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Process Evaluation to Provide Sustainable Arsenic Compliance for a Potable Water Treatment System; St. Michaels, MD
Christopher Curran, PE
Christopher Walker, PE
Mark Prouty, PE
PA AWWA ConferenceApril 23, 2015
Background
Arsenic Treatment Technologies
Existing System Challenges
Evaluation Approach
Evaluation Findings
Alternatives
Recommendations
Presentation Outline
Background - Arsenic
Water Treatment Facility Evaluation - St. Michaels, MD
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• What is Arsenic?
• Sources of Environmental Arsenic
• Effects of Arsenic on Human Health
• US EPA Regulations
Background - Arsenic
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Background – Source Water
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Town of St. Michaels
Background
6
• St. Michaels – Vibrant Tourism
• Existing System Description
Glory Ave WTP (250,000 gpd)
Marengo St WTP (125,000 gpd)
Water Treatment Facility Evaluation - St. Michaels, MD
Arsenic Treatment Technologies
• Adsorption Process– Granular Ferric Hydroxide (GFH)– Granular Ferric Oxide (GFO)– Activated Alumina { Lower pH Req’d }– Media Disposal
• Ion Exchange Process– Pressure Vessel – Media Regeneration
• Oxidation/Co-Precipitation/Filtration– Ferric Chloride Addition– pH Adjustment– Pressure Filtration– Backwash Needs
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Existing System Challenges
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• New Arsenic Systems Installed in 2006 to Meet EPA MCLs
• Ex. Treatment Systems -Arsenic Breakthrough
• Reduced Bed Life of Media
• Solids Accumulation in Filters
• Backwash Management
• Aged Raw Water / Well Pump Piping and Valving
• Operational Challenges
Water Treatment Facility Evaluation - St. Michaels, MD
Existing System – Glory Ave WTP
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• Raw H2O As: 32 – 48 ppb
• 2006 IBS System Installation (Bayoxide®)
• Media Change-Outs�2010 & 2012 & 2014
Existing System - Marengo St WTP
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• Raw H2O As: 32 – 48 ppb
• 2006 IBS System Installation
�Media Change-Outs• 3/10, 8/10 & 10/10 (Breakthrough)
• 4/2011 Ion Exchange Installation (Purolite FerrIX A33)
�Media Change-Outs• 9/11, 11/11, 6/12
• December 2012 Permanently Offline
Project Approach
• Review Data and Operations Records
• Engage Operations Staff and Include in Team
• Identify Alternatives
• Evaluate Alternatives in Matrix Evaluation for Cost Effectiveness and Overall Benefit
• Submit Alternative Evaluation Report to Town
• Gain Regulatory Concurrence
• Prepare Grant Application
• Develop & Execute Implementation Plan
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General Alternatives
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Project Evaluation - Items Evaluated
1. Water Quality Parameters• Develop Sampling Program• Review Data
2. Operational Review• System Control Logic• Review Operational Set Points• Review Operations Data• Investigate Backwash Activities• Investigate Potential Cross-Connections• Verify Loading Rates and Compliance with Manufacturer O&M
Guidelines
3. Review Previous Engineering Reports
4. Discussions with Equipment Manufacturers
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Important Water Quality Parameters
�Arsenic Speciation
�pH
�Chloride
�Selenium
�Fluoride
�Silica
�Sulfate
�Nitrate
�Phosphate
�Total Dissolved Solids
�Total Organic Carbon
�Iron
�Manganese
�Turbidity
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Project Findings – Water Quality DataRaw Water Quality Parameter
Acceptable Range
Detected RangeMarengo WTP
Detected RangeGlory WTP
Total Arsenic ** 32-48 32-48
pH 5.5-9.0 6.9-9.4 7.7-8.8
Ferrous Iron <0.25 ppm 0.13 0.18
Manganese <0.05 ppm 0.014-0.037 ND
Aluminum <0.2 ppm 0.089-0.096 ND
Silica <20 ppm 12.4-13.8 12.0-15.0
Phosphate <0.05 ppm 0.05-0.076 0.02-0.31
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Evaluation Findings – pH Effect on IBS
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Courtesy of Siemens
Project Findings – Filter Inspections
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Marengo WTP Filters
Project Findings – Filter Inspections
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Marengo WTP Lead Bed – Inlet Piping / Strainer
Project Findings – Filter Inspections
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Marengo WTP Lag Bed – Uneven Media Surface
Uneven Media Surface
Project Findings – Filter Inspections
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Marengo WTP Lead Bed – Underdrains
