volume of the mixing reactor for a semi-continuous process is 50 L; the reaction
lasted for ca 30 min including the time for emptying the reactor. 100 L of raw water
could be processed within 1 h. The pH values, the oxidation–reduction potential, and
temperature were measured continually. The maximum value of E h during the
reaction was 850 mV. Each dose of ferrate was verified in duplicate on the semipilot plant. In order to evaluate the effectivity of the As separation on the semi-pilot
plant, four different samples were collected—raw water (input), water after sand
filter (PF), water after microfiltration 1 μm (MF), and water after ultrafiltration (UF),
i.e., the treated water. The chemical analysis of the samples was carried out in an
accredited commercial laboratory (ALS). The final concentrations of As after applying the target doses of commercial ferrates in each locality are shown in Table 13.3.
Arsenic concentrations in the treated water from both localities were below the set
limit for drinking water (max. 10 μg/L). The optimum dose of a commercial ferrate
for MEZ water was 10 mg/L, for KLU water 15 mg/L. It is highly likely that the
12.5 μg/L value achieved in the first test (A) was due to the previous test with a lower
dose of a commercial ferrate (10 mg/L), which was proved to be insufficient for
arsenic removal from KLU locality (Filip et al. 2017).
The agents used for arsenic removal from groundwater obviously affect the
quality of the remediated water. Ferrates (K 2 FeO 4 ) raise the concentration of K,
Fe, and the pH. Table 13.4 shows the example of such changes. Specifically, herein
we present the results of a duplicate test on KLU water after applying a 15 mg/L dose
Table 13.3 Arsenic removal using ferrates, semi-pilot plant, duplicate testing of each dose of
commercial ferrate
As separation Semipilot tests
INPUT As
(μg/L)
OUTPUT As (μg/L)
ENVIFER
5 mg/L
ENVIFER
10 mg/L
ENVIFER
15 mg/L
ENVIFER
20 mg/L
A
B
A
B
A
B
A
B
Water MEZ
89
11
17
<5
<5
<5
<5
<5
<5
Water KLU
102
–
–
13
17
12
<5
<5
5
Table 13.4 The effect of
ferrates on the water in KLU
locality after using 15 mg/L of
commercial ferrate, duplicate
test (A, B)
Sample
As
Fe
K
pH
μg/L
mg/L
mg/L
–
Detection limit
0.0050
0.0020
0.0150
1
A – INPUT
102
0.0035
2.5
7.44
A – After PF
69
1.26
9.03
6.59
A – After MF
24.9
0.252
8.73
7.35
A – After UF
12.5
0.0814
8.75
7.22
B – INPUT
102
0.0035
2.5
7.44
B – After PF
62.5
1.3
9.26
7.39
B – After MF
43.2
0.784
9.37
7.37
B – After UF
<0.005
0.0746
9.85
7.25
50 L Water KLU + 750 mg Commercial Ferrate +0.5 mL Flocculant +4.0 mL 10% HCl
306
M. Heřmánková et al.
lasted for ca 30 min including the time for emptying the reactor. 100 L of raw water
could be processed within 1 h. The pH values, the oxidation–reduction potential, and
temperature were measured continually. The maximum value of E h during the
reaction was 850 mV. Each dose of ferrate was verified in duplicate on the semipilot plant. In order to evaluate the effectivity of the As separation on the semi-pilot
plant, four different samples were collected—raw water (input), water after sand
filter (PF), water after microfiltration 1 μm (MF), and water after ultrafiltration (UF),
i.e., the treated water. The chemical analysis of the samples was carried out in an
accredited commercial laboratory (ALS). The final concentrations of As after applying the target doses of commercial ferrates in each locality are shown in Table 13.3.
Arsenic concentrations in the treated water from both localities were below the set
limit for drinking water (max. 10 μg/L). The optimum dose of a commercial ferrate
for MEZ water was 10 mg/L, for KLU water 15 mg/L. It is highly likely that the
12.5 μg/L value achieved in the first test (A) was due to the previous test with a lower
dose of a commercial ferrate (10 mg/L), which was proved to be insufficient for
arsenic removal from KLU locality (Filip et al. 2017).
The agents used for arsenic removal from groundwater obviously affect the
quality of the remediated water. Ferrates (K 2 FeO 4 ) raise the concentration of K,
Fe, and the pH. Table 13.4 shows the example of such changes. Specifically, herein
we present the results of a duplicate test on KLU water after applying a 15 mg/L dose
Table 13.3 Arsenic removal using ferrates, semi-pilot plant, duplicate testing of each dose of
commercial ferrate
As separation Semipilot tests
INPUT As
(μg/L)
OUTPUT As (μg/L)
ENVIFER
5 mg/L
ENVIFER
10 mg/L
ENVIFER
15 mg/L
ENVIFER
20 mg/L
A
B
A
B
A
B
A
B
Water MEZ
89
11
17
<5
<5
<5
<5
<5
<5
Water KLU
102
–
–
13
17
12
<5
<5
5
Table 13.4 The effect of
ferrates on the water in KLU
locality after using 15 mg/L of
commercial ferrate, duplicate
test (A, B)
Sample
As
Fe
K
pH
μg/L
mg/L
mg/L
–
Detection limit
0.0050
0.0020
0.0150
1
A – INPUT
102
0.0035
2.5
7.44
A – After PF
69
1.26
9.03
6.59
A – After MF
24.9
0.252
8.73
7.35
A – After UF
12.5
0.0814
8.75
7.22
B – INPUT
102
0.0035
2.5
7.44
B – After PF
62.5
1.3
9.26
7.39
B – After MF
43.2
0.784
9.37
7.37
B – After UF
<0.005
0.0746
9.85
7.25
50 L Water KLU + 750 mg Commercial Ferrate +0.5 mL Flocculant +4.0 mL 10% HCl
306
M. Heřmánková et al.