9 Struvite Crystallization: An Effective Technology …
153
Table 9.4 Alternative sources of Mg applied for MAP recovery
Mg alternative
Wastewater type
Reference
Source
Mg content
Seawater
1,248 mg/L
Source-separated urine Liu et al. (2013a, b)
Brine *
2,374 mg/L
NF brine †
8,000 mg/L
Municipal-wastewater
sludge centrifuge
supernatant
Lahav et al. (2013)
Seawater bittern
27.5 g/L
Source-separated urine Etter et al. (2011)
32 g/L
Adjusted biologically
treated wastewater
Lee et al. (2003)
69 g/L *
Calf manure digestate
Siciliano and De Rosa
(2014)
48.5 g/L
Landfill leachate
Siciliano et al. (2013)
9.22 g/L
Li and Zhao (2002)
24.9 g/L
Technical-grade MgO
84–86%
Industrial wastewater
Borojovich et al.
(2010)
Natural magnesite
(MgCO 3 )
98% as MgCO 3 Landfill leachate
Gunay et al. (2008b)
Magnesite calcination
by-product
53% as MgCO 3
Huang et al. (2014)
Natural brucite
(Mg(OH) 2 )
65% as MgO
Rare-earth wastewater
Huang et al. (2011a, b)
* Prepared synthetically, † Real nanofiltration brine
9.4.3.4 Phosphorus Sources
Phosphorus is a non-renewable source that is mainly mined from phosphate ores
(apatites). Different types of P reagents have been applied as reported in the literatures. For the recovery of MAP from LL, different P salts were used such as
disodium hydrogen phosphate dihydrate (Na 2 HPO 4 · 2H 2 O), sodium dihydrogen
phosphate (NaH 2 PO 4 ) and potassium hydrogen phosphate (K 2 HPO 4 ). In parallel
with the high solubility of these reagents, they do not produce any side elements or
compounds that may negatively affect the MAP reaction. As both Na 2 HPO 4 · 2H 2 O
and NaH 2 PO 4 have similar solubilities, there is no significant difference between
them in MAP reaction. In fact, the two reagents were used in literature and showed
high efficiency. On the other hand, because of the high cost of chemical reagents,
they were mostly used in lab-scale studies. Besides, phosphoric acid (H 3 PO 4 ) was
applied as a P reagent, which had benefited in improving the solubility of Mg reagent
(MgCO 3 ) (Gunay et al. 2008b) and reducing the chemical cost (Di Iaconi et al. 2010).
Generally, the cost of struvite recovery is mainly contributed by the consumption
of P salts (Siciliano et al. 2013), which are basically produced from the apatite’s
153
Table 9.4 Alternative sources of Mg applied for MAP recovery
Mg alternative
Wastewater type
Reference
Source
Mg content
Seawater
1,248 mg/L
Source-separated urine Liu et al. (2013a, b)
Brine *
2,374 mg/L
NF brine †
8,000 mg/L
Municipal-wastewater
sludge centrifuge
supernatant
Lahav et al. (2013)
Seawater bittern
27.5 g/L
Source-separated urine Etter et al. (2011)
32 g/L
Adjusted biologically
treated wastewater
Lee et al. (2003)
69 g/L *
Calf manure digestate
Siciliano and De Rosa
(2014)
48.5 g/L
Landfill leachate
Siciliano et al. (2013)
9.22 g/L
Li and Zhao (2002)
24.9 g/L
Technical-grade MgO
84–86%
Industrial wastewater
Borojovich et al.
(2010)
Natural magnesite
(MgCO 3 )
98% as MgCO 3 Landfill leachate
Gunay et al. (2008b)
Magnesite calcination
by-product
53% as MgCO 3
Huang et al. (2014)
Natural brucite
(Mg(OH) 2 )
65% as MgO
Rare-earth wastewater
Huang et al. (2011a, b)
* Prepared synthetically, † Real nanofiltration brine
9.4.3.4 Phosphorus Sources
Phosphorus is a non-renewable source that is mainly mined from phosphate ores
(apatites). Different types of P reagents have been applied as reported in the literatures. For the recovery of MAP from LL, different P salts were used such as
disodium hydrogen phosphate dihydrate (Na 2 HPO 4 · 2H 2 O), sodium dihydrogen
phosphate (NaH 2 PO 4 ) and potassium hydrogen phosphate (K 2 HPO 4 ). In parallel
with the high solubility of these reagents, they do not produce any side elements or
compounds that may negatively affect the MAP reaction. As both Na 2 HPO 4 · 2H 2 O
and NaH 2 PO 4 have similar solubilities, there is no significant difference between
them in MAP reaction. In fact, the two reagents were used in literature and showed
high efficiency. On the other hand, because of the high cost of chemical reagents,
they were mostly used in lab-scale studies. Besides, phosphoric acid (H 3 PO 4 ) was
applied as a P reagent, which had benefited in improving the solubility of Mg reagent
(MgCO 3 ) (Gunay et al. 2008b) and reducing the chemical cost (Di Iaconi et al. 2010).
Generally, the cost of struvite recovery is mainly contributed by the consumption
of P salts (Siciliano et al. 2013), which are basically produced from the apatite’s