Avon Lake Corrosion

Control Study and

Orthophosphate

Implementation

Andrew Skeriotis, Stantec

Greg Yuronich, Avon Lake Regional Water

Agenda

1 History and Background of Avon Lake

2 Lead and Copper in Water

3Avon Lake Corrosion Control Study

4 Implementation

5 Questions

Background

Avon Lake Water Filtration Plant

– Built in 1926- originally a 2 MGD

plant serving 1,000 people

– Serves 225,000 people in a 680-

square mile service area

– 85% of the water produced

goes outside of Avon Lake

– Seasonal approved capacity of

50 MGD in the summer and 40

MGD in the winter.

• 3 Million Gallons

• Scheduled to be in operation

November of this year

• Will compliment the new 3 million

gallon clearwells that went in to

service December 2016 to provide

increase in finished water storage

Plant Layout

LEAD…• Ever since Flint, lead is something no one

wants to hear mentioned in the same

sentence as their water system.

HOSPITAL IN FLINT, MI OCTOBER 2015

Avon Lake Pb and Cu SamplingMonitoring Period No. of Sites 90% Pb (μg/L) 90% Cu (μg/L)

1992 60 9.0 61.0

1993 60 6.1 96.8

1994 30 2.5 116

1995 30 < 2.2 75.2

1996 30 2.4 38.6

1999 30 5.6 80.0

2001 30 < 3.0 28.4

2004 30 < 3.0 90.8

2007 30 6.5 93.0

2010 30 < 3.0 49.5

2013 30 < 3.0 60.9

2016 30 < 3.0 52.0

• Neither Avon Lake Regional Water nor any of our

bulk customers have ever had a problem with

lead exceeding the action level.

• One action level exceedance would be one too

many and we wanted to make sure we maintain

the highest level of safety for our customers.

• After much internal discussion and debate, we

decided to start looking into ways we could

further safeguard our water…

Lead News Not Going Away

Anytime Soon…

Lead in Water

Sources of Lead and Copper:

1. Lead is rarely found in source water.

2. Lead release typically occurs in lead

service lines and household plumbing.

Factors that Influence CorrosionFactor Effect

Physical

- Flow- Corrosion rates have been observed to increase withincreasing and/or fluctuating water velocity

- Temperature - Increases corrosion rates and precipitation of CaCO3

Chemical

- pH- Low pH may increase corrosion rate; high pH mayprotect pipes and decrease corrosion rates

- Alkalinity- May help form protective CaCO3 coating; helps controlpH changes, reduces corrosion

- Dissolved oxygen- Increases rate of many chemical reactions, typically

increases corrosion, absence of DO can lead toanaerobic biological corrosion

- Chlorine residual Increases metallic corrosion, may form Pb coating

- Total dissolved solids (TDS) - High TDS increase conductivity and corrosion rate

- Hardness (calcium and magnesium)- Ca may precipitate as CaCO3 and thus provideprotection and reduce corrosion rates

- Chloride, sulfate- High levels increase corrosion of iron, copper andgalvanized steel

- Hydrogen sulfide - Increases corrosion rates

- Silicate, phosphates - May form protective films

- Natural color, organic matter - May decrease or increase corrosion

- Iron, zinc or manganese- May react with compounds on interior of pipe to formprotective coating

Biological

- Aerobic and anaerobic bacteria - May induce corrosion

Reference: (AWWARF/DVGW 1985 and USEPA 1984)

Corrosion Control Alternatives

• Calcium Carbonate Precipitation

• pH/Alkalinity/DIC Adjustments

• Phosphate Inhibitors• Silicate Inhibitors

Corrosion Control Alternatives

Carbonate PassivationOptimal Conditions (pH=9.3)

- Lowest theoretical lead solubility

- Extremely low copper solubility

- High pH values impact compliance with DBP regulations

- Very depositing water; potential for scale deposition in water pipes

- Reduced chlorine efficiency for disinfection

Calcium Carbonate PrecipitationOptimal Conditions (CCPP=6)

- Option is effective for corrosion control

- Sloughing off of deposits could result in periodic higher lead concentrations

- Difficult to maintain a uniform film throughout the distribution system

- Lines closed to WTP need to be flushed periodically

Polyphosphate Inhibitor - Tends to revert to orthophosphate reducing lead solubility

- Beneficial for other water quality concerns (sequestering agent)

- Potential for reduced lead solubility

- Uncertain effectiveness for corrosion control

- Potential for lead solubilizationif orthophosphate is not present

- Effectiveness depends on formulation characteristics

- Uncertain effectiveness for corrosion control

Treatment Option Advantages Disadvantages

Corrosion Control Alternatives

Orthophosphate Inhibitor - Effective for lead and copper corrosion control in similar systems

- Raw water is suitable for orthophosphate addition

- Lower pH value (lower TTHMs may increase

HAAs)- Lower chemical feed

requirements- Reduced corrosion

rates for various pipe types (iron, asbestos-cement, galvanized pipes, etc.)

