water before AFM® using an aggressive static mixer such as our ZPM to insure efficient use of NoPhos
and removal of ortho-phosphate.
The process is simple, reliable and sustainable; however Lanthanum is an expensive product. Ferric
chloride is a lower cost substitute for Lanthanum chloride. The performance of ferric is not quite as good
as lanthanum, in order to compensate for the reduce performance; typical a 2 to 4 excess molar ratio is
applied. More ferric may be required if there is a higher concentration of solids or dissolved organics in
the water to be treated.
Ferric chloride is injected into the water via a ZPM or aggressive static mixer. Ideally there should be a
10-minute contact tank, which is aerated. The dissolved oxygen content must be above 2 mg/l or redox
potential above 300mv. AFM® is perfect for removal of ferric, arsenic and manganese and as such it is
also a good solution for the removal of ferric phosphate salt.
Chemical
parameter
Phosphate
Soluble reactive
Soluble fraction Insoluble
PO 42- (Fe 3+ ) 2 (PO 42- ) 3
Mg 2+ NH 4+ PO 42-
Drinking
water
standard
No limit
Performance
>95%
The details below provides a list of phosphate minerals that will form insoluble precipitates
•
•
triphylite Li(Fe,
Mn)PO 4
monazite (Ce,L
a,Y,Th)PO 4
hinsdalite PbAl
3 (PO 4 )(SO 4 )(OH)
6
•
•
•
•
•
pyromorphite P
b 5 (PO 4 ) 3 Cl
vanadinite Pb 5 (
VO 4 ) 3 Cl
erythrite Co 3 (A
sO 4 ) 2 ·8H 2 O
amblygonite Li
AlPO 4 F
lazulite (Mg,Fe)
Al 2 (PO 4 ) 2 (OH) 2
•
•
•
•
•
•
•
Dryden Aqua Ltd
Butlerfield-Bonnyrigg,
Edinburgh EH19 3JQ Scotland
wavellite Al 3 (PO 4 ) 2 (
OH) 3 ·5H 2 O
turquoise CuAl 6 (PO
4 ) 4 (OH) 8 ·5H 2 O
autunite Ca(UO 2 ) 2 (
PO 4 ) 2 ·10-12H 2 O
carnotite K 2 (UO 2 ) 2 (
VO 4 ) 2 ·3H 2 O
phosphophyllite Zn
2 (Fe,Mn)(PO 4 ) 2 •4H 2
O
struvite (NH 4 )MgP
O 4 ·6H 2 O
Xenotime-Y Y(PO 4 )
•
•
•
•
•
Apatite group
Ca 5 (PO 4 ) 3 (F,Cl,OH)
hydroxylapatite C
a 5 (PO 4 ) 3 OH
fluorapatite Ca 5 (P
O 4 ) 3 F
chlorapatite Ca 5 (P
O 4 ) 3 Cl
bromapatite
Mitridatite group:
Arseniosiderite-
mitridatite series
(Ca 2 (Fe 3+ ) 3 [(O) 2 |(AsO 4 ) 3 ]·3H
2 O --
Ca 2 (Fe 3+ ) 3 [(O) 2 |(PO 4 ) 3 ]·3H 2
O) [1]
• Arseniosiderite-
robertsite series
(Ca 2 (Fe 3+ ) 3 [(O) 2 |(AsO 4 ) 3 ]·3
H 2 O --
Ca 3 (Mn 3+ ) 4 [(OH) 3 |(PO 4 ) 2 ] 2 ·
3H 2 O) [2]
•
•
Page 37 of 44
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