638 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
of less than 3. An adequate rinse with acid permeate solu-
tion before the air scour stage is required to help mitigate
the precipitation of dissolved solutes. This air scour step
occurs during the backwash procedure and helps decrease
the membranes from fouling.
The presence of bacteria and algae in the system sug-
gested biological fouling, which was effectively controlled
using a 2% sodium hypochlorite oxidizing reagent.
Based on the results of the different backwashes tested
at both low and high pH’s, it was concluded that regular
backwashes followed by chemically enhanced backwashes
(CEB) at low pH alone are not sufficient for proper clean-
ing of the UF membranes. It is necessary to have oxidizing
washes at high pH to remove solids and control fouling by
bacteria.
During the piloting, a heater was not available for the
clean in place (CIP) procedure. The air scour injection
which occurs during the backwash cycles was also found to
be insufficient, making it difficult to improve the backwash
procedures. Future testing will be performed and will con-
sider the addition of a heater and a proper air injection to
improve the CIP and backwash procedures.
Results of the High Density Sludge Process:
In this process all metals that are in a soluble state were
precipitated with the addition of a lime slurry. The unit size
required for this treatment is 30% of the total feed flow
since it only treats the concentrate flow of the RO plant.
This is an advantage when compared to conventional water
treatment configurations where this technology is the first
stage of treatment.
Due to the high load of Fe, Al and Mn in the HDS feed
solution, the tests carried out indicated that the best treat-
ment option is with the use of three reactors to precipitate
metals prior to the thickener.
Three reactors for precipitation of metals were consid-
ered, the first (B1 reactor) operated at pH 4.0 to promote
iron precipitation with air injection. For second and third
reactors (B2 and B3), two configurations were tested at
Figure 11. Pourbaix iron-water diagram safe zone of
operation at pH less than 2.5
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
10.0
0.0
2.0
4.0
6.0
8.0
10.0
12.0
Feed -Ultrafiltration
Flow pH
Figure 12. Feed flow to Ultrafiltration, the variation shown in flow is as part of testing by
reducing flux (flow through membrane area), typical pH of 2.4
0001
-
16
Mar
22
0099
-
13
Abr
22
0197
-
21
Abr
22
0295
-
30
Abr
22
0393
-
08
May
22
0491
-
18
May
22
0589
-
25
May
22
0687
-
01
Jun
22
0785
-
16
Jun
22
0883
-
05
Ago
22
0981
-
14
Ago
22
1079
-
27
Ago
22
1176
-
03
Set
22
1274
-
10
Set
22
1372
-
19
Set
22
1469
-
01
Oct
22
1567
-
09
Oct
22
1665
-
27
Oct
22
1763
-
06
Nov
22
1861
-
18
Nov
22
1959
-
26
Nov
22
2057
-
16
Dic
22
2155
-
26
Dic
22
2253
-
03
Ene
23
2351
-
19
Ene
23
2449
-
28
Ene
23
2547
-
10
Feb
23
2645
-
21
Feb
23
pH
Fl
-
m3/h
of less than 3. An adequate rinse with acid permeate solu-
tion before the air scour stage is required to help mitigate
the precipitation of dissolved solutes. This air scour step
occurs during the backwash procedure and helps decrease
the membranes from fouling.
The presence of bacteria and algae in the system sug-
gested biological fouling, which was effectively controlled
using a 2% sodium hypochlorite oxidizing reagent.
Based on the results of the different backwashes tested
at both low and high pH’s, it was concluded that regular
backwashes followed by chemically enhanced backwashes
(CEB) at low pH alone are not sufficient for proper clean-
ing of the UF membranes. It is necessary to have oxidizing
washes at high pH to remove solids and control fouling by
bacteria.
During the piloting, a heater was not available for the
clean in place (CIP) procedure. The air scour injection
which occurs during the backwash cycles was also found to
be insufficient, making it difficult to improve the backwash
procedures. Future testing will be performed and will con-
sider the addition of a heater and a proper air injection to
improve the CIP and backwash procedures.
Results of the High Density Sludge Process:
In this process all metals that are in a soluble state were
precipitated with the addition of a lime slurry. The unit size
required for this treatment is 30% of the total feed flow
since it only treats the concentrate flow of the RO plant.
This is an advantage when compared to conventional water
treatment configurations where this technology is the first
stage of treatment.
Due to the high load of Fe, Al and Mn in the HDS feed
solution, the tests carried out indicated that the best treat-
ment option is with the use of three reactors to precipitate
metals prior to the thickener.
Three reactors for precipitation of metals were consid-
ered, the first (B1 reactor) operated at pH 4.0 to promote
iron precipitation with air injection. For second and third
reactors (B2 and B3), two configurations were tested at
Figure 11. Pourbaix iron-water diagram safe zone of
operation at pH less than 2.5
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
10.0
0.0
2.0
4.0
6.0
8.0
10.0
12.0
Feed -Ultrafiltration
Flow pH
Figure 12. Feed flow to Ultrafiltration, the variation shown in flow is as part of testing by
reducing flux (flow through membrane area), typical pH of 2.4
0001
-
16
Mar
22
0099
-
13
Abr
22
0197
-
21
Abr
22
0295
-
30
Abr
22
0393
-
08
May
22
0491
-
18
May
22
0589
-
25
May
22
0687
-
01
Jun
22
0785
-
16
Jun
22
0883
-
05
Ago
22
0981
-
14
Ago
22
1079
-
27
Ago
22
1176
-
03
Set
22
1274
-
10
Set
22
1372
-
19
Set
22
1469
-
01
Oct
22
1567
-
09
Oct
22
1665
-
27
Oct
22
1763
-
06
Nov
22
1861
-
18
Nov
22
1959
-
26
Nov
22
2057
-
16
Dic
22
2155
-
26
Dic
22
2253
-
03
Ene
23
2351
-
19
Ene
23
2449
-
28
Ene
23
2547
-
10
Feb
23
2645
-
21
Feb
23
pH
Fl
-
m3/h