R. Brown, EE&T, Inc. D. Cornwell, EE&T, Inc. M. Schmelling, DC Water

Transcription

1 R. Brown, EE&T, Inc. D. Cornwell, EE&T, Inc. M. Schmelling, DC Water 11

2 Funding WRF 4584 TC = DC Water & WRF Participating Utilities Four water systems PI David Cornwell WRF PM Jonathan Cuppett PAC A. Putz, M. Freidman, N. Charlton, M. Corson 22

3 Disturbances during LSLR have been shown to increase particulate and total lead in weeks/months following replacement Can in-home, high velocity flushing eliminate or mitigate these impacts? Flush by opening all taps inside the house for several minutes to dislodge and remove particulate lead from premise plumbing and from the service line after replacement Can this same type of flushing help other high lead households (e.g., with or without LSLR) 33

4 Traditional flushing - displacement Performed to displace old stagnant water Not necessarily for particulate removal High velocity flushing - dislodgement Analogous to unidirectional flushing of dist. sys. Objective is to dislodge, and then remove particulate material from pipes, fittings, and other parts of plumbing In this case to remove all loose particulate material between household taps and water main 44

5 Dislodge particulate lead that may otherwise be subsequently released to customer Mobilize and remove Remove aerators and screen Run long enough duration and high enough rate to dislodge particles and move them to tap Water from tap goes to drain (i.e., lead is not in pipes any more) 55

6 Many unidirectional flushing programs used in the distribution system target 6 to 8 ft/s. We often find success is possible at velocities near 2.5 ft/s; however, it requires longer flush duration. Examples ¾-in pipe at 3.5 gpm (9.5 L/min) velocity of about 2.5 ft/s (0.78 m/s) 1-in pipe at 10 gpm (~38 L/min) - typical this study ~4 ft/s (1.2 m/s) 30 min duration for this study 66

7 Flush - use one of three types after PLSLR Flush hose bibs - outside the house (SL only) group A Same as A but longer duration = group B Whole-house flush (by customer) = group C Findings Little improvement with 2 methods of flush for LSL only (outside the house) Improvement by 1st mo after whole-house flush (customer) 7

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9 Pb Concentration (mg/l) L L L A01 A02 A03 A04 B01 B02 C01 C02 C03 C L L L 99

10 Pb Concentration (mg/l) L L L A01 A02 A03 A04 B01 B02 C01 C02 C03 C L L L 10

11 Pb Concentration (mg/l) L L L A01 A02 A03 A04 B01 B02 C01 C02 C03 C L L L 11

12 One-time Flush 30 min, at least one tap per floor, aerator off, highest rate (esp. bathtubs) Collect 12 or more consecutive 1L samples Aerator off After 6 hr stagnation normal flow rate (see next slide) Analyze total & dissolved Pb, Mn, and Cu Some utilities analyzed other metals too (e.g., Fe) Sequence This presentation will focus on total Pb Most locations = Sample, flush, collect 1 day later, then monthly intervals thereafter Eight locations = sample, PLSLR, flush, collect 1 day later, monthly intervals thereafter 1212

13 Rates at all locations were consistent with normal water use Worked out to be about 25s to fill a 1L bottle, or 2.4 L/min Locations at PWS 2 followed the normal velocity samples with high rate samples These were about 4 to 6s per L, or 15 to 10 L/min 1313

14 Table 2.1 Participating utilities PWS 2 PWS 6 PWS 4 PWS 3 Lead control strategy ph and alkalinity adjustment yes Pb(IV) yes Orthophosphate yes yes yes Residual disinfectant Free Chlorine yes yes Chloramines yes yes Water chemistry Entry point ph Alkalinity (mg/l as CaCO 3 ) Free chlorine residual (mg/l as Cl 2 ) >1 0.6 Combined residual (mg/l as Cl 2 ) PO 4 residual (mg/l as P) Sample collection Sample collection by B A A B A = customers in their own homes (mostly were staff homes or homes of relatives) B = trained PWS staff at customer homes 1414

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16 Impact of flush w/ vs w/o aerator removed 16

17 Total Lead (µg/l) Location XM - PLSLR and household flush w/ aerator on 07/08/2015, 2 nd whole house flush aerator off 07/13/2015 pre-lslr (06/23) post-lslr & flush w/ aerator on (07/09) post-flush w/ aerator off (07/14) later post-flush (07/30) below DL one 07/09/2015 value not shown 7th L, 199 µg/l Profile Volume (L) 17

18 normal flow = no improvement high rate = improvement 18

19 H1 H2 H3 H4 H5 H6 H7 H8 H9 H10 H11 H12 H13 H14 H15 H16 H17 H18 H19 H20 Total Lead (µg/l) Location MT (Flush and PLSR 04/2015) initial 1 day 1 mo 2 mo 3 mo 4 mo Household plumbing: no lead SL: L (before PLSLR) L (after PLSLR) LSL: L (before PLSLR) L (after PLSLR) Normal sampling velocity High sampling velocity Profile Volume (L) 19

20 improvement between 1 st and 2 nd month Especially in first 11 L (inside house till end of SL) 20

21 H1 H2 H3 H4 H5 H6 H7 H8 H9 H10 H11 H12 H13 H14 H15 H16 H17 H18 H19 H20 Total Lead (µg/l) Location TN (Flush and PLSR 05/2015) 1000 initial 1 day 1 mo 2 mo 3 mo 4 mo Household plumbing: unknown material SL: L (before PLSLR) 5-11 L (after PLSLR) LSL: L (before PLSLR) L (after PLSLR) Profile Volume (L) 21

