146
M. Darwish et al.
The operational cost of ammonia treatment is a significant factor that should
be considered for any applied method. It is worthy to mention that the current
applied techniques for ammonia treatment in LL cost around 4.5–12 USD/m
3 (Wu
et al. 2016), which has to be reduced through innovative approaches. One of these
approaches is an integrated system, developed by Wu et al. (2016), which removes N
from LL using biological and electrochemical techniques. The authors could reduce
the operational cost to 0.8 USD/m
3 , regarding struvite technology. Huang et al. (2012)
mentioned that, if the conventional reagents were applied, the operational cost would
be more than 10 USD/m
3 . However, based on the estimations of Huang et al. (2012),
MAP technology is more competitive when low-cost Mg and P reagents are applied,
or when struvite is recycled, at which the operational cost could be reduced to 0.94
USD/m
3 . Furthermore, a combination of cost reduction methods could reduce the
operational cost to more significant values (Table 9.2).
9.3.1 Struvite Characteristics
Struvite is an orthophosphate crystalline mineral with the chemical formula of
MgNH 4 PO 4 · 6H 2 O, which takes the orthorhombic structure (i.e. straight prisms
with a rectangular base). The main characteristics of struvite are shown in Table 9.3.
Struvite is a thermally unstable compound; its structure and morphology can be
altered at a temperature of around 55 °C (Bhuiyan et al. (2008).
Struvite was later confirmed by Borgerding (1972), who detected it on the walls
of an anaerobic digester at a treatment plant in Los Angeles in 1963. So, struvite
was initially considered more of a problem to eliminate (using acidic treatment)
before its economic benefits were explored. In practice, the presence of struvite mineral in precipitates can be inspected using different analytical techniques such as
X-ray diffraction (XRD) (Capdevielle et al. 2013), X-ray fluorescence (XRF) (Liu
et al. 2013a, b), Fourier transform Infrared (FT-IR) and thermogravimetric analysis
(TGA) (Wang et al. 2010). The shape of the crystals is usually explored using scanning electron microscopy (SEM). Besides, quantitative analysis with high level of
accuracy can be carried out by XRD (Lu et al. 2016; Yan and Shih 2016). However,
other techniques such as inductively coupled plasma (ICP) and atomic absorption
spectrophotometry (AAS) should be used to detect the exact content of struvite in
the solid precipitates. Hao et al. (2008) developed an acidic dissolution method to
analyze the elemental composition of struvite, which enables to evaluate its purity.
Struvite has been involved in other fields of study. For instance, it has often been
studied in the medical field as it is one of the main components of the urinary stones
(Suguna et al. 2012). Additionally, it has been applied in soil treatment field for heavy
metals immobilization, which showed high efficiency in the immobilization of Cu,
Pb and Cr (Wang et al. 2016).
M. Darwish et al.
The operational cost of ammonia treatment is a significant factor that should
be considered for any applied method. It is worthy to mention that the current
applied techniques for ammonia treatment in LL cost around 4.5–12 USD/m
3 (Wu
et al. 2016), which has to be reduced through innovative approaches. One of these
approaches is an integrated system, developed by Wu et al. (2016), which removes N
from LL using biological and electrochemical techniques. The authors could reduce
the operational cost to 0.8 USD/m
3 , regarding struvite technology. Huang et al. (2012)
mentioned that, if the conventional reagents were applied, the operational cost would
be more than 10 USD/m
3 . However, based on the estimations of Huang et al. (2012),
MAP technology is more competitive when low-cost Mg and P reagents are applied,
or when struvite is recycled, at which the operational cost could be reduced to 0.94
USD/m
3 . Furthermore, a combination of cost reduction methods could reduce the
operational cost to more significant values (Table 9.2).
9.3.1 Struvite Characteristics
Struvite is an orthophosphate crystalline mineral with the chemical formula of
MgNH 4 PO 4 · 6H 2 O, which takes the orthorhombic structure (i.e. straight prisms
with a rectangular base). The main characteristics of struvite are shown in Table 9.3.
Struvite is a thermally unstable compound; its structure and morphology can be
altered at a temperature of around 55 °C (Bhuiyan et al. (2008).
Struvite was later confirmed by Borgerding (1972), who detected it on the walls
of an anaerobic digester at a treatment plant in Los Angeles in 1963. So, struvite
was initially considered more of a problem to eliminate (using acidic treatment)
before its economic benefits were explored. In practice, the presence of struvite mineral in precipitates can be inspected using different analytical techniques such as
X-ray diffraction (XRD) (Capdevielle et al. 2013), X-ray fluorescence (XRF) (Liu
et al. 2013a, b), Fourier transform Infrared (FT-IR) and thermogravimetric analysis
(TGA) (Wang et al. 2010). The shape of the crystals is usually explored using scanning electron microscopy (SEM). Besides, quantitative analysis with high level of
accuracy can be carried out by XRD (Lu et al. 2016; Yan and Shih 2016). However,
other techniques such as inductively coupled plasma (ICP) and atomic absorption
spectrophotometry (AAS) should be used to detect the exact content of struvite in
the solid precipitates. Hao et al. (2008) developed an acidic dissolution method to
analyze the elemental composition of struvite, which enables to evaluate its purity.
Struvite has been involved in other fields of study. For instance, it has often been
studied in the medical field as it is one of the main components of the urinary stones
(Suguna et al. 2012). Additionally, it has been applied in soil treatment field for heavy
metals immobilization, which showed high efficiency in the immobilization of Cu,
Pb and Cr (Wang et al. 2016).