Chloramination, The Science
Methods of Application & Other Stuff
Ron Hidu, PE
COMMITMENT & INTEGRITY DRIVE RESULTS Ammonia Source
▀ Naturally Occurring
▀ Anhydrous Ammonia
▀ Aqueous Ammonia
▀ Ammonium Sulfate
COMMITMENT & INTEGRITY DRIVE RESULTS 000000.00 2 Aqueous Ammonia – NH4OH • H2O
▀ Ammonium Hydroxide
▀ 19, 25, 40 %...typically 19%
▀ SG = 0.926 7.8 lbs/gal
▀ Boiling point = 86º F
▀ Odor threshold = 5 ppm
▀ Fed directly
▀ 19% concentration provides 15.6% N by wt.
COMMITMENT & INTEGRITY DRIVE RESULTS 000000.00 3 Ammonium Sulfate - (NH4)2SO4
▀ 50 lb bags ▀ Granular; little issue with dusting ▀ Solubility up to about 40% solution @ 77º F ▀ Easiest to mix as 12% solution (i.e. 1 lb chemical to 1 gal water) ▀ Molecular wt. = 132.14 ▀ Ammonium Sulfate is 21% N by wt. ▀ Also proprietary products ▀ NSF 60
COMMITMENT & INTEGRITY DRIVE RESULTS 000000.00 4 Cost Comparison
▀ Ammonium Sulfate ▀ ~ 65¢ / lb (in pallet quantities, 2000 lbs, 40 bags) ▀ 21% N by wt. ▀ Equates to $3.09 / lb N
▀ 19% Aqueous ▀ ~ 16¢ / lb (6000 gal delivery; 7300 lbs N) ▀ ~ 40¢ / lb (400 gal delivery; 500 lbs N) ▀ 15.6% N by wt - 7.8 lbs / gal ▀ Equates to $2.56 / lb N (400 gal delivery)
COMMITMENT & INTEGRITY DRIVE RESULTS 000000.00 5 Cost Example
▀ 1 MGD
▀ 1.5 mg/l Cl2 ▀ Usage would be 3.0 lbs/day N (see table)
▀ Ammonium Sulfate = $9.27 / day
▀ Aqueous Ammonia = $7.68 / day
COMMITMENT & INTEGRITY DRIVE RESULTS 000000.00 6 Plant Flow Rate 700 GPM
4.2 Ratio 4.2:1 CL2-N 50# Bag (99.5%) 49.75 lbs. For 12% Solution 414.58 lbs. Water For 12% Solution 49.71 gal. Water Mix 1 Bag Ammonium Sulfate to 50 gallons of water
Total Chlorine Residual Feed Rate Feed Rate mg/l as Cl 2 lb/hr as N lb/hr as (NH4)2 (SO4) hrs/bag gal/hr ml/min 0.2 0.0167 0.0786 632.7 0.08 5.0 0.3 0.0250 0.1180 421.8 0.12 7.4 0.4 0.0334 0.1573 316.3 0.16 9.9 0.5 0.0417 0.1966 253.1 0.20 12.4 0.6 0.0500 0.2359 210.9 0.24 14.9 0.7 0.0584 0.2752 180.8 0.28 17.3 0.8 0.0667 0.3145 158.2 0.31 19.8 0.9 0.0751 0.3539 140.6 0.35 22.3 1.0 0.0834 0.3932 126.5 0.39 24.8 1.1 0.0917 0.4325 115.0 0.43 27.3 1.2 3 lbs N /day 0.1001 0.4718 105.4 0.47 29.7 1.3 0.1084 0.5111 97.3 0.51 32.2 1.4 0.1168 0.5504 90.4 0.55 34.7 1.5 0.1251 0.5898 84.4 0.59 37.2 1.6 0.1334 0.6291 79.1 0.63 39.7 1.7 0.1418 0.6684 74.4 0.67 42.1 1.8 0.1501 0.7077 70.3 0.71 44.6 1.9 0.1585 0.7470 66.6 0.75 47.1 2.0 0.1668 0.7863 63.3 0.79 49.6 2.1 0.1751 0.8257 60.3 0.83 52.0 2.2 0.1835 0.8650 57.5 0.86 54.5 2.3 0.1918 0.9043 55.0 0.90 57.0 2.4 0.2002 0.9436 52.7 0.94 59.5 2.5 0.2085 0.9829 50.6 0.98 62.0
3 ½ days / bag in 50 gal of water
COMMITMENT & INTEGRITY DRIVE RESULTS 000000.00 7 Materials of Construction
▀ Poly tanks
▀ SCH 80 PVC (not for Anhydrous…SS)
▀ PE, PP, PTFE tubing
▀ No copper, brass, etc.
▀ If using peristaltic pumps with Aqueous, careful with hose (use silicone, Tygon, Bioprene©… not nitrile, rubber)
COMMITMENT & INTEGRITY DRIVE RESULTS 000000.00 8 Chemical Addition
▀ NH3 then NaOCl Doesn’t matter…Typically OCl- first since ▀ NaOCl then NH3 } you usually have to meet a CT requirement.
▀ Reaction is rapid ▀ Monochloramine kinetics optimized at pH 8.5 and takes < 1 min. ▀ Drive pH higher due to Pb solubility (9.8)
▀ Often difficult to find a chem feed pump that will operate well at the low dosages used (Prominent Mikro line??)
