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CEEB313 – WATER & WASTE WATER ENGINEERING

DESIGN OF A WATER RETICULATION FOR SECONDARY DISTRIBUTION SYSTEM

TABLE CONTENT

BIL TITLE PAGE

1 INTRODUCTION 2

2IMPACT OF THE SECONDARY

DISTRIBUTION SYSTEM8

3 DESIGN AND CALCULATION 13

4 CONCLUSION 26

5 REFERENCES 27

1.0 : INTRODUCTION

The secondary water distribution system is used as a link between the main distribution

pipe and the house connection including the fire hydrants.The design must achieve the sufficient

preassure and quantity of water in the most cost effective manner. The transmission of water

from the source or water treatment plant to the various consumers is usually done in two stages,

distribution and reticulation.

The former term is generally used to describe the system of bigger (or trunk) mains,

reservoirs and, in some situations, pumping systems. In bigger systems such as in cities, the

distribution function is well-defined and often operated separately. In large systems or where

water is delivered to separate water suppliers, the initial delivery can be through bulk or trunk

mains. The term reticulation is normally used to describe the street mains and connections to

properties. However, use of these terms does tend to be interchangeable.

The distribution system is designed to:

reliably distribute bulk water supplies to the suburbs, or supply points

provide water at the correct elevation and/or pressure

buffer the diurnal peaks in demand from the consumers

maintain the water quality.

To achieve these objectives, particular combinations of reservoir storage, ring mains and

pumping arrangements are used, depending upon the system topography and size.

A distribution system may also be made up of distribution zones. A distribution zone is a

part of the distribution system in which all consumers receive drinking-water of identical

quality, from the same or similar sources, with the same treatment and usually at the same

pressure and is usually clearly separated from other parts of the network, generally by location,

but in some cases by the layout or composition of the pipe network. In these Guidelines the term

distribution system is used to include specific zones.

Developing a system to distribute water to customers is a big investment for a

community. Because a water distribution system is intended to serve a community for more than

50 years and it is buried and difficult to access, careful planning and consideration is needed.

Water distribution systems have three major components: pipes, valves, and flush

hydrants. Each part plays a role in ensuring adequate water service and in maintaining quality

water.

Because the pipes and valves are buried, a detailed map is needed to gain quick access to

the system for maintenance and repairs. A map is also an important planning tool for upgrades

and expansions. It is common for an experienced operator or town employee to have detailed

knowledge of the location of all distribution system components. Relying solely on memory,

however, can put the distribution system at risk if problems occur when the responsible person is

unavailable. A detailed map ensures that the investment in the community infrastructure is

documented, and can be studied and shared with interested parties.

a) Pipes

Water pipes should be laid out in loops to avoid dead-ends that create stagnant water.

Water pipes must be buried at least 48 inches below the ground surface in Ohio to protect them

from freezing.

Two types of water pipes are needed in a water system—transmission lines and

distribution lines. Transmission lines are the pipes that carry the water from the source to the

storage system. Transmission lines are the largest, thickest pipes in the system making them the

most expensive. When planning a water system, try to keep the treatment and storage tanks close

to the water source to reduce the cost of transmission lines.

Distribution pipes carry water out to the users. To protect water quality, water pipes must

be at least 10 feet from sewer pipes and laid in separate trenches. The absolute minimum

diameter for a distribution pipe is two inches. A six-inch diameter pipe is the minimum needed

for fire flows and for serving fire hydrants.

Since water pipes will be used for at least 50 years, most communities look ahead to

expanded service and often use bigger pipe than the minimum. Too large a pipe, however, can

lead to water quality problems. If water stands too long in large pipes, the chlorine residual

diminishes, metals can dissolve in the water, and biological films can grow.

b) Valve

Values are a critical part of a water system and are often an afterthought. Valves isolate

portions of the water system for servicing. By carefully considering the placement of valves,

water system repairs and maintenance can be conducted with minimal loss of service.

Valves that are not used for years may not function when the need arises. Valves can

stick and even break if neglected. A valve exercise program is a necessary part of water

distribution system maintenance.

c) Flush Hydrants

Flush hydrants are the most visible part of the water distribution system. They must be at

the end of all lines to remove accumulated corrosion products from dead-ends. Flush hydrants

should also be installed throughout the system to provide for periodic flushing to maintain high

water quality. Sometimes people mistake flush hydrants for fire hydrants. Fire hydrants are

larger and are often connected to larger pipes.

d) Critical points in a distribution system

Critical points are those points where procedures for equipment failure would lead to a

public health hazard. Specific critical points are discussed in this chapter to highlight and

differentiate the types of risk that are present in a distribution system. There are two types of

critical points in the distribution system, those critical to continuity of supply and those critical

to water contamination.

