PowerPoint PresentationAugust 30, 2018 Columbus, OH
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 Storage Tank • In operation November of 2017 • Will compliment the new 3 million
gallon clearwells that went in to service December 2016 to provide increase in finished water storage
Plant Layout
Sedimentation, Filtration, Disinfection, Pumping
Flint Crisis • 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
Lead News Not Going Away Anytime Soon…
Avon Lake Pb and Cu Sampling Monitoring 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
AVE = < 4.1 (ug/L)
• “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.”
Greg Yuronich – Water Treatment Plant Manager
Proactive vs. Reactive
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.
Physical
- Flow - Corrosion rates have been observed to increase with increasing and/or fluctuating water velocity
- Temperature - Increases corrosion rates and precipitation of CaCO3
Chemical
- pH - Low pH may increase corrosion rate; high pH may protect pipes and decrease corrosion rates
- Alkalinity - May help form protective CaCO3 coating; helps control pH changes, reduces corrosion
- Dissolved oxygen - Increases rate of many chemical reactions, typically increases corrosion, absence of DO can lead to anaerobic 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 provide protection and reduce corrosion rates
- Chloride, sulfate - High levels increase corrosion of iron, copper and galvanized 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 form protective coating
Biological - Aerobic and anaerobic bacteria - May induce corrosion
Reference: (AWWARF/DVGW 1985 and USEPA 1984)
Corrosion Control Alternatives
Corrosion Control Alternatives
- Lowest theoretical lead solubility
- Extremely low copper solubility
- Very depositing water; potential for scale deposition in water pipes
- Reduced chlorine efficiency for disinfection
Calcium Carbonate Precipitation Optimal Conditions (CCPP=6)
- Precipitation no longer accepted as a viable corrosion control technique (USEPA, 3/16)
- 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 solubilization if orthophosphate is not present
- Effectiveness depends on formulation characteristics
- Uncertain effectiveness for corrosion control
Treatment Option Advantages Disadvantages
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
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
Parameter
120
124
109
114
167
170
22
22
Ca++ Hardness (mg/L as CaCO3) 112 118.43
Alkalinity (mg/L as CaCO3) 91 83.80
pH 7.8 7.29
Langelier Index -0.34 -0.87 Buffer Capacity (mg/L-pH) 8.47 21.73
Dissolved Inorganic Carbonate (mg C/L) 22.6 22.6
Ryznar Index 8.49 9.02
Corrosion Inhibitor Treatment
Determining OCCT
1. Is iron or manganese present in the finished water?
2. Is copper only removal desired? 3. What is the pH of the finished
water? 4. What is the DIC of the finished
water?
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
Results and Lessons Learned
• During 3-month implementation period, PO4 dose was gradually increased from 0.5 mg/L to 1.5 mg/L.
• Finished water turbidities increased from 0.05 (NTU) to 0.18 (NTU).
• Eventually system stabilized and turbidities dropped down to 0.08 (NTU).
• After 3 months with PO4 at 1.5 mg/L dose, maintenance dose was set at 0.6 mg/L.
• Turbidities now run at average of 0.07 (up from pre- implementation level of 0.05 (NTU).
Acknowledgements
Steve Heimlich, Water Plant Manager (retired) – Avon Lake Regional Water
Dr. Timothy Wolfe – Stantec Dr. Stan Zachopoulos – Stantec
Questions
Slide Number 1