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Louisville’s Water Works
Celebrating 150 Years
of Service
Maintaining Louisville Water’s Best Tasting Tap Water
Water System Optimization ConferenceOctober 29, 2015
Vince MonksRengao Song, Ph.D.
Eric Zhu, Ph.D.Chris Bobay
Presentation Outline
• Background & Challenges
• LWC’s optimized disinfectant residual management approach
• Take-home Message
• Q/A
Best Water Must Meet 3 StandardsMeet/exceed stringent and complex regulations: health risk issues or safe to drink
– Pathogens – Organics (spills & pesticide contamination) – Inorganics (lead and copper)– Distribution water quality and residual management
90+ contaminants required for simultaneous compliance
Maintain/improve customer satisfaction: aesthetics issues or best tasting
– Taste & Odor (algae, di-chloramine) – Discolored water (red water, black water)
Customers often use aesthetic parameters as water safety indicators
Maintain public understanding and trust: perceived risks– Detection of unregulated chemicals: Dose makes the poison!– NGO, media, societal and political pressures: Upgrade treatment goals
Customer response to the EWG report on Cr-6 exceeded the response to the annual rate increase
• 1T = 1 Team with 5Cs of character, comprehensiveness, communication, commitment, and creativity
• 2G = 2 Goals (WIG/Bread & PIG/Ice-cream)
• 3A = 3 Approaches (Optimization-empowerment, Emergency-management, Data-driven process)
1T2G3A
1 Team with 2 Goals• WQ Compliance & Process Control
Assure WQ compliance (federal, state, & local)
Monitor WQ for treatment & distribution operations
Provide WQ analysis for internal & external customers
• WQ and Treatment Research
Provide guidance & technical support to Operations
Provide Process Engineering (RBF, Blending Studies, etc.)
Research (Cr-6, Ozone, RBF,…)
• Distribution WQ Management
Maintain disinfectant residual throughout DS
Address/minimize WQ customer complaints
Manage cross-connection control
Distribution System Optimization ProgramLWC Achievements
• Phase I – Charter member (2010)
• Phase II – Annual data collection (2010-2012)
• Phase III – Directors and Excellence Award for focus on self-assessment and improvement planning (2013)
• Phase IV – Implementation of identified optimization strategies(IN PROCESS)
6
LWC DS
• 625 sq. miles & 3 county retail service area
• 309,000 services/>850,000 customers
• >4,200 miles of pipeline
• >30 tanks: 100,000 to 30MG
• 40 booster stations
• 24,000 fire hydrants and 52,000 valves
• 30 different pressure zones
• Decreasing Consumption
• Expanding Infrastructure
• Nitrification
LWC Disinfectant Residual Management Challenges
LWC Residential Consumption (1975-2014)
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• Weather impacts
• Transition from manufacturing to service economy
• Federal regulation on low flow appliances
• Increasing rates (water and wastewater)
• Economic impacts (recession periods)
• Improvements in water productivity and water mgmt
• Conservation awareness and practice
Factors for Declining Consumption
• Building a primary and secondary transmission grid/storage for fire flow in accordance with the National Fire Protection Association (NFPA) standards
• Creation of a modified urban system in the 1990’s to extend main to very low density areas
• Future demand planning assumptions
• Expansion of the core infrastructure to receive new and/or potential customers, including future regional supply solutions.
LWC DS Growth Rationales
11
Nitrification in DS
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• Water age• Temperature
• Free NH3• Cl2 residual
Comprehensive Evaluation of LWC’s Disinfectant Residual Challenges
• Water Age Analysis
• Chloramine Decay Profiling
• Daily Demand/Main Mileage Relationship – Innovative Approach
• Hydraulic/Water Quality Modeling
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LWC Aveg Water Age
14
29 miles
45 m
iles
Analysis performed using InfoWater MSX Software (Innovyze, Inc.)
Zone 1 & 2 Characteristics • Customer Base
Light commercial Low density single family residential development Agricultural/rural water use
• Hydraulics Over-sized infrastructure for
fire flows & future build-out Long Hydraulic Retention Time
• Water Quality High water age T&O customer complaints Nitrification in DS and tank Lower average chlorine residual
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Chloramine Decay Profiling
• Establish decay baseline for LWC waters
• Assist in nitrification risk assessment
• Support model development
• Guide future DS treatment design
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
0 2 4 6 8 10 12 14
Tota
l Ch
lori
ne
, mg/
L
Days
CHFP BEP 1:1 Blended
0.0
0.1
0.1
0.2
0.2
0.3
0 2 4 6 8 10 12 14
Fre
e N
H3-
N, m
g/L
Days
CHFP BEP 1:1 Blended
Louisville vs. A Mid-West Utility
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# CustomersMain Miles
(MM)Aveg. Daily
Demand (DD)
System DD (MG)
MM (100’s)
DD/MM
Ratio
Louisville 116.0 41.5 2.7
A Mid-West Utility 427.0 51.6 8.3
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DD/MM Ratio vs. DWQ Mgmt “Effort”
LWC WQ Modeling
• Water Age Model:
Full-system/all-pipe model
A snap-shot hydraulic calibration (summer/winter) based on operational data and field collected data
Water age modeling strongly correlates to DS samples
• Model Enhancement Needs
Improved hydraulic base model (ongoing maintenance)
Multi-species modeling (chloramine, ... )
Real-Time/predictive modeling
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Optimized Approaches in Disinfectant Residual Management & Maintenance
• Treatment Optimization
• DS WQ Surveillance & Monitoring
• Storage Tank Management/Flushing
• Cross-connection Control
• Coordination with Capital Project
• DS Treatment & Nitrification Control
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Residual Management Starts @ Water Treatment Plant
• Minimize chloramines decay potential
Maintain pH >8.5
Ferric/Poly-DADMAC co-coagulation strategy
pH adjustment
Chlorine/ammonia ratio (3.25:1, <55◦ F)
• Minimize nitrification potential
When >65◦ F, minimize free ammonia (<0.1mg/L) by maintaining chlorine/ammonia ratio of 3.5:1
Plant on-line monitoring (free ammonia, total ammonia, monochloramine, and total chlorine)
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Plant On-line Monitoring
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DS WQ Surveillance and Monitoring
• It’s a Numbers Game!