Operational Parameters Effect: IBS Bed Life (GFH)
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Courtesy of Siemens
Evaluation Findings – Well Production
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0
50
100
150
200
250
300Ja
n-0
6
Ap
r-0
6
Ju
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6
Oct-
06
Ja
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Ap
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7
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Oct-
07
Ja
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8
Ap
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8
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Oct-
08
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Oct-
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Flo
w R
ate
(1
,00
0 G
PD
)
Well Flow Rates
Well #2 - Marengo StWTP
Well #3 - Glory AveWTP
Well #3 Target Flow Rate = 250,000 GPD
Well #2 Target Flow Rate = 125,000 GPD
Evaluation Findings – Hydraulic Loading
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Parameter Target Value Marengo WTP Glory WTP
Empty Bed Contact Time (min)*
3.5 – 5.0 2.64 3.68
HydraulicLoading (gpm/sf)
8 10 gpm/sf 8.1 gpm/sf
Flow Rate Marengo (gpm) 211 280 --
Flow Rate Glory (gpm) 400 -- 408
Underdrain Loading Rate (gpm/sf)
N/A 724 272
* EBCT was 28% Lower at Marengo WTP than Glory WTP
Evaluation Findings – Backwashing
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• Glory WTP� Operator Intensive – Hoses� Supply Water From Well Pump� Receiving Pump Station Lacks Capacity� No Floor Drains
• Marengo WTP� Operator Intensive – Hoses� Supply Water From Well Pump� No Floor Drains
Evaluation Findings - Summary
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• Competing Chemical Compounds in
Raw Water
• Poor Hydraulics Through Vessels
• Insufficient Contact Time with Media
(Marengo WTP)
• Better Control on Water Production
and Flow Rate Necessary at Both
WTPs
Evaluation Findings - Summary
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• Testing Indicated IX Media was Only 50% Exhausted at
Breakthrough
• Odors Generated from Ion Exchange Media Following
Idle Periods
• Lack of Backwash Disposal Capacity at Glory Street WTP
• Lack of Backwash Drainage Appurtenances at Both Wells
Alternatives
• Oxidation / Co-Precipitation / Filtration with Catalytic Greensand Plus®
– Pre-oxidation
– Ferric Chloride Addition
– pH Adjustment
– Backwash
• Proven Technology
• Removes Iron
• Minimum Operational Complexity
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Alternatives
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• Iron Based Sorption Media Improvements
• Flow Control
• pH Adjustment
• Hybrid Approach
• Maintain IBS System at Glory WTP
• Install Co-Precipitation / Filtration System at Marengo WTP
Alternatives
Alternative Capital Cost Annual Cost Present Worth
IBS Media $770,000 $73,900 $1,774,325
CatalyticOxidation/Filtration $1,490,000 $21,800 $1,786,171
Hybrid Approach $1,110,000 $48,393 $1,767,677
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Recommendations
• Install Catalytic Oxidation System at Marengo Street
• Implement Improvements to Ex. Treatment System (Glory)
– Precondition Raw Water
• Provide Backwashing Improvements
– Backwash Supply / Metering
– Backwash Holding Tanks
– Backwash Recycle (Marengo WTP)
• Well Flow Control Improvements (Need VFDs)
• Safety Improvements – Convert to NaOCl
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Recommendations – Marengo WTP
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Well House
Generator
Well
Filter Building
Recommendations – Marengo WTP
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New Chemical Room
Blow-off
Backwash Tank
New FiltrationEquipment
New Piping Gallery /Trench Drain
Recommendations – Marengo WTP
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Backwash Tank
Backwash Pipe to 12,000 gal Aqua StoreBackwash Recycle Tank
Backwash Tank
Recommendations – Glory WTP
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Well HouseGenerator
Well
Filter Building
Recommendations – Glory WTP
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25,000 gal Concrete Backwash Holding Tank
Backwash Tank
New Chemical Room
New Piping Gallery /Trench Drain
Well House
Filter Building
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Acknowledgements
Town of St. Michaels
• Jean Weisman (Town Administrator)
• Jeff Richardson (Public Works Director)
April 23, 2015
Questions
Contact Information:Christopher Curran, P.E.Sabre Building, Suite 300
4051 Ogletown Road, Newark, DE 19713
302.781.5888
