A Holistic Look at Lead in Drinking Water Distribution Systems Paul Hargette, P.E.

Senior Process Engineer

13 November 2017

Agenda

• Background and drivers• Factors affecting lead release• What are utilities doing

• Risk evaluation• Water chemistry evaluation• Modeling• Materials inventory

• Demonstration testing• Pipe wall scale analysis• Bench scale testing• Pipe loop testing

• Putting it all together

Distribution System Considerations

Increased public understanding of distribution system water quality3

• Regulations / public health

• Aesthetics

• Distribution System Integrity

Lead Release in the News

From a Reuters investigation “The thousands of U.S. locales where lead poisoning is worse than in Flint” – not solely caused by lead release in water

4

Lead Release Events – Common Themes

Increased public pressure for action5

• Change in source, treatment, or chemistry • Elevated lead levels at customer tap samples• Deterioration of water quality beyond lead• Simultaneous compliance • Outcomes:

• Increased public awareness and dialogue

• Increased industry knowledge base

• Changes in the regulations “Tap water in Flint’s hospital on October 16” by Joyca Zhu/Flint Water Study in “The Conversation” licensed by CC BY-ND 4.0

5

Regulatory Drivers• Lead and Copper Rule

• 1991, 2000, 2004, 2007, 2017?

• Proposed changes to the LCR• Sampling protocols and voluntary sampling• Increase public education and transparency• Expanded OCCT requirements• Single household action level• Revised copper requirements• Proactive LSLR program / full replacement

• State-specific regulations on the rise

Is your utility positioned for compliance with the long-term revisions?6

FACTORS AFFECTING LEAD RELEASESOLUBLEPARTICULATEMICROBIAL INFLUENCE

Factors Affecting Lead Release

• Water chemistry and microbiology

• Piping materials

• Operational practices

• Treatment changes

• Know your system-specific risk factors

Need to look at soluble and particulate lead separately8

Hydraulic / Quality Analysis

Risk-Consequence

Prioritized Improvements

8

Distribution System Water Quality

99

Metals Solubility

• pH • Master variable for all water processes• Lead solubility decreases with

increasing pH (for MOST waters)

• Alkalinity

• Dissolved Inorganic Carbon (DIC)

• Consider secondary complexes

Good indicator of relative potential for lead release10

Figure Source: Water Research Foundation, 2015.

Lead

Sol

ubili

ty, m

g/L

Low DIC

High DIC

Common “Corrosion” Indices

Additional indices useful in specific cases

• Calcium Carbonate Based• Langelier Saturation Index (LSI)

• Calcium Carbonate Precipitation Potential (CCPP)

• Chloride to Sulfate Mass Ratio (CSMR)

• 𝑳𝑳𝑳𝑳𝑳𝑳𝑳𝑳𝑳𝑳𝐧𝐧′𝑳𝑳 𝑹𝑹𝑳𝑳𝑹𝑹𝑹𝑹𝑳𝑳 = 𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝒂𝑪𝑪𝒂𝒂−+𝑺𝑺𝑺𝑺𝟒𝟒

𝟐𝟐−

11

Scale Release

Impacted by secondary metals and changing water conditions12

Biostability

• Temperature, organic carbon, and nutrients

• Disinfectant residual and ORP• Maintain residual throughout system

• Measure overall microbial activity• ATP or HPC• TCR data• Nitrification in chloraminated systems

(NO3-, NO2

-, NH3)

Impacts both soluble and particulate metals release

Dual-species microbial biofilm stained with fluorescent labels

captured with confocal microscopy

13

Impacts of Nitrification

• Loss of chlorine residual• Increased HPC and general microbial growth• Formation of nitrite and nitrate• Drop in pH and alkalinity• Increase in rate of corrosion and metals release• Increased potential for legionella

14

Corrosion Inhibitors

• Orthophosphates and silicates

• Aid in formation of passivating layer

• Stabilize existing scale; lower lead solubility

• Polyphosphates – sequester metal ions, NOT effective for corrosion control

Need to consider secondary impacts1515

WHAT ARE UTILITIES DOING?

