Distribution System Infrastructure

DISTRIBUTION SYSTEM INFRASTRUCTURE &

WATER QUALITY COMBINED WORKSHOPS

Workshop developed by RCAP/AWWA and funded by the USEPA

DISTRIBUTION SYSTEM INFRASTRUCTURE


This project has been funded wholly or in part by the United States Environmental Protection Agency under an EPA Training and Technical Assistance for Small Drinking Water Systems to Achieve and Maintain Compliance. The contents of this document do not necessarily reflect the views and policies of the Environmental Protection Agency, nor does the EPA endorse trade names or recommend the use of commercial products mentioned in this document.

DISCLAIMER

Protecting Public Health is THE purpose of drinking water treatment. Today, we will discuss how to support this purpose by presenting information on the following:

Purpose

How problems with common Distribution System components can drastically affect

water quality, and as a result, public health

Learn preventive actions and solutions you can implement

immediately

Learning Objectives

vital components of a distribution system, and how they can impact water quality

Describe

potential areas of water quality concern in your system, and consider ways to improve them

Identify

As a result of this presentation, you will be able to:

Storage tanks5

Agenda

Cross connections4

Distribution piping systems3

Valves2

Hydrants1

• Fire protection• Flushing

• To improve water quality• Caution – water hammer

1. Hydrants

• Flushing, scouring and cleaning (planned/unplanned)

• Cross connection potential

• Poor sampling points• Water can be trapped in the barrel of the hydrant when

closed, resulting in unrepresentative samples

Hydrant Impacts on Water Quality

• Most commonly operated and widely dispersed components of distribution systems

• Types of valves• Flushing• Pressure regulating• Flow control• Isolation• Backflow prevention• Air release• Buried-under-the-pavement valves

2. Valves

• Isolate parts of the distribution system in case of leaks, maintenance, or water quality emergencies

• Control flow and/or pressure• Release air that can accumulate in high points of the

distribution system

Valves - Uses

• Closed valves create dead ends in the distribution system• Stagnation• Increased water age• Biofilm development• Sediment built up

• If opened or closed rapidly, water hammer can develop

Valves - Effect on Water Quality

Which of the following valve issues have you encountered? How did you solve them?

1. There are no records of the valve2. The valve box is paved over or buried3. Valve is inoperable due to lack of use4. Direction to open/close the valve is unknown

Discussion: Common Valve Problems

• Different aspects of pipe networks can have impacts on water quality• Dead ends• Cross connections

3. Pipe systems

• Effect on water quality• Extended water age

• Decay of chlorine residual• Increased DBPs• Increased microorganisms

PREVENT FAILURESIf there is a failure – some customers will not have water service.

Pipe systems - dead ends

• Pipe loops

• Flushing valves

• Flushing programs

Solutions to dead ends we will cover:

• Pipe loops make the distribution system more robust

Pipe loops

• Allow more than 1 way for water to get to different points of distribution system

Effects on water quality:

• Decrease water age

• Help maintain disinfectant residual

• Potentially reduce DBPs and microbiological concentrations

Pipe Loops

Poll Question

• Flushing valves

• Flushing programs

Dead end solutions – flushing

• Has anyone addressed a dead end in your system?

• What did you do?

Experiences with Dead Ends?

• Any point in a water distribution system where chemical, biological, or other contaminants may come into contact with potable water

• These contaminants can bedrawn or pushed back into the water distribution systemduring a backflow event

4. Cross Connections

What is the Cross Connection?

• Backflow• Backpressure• Backsiphonage

• High Hazard vs Low Hazard• Testable vs Non-Testable• Inspection vs Testing• Isolation vs Containment

Cross Connection Terms

• Certified cross connection technician• & Inspections

• Cross connection control plan

Cross Connections - Solutions

• Has anyone addressed a cross connection in your system?

• What did you do?

Experiences with Cross Connections?

Purpose• Improve system hydraulics• Peak flow/fire flow • Balance treatment needs

5. Storage Tanks

• Stratification vs mixing• Inlet/outlet configuration• External contamination• Increased water age• Loss of chlorine residual• Formation of DBPs• Microscopic critters in the water• Big critters in the water

Factors that Impact Water Quality in Storage

• Finished water storage not properly covered

• Cracks in the walls or storage cover

• Accesses and vents not protected with proper screen or other approved devices

• Storage facility not structurally sound

• Lack of normal maintenance and inspection schedule for storage tanks

Some common storage tank problems:

Poll Question

Loss of integrity of storage facilities

Knot hole in a spring box

Hole in storage tank wall

Courtesy Robert Clement, USEPA

At least 3 bloated mice

At least 7 snakes

Inside the spring box with a knot hole

Courtesy Robert Clement, USEPA

Have you encountered any of these storage tank problems, and if so, what did you do about them?

Discussion

What can be done to maintain or improve water quality in storage?

REDUCE WATER AGE

BOOSTER CHLORINATION

INSPECTION AND MAINTENANCE

Identify vulnerable aspects of the distribution system, dead ends, pipe loops, storage etc.

http://www.epa.gov/water-research/epanet

EPANET Demonstration

http://www.epa.gov/water-research/epanet

Distribution System Components Activity:

Water Treatment

Plant

Storage Tanks

Dead Ends

Where would you expect to find water with the greatest age?

