Evaluating Water Quality from Source to Tap: Using Hydraulic Modeling, Statistical Analysis and Other Tools to Improve Water Quality

Evaluating Water Quality from Source to Tap: Using Hydraulic Modeling, Statistical Analysis and Other Tools to Improve Water Quality Phil Brandhuber PhD 2014 HDR, all rights reserved. 2018 Surface Water Treatment Workshop

Topics Overview of Distribution System Water Quality Tools for Evaluating Distribution System Water Quality Example Combining Distribution System Modeling and Water Quality Analysis 2014 HDR, all rights reserved.

The Point of this Talk Quality of water leaving plant Quality of water at customer tap

TTS Three Characteristics of Distribution Systems That Cause Changes in Water Quality Characteristic Description Implication T Time Water resides for hours to days Slow chemical reactions are important T Temperature Water temperature adjusts to match ground conditions Chemical reactions proceed at different pace than plant Effects change by seasons S Surfaces Large surface areas for water to contact Reactions at pipe/tank surfaces can dominate water quality Smallest pipes closest to consumer Treatment disturbs chemical equilibrium the distribution system ties to restore chemical equilibrium

Examples of TTS Time o DPB formation o Free chlorine decay o Chloramine decomposition Temperature o Nitrification o Calcium carbonate scaling Surface o Lead/copper release o (Dis)colored water (Fe/Mn) o Slim/biogrowth o Opportunistic pathogens o Taste and odor

Time is Key Factor in TTHM Formation

When Temperature Increases so can Nitrification Temperature Total Cl 2 :Nitrite

A Lot Goes on at a Pipe s Surface Center for Biofilm Engineering Montana State University

Features of Hydraulic Design Impact Distribution System Water Quality Get water to consumer Match supply to demand Deliver adequate pressure Provide fire flow Unlike wine, water does not get better with age More storage Greater water age Reduced water quality

Maintaining Water Quality in Distribution Systems is not a New Concept. Pompeii Drinking Water Distribution System AD 79 (Ref C.K. Rasmussen 2017)

But we All Know What Happened to Rome

Tools for Distribution System Water Quality Analysis Water quality mapping o Min/max/average o Box and whisker diagrams Cumulative distribution diagrams Formation and decay studies Hydraulic modeling o Water age o Source trace/blend ratio

Min/Max/Average Water Quality Maps Total chlorine (mg/l)

Box & Whisker Water Quality Diagram Maximum 90 th percentile Average Medium 10 th percentile Minimum

Cumulative Distribution Water Quality Diagram X-Axis Y-Axis Lowest Average Site 0% Sites in between Highest Average Site 100% Chloramine system Sites with possible nitrification

Average Cl 2 Residual at Distribution System Sampling Sites Lower residual Greater water age More storage Greater Cl 2 demand 0.2 0.4 0.6 0.8 1.0 1.2 1.4 Cl 2 mg/l

Average Cl 2 Residual at Distribution System Sampling Sites Greater residual Less water age Less storage Reduced Cl 2 demand 0.2 0.4 0.6 0.8 1.0 1.2 1.4 Cl 2 mg/l

Formation and Decay Studies Useful Studies Chlorine demand/decay Chloramine demand/decay Chloramine decomposition DPB formation o Formation potential (FP) o Simulated distribution system (SDS) o Uniform formation potential (UFP)

Hydraulic Modeling (EPANET Example) From EPA Website Compute friction head loss Calculate minor head losses Model constant or variable speed pumps Compute pumping energy and cost Model various types of valves, Account for any shape storage tanks Consider multiple demand And so on.

Colorado Case Study Serve 1.3 million people o 350 MGD summer demand o 130 MGD fall demand 3 WTPs 160 Pressure Zones 26 Pump Stations 35 Storage Reservoirs o 375 MG Storage Free chlorine disinfection Chloramine residual

Project Scope Conduct system-wide tracer test Complete system-wide water quality evaluation Using improved model recommend improvements for areas of nitrification and low chlorine residual

The Process Calibrate Hydraulic Model Historic Water Quality Data Analysis Laboratory Analysis Total Cl 2 Decay Identify Problematic Sites Out of Family Sites

The Process Calibrate Hydraulic Model

Tracer Chemical Fluoride Considered and Rejected o Background concentration too high Calcium Chloride Selected o Chloride easily measured by conductivity o Acceptable to Colorado Department of Health X

Tracer Make-up NSF-approved/food grade 2-7000 gallon tanker trucks Targeted dose to provide 3X background conductivity o Background - 300 µs/cm o Dose - 900 µs/cm Check for localized CaCO 3 precipitation Taste test before release!

Tracer Monitoring Locations 37 Permanent Locations + 26 Temporary Locations 63 Total Locations

Tracer Slug Release Performed in Fall 2015 130 MGD Demand o 100 MGD from WTP#1 o 30 MGD from WTP#2 o WTP#3 offline Released over 3.5 hours from Tank at WTP#1 CaCl 2 Introduced Pulse Released

Tracer Results 7 hour travel time site

Comparing Model to Tracer 7 hour travel time site Approximately 7 hours following release of Primary Pulse Approximate Pulse Length = 3.5 hours Approximately 4.5 days later emptying of remaining tracer from Reservoir No. 3 into system

Comparing Model to Tracer: 24 hour travel time site Excellent match time of travel

Comparing Model to Tracer 24 hour travel time site Conductivity not as good

Example SCADA Error: valve indicated closed when open Valve actually open Valve erroneously indicated closed

Calibrated Model - Baseline Water Age Results

Baseline Total Chlorine Residual Results

The Process Historic Water Quality Data Analysis

Cumulative Percentage (%) Cumulative Distributions of Average Total Chlorine Residual at Distribution System Sample Points 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% 0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 Total Cl2 (mg/l) 2015 2014 2013 2012 2011 2010 2009

Identification of Problematic Distribution Sample Sites Characteristic The lowest average total chlorine concentration (< 10 th percentile) for the entire system The lowest individual samples of total chlorine concentration (< 10 th percentile) for the entire system Greatest variability (difference between lowest and greatest) in total chlorine concentration over the course of the year Indication of Consistently high water age Very high water age Nitrification Large variation in age of water provided to site Nitrification Impact of reactive flushing or other system operations targeted at WQ

The Process Laboratory Analysis Total Cl 2 Decay

Treated Water Total Chlorine Decay Tests Two Conditions (2015) o June (run-off) o September (baseflow) 4 treated waters o WTP#1, o WTP#2, o WTP#3 o WTP #2/#3 blend 240 hour test length Results fitted to second order decay curve

Inherent Bulk Water Residual Decay Test June 2015 - Run-off

The Process Identify Problematic Sites Out of Family Sites

Residual Decay due to Distribution System Basis of Out of Family Analysis

Combining Decay Study and Model

Identification of Problematic Total Cl 2 Sample Sites

Locations of Excessive Residual Decay Out of Family Analysis

Additional Recommendations Made by Study Accelerate schedule for seasonal removing tanks from system Seasonally reduce levels in tanks Seasonal deep cycling of tanks Rerouting for some flows to improve mixing Modify nitrification monitoring program Consider base loading WTP#3 rather than WTP#1 during late fall Add/modify location of sample points Better characterize inherent residual decay rates from each plant

Wrapping - up Water quality leaving plant quality at customer tap Tools exist for evaluating changes to water quality caused by the distribution system Combining hydraulic modeling and water quality analysis improves customer water quality

Questions? Phil Brandhuber Philip.Brandhuber@hdrinc.com Kathryn Jones Patrick Haney Brian King