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 NH 3 /NH 4 + 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 (Phase 1) Regeneration (Phase 2) Conversion (Phase 3) Treated Effluent NH 4 N 2 NH 4 IX IX Regenerant Tank Electrochemical Reactor Wastewater (NH 4 )
AmmEL Reactions 2NH + 4 N 2 + 8H + + 6e 2Cl Cl 2 + 2e Cl 2 + H 2 O HOCl + HCl 2NH + 4 + 3HOCl N 2 + 3H 2 O + 5H + + 3Cl
The AmmEL Advantage Eliminates nitrogen loading by converting ammonia directly into innocuous N 2 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 ph adjustment station for the inlet water stream 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 Ammonia Concentration (mg/l) 35 25 20 15 10 5 0 99 98 97 96 92 32 90 88 31 31 31 86 29 29 84 29 28 28 79 28 27 27 75 67 58 53 14.2 11.6 9.6 7.6 6.5 4.5 5.1 3.7 2.2 2.7 0.3 0.5 0.8 1.2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Run Time (h) % Removed Inlet Ammonia Outlet Ammonia Breakthrough Curve at 18 L/min 100 90 80 70 60 50 40 20 10 0 Ammonia Removed (%)
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 Ammonia Concentration (mg/l) 25 20 15 10 5 0 96 96 96 96 27 27 25 24 94 92 90 87 24 24 23 21 20 85 84 22 80 23 76 22 22 21 21 68 20 63 58 50 11.1 9.3 7.8 6.3 4.6 5.1 1.1 1.0 1.0 1.1 1.5 1.8 2.4 2.5 3.3 3.6 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Time (h) % Removed Inlet Ammonia Outlet Ammonia Ammonia Loading, Columns C2 & C1 100 90 80 70 60 50 40 20 10 0 Ammonia Removed (%)
Series Column Results 35 ) /L g /L 25 (m (m n tio tio tra 20 tra n e c n o C 15 ia n ia o m m 10 A 5 0 99 99 99 98 97 96 94 33 33 32 32 32 32 91 32 88 90 32 32 32 32 87 82 78 72 24 66 10.8 8.7 7.3 5.7 4.2 3.5 2.8 3.2 0.1 0.3 0.4 0.6 0.9 1.3 1.9 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Time (h) 100 90 80 70 60 50 40 20 10 0 ) (% (% d e v o m e R ia n ia o m m A % Removed Inlet Ammonia Outlet Ammonia Ammonia Loading, Columns C1 & C3
Series Column Results Ammonia Concentration (mg/l) 40 35 25 20 15 10 5 0 96 97 96 95 94 91 37 37 37 37 37 35 35 35 90 35 35 85 34 32 32 82 82 79 76 73 10.0 7.7 8.4 6.5 6.8 5.0 3.2 3.7 1.1 1.1 1.4 1.7 2.2 1 2 3 4 5 6 7 8 9 10 11 12 13 Time (h) % Removed Inlet Ammonia Outlet Ammonia Ammonia Loading, Columns C3 & C2 100 90 80 70 60 50 40 20 10 0 Ammonia Removed (%)
Series Column Results C 2 & C 1 C 1 & C 3 C 3 & C 2 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 NH 3 (mg/l) 23.0 31.0 35.3 Average Outlet NH 3 (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 The efficiency of the AmmEL LC was not affected by low water temperatures (>6 C) Operating costs were relatively low ($0.10/m 3 of water treated)
Full Scale Installation Full scale installation commissioned March 10, 2010 in Timmins, Ontario Three zeolite filled cm (i.d.) x 6 m ion exchange columns Electrochemical reactor 18 m 2 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 m 3 of mine waste per day containing an average of mg of ammonia nitrogen/l Emission levels are 10 mg NH 3 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