Where would you expect to find water with the greatest age?

Summary

Vital components of distribution systems, how they can impact water quality, and

solutions you can use

Components covered:• Hydrants• Valves• Piping systems• Cross connections• Storage tanks

DISTRIBUTION SYSTEM WATER QUALITY


Protecting Public Health is THE purpose of drinking water treatment. Today, we will discuss how to support this purpose by presenting information on the following:

Purpose

Why Water Quality

Parameters are vital to safe

drinking water

How you can use knowledge about

water quality parameters in

your work

Learning Objectives

what water quality parameters tell us about the condition of distribution system water quality

Identify

key practices for managing water age and quality during storage

Apply

As a result of this presentation, you will be able to:

Agenda

Taste and Odor, Customer Feedback7

Temperature, Bacteria, and Heterotrophic Plate Count6

Storage Related Issues5

Capacity, water age, and water quality4

Chlorine residual3

pH2

Distribution system water quality parameters1

CFU – Colony forming unitsCT – Contact timeDBP – Disinfection by-productsGWUDI – Groundwater under the direct influenceHPC – Heterotrophic plate countMDRL - Maximum disinfectant residual level MIB – 2-MethylisoborneolNOM – Natural organic matterPWC – Public water systemsRTCR – Revised Total Coliform RuleTCR – Total Coliform RuleTTHM – Total trihalomethaneTOC – Total organic carbon

Acronyms

• Protect public health

• Comply with regulations

• Impact distribution system operation

• Impact aesthetics (taste, odor, color)

Importance of Water Quality

Water Quality Parameters

1. pH2. Chlorine residual3. Capacity & water age4. Temperature5. Heterotrophic plate count6. Taste and odor7. Other issues

Discussion

1. List all the water quality parameters your utility measures in the distribution system

2. Rank them in order of importance

• pH is a measure of acidity or alkalinity of a solution on a logarithmic scale

• It is also defined as the hydrogen ion (H+) concentration of solution

pH = -log [H+]

1. pH Definition

• pH measurements range from 0 – 14 • pH 7 being neutral• pH less than 7 is acidic• pH greater than 7 is basic

EPA secondary standard: 6.5 to 8.5

pH Measurement

• pH Too High:• May precipitate excessive calcium

carbonate in distribution system• Restrict water flow in pipe

• pH Too Low:• May corrode water pipes

• Red water issue (iron particulates)• Pipe failure and rupture• Lead and copper issues

Impacts of pH

Poll Question

• pH impacts the form of chlorine• Chlorine is most effective between pH 5.5 – 7.5• pH impacts TOC removal

• Lower pH = better removal• pH affects DBP formation

• Higher pH = more TTHMs

Cl- + H2O HOCl + H+ + Cl-

Impacts of pH on Chlorine Disinfection

Reaction is pH dependent

• Surface Water Treatment Rule (SWTR) 1989

• Interim Enhanced Surface Water Treatment Rule (IESWTR) 1998

• Long Term 1 Enhanced Surface Water Treatment Rule (LT1ESWTR) 2002

2. Chlorine Residual - USEPA Rules

• Maintain a detectable chlorine residual

Chlorine Residual

• Stage 1 Disinfectants and Disinfection Byproducts Rule 1998

• Stage 2 Disinfectants and Disinfection Byproducts Rule 2006

Chlorine | Chloramines• Maximum Residual Disinfection Level – 4.0 ppm as Cl2

• Compliance with the 4.0 mg/L MRDL is based upon an annual average; therefore, the MRDL does not apply to individual samples that are allowed to be higher than the MRDL

Maximum Chlorine Residual - USEPA Rules

1. Why do you maintain a chlorine residual in the Distribution System to protect public health?

2. Can you think of a time when you would want to go above the 4.0 ppm limit?

Knowledge Check


One Answer: Coliform issues may be a reason to go above the 4.0 PPM MRDL

• Chlorine degrades in the distribution system• Rate of decay can be affected by

• Water age • Temperature• Biological growth/nitrification• Amount and type of chlorine-demanding compounds

(organic and inorganic)• Rapid decay can be an indicator of a distribution system

problem

Chlorine Decay

Capacity

3. Capacity and Water Age

Water Age

Water Quality

Capacity

Major components of a water distribution system

• Pumps• Pipes• Valves• Storage

The average time it takes for water to travel from the treatment facility to the customer.

Factors affecting water age:• Water production rate• Water demand• Pipe size• Pipeline and storage tank operations

Water Age

The average time it takes for water to travel from the treatment facility to the customer.

• Methods for determining water age:• Hydraulic modeling• Tracer studies• Estimates from water quality data

Determining Water Age

Water age is a function of system design and use.

What distribution system design and use considerations could contribute to water age?

Discussion: Water Age

Distribution System Water Quality Challenge:

As water age increases, disinfectant residuals decrease, microbial activity increases, and disinfection by-products

increase.