RISK ASSESSMENTS

Proactive Corrosion Risk Assessment

Goal: Always remain in compliance and ahead of regulation changes17

Lead Risk Assessment Components

• Distribution system materials evaluation

• Distribution system monitoring plan

• Desktop water quality analysis

• Hydraulic modeling / Operations Review

• Risk management strategies prioritization

How optimized is your distribution system?18

Utility-specific

Materials Evaluation• Distribution piping and service line material

• Plumbing, fixtures, and faucets

• Re-selection of Tier 1 homes

• Updating service line material inventory – WRF #4693

Galvanized pipes downstream of replaced LSLs can continue to release lead19

Distribution System Monitoring Plan• pH, alkalinity, DIC

• Calcium, magnesium, silica, phosphate

• Chloride and sulfate

• Iron, manganese, and aluminum

• HPC, disinfectant residual, temperature• Ammonia, nitrate, nitrite

• Residential lead sampling to supplement LCR sampling

Selection of representative sampling sites is key20

Water Quality Evaluation

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• Seasonal patterns • Spatial patterns

• Historical compliance data review • System-specific modeling

Benefits of Water Quality Modeling• Identify high water age and focus sampling sites

• Trace introduction of new source(s)

• Identify changes in velocity or flow direction

• Evaluate benefits of potential operational changes

• “What-if” scenarios to find most effective solution

2222

Operations Affecting Corrosion & Lead Release

• Water age / Tank water levels

• Flushing program

• Operational parameters or treatment changes• Enhanced coagulation / Switch in coagulants• Addition of a new source / Change in source• Change in disinfectant type• Addition of new treatment process• Maintenance in the distribution system• LSL replacement programs

23

WHAT ARE UTILITIES DOING?

DEMONSTRATION TESTING

Optimal Corrosion Control Treatment

Narrow down the options before you begin testing

From USEPA, March 2016

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Demonstration Testing Considerations• Pipe wall scale analysis

• Harvested pipe samples

• Bench scale testing• Quickly screen water quality conditions and materials• Typically static conditions and shorter testing duration• Can use new or harvested materials

• Pipe loop testing• Captures hydraulic effects; reflects full scale conditions• Longer testing period, can capture seasonal results• Can use new or harvested materials

Testing program designed to meet specific project needs26

Pipe Wall Scale Analysis

Most common tools for scale analysis include SEM – EDS, XRD, elemental analysis27

Typical XRD patterns for lead-containing scalesPipe sections are cut longitudinally for analysis of internal scale

From AWWA Manual M58 From AWWA Manual M58

SEM-EDS Analysis

Bench Testing Configurations

Metal coupon placed in a small container filled with various test waters28

“Storage Stability of Fuels”, book edited by Krzysztof Biernat under CC BY 3.0

Flintwaterstudy.org

Source: Black & Veatch Source: Black & Veatch

Hybrid Bench/Pipe Loop Scale Systems

• Can create stagnating and flowing conditions

• Compact design

29

From WRF #4286 - Distribution System Water Quality Control Demonstration

Welter, G., Giammar, D., Wang, Y., and A. Cantor. 2013. Galvanic corrosion following partial lead service line replacement. Project 4349. Water Research Foundation, Denver, Colorado.

Pipe Loop Configurations

From Zhang et. al., JAWWA 2012

From WRF 4317 Non-Intrusive Methodology for Assessing Lead and Copper Corrosion

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From Welter, Schock, Miller, Razza, and Giammar, WQTC 2015

Pipe Loop Configurations

From Integration of desalinated seawater into a distribution system: A corrosion pilot study. 2008. Journal – AWWA. From Zhang et. al., JAWWA 2012

31

• Use data to compare lead release from various test cases and conditions.• Must include statistical representation; Replicates are important.• Need to allow for sufficient time for steady state conditions to establish and persist• Use secondary water quality parameters to help explain results

0

50

100

150

200

250

300

350

1 2 1 2 1 2 1 2 1 2

Tota

l Pb

(µg/

L)

Mean

Condition 5Condition 3Condition 2Condition 1 Condition 4

max

median

min

75th percentile

25th percentile

Modified from Wang, Mehta, Welter, and Giammar Journal AWWA, 2013

Example Data Analysis

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SUMMARY

Understand How To Use Available Tools

• Factors affecting lead release

• System-specific risk assessment

• Demonstration testing

• Consider using pipe loops as standard practice

• Shift from compliance to optimization mindset

• Understand public concerns and increase communication

Provides an opportunity to limit lead release34

Senior Process EngineerHargettePH@bv.com

Paul Hargette, P.E.13 November 2017