Water contamination is an obvious and direct risk to public health. It can occur directly

by intrusion of contaminants into the system or by chemical reactions within the system (such as

chemical reactions with the pipe structure). The contamination of water within the distribution

system is discussed in detail in this chapter

Supply loss is also a critical point for public health, but is not the subject of these

Guidelines. For the initial time (say several hours), the risks to the community are not those of

thirst, they are those of fire fighting, minimal interruptions to industry, inadequacy of water for

flushing away sewage, and for personal hygiene. The factors that could lead to supply loss

include:

loss of source water supply

treatment failure

water main failure

service reservoir valve operation: inlet fails to open, drain fails to close

water contamination, meaning supply must be stopped.

Emergency storage is required in order to continue supply when the inlet main is broken,

during upstream system maintenance, or during some other loss of supply situation.

In practice, most supply losses involve a dual failure: a mechanical/electrical defect or

human error that occurs and an alarm system that fails to provide warning in time to take

corrective action. Therefore the alarm system needs regular testing and valves need regular

working and testing, and staff needs regular training. Situations that can lead to loss of supply

should be addressed in the water safety plan or other appropriate manual.

2.0 : IMPACT OF THE SECONDARY DISTRIBUTION SYSTEM

2.1 Introduction

The drinking water industry is striving to implement new regulations for

secondary disinfection to prevent unwanted microbial contamination in the distribution

system while minimizing the formation of disinfectant by-products (DBPs). From a

public health perspective the need to increase disinfectant residual concentrations and/or

switch disinfectants will be a critical factor indeveloping these regulations. However,

these decisions can potentially lead to significant degradation of both water quality and

distribution system materials via corrosion.

Aesthetic Effects

Odor and Taste are useful indicators of water quality even though odor-free water

is not necessarily safe to drink. Odor is also an indicator of the effectiveness of different

kinds of treatment. However, present methods of measuring taste and odor are still fairly

subjective and the task of identifying an unacceptable level for each chemical in different

waters requires more study. Also, some contaminant odors are noticeable even when

present in extremely small amounts. It is usually very expensive and often impossible to

identify, much less remove, the odor-producing substance.

Standards related to odor and taste: Chloride, Copper, Foaming Agents, Iron,

Manganese pH, Sulfate, Threshold Odor Number (TON), Total Dissolved Solids,

Zinc.

Color may be indicative of dissolved organic material, inadequate treatment, high

disinfectant demand and the potential for the production of excess amounts of

disinfectant by-products. Inorganic contaminants such as metals are also common causes

of color. In general, the point of consumer complaint is variable over a range from 5 to

30 color units, though most people find color objectionable over 15 color units. Rapid

changes in color levels may provoke more citizen complaints than a relatively high,

constant color level.

Standards related to color: Aluminum, Color, Copper, Foaming Agents, Iron,

Manganese, Total Dissolved Solids.

Foaming is usually caused by detergents and similar substances when water has

been agitated or aerated as in many faucets. An off-taste described as oily, fishy, or

perfume-like is commonly associated with foaming. However, these tastes and odors

may be due to the breakdown of waste products rather than the detergents themselves.

Standards related to foaming: Foaming Agents.

Cosmetic Effects

Skin discoloration is a cosmetic effect related to silver ingestion. This effect,

called argyria, does not impair body function, and has never been found to be caused by

drinking water in the United States. A standard has been set, however, because silver is

used as an antibacterial agent in many home water treatment devices, and so presents a

potential problem which deserves attention.

Standard related to this effect: Silver.

Tooth discoloration and/or pitting is caused by excess fluoride exposures during

the formative period prior to eruption of the teeth in children. The secondary standard of

2.0 MG/L is intended as a guideline for an upper boundary level in areas which have high

levels of naturally occurring fluoride. The level of the SMCL was set based upon a

balancing of the beneficial effects of protection from tooth decay and the undesirable

effects of excessive exposures leading to discoloration. Information about the Centers for

Disease Control's (CDC) recommendations regarding optimal fluoridation levels and the

beneficial effects for protection from tooth decay can be found on its Community Water

Fluoridation page.

http://www.cdc.gov/fluoridation/

http://www.cdc.gov/fluoridation/

Standard related to this effect: Fluoride.

Technical Effects

Corrosivity, and staining related to corrosion, not only affect the aesthetic quality

of water, but may also have significant economic implications. Other effects of corrosive

water, such as the corrosion of iron and copper, may stain household fixtures, and impart

objectionable metallic taste and red or blue-green color to the water supply as well.

Corrosion of distribution system pipes can reduce water flow.

Standards related to corrosion and staining: Chloride, Copper, Corrosivity, Iron,

Manganese, pH, Total Dissolved Solids, Zinc.

Scaling and sedimentation are other processes which have economic impacts.

Scale is a mineral deposit which builds up on the insides of hot water pipes, boilers, and

heat exchangers, restricting or even blocking water flow. Sediments are loose deposits in

the distribution system or home plumbing.

Standards related to scale and sediments: Iron, pH, Total Dissolved Solids,

Aluminum.

How can these problems be corrected?

Although state health agencies and public water systems often decide to monitor and

treat their supplies for secondary contaminants, federal regulations do not require them to do

this. Where secondary contaminants are a problem, the types of removal technologies discussed

below are corrective actions which the water supplier can take. They are usually effective

depending upon the overall nature of the water supply.