- Potential for bacteria increase in distribution system (PO4 is a nutrient)

- Relatively long detention times for film formation

- Requires periodic flushing of distribution system

Treatment Option Advantages Disadvantages

Study Objectives

1. Present an overview of the LCR,

2. Analyze the stability of the raw and

finished water from Avon Lake

Regional Water,

3. Evaluates viable corrosion control

treatment alternatives, and

4. Outline a recommended corrosion

control plan for Avon Lake Regional

Water and their consecutive systems.

Overview of LCR

Avon Lake Water Quality Parameters

• Potassium permanganate 0.12 mg/L;

• Alum 27.5 mg/L;

• PAC 0.5 to 8.5 mg/L (on an as needed basis);

• Lime 3.5 mg/L;

• Chlorine 3.5 mg/L; and

• Sodium silicofluoride 1.3 mg/L.

Parameter Raw Water (Lake Erie)

WTP Finished Water

pH 7.8 7.3 Temperature, oC 11 11

Alkalinity, mg/L as CaCO3 91 81 Total Hardness, mg/L as CaCO3 120 124

Calcium Hardness, mg/L as CaCO3 109 114 Total Dissolved Solids (TDS), mg/L 167 170

Dissolved Inorganic Carbonate (DIC), mg/L as C 22 22

Avon Lake Corrosivity Parameters

OUTPUT

Calculated Parameters

Ca++

Hardness (mg/L as CaCO3)

Alkalinity (mg/L as CaCO3)

pH

CCPP* (mg/L CaCO3)

* Calcium Carbonate Precipitation Potential

Langelier Index

Buffer Capacity (mg/L-pH)

Acidity (mg/L as CaCO3)

Dissolved Inorganic Carbonate (mg C/L)

Ryznar Index

101

91

7.84

-3.65 -27.11

-1.17

30.86

110.03

8.59 9.43

22.6 22.6

Before

Chemical Adiition

After

Chemical Addition

-0.37

8.00

96.95

107.25

77.93

7.08

Treatment Alternatives

DescriptionAlkalinity and pH

Adjustment

Corrosion Inhibitor

Treatment

Inhibition

MechanismPassivation Passivation

Critical Water

Quality

Parameters

pH, Alkalinity, Dissolved

Inorganic Carbonate

(DIC), Total Dissolved

Solids (TDS), and

Temperature

pH, Alkalinity, DIC,

Metals of Interest,

Hardness, and

Temperature

Determining OCCT

Determining OCCT

Lead Solubility Diagram at various PO4

Doses (pH=7.5, I=0.005, T=25 ° C)

Considerations

Recommendations• Initiate the procedure for designing and installing

orthophosphate storage-and-feed facilities in accordance

with requirements of the RSWW.

• Ohio EPA (i.e., a backup feed pump and 30-days of storage).

• Develop the protocol for a rigorous program for initially

flushing the distribution system including coordination with

consecutive PWSs utilizing unidirectional flushing before the initial orthophosphate dose.

• Initiate a public educational program to inform the customers

for expected changes in the finished-water quality, especially during the initial application of the corrosion inhibitor. These

changes may be discoloration, red-water, sediment, and

taste and odor issues, however, the initial unidirectional

flushing will help alleviate many water quality issues. Keeping a customer comment log will help the PWSs target problem

areas.

Recommendations

• Inform the local wastewater treatment facilities

for the expected changes in the finished-water

quality and coordinate with the wastewater

treatment facilities (including the consecutive

PWSs) to minimize the potential problems

associated with the presence of phosphate and

the potential presence of zinc in the finished

water.

Implementation• Apply an initial orthophosphate dose of approximately 2 mg/L for a

3-month period; then reduce the dose to 0.5 to 1.0 mg/L.

Implement a partial-system testing program (coordinating with

consecutive PWSs) for corrosion control:

• After 3 months from the initiation of orthophosphate feed, flush the

system to remove any corrosion byproducts and tuberculation

utilizing unidirectional flushing coordinating with the consecutive

PWSs.

• After the system has settled down, collect 30, first-draw samples from

consumers’ taps in accordance with the LCR.

• These samples are to be used as the baseline for the current

treatment practice for corrosion control. Sample collection shall

also be coordinated with the consecutive PWSs.

Unidirectional Flushing vs.

Conventional Flushing

It has

begun!

Questions

Thank you for your time!