▀ Like to have a static mixer or orifice plate
COMMITMENT & INTEGRITY DRIVE RESULTS 000000.00 9 Monitoring
▀ Ahead of dosing point:
▀ Free Chlorine
▀ pH
▀ At entrance to system:
▀ Total chlorine
▀ pH
▀ Within system:
▀ Total chlorine
▀ pH (keep high, no Di, no need to monitor for Mono using APA6000)
▀ Trace free chlorine but no free NH3
COMMITMENT & INTEGRITY DRIVE RESULTS 000000.00 10 Chloramine Species
Species Formula Odor Threshold Taste Threshold (mg/l) (mg/l)
Monochloramine NH2Cl 0.48 0.65
Dichloramine NHCl2 0.13 0.15
Trichloramine NCl3 0.02 0.02
COMMITMENT & INTEGRITY DRIVE RESULTS 000000.00 11 Chemistry Cl + H 0 HOCl + HCl 2 2 (hydrolysis) Free chlorine species NaOCl + H20 HOCl + NaOH hypochlorous acid
Unbuffered water… Cl2 reduces pH; NaOCl raises pH
+ - HOCl H + OCl (dissociation) Equilibrium based on pH & temp hypochlorite ion Then add N either naturally or by NH3 source:
HOCl + NH3 NH2Cl + H2O HOCl + NH2Cl NHCl2 + H20 HOCl + NHCl2 NCl3 + H20
Too much chlorine (too high Cl2:N ratio) drives toward Tri., too little leaves excess free nitrogen…range 3:1 to 5:1 (4.2 stoichiometric), but differs for individual water chemistry
COMMITMENT & INTEGRITY DRIVE RESULTS 000000.00 12 COMMITMENT & INTEGRITY DRIVE RESULTS 000000.00 13
40
9.8 pH
5 COMMITMENT & INTEGRITY DRIVE RESULTS 000000.00 16 COMMITMENT & INTEGRITY DRIVE RESULTS 000000.00 17 COMMITMENT & INTEGRITY DRIVE RESULTS 000000.00 18 COMMITMENT & INTEGRITY DRIVE RESULTS 000000.00 19 COMMITMENT & INTEGRITY DRIVE RESULTS 000000.00 20 Case Studies
▀ Bath – 2003
▀ ~3 MGD, Microfloc
▀ Plant upgrade included setup to go to chloramines using Aqueous ammonia
▀ 2) 750 gal bulk tanks
▀ PVC & CPVC piping
▀ Deliveries twice/yr
▀ Considered Ammonium sulfate (4 ½ bags / week), but plant had no provisions for dry chemical delivery and handling.
▀ Staff used to handling bulk hypochlorite and chlorine dioxide
COMMITMENT & INTEGRITY DRIVE RESULTS 000000.00 21 Case Studies (continued)
▀ Bangor – 2003 – Mutual Aid Study
▀ Bangor, Brewer, Hampden, Orono-Veazie, Old Town
▀ Blending chloraminated and non-chloraminated waters
▀ pH variations
▀ Segregating waters
▀ Bangor – 2007 – Anhydrous to Aqueous Conversion
▀ Reuse of equipment
▀ Cl2 to NaOCl conversion
COMMITMENT & INTEGRITY DRIVE RESULTS 000000.00 22 Case Studies (continued)
▀ Millinocket – 2001 ▀ 0.5 MGD IDI Advent, prechlorinate for filter runs, high organics, high DBPs ▀ 600 gpm ▀ Ammonium sulfate
▀ Bar Harbor – 2009 ▀ 3 MGD unfiltered, gravity flow ▀ Chlorine gas ▀ Ammonium sulfate at remote location (transmission line contactor)
COMMITMENT & INTEGRITY DRIVE RESULTS 000000.00 23 Case Studies (continued)
▀ Vinalhaven I – 2005 ▀ 60,000 gpd, unfiltered (100 gpm) ▀ Ammonium sulfate ▀ Remote addition point, long transmission line contactor ▀ In-system mixing
▀ Vinalhaven II– 2010 ▀ 60,000 gpd, bags, UV, OCl- (60 gpm) ▀ Ammonium sulfate ▀ Short CT contact time
▀ NH3 addition in proximity to pump station.
COMMITMENT & INTEGRITY DRIVE RESULTS 000000.00 24 Case Studies (continued)
▀ Great Salt Bay – 2009
▀ 160,000 gpd, unfiltered (300 gpm)
▀ UV, OCL-,Chloramine
▀ Ammonium sulfate
▀ NH3 addition in separate building after short transmission line contact for CT
▀ pH adjustment to 9.8 using soda ash
COMMITMENT & INTEGRITY DRIVE RESULTS 000000.00 25 Case Studies (continued)
▀ Hampden – 2001 & 2010
▀ 340,000 – 440,000 gpd, consecutive system
▀ Rechlorination, pH adjustment
▀ LDA – 2010
▀ 120,000 to 2 MGD, conventional filtration (Leopold)
▀ UV, OCL-, chloramines
▀ Long transmission line
▀ Ammonium sulfate
COMMITMENT & INTEGRITY DRIVE RESULTS 000000.00 26