Patented AmmEL Process
for the Treatment of
Ammonia in Low
Temperature Mine
Wastewater;
Ammonia Converted to
Environmentally–Friendly
Nitrogen Gas
Gene S. Shelp, Leonard P. Seed, Daren Yetman and John M. Motto
ENPAR Technologies Inc.,
Guelph, Ontario, Canada
Introduction
• Ammonia listed as a toxic substance by
Environment Canada
• One approach employed by the mining
industry has been to lower the pH of the
wastewater to render it less toxic (due to a
shift in the NH3/NH4+ equilibrium)
• While this approach has assisted in
meeting acute lethality discharge
requirements, the total ammonia-N
released into the environment is not
reduced
• Current technology for treating ammonia
relies heavily on biological activity (e.g.
nitrification) to convert ammonia to
nitrate
Introduction
• Total nitrogen removal requires additional
biological processes to remove nitrate from
wastewater prior to discharge
• Biological treatment systems are adversely
affected by cold temperatures and changes
in effluent composition
• A novel and patented ionexchange/electrochemical treatment
technology (the AmmEL system) has been
developed by Enpar Technologies, Inc.
which is not adversely affected by low
temperature
The AmmEL Process
Loading
Regeneration
Conversion
(Phase 1)
(Phase 2)
(Phase 3)
Treated Effluent
NH4
IX
Wastewater
(NH4)
IX
NH4
Regenerant
Tank
N2
Electrochemical
Reactor
AmmEL Reactions
2NH4+ → N2 + 8H+ + 6e2Cl- → Cl2 + 2e-
Cl2 + H2O → HOCl + HCl
2NH4+ + 3HOCl → N2 + 3H2O + 5H+ + 3Cl-
The AmmEL Advantage
• Eliminates nitrogen loading by converting ammonia directly
into innocuous N2
• Does not produce nitrate and the GHG nitrous oxide
associated with biological treatment
• Not affected by low temperature
• Intermittent operation -- no start-up delays
• Can be fully automated -- low maintenance
System Applications
• Mining effluent or process streams containing
ammonia derived from the use of ammonia
based blasting powder and/or the oxidation of
cyanide
• Tertiary treatment for municipal waste water
treatment plants (MWTP) and lagoon systems
• Process streams related to steel, fertilizer and
chemical industries
Pilot Study
The AmmEL-LC System
AmmEL-LC Pilot Unit Specifications
• 3-20 cm x 3.05m fluidized bed IX columns, BV = 59.3L
• 1.5 kW electrochemical reactor
• The main operating conditions for the system were as follows:
–
–
–
–
Wastewater flow rate: 18-20 L/min
Recharge brine flow rate: 8-10 L/min
Brine NaCl concentration: 3-4%
Cell current: 150 A
• Designed to allow for single column operation as well as series
column operation
• Typical treatment mode was to operate the system with two
columns in series in a lead-lag arrangement
• Third column was either involved in a regeneration cycle or
was in standby
• Following a regeneration cycle, the regenerated column was
rinsed with a small amount of treated water to remove any
extraneous brine
• The rinse stream was directed into a 200L holding tank for
testing prior to release back into the holding pond
IX 3
IX 2
IX 1
Reactor
Single Column Results
99
98
97
100
96
92
30
Ammonia Concentration (mg/L)
27
28
28
29
90
32
31
88
29
31
86
31
30
84
29
79
27
30
28
80
75
25
90
70
67
58
20
60
53
50
14.2
15
40
11.6
9.6
10
6.5
5
0.3
0.5
0.8
