Water System Infrastructure Instructors mention that in this module, as part of distribution system infrastructure we will cover piping, valves, storage tanks, and hydrants Presented by Dinah Foreman, CET Communities Unlimited, Inc. Workshop developed by RCAP/AWWA and funded by the USEPA Developed by American Water Works Association with funds from the U.S. Environmental Protection Agency, Published 2015

Learning Objectives Be able to describe key components of the water system Determine how the key components can impact water quality Be able to describe potential areas of water quality concern in your system Consider ways to make improvements in the water system that may improve water quality

Components We Will Discuss Distribution System Piping Valves Hydrants Storage Tanks

Distribution System Piping Different aspects of pipe networks can have impacts on water quality Dead ends Cross connections Line breaks Condition of the pipe

Dead Ends Effect on water quality Extended water age Other concerns Increased DBPs Decay of chlorine residual Increased microorganisms Other concerns Positive RTCR samples If there is a failure some customers will not have water service

Solutions to Dead Ends? Loop dead end lines Flushing

Dead End Solutions: Pipe Loops Allows more than one way for water to get to different points of distribution system Effect on water quality Decrease water age Potentially reduce DBP Help maintain disinfectant residual Potentially reduce microbiological concentrations

Dead End Solutions: Flushing Flushing valves/systems Flushing programs

Discussion Has anyone addressed a dead end in your system? What water quality issue did you have? What did you do? Did it correct the problem? What water quality parameters do you use to determine if a line has been flushed adequately?

Valves Most commonly operated and widely dispersed components of distribution systems Why do we install valves in the distribution system? Isolate parts of the distribution system in case of leaks, maintenance, water quality issues and emergencies Control flow and/or pressure Release air that can accumulate in high points of the distribution system

Valves Most commonly types of valves Flushing Pressure regulating Flow control Isolation Backflow prevention Air release Buried-under-the-pavement valves? Are your valves accurately marked on the water system map?

Valves: Effect on Water Quality 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 Stirs up sediment Line breaks

Valves: Solutions What can be done to limit water quality impacts? - Survey valves to be sure they are open - Exercise valves - Open and close valves slowly

Why do we have hydrants in our Distribution System? Fire protection Flushing To improve water quality Caution – Opening and closing hydrants too quickly can cause water hammer

Hydrant Impacts on Water Quality 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

Storage Tanks Purpose? Improve system hydraulics Peak flow/fire flow Balance treatment needs

Factors that Impact Water Quality in Storage Increased water age Stratification vs mixing Inlet/outlet configuration Formation of DBPs Loss of chlorine residual Microscopic critters in the water External contamination BIG critters in the water

What can be done to maintain or improve water quality in storage? Reduce water age Booster chlorination Warning: Additional chlorination may increase DBPs Inspection and maintenance of storage facility

AWWA recommends water age of less than 7 days The residence time of water in the distribution system before reaching the customers 2 Days Storage Facility 4 Days Water Supply Customer AWWA recommends water age of less than 7 days 19

Activity

Distribution System Components Dead Ends Storage Tanks WTP

Where would you expect to find water with the greatest age? Dead Ends Storage Tanks WTP

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

EPANet Free Software from EPA Software That Models the Hydraulic and Water Quality Behavior of Water Distribution Piping Systems http://www.epa.gov/water-research/epanet EPANET is software that models water distribution piping systems. EPANET is public domain software that may be freely copied and distributed. It is a Windows 95/98/NT/XP program. EPANET performs extended period simulation of the water movement and quality behavior within pressurized pipe networks. If time permits, provide a demonstration of EPANet

Storage Facilities Inspections & Maintenance Finished water storage not properly covered Uncovered finished water storage prohibited Cracks in the walls or storage cover Storage facility not structurally sound Accesses do not close properly Vents & overflow pipes not protected with proper screen or other approved devices Lack of normal maintenance No inspection schedule for storage tanks

Loss of Integrity of Storage Facilities

Inside Storage Tank

At least 7 snakes At least 3 bloated mice Courtesy Robert Clement, USEPA

Dead Frog Dead Squirrel

Inspections & Maintenance Inspection and maintenance AWWA Manual M42 – Recommends every 3 years MSDH requires that tanks be inspected every 5 years to receive credit for T2-3 on the annual water system inspection

Questions?