Water Age

How are capacity and water age connected?

Knowledge Check


Answers:• Water demand

(pumping)• Pipeline operations• Storage tank

operations

• Manage hydraulics in storage facilities

• Inlet/outlet configuration, baffling

• Increase turnover rate

• Pumping schedules (deep cycling)

• Mixing

Managing Water Age and Quality

• Manage chemistry

• Increase chlorine residual

• Shock chlorination

• Aeration (radon, TTHM, hydrogen sulfide, etc)

Managing Water Age and Quality

1. Do you know the typical / average water age of your distribution system?

2. Where is your water age the highest?

Questions

• Adding baffle walls in the storage facility• Make the interior “channel-like” to enhance a “plug-flow” condition• Make water age more uniform and reduce short circuiting

Baffling Systems

Achieved by:

• Decreasing storage volume

• Partially draining and refilling

• Account for seasonal water usage variations• Close some facilities during cold seasons or operate with

lower volumes

Turnover Rate

• Important to ensure a certain minimum storage at all time for emergency purposes (e.g. fire flow)

• Important to maintain a minimum tank level to maintain distribution system pressures

• Set a minimum water level to prevent re-suspending any sediments

Turnover Rate

• Even in a storage facility with high turnover, older water zones can still occur

• Thermo stratification• Short circuiting

• Mixing can promote consistent water quality

Tank Mixing

Source: Pittsburg Tank & Tower Group

CT ConceptThe CT Concept is a simplified way to determine the level of inactivation or disinfection taking place.

- The "C" is the residual disinfectant concentration.- The "T" is the contact time.

CT measures the effectiveness of the disinfection process

CT = C x T

C = disinfectant residual concentration, mg/LT = time, min

Calculating CT

Step 1: Determine time at peak flow

Time, min = tank volume, gal x baffling factorpeak hourly flow, gal/min

Step 2: Determine CT

CT, min mg/L = Time, min X Cl2 concentration, mg/L

Step 3: Find CTrequired from EPA tables

Step 4: Is activation ratio greater than 1?

Poll Question

• Corrosion• Sedimentation• Leaching• Hydrogen sulfide release• Biological issues

• Regrowth• Nitrification• Birds, insects, rodents, reptiles, etc…..

Other Storage Related Issues

What water quality issues have you seen in storage facilities?

Discussion – Water Quality Changes

4. Temperature

• Water temperature can vary daily, and seasonally

• High water temperature:• Quicker loss of chlorine residual• Increased disinfection by-products• More bacterial regrowth• Nitrification

From Standard Methods

Heterotrophic plate count (HPC), formerly known as the standard plate count, is a procedure for estimating the number of live, culturable heterotrophic bacteria in water and for measuring changes in swimming pools or during water treatment and distribution.

5. Heterotrophic Plate Count (HPC)?

• An estimation of the number of live bacteria

• Quantified as the number of colony forming units (cfu) per 100 mL of water

• Indicator of water quality• Excellent indicator for nitrification in

chloraminated system• To identify causes of low chlorine

residual

Heterotrophic Plate Count

• A public health and compliance concern

• May contain total coliform which leads to RTCR compliance issues downstream

• May contain microorganisms

• Nitrification

• Loss of chlorine residual

Microbial Growth Challenges

What does HPC tell us?

Knowledge Check


Answer: • Indicator of water quality• Excellent indicator for

nitrification in chloraminated system

• Identifies causes of low chlorine residual

• Chlorine taste and smell• Chlorinated organic from source water• Di-and trichloramine• Excess residual concentration

• Earthy-musty odor• Natural Algae products (MIB and Geosmin)• Algae under chlorine exposure

6. Taste and Odor

•Swampy or rotten egg odor• Hydrogen sulfide

•Others (e.g. gasoline, metallic)• From contaminations of various sources

Taste and Odor

• Taste and odor issues can be a symptom pointing to other problems in the system, for example:

• Excessive chlorine taste may indicate chlorine overfeed

• Back flow through cross connections may be first noticed by change in taste/odor

Customers are a great source of water quality information

• Track customer complaints

• Investigate the origin of the problem

Use Customer Information

You received several complaints from customers. How do you respond?

1. Swimming pool smelling water

2. Red water coming out of the tap

Discussion: Aesthetic Issues

Other distribution system water quality parameters that need to be considered:

• DBPs• Lead and copper• Leaching of metals, corrosion potential, etc.

7. Other Issues

Emerging Microbial Contaminants

• Naegleria fowleri• Legionella pneumophilia• Norovirus

Summary

• Importance of Water Quality and Intro to Water Quality Parameters

• pH and Chlorine Residual • Capacity, Water Age, and Water Quality

• Storage Related Issues • Temperature, Bacteria, and Heterotrophic

Plate Count• Taste and Odor, Customer Feedback

THANKS FOR ATTENDING!

Russ BoesRCAP Operator

[email protected]

Todd BrandenburgRCAP Operator

[email protected]

mailto:[email protected]

mailto:[email protected]

Documents

Distribution System Infrastructure