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23 Little improvement in normal velocity samples, much greater improvement in high velocity samples Household through SL 23

24 Total Lead (µg/l) Location HX (Flush no PLSR 10/2014) initial 1 mo 2 mo Household plumbing: no lead SL: L All SL is unknown material H1 H2 H3 H4 H5 H6 H7 H8 H9 H10 H11 H12 Profile Volume (L) 24

25 Total Lead (µg/l) Location TH (Flush no PLSR 02/2015) 50 initial 1 mo 2 mo Household plumbing: some lead SL: L LSL: L Profile Volume (L) 25

26 improvement in 1 st mo return to pre-flush by 2 nd mo. 26

27 Total Lead (µg/l) Location KQ (Flush no PLSR 08/2014) initial 1 mo 2 mo Household plumbing: some lead SL: L L is unknown material LSL: none H1 H2 H3 H4 H5 H6 H7 H8 H9 H10 H11 H12 Profile Volume (L) 27

28 Lead levels increase after flushing but no samples after 2 nd month 28

29 Total Lead (µg/l) Location KS (Flush no PLSR 05/2014) initial 1 mo 2 mo service line LSL 30 Household plumbing: no lead Profile Volume (L) 29

30 Slightly worse during first 2 mo, improvement thereafter Improvement continues up to 16 mo after single flush event 30

31 Total Lead (µg/l) Location HA (Flush 07/2014) initial 1 day 1 mo 2 mo 3 mo 4 mo 7th mo 16th mo service line LSL Profile Volume (L) 31

32 Lead levels decrease after flushing Lower levels maintained up to at least 10 mo Some higher Pb on 1 st day 32

33 Total Lead (µg/l) Location AW (Flush July 27, 2014) 80 initial 1 day 1 mo 2 mo 10 mo service line LSL Profile Volume (L) 3333

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35 Peak Total Lead Difference relative to pre-flush Positive = increase Negative = decrease 3535

36 Difference in Peak Lead Versus Pre-flush (µg/l) 80 Difference after in-home flush = 1 day ("+" means pre-flush higher, "-" means post-flush higher) PLSLR w/ flush flush - no PLSLR µg/l HM MT TN TT XM XF XO XA HX KQ KS KX OG QJ TH AW QA AE AK HA HJ µg/l -40 Location

37 Difference in Peak Lead Versus Pre-flush (µg/l) 80 Difference after in-home flush = 1 month ("+" means pre-flush higher, "-" means post-flush higher) PLSLR w/ flush flush - no PLSLR µg/l HM MT TN TT XM XF XO XA HX KQ KS KX OG QJ TH AW QA AE AK HA HJ µg/l -40 Location

38 Difference in Peak Lead Versus Pre-flush (µg/l) 80 Difference after in-home flush = 2 months ("+" means pre-flush higher, "-" means post-flush higher) PLSLR w/ flush flush - no PLSLR 60 +1,964 µg/l HM MT TN TT XM XF XO XA HX KQ KS KX OG QJ TH AW QA AE AK HA HJ µg/l - 41 µg/l -40 Location

39 Difference in Peak Lead Versus Pre-flush (µg/l) 80 Difference after in-home flush = 3 months ("+" means pre-flush higher, "-" means post-flush higher) PLSLR w/ flush flush - no PLSLR HM MT TN TT XM XF XO XA HX KQ KS KX OG QJ TH AW QA AE AK HA HJ µg/l - 61 µg/l -40 Location

40 Difference in Peak Lead Versus Pre-flush (µg/l) 80 Difference after in-home flush = 4 months ("+" means pre-flush higher, "-" means post-flush higher) PLSLR w/ flush flush - no PLSLR HM MT TN TT XM XF XO XA HX KQ KS KX OG QJ TH AW QA AE AK HA HJ µg/l - 68 µg/l -40 Location

41 Difference in Peak Lead Versus Pre-flush (µg/l) 80 Difference after in-home flush = >6 months ("+" means pre-flush higher, "-" means post-flush higher) PLSLR w/ flush flush - no PLSLR HM MT TN TT XM XF XO XA HX KQ KS KX OG QJ TH AW QA AE AK HA HJ Location

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43 Add total lead in all 12 samples for 1 st L + 2 nd L + 3 rd L + etc. (normal rate) Each date Each location <DL = 0 With and without PLSLR 4343

44 Post-Flush Cumulative Total Lead (µg) PLSLR, then flush day 1 mo 2 mo 3 mo 4 mo Pre-Flush Cumulative Total Lead (µg)

45 Post-Flush Cumulative Total Lead (µg) Flush, no PLSLR day 1 mo 2 mo 3 mo 4 mo 6 mo or more Pre-Flush Cumulative Total Lead (µg)

46 High velocity flushing after PLSLR PLSLR already known to disturb lead for a few months PWS provides instructions for water use in the 1 st few months after PLSLR Flushing appears to make it better during this period (i.e., ~2 mo instead of longer w/o flushing) Some data shows immediate improvement after whole house flush but other times it takes longer (~2 months) High velocity flushing without PLSLR increased disturbance may cause higher lead in 1 st couple of months Lead levels come down in subsequent months Both Data suggest higher velocity, longer flush, and/or repeat flush events may be needed 4646

47 Lead scale analysis Lead isotopes (source/fate tracking) 4747

48 EE&T Further Pioneering Analysis: XRD-crystalline Structures XRF and Raman-amorphous structures SEM/EDS-elemental analysis Pb Isotope Analysis for source and fate tracking 48

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50 Shows Turbicule Cross-section 37

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52 Richard Brown 712 Gum Rock Court Newport News, Virginia (757) (757) Fax 52