Corrosion control is perhaps the single most cost-effective method a system can use to

treat for iron, copper and zinc due to the significant benefits in

1. reduction of contaminants at the consumer's tap,

2. cost savings due to extending the useful life of water mains and service lines,

3. energy savings from transporting water more easily through smoother, uncorroded

pipes, and

4. reduced water losses through leaking or broken mains or other plumbing.

This treatment is used to control the acidity, alkalinity or other water qualities which

affect pipes and equipment used to transport water. By controlling these factors, the public water

system can reduce the leaching of metals such as copper, iron, and zinc from pipes or fixtures, as

well as the color and taste associated with these contaminants. It should be noted that corrosion

control is not used to remove metals from contaminated source waters.

Conventional treatments will remove a variety of secondary contaminants. Coagulation

(or flocculation) and filtration removes metals like iron, manganese and zinc. Aeration removes

odors, iron and manganese. Granular activated carbon will remove most of the contaminants

which cause odors, color, and foaming.

Non-conventional treatments like distillation, reverse osmosis and electrodialysis are effective

for removal of chloride, nitrates, total dissolved solids and other inorganic substances. However, these

are fairly expensive technologies and may be impractical for smaller systems.Non-treatment options

include blending water from the principal source with uncontaminated water from an alternative

source.

Contaminant SecondaryMCL

Noticeable Effects above the Secondary MCL

Aluminum 0.05 to 0.2mg/L*

colored water

Chloride 250 mg/L salty taste

Color 15 color units visible tint

Copper 1.0 mg/L metallic taste; blue-green staining

Corrosivity Non-corrosive metallic taste; corroded pipes/ fixtures staining

Fluoride 2.0 mg/L tooth discoloration

Foaming agents 0.5 mg/L frothy, cloudy; bitter taste; odor

Iron 0.3 mg/L rusty color; sediment; metallic taste; reddish or orange staining

Manganese 0.05 mg/L black to brown color; black staining; bitter metallic taste

Odor 3 TON (threshold odor number)

"rotten-egg", musty or chemical smell

pH 6.5 - 8.5 low pH: bitter metallic taste; corrosionhigh pH: slippery feel; soda taste; deposits

Silver 0.1 mg/L skin discoloration; graying of the white part of the eye

Sulfate 250 mg/L salty taste

Total Dissolved Solids (TDS)

500 mg/L hardness; deposits; colored water; staining; salty taste

Zinc 5 mg/L metallic taste

http://water.epa.gov/drink/contaminants/secondarystandards.cfm#tablefooter

3.0 : DESIGN AND CALCULATION

A new township development developed by PKNS located in Daerah Hulu Selangor,

Selangor Darul Ehsan. There comprises of256 unit of single storey terrace house, day school for

700 students, surau for 300 person and wet market of 22 stall.By reffer the table 6.3, water

consumption can be calculated as follow.The calculation which done for and :

Type of Development Water

Consumption Rate

No. of Units Total Water

Consumption (L/d)

Single Storey Terrace

Houses

1300 256 332,800

Surau 50 300 15,000

Day School 50 700 35,000

Wet Market 1500 22 33,000

TOTAL 415,800

So for convert Water Demand

Total Water Demand, Q =

PEAK FLOW (CASE 1) :

FOR calculating :

Peaking factor = 2.5

12.03 L/s

AVERAGE FLOW AND FIRE FLOW (CASE 2) :

Fire Flow: 1140 L/s (19 L/s)(UTG)

Q = 4.813 L/s + 19.0 L/s = 23.81 L/s

Designing of the nodes the loops design base on two cases which are the peak flow case

and average flow + fire flow. The needed fire flow is the rate of water flow required for

firefighting to confine a major fire to the buildings within a block or other group complex with

minimal loss. From the guidelines for developers, we get that it is equal to 1140 L/d in which we

convert it to L/s and get a value of 19L/s. The head pressure loss is 100.84 according to the plan

layout. However, on the other side we have to get the flow at each node after we get the actual

pressure head loss. Therefore, we need to design the nodes and draw the pipes to construct

through software called EPANET.

3.1 : DESIGN AND DATA BASED ON AVERAGE FLOW AND FIRE FLOW

NODE DETAILS

PIPE DETAILS

3.2 DESIGN AND DATA BASED ON PEAK FLOW RATE

NODE DETAILS

PIPE DETAILS

4.0 : CONCLUSION

Finally, by using the software called EPANET, we have finished the design of a water

reticulation for secondary distribution system. The system was designed based on average flow

case and peak flow case. The values for the average flow case and peak flow case were 23.81

L/s and 12.03 L/s respectively. In both cases, the designs were designed with the same length of

pipes and diameters. The only difference made was the base demand at each nodes. For both

design there are a total number of junction and pipes are 39 and 48 respectively.

5.0 REFERENCES

http://water.epa.gov/drink/contaminