Engineering consultant inspected and measured plumbing in houses. ⢠First draw 1L, waste volume then 3-â250 mL samples to represent LSL. ⢠Minimum of 6 ...
Peak Lead Levels and Diagnostics in Lead Service Lines Dominated by PbO2 Michael Schock U.S. Environmental Protec2on Agency ORD, NRMRL, WSWRD, TTEB, Cincinna2, Ohio 45268 Simoni Triantafyllidou and Michael K. DeSan8s ORISE Postdoctoral Fellow, ORD, NRMRL, WSWRD, TTEB Cincinna2, Ohio 45268
Presentation Outline • The Importance of PbO2 Scales • Some Gaps in Understanding of PbO2 • Profile Sampling Concepts Used to Find Peak Lead Levels to Determine OCCT • Three Case Studies § § §
Oakwood, OH Newport, RI Cincinna2, OH
• Conclusions
Importance of PbO2 Scales • Found in approximately 1/3 of 53 water systems whose • • • •
pipes have been examined by USEPA Found to be major mineral phase in small number of tested systems Several research groups have shown it forms from Pb(II) carbonate and hydroxycarbonate when ORP is sufficiently high and persistent Laboratory inves2ga2ons suggest very low solubility Some research suggests chemical condi2ons also favor reversal of galvanic couple of Pb:Cu 3
Modes of PbO2 in LSL Scales
4
Gaps in Knowledge of PbO2
• How widespread are these scales? • How does Pb release from PbO2 scales compare
to typical and op2mal Pb(II) release levels? • Are there major water chemistry dependencies to the lead release, aside from ORP? • Does Pb(IV) form any significant hydroxide, carbonate or other aqueous complexes with common ligands such as bicarbonate, carbonate, sulfate or chloride? 5
These 3 Case Studies
• Three u2li2es of varying pH and alkalinity • Timeframe 1989-‐2013 • Numerous LSL analyses show nearly complete scale coverage by PbO2 in these systems • Stable long-‐term (many years) water treatment and chemistry with respect to cri2cal water parameters • Slightly different sampling protocols used 6
Major Parameters for Our 3 Cases Location pH Alkalinity (mg/L as CaCO3) TIC (mg/L as C) Disinfectant Type Free Cl2 Residual (mg/L) ClO2 Residual (mg/L) Ca2+ (mg/L) Mg2+ (mg/L) Na+ (mg/L) K+ (mg/L)
NE (Newport, RI) 9.1 (8.7-9.5)
CI (Cincinnati, OH) 8.6 (8.3 - 8.9)
OK (Oakwood, OH) 7.1 (7.0-7.1)
26 (19-37)
74 (44 - 109)
341 (285-362)
6 (4.4-7.5) Free Chlorine + ClO2
17(10-26)
91(81-102)
Free Chlorine
Free Chlorine
1.4 (1.0-1.9)
1.26 (0.94-1.62)
--
0.3 (0.04-0.7)
NA
NA
19 (9-27) 3.2 (2.3-3.6) 35 (24-53) 3 (2-3)
36 (31 - 40) 8 (4 - 11) 26 (13 - 51) --
101 (73-141) 41 (32-52) 77 (47-98) 3 (2.5-2.6)
Anions & Minor Constituents Location
NE (Newport, RI)
CI (Cincinnati, OH)
OK (Oakwood, OH)
Al3+ (mg/L)
0.06 (0.02-0.1)
0.08 (0.0-0.3)
--
FeT (mg/L)
0.01 (0.00-0.02)
--
0.1 (0.0-0.3)
MnT (mg/L)
0.01 (0.00-0.02) 0.01 (0.00-0.01)
0.1 (0.0-0.4)
Cl- (mg/L)
61 (37-83)
27 (18 - 34)
148 (127-160)
SO42- (mg/L)
31 (22-36)
70 (46 - 115)
59 (52-66)
F- (mg/L)
0.9 (0.4-1.4)
0.98 (--)
--
NO3--N (mg/L)
0.3 (0.0-1.3)
0.8 (0.5 - 1.1)
-- 8
Oakwood Study (1989) •
Hard, high alkalinity ground water at 2me of sampling § §
• •
Small SW area of Oakwood had occasional connec2on with Montgomery County supply (lime sodened, poly-‐P), so least “pure” PbO2 of this study Total of 9 LSL scale samples analyzed (1989-‐2002) § §
• • •
Greensand filtra2on Free chlorine
PbO2 was dominant scale mineral Two samples had more mixed-‐mineral scales
Engineering consultant inspected and measured plumbing in houses First draw 1L, waste volume then 3-‐250 mL samples to represent LSL Minimum of 6 hrs stagna2on, no pre-‐flush 9
Pb in water (µg/L)
Pb Levels from Full LSL Sites 20 18 16 14 12 10 8 6 4 2 0
OK-1, 6/89 (n=3) OK-2, 6/89 (n=4) OK-3, 6/89 (n=1) OK-4, 6/89 (n=2)
27-130
FAUCET LSL1
LSL2
LSL3
MAIN1
MAIN2
Sample Type (6h+ water stagnation) 10
Newport Study • • • • •
Analysis of 28 LSL scales for corrosion control study conducted by CDM in 2006-‐7 Nearly pure PbO2 with only traces of Pb(II) compounds CDM team took detailed measurements of premise plumbing and calculated volumes represented by samples Sequence of 1 L samples taken to assure all the way to main Premise plumbing § §
•
Interior = copper to meter SL = galvanized meter to curb stop
Only certain samples analyzed to target LSL ($ issue)
11
Pb in water (µg/L)
Plumbing Schematic NE1 20 18 16 14 12 10 8 6 4 2 0
Plumbing sequence corresponding to water volume Faucet Cu Galv LSL M Pipe pipe
Water Main
NE-1, 4/09
-1
0
1 2 3 4 5 6 7 Cumulative Water Volume (L)
8
Pb in water (µg/L)
Plumbing Schematic NE2 20 18 16 14 12 10 8 6 4 2 0
Plumbing sequence corresponding to water volume LSL Water Cu pipe Cu pipe Faucet M Main NE-2, 4/09
-1
0
1 2 3 4 5 6 7 Cumulative Water Volume (L)
8
Newport Conclusions
• Highest Pb in first liter or possibly downstream galvanized segment • Very low Pb release, < 4 µg/L • Hard to dis2nguish from galvanized sec2on
14
Cincinnati Study • Total of 11 LSLs analyzed, almost en2rely PbO2 • Two houses sampled by experienced personnel 2011-‐2013 • Different ages, both fed by Miller Plant water § §
CI1: 1922 CI2: 1883
• Both had PLSLR with copper, main to curb stop, 2001 • One site had detailed sampling, the other evenly-‐spaced 1 L sample bonles • Larger bonles were wide-‐mouth to capture “normal” household flow rate.
15
Cincinnati Study Sampling Sites
16
Identifying Pb Sources with Mixed Volumes S4
54”
46 1/4”
S5
141 1/4”
S6
42”
S8
S7
31
S1
1/2
”
S2
37 3/4”
69
S9
”
50 1/2 ”
S3 22" 1/2”
copper premise plumbing 2 3/4” 2”
10"
S1
Sequential sample #
4 1/2”
7 1/2”
S10
8 1/2”
Plumbing Material Copper Brass Lead Pb : Sn solder or soldered copper
water meter
1/2” Sch. 40
brass
3/4” ID lead
service line 7 1/2” exposed
To curb stop
S11
17
Including Cu, Zn and Fe is Very Useful Sharp rise in copper coupled with no increase in zinc and modest increase in iron suggested par2al replacement. GCWW records confirmed replacement by copper from main to curb stop in 2001!
18
Pb Concentration (µg/L)
20 18 16 14 12 10 8 6 4 2 0
Cl1: Cincinnati, OH Plumbing sequence corresponding to water volume Faucet LSL Water Main M
Cu pipe Brass Cu pipe
CI-1, 10 h, 12/09 CI-1, 10 h, 04/10
-1 0
1 2 3 4 5 6 7 8 9 10 11 Cumulative Water Volume (L)
20 18 16 14 12 10 8 6 4 2 0
LSL
1.0 0.8
Pb, 101 h, 03/11 Pb, 10 h, 02/13 Cl2, 10 h, 02/13 Cl2, 101 h, 03/11
0.6 0.4 0.2 0.0
Free Chlorine residual (mg/L)
Pb Concentration (µg/L)
CI1: Prolonged Stagnation Pb & Cl2
1 2 3 4 5 Cumulative Water Volume (L) 20
Pb Concentration (µg/L)
20 18 16 14 12 10 8 6 4 2 0
Cl2: Cincinnati, OH Plumbing sequence corresponding to water volume Faucet
Cu Pipe
M
LSL Cu Water Main
CI-2, 27 h, 06/12
-1 0
1 2 3 4 5 6 7 8 9 10 11 Cumulative Water Volume (L) 21
Pb Concentration (µg/L)
Impact of Prolonged Stagnation 20 18 16 14 12 10 8 6 4 2 0
CI-2, 27 h, 6/12 CI-2, 72 h, 9/12
0
1
LSL
2 3 4 5 6 7 8 9 10 11 22 Cumulative Water Volume (L)
0.8
LSL
0.6 0.4
10.5
9.5
8.5
7.5
6.5
5.5
4.5
3.5
2.5
1.5
0.2 0.0
Free Chlorine residual (mg/L)
1.0
Pb, 27 h, 6/12 Pb, 74 h, 9/12 Cl2, 27 h, 6/12 Cl2, 74 h, 9/12
0.5
20 18 16 14 12 10 8 6 4 2 0
0.25
Pb Concentration (µg/L)
CI2: Prolonged Stagnation Pb & Cl2
Cumulative Water Volume (L) 23
Pb in LSL water (µg/L)
Average & Range of Replicate Sampling Events 20 18 16 14 12 10 8 6 4 2 0
Sample Site, Water Stagnation Time
24
Conclusions
• Pb release from LSLs with [nearly] complete PbO2 scales § §
Usually well below 10 μg/L Oden
