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Distribution System Research
Two water distribution system simulators
(DSS) are in operation at the U.S. EPA Test and Evaluation (T&E) Facility
in Cincinnati, Ohio. The T&E Facility is a multifaceted research resource
in which a wide variety of water treatment and other environmental protection
technologies are conceived, designed, and evaluated in the laboratory,
bench, and pilot plant scale. The EPA designed and fabricated the DSS
systems to evaluate and understand the dynamics which influence water
quality within water distribution infrastructure systems in the United
States and abroad. 
The
first distribution system simulator (DSS-1) has continuous flow conditions.
There are six individual 75 ft (25 meter) lengths of 6 in (15 cm) diameter
ductile iron pipe arranged into "pipe loop" configurations to simulate
a distribution system. This pipe loop system can be configured to operate
as; independent/individual loops, collectively as one unit, or in various
experimental configurations to complement EPA's experimental research.
DSS-1 is equipped with two 1500 gallon reservoir tanks to simulate a comprehensive
distribution infrastructure system. This unique engineering design permits
operating any combination and configuration of the six loops under various
experimental operating parameters (Table
1.0) | Table 1.0 - 508 Compliant). Each loop
is insulated and fitted with a heat exchanger to maintain constant temperature
conditions during operation. The DSS is interfaced with a Supervisory
Control and Data Acquisition (SCADA) system, which is used to monitor,
control, and archive operating conditions and collected data continuously.
Biofilm samples are collected on coupons [ View1
(JPG, 46 Kb) | View2
(JPG, 64 Kb)] which are set flush with the interior surface of the pipe
wall. The coupons may be removed for sampling and analysis without disrupting
water flow.
The second distribution system (DSS-2)is over 300 feet long and is a once
through system composed of six inch diameter PVC pipe. This unit is being
utilized to evaluate water quality in a dead end branch of a distribution
system and to develop design models for water distribution. Both DSS units
are located above ground to permit easy access to the entire pipe network.
Experimental studies (Table
2.0) are ongoing to understand the physical, chemical, and biological
activities that occur in drinking water distribution systems.
Objectives:
The DSS provides researchers with a mechanism to study how water quality
is affected during distribution. Results from research studies (Table
2.0) will be used to provide guidance on how to maintain a high level
of water quality during distribution. A secondary objective to this project
is to develop, evaluate, and demonstrate real time monitoring of water
quality parameters within distribution systems using remote telemetry.
Results from research will be used to provide guidance on how to utilize
remote monitoring of water quality to detect changes in water quality
within distribution systems.
Relevance:
Throughout the world there are millions of miles of water distribution
pipe lines which provide drinking water for use by individuals and industry.
Although these distribution systems provide drinking water to the world,
very little is known about the physical, chemical, and biological activities
that occur within them. Some of these water distribution systems have
been in service well over one hundred years. DSS-1 has been in operation
for over three years, as water moves through distribution systems, it
comes into contact with a wide range of material some of which can cause
significant changes to the quality of the finished water supply. Suspended
solids in finished water can settle out under low flow conditions and
can be suspended during high flow. Various disinfection agents and water
additives react with organic and inorganic materials within a distribution
system generating by-products which may be undesirable in the water supply.
Oxidant resistant microorganisms colonize pipe surfaces producing a complex
micro environment known as "biofilm." Biofilms are highly resistant to
many disinfection methods and techniques. Our research looks at the various
experimental test parameters which influence biofilm growth. This work
will also help EPA develop a better understanding of the dynamics inside
distribution systems.
Research Goals:
Fabricate aboveground water distribution system simulator's which permit
easy access and can be operated under controlled conditions. Conduct studies
to develop a better understanding of the dynamics that occur in drinking
water distribution systems. Determine what physical, chemical, and biological
factors influence biofilm growth within such systems. Develop and test
mechanisms for the enhancement and control of biofilm growth within a
simulated distribution system. Additionally, develop and evaluate real
time monitoring, data collection, and archiving of water quality parameters
within water distribution systems using remote telemetry. Results will
be used to develop and provide guidance on ways to maintain high levels
of water quality through distribution systems.
EPA Contacts:
Mark C. Meckes
U.S. EPA
Microbial Contaminants Control Branch
26 West Martin Luther King Drive
Cincinnati, Ohio 45268
Phone: (513) 569-7348
E-Mail: meckes.mark@epa.govRoy C. Haught
U.S. EPA
Water Quality Management Branch
26 West Martin Luther King Drive
Cincinnati, Ohio 45268
Phone: (513) 569-7076
E-Mail: haught.roy@epa.gov
Table 1.0 Operating Parameters of the Distribution System Simulator
| Parameter | Normal Operation | Experimental Test Conditions |
|---|---|---|
| Distribution System Simulator | Parallel (6 individual Distribution System Simulators) | Parallel or Series in groups of 6, 3, 2, or 1 |
| Housing | Ductile Iron (Non-lined) | Ductile Iron (Non-lined) |
| Flow | 88 g.p.m. or 1 ft/sec | No Flow to 140 g.p.m. or 0 to 1.6 ft/sec |
| Temperature | 60 o F (15.5 o C) | 35 o F (1.6 o C) to Ambient |
| Chemical Control | Free Chlorine 1.0 ppm | Chemical control as needed |
| pH | 7.0 to 7.5 | Control/monitor as needed |
| Turbidity | < 0.5 NTU | Control/monitor as needed |
| Water Supply | Cincinnati - Tap water (Chlorinated) | Dechlorinated, Deionized, Tanked, Surface Water (River) |
Table 2.0 Proposed DSS Studies
| No. | Title of Proposed Study |
|---|---|
| 1 | Preliminary Studies of Biofilm Formation in Pilot-Scale Distribution Systems |
| 2 | Opportunistic Pathogens in Biofilms |
| 3 | Effect of a Pollution Event on a Simulated Water Distribution System |
| 4 | Impact of Nutrient Removal on Growth Potential for Bacteria |
| 5 | Impact of Alternative Treatment on Biofilm Growth |
| 6 | Real-time Monitoring and Control of Distribution Systems |
| 7 | Effects of pH Changes on Biofilm Growth in a Distribution System |
| 8 | Bacterial Growth in Distribution Systems |