1.2
2.2
2.7
3.7
4.5
30
7.6
20
5.1
10
0
0
1
2
3
4
5
6
7
8
9
10
11
12
Run Time (h)
% Removed
Inlet Ammonia
Outlet Ammonia
Breakthrough Curve at 18 L/min
13
14
Ammonia Removed (%)
35
Typical Single Column Results
Flow rate (L/min)
18.0
Total run time (h)
14
Total volume treated (L)
15,120
Water temperature (°C)
5.7
Inlet pH
7.76
Outlet pH
7.85
Avg inlet ammonia (mg/L)
29.1
Avg outlet ammonia (mg/L)
5.1
Series Column Results
96
96
27
96
96
94
27
100
92
90
25
24
Ammonia Concentration (mg/L)
25
24
87
24
85
23
21
90
84
22
80
23
76
21
68
20
20
20
21
22
22
80
70
63
58
60
50
15
50
11.1
40
9.3
10
30
7.8
6.3
4.6
5
1.1
1.0
1.0
1.1
1.5
1.8
2.4
2.5
3.3
5.1
20
3.6
10
0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Time (h)
% Removed
Inlet Ammonia
Outlet Ammonia
Breakthrough Curve, 18L/min, Columns C2 & C1
Ammonia Removed (%)
30
Series Column Results
99
99
99
32
98
32
97
32
96
32
30
94
33
91
32
88
30
30
32
90
100
33
32
32
32
87
30
90
82
Ammonia Concentration (mg/L)
78
25
80
72
24
66
70
60
20
50
15
40
10.8
30
8.7
10
7.3
20
5.7
5
0.1
0.3
0.4
0.6
0.9
1.3
1.9
2.8
3.5
3.2
4.2
10
0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Time (h)
% Removed
Inlet Ammonia
Outlet Ammonia
Breakthrough Curve, 18L/min, Columns C1 & C3
Ammonia Removed (%)
35
Series Column Results
Ammonia Concentration (mg/L)
35
96
97
96
95
35
35
94
35
100
37
91
37
90
35
37
37
35
85
34
32
37
32
82
79
90
82
76
30
80
73
70
25
60
20
50
40
15
10.0
10
6.5
5
1.1
1.1
1.4
1.7
2.2
3.2
3.7
7.7
30
8.4
6.8
20
5.0
10
0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
Time (h)
% Removed
Inlet Ammonia
Outlet Ammonia
Breakthrough Curve, 18L/min, Columns C3 & C2
Ammonia Removed (%)
40
Series Column Results
C2 & C1
C1 & C3
C3 & C2
Flow Rate (L/min)
18.2
18.1
18.3
Total Run Time (h)
16
15
13
Water Temperature (°C)
5.9
6.0
5.9
Inlet pH
7.79
7.84
7.82
Outlet pH
7.86
7.86
7.91
Average Inlet NH3 (mg/L)
23.0
31.0
35.3
Average Outlet NH3 (mg/L)
4.0
3.4
4.5
Pilot Study Conclusions
• The AmmEL-LC system can readily remove ammonia from
mine waste water to below the discharge requirement of 10
mg/L
• No pretreatment of the stream was required
• Operating costs were relatively low ($0.10/m3 of water
treated)
Full-Scale Installation
• Full-scale installation commissioned March 10, 2010 in Timmins,
Ontario
• Three zeolite filled 30 cm (i.d.) x 6 m ion exchange columns
• Electrochemical reactor → 18 m2 of anode surface area; 16V, 2000A
DC rectifier
• Chlorine gas scrubber to comply with Ontario MOE chlorine emission
levels
• The system is designed to treat 400 m3 of mine waste per day
containing an average of 30 mg of ammonia-nitrogen/L
• Average effluent levels are 10 mg NH3-N/L year round including
during the winter months when mine water can reach temperatures
slightly above freezing
Ion Exchange Columns
Electrochemical Reactor
DC Rectifier
Chlorine Gas Scrubber
Ongoing Developments
• New modified zeolite currently under development for use in
IX columns
– Selective in adsorption of ammonium ions vs. calcium and magnesium
ions during effluent treatment
– 6-fold decrease in transfer of calcium and magnesium to brine during
recharge cycle
– Pilot studies indicate instances of reactor cleaning and brine
conditioning significantly reduced