Avon Lake Corrosion Control Study and Orthophosphate Implementation. Andrew Skeriotis, Stantec Greg Yuronich, Avon Lake Regional Water

Transcription

1 Avon Lake Corrosion Control Study and Orthophosphate Implementation Andrew Skeriotis, Stantec Greg Yuronich, Avon Lake Regional Water

2 Agenda 1 History and Background of Avon Lake 2 Lead and Copper in Water 3 Avon Lake Corrosion Control Study 4 Implementation 5 Questions

3 Background Avon Lake Water Filtration Plant Built in 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.

4 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

5 Plant Layout

6 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

7 Avon Lake Pb and Cu Sampling Monitoring Period No. of Sites 90% Pb (μg/l) 90% Cu (μg/l) < < < < < <

8 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

9 Lead News Not Going Away Anytime Soon

10 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.

11 Factors that Influence Corrosion Physical - Flow Factor Effect - Corrosion rates have been observed to increase with increasing and/or fluctuating water velocity - Temperature - Increases corrosion rates and precipitation of CaCO 3 Chemical - ph - Alkalinity - Low ph may increase corrosion rate; high ph may protect pipes and decrease corrosion rates - May help form protective CaCO 3 coating; helps control ph changes, reduces corrosion - Increases rate of many chemical reactions, typically - Dissolved oxygen 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 CaCO 3 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)

12 Corrosion Control Alternatives Calcium Carbonate Precipitation ph/alkalinity/dic Adjustments Phosphate Inhibitors Silicate Inhibitors

13 Corrosion Control Alternatives Treatment Option Advantages Disadvantages Calcium Carbonate Precipitation Optimal Conditions (CCPP=6) Carbonate Passivation Optimal Conditions (ph=9.3) - Option is effective for corrosion control - Lowest theoretical lead solubility - Extremely low copper solubility - 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 - High ph values impact compliance with DBP regulations - Very depositing water; potential for scale deposition in water pipes - Reduced chlorine efficiency for disinfection 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

14 Corrosion Control Alternatives 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, asbestoscement, galvanized pipes, etc.) - Potential for bacteria increase in distribution system (PO 4 is a nutrient) - Relatively long detention times for film formation - Requires periodic flushing of distribution system

15 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.

16 Overview of LCR

17 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 WTP Finished (Lake Erie) Water ph Temperature, o C Alkalinity, mg/l as CaCO Total Hardness, mg/l as CaCO Calcium Hardness, mg/l as CaCO Total Dissolved Solids (TDS), mg/l Dissolved Inorganic Carbonate (DIC), mg/l as C 22 22

18 Avon Lake Corrosivity Parameters OUTPUT Calculated Parameters Ca ++ Hardness (mg/l as CaCO 3 ) Alkalinity (mg/l as CaCO 3 ) ph CCPP* (mg/l CaCO 3 ) * Calcium Carbonate Precipitation Potential Langelier Index Buffer Capacity (mg/l-ph) Acidity (mg/l as CaCO 3 ) Dissolved Inorganic Carbonate (mg C/L) Ryznar Index Before Chemical Adiition After Chemical Addition

19 Treatment Alternatives Description Alkalinity and ph Adjustment Corrosion Inhibitor Treatment Inhibition Mechanism Passivation 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

20 Determining OCCT

21 Determining OCCT Lead Solubility Diagram at various PO 4 Doses (ph=7.5, I=0.005, T=25 C)

22 Considerations

23 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.

24 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.

25 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.

26 Unidirectional Flushing vs. Conventional Flushing

27 It has begun!

28 Questions Thank you for your time!