• Maintain Stringent Disinfectant Residual Guidelines
1.5 mg/L
Time
Tan
k To
tal C
hlo
rin
e (
mg
/L)
0.5 mg/L - Regulation
~4D ~1.5D
DS WQ Surveillance and Monitoring
• Storage Facility Monitoring
Grab sample - Analyzed for key signs of nitrification
Online Instrumentation (total chlorine)
• Master Meters to Consecutive Systems
Sampling 2x/month: >55◦ F, 1x/month: <55◦ F
Building in Online Instrumentation (total chlorine)
• WQ Customer Complaint Monitoring System-wide complaints: Treatment related Area-wide complaints: Treatment, DS,
both or single event related Individual complaints: Premise plumbing
issues/DS issues - deadends/closed valves24
DS WQ Surveillance and Monitoring
• Online vs. Grab Sample (denoted by *)
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• Assure timing of grab sample or install online WQ instrumentation.
2.7 mg/L
2.4 mg/L
WQ in Tank Appears Acceptable by Grab Sample Results~2.0 mg/L Swing
* 2.0 mg/L
**
Floating Tank in LWC DSTotal Chlorine Residual (mg/L)
Data-driven Flushing• Multiple Flushing Approach
Preemptive flushing Reactive flushing Customer complaint flushing Active routine flushing Dead-end flushing/master meter Boundary valve by-pass
• Multiple Flushing Techniques Permanent auto-flushing (long term) Portable auto-flushing (short term) Blow-offs Flushing crews (manual)
• Spot flushing• Localized flushing• Unidirectional flushing 26
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Storage Facility Management
• Temporarily Reduce Storage Volume Take redundant “floating” tanks out of service when possible Change operating range of tank
• Pumping Strategies Mandatory >30% daily turnover (temp > 55◦ F) on tanks
operated by BPS (goal: 100% turnover ~3 days). Increase flow into pressure zone by turning on all pumps
during fill cycle (Increases velocity in tank for stratification issues/decreases overall cycle time)
• Mixing LWC selectively employs passive and active systems Should be tank specific – may not be one size fits all Determine when mixing system, if any, will help
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Cleaning & Inspection• Removes sediment/biofilms
• Identifies sanitary/structural deficiencies
• Industry/AWWA = every 3-5 yrs; BMP = annually
• LWC employs a weighted scoring decision tool for frequency
Stee
l Tan
k (C
hem
ical
)
During
After
Co
ncr
ete
Tan
k (W
ash
ou
t)
Before
After
• Joint Effort Among LWC, Customers and Contractors
• LWC Owns CCP Administration (by federal EPA) Staffed Program Manage customer database Manage annual contractor testing including notifications Enforcement (LWC SR&Rs, Metro Ordinance, DOP) QA/QC (LWC inspections and contractor testing) Educate public/partnership with regulatory agencies Self-sustained Program (administration fee charged)
LWC CCP Administration LWC QC (Office/Field)
Risk assessment through inspections
• Customers/Contractors BFPD installation & annual testing
LWC CCP
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30
Risk is Spatially Located
Work on the Front-end (Capital)
• Influence Capital Projects from WQ View Develop internal WQ review process
• Refine Infrastructure Design Criteria Level of service evaluation: pressure/flow (urban vs. rural) Design alternative fire flow infrastructure Phased-in design solutions: PRV => VFD => Tank
• Assure Proper Storage Tank Design Influence location, size, type, etc. Assure proper mixing (Evaluate inlet nozzle changes vs.
active mixing systems to assure effectiveness)
• Reduce Dead-ends: Looping/Grid-tie Projects
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Chlorite Nitrification Inhibitor in DS (Zone 1)
• Low level dosage of ~0.4 mg/L is effective for control
• Early application prior to nitrification development is needed
• Less effective where nitrification is already proliferating
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Time
To
tal C
hlo
rin
e R
esid
ual, m
g/L
0.000
0.050
0.100
0.150
0.200
0.250
0.300
Nit
rite
, m
g/L
Total Chlorine NitriteS
top
ped
Ch
lori
te A
pp
licati
on
Sta
rted
Ch
lori
te A
pp
licati
on
2007 and 2012 Comparisons
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Area
2007 2012
DD/MM
Ratio
Avg. Total Cl (mg/L)
DD/MM
Ratio
Avg. Total Cl (mg/L)
LWC 3.5 2.7 2.9 2.6
LWC Bullitt County 1.4 2.0 1.2 2.2
Zone 1 0.8 1.5 0.8 2.1
Zone 2 0.4 1.2 0.3 1.4
• Zone 1: Chlorite (2008-12), 56% => 81% of LWC Avg.
• Zone 2: No Chlorite (2007-12), 44% => 54% of LWC Avg.
Take-home Message
• Understand your distribution system in order to find right solutions for disinfectant residual management – like DD/MM may be a good utility specific indicator of potential issues
• Yesterday’s disinfectant residual management strategies are not adequate for today’s challenges
• Development of a holistic/multi-pronged & utilization of new technologies/strategies are necessary to address this issue
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