their study, Alslaibi et al. (2011) revealed that NH 4 −N concentration
(>8 mg/L) was higher than natural concentration (0.2 mg/L) in groundwater, near
landfill sites in Gaza Strip, Palestine. In Malaysia as well, it has been found that
LL pollutes some rivers and increases the concentration of NH 4 −N to above the
Interim National Water Quality Standard (INWQS) Class IIA/IIB river for Malaysia
(>0.3 mg/L) (Yusof et al. 2009). These studies showed obviously the high risk of
disposing LL without a proper treatment of NH 4 −N. For these reasons, recovery of
NH 4 −N from LL is crucial for environmental protection.
9.2 Characteristics of Landfill Leachate
Fundamentally, physical and chemical characteristics of LL are strongly influenced
by the composition of wastes, climate conditions and landfill age. Age of landfill is
the driving factor, and accordingly, LL can be classified into three main types: young,
medium-aged and old (mature). Besides, LL is usually characterized by the basic
parameters, which are pH, COD, BOD, NH 4 −N, total Kjeldahl nitrogen (TKN),
heavy metals and SS.
Table 9.1 presents the main characteristics of LL in some literatures. It can be
noticed that the age of landfill, and hence the degree of wastes stabilization, has a
significant effect on LL characteristics. It is also important to mention that NH 4 −N
constitutes nearly 90% of total nitrogen in old LL (Gunay et al. 2008a; Siciliano et al.
2013), which indicates that the organic content is almost completely stabilized. The
ratio of BOD 5 /COD is much lower in stabilized LL due to the release of recalcitrant
organics from the solid wastes. Therefore, old LL can be characterized by the low ratio
of BOD 5 /COD and the high concentration of NH 4 −N, while young and medium-aged
leachates often have higher BOD 5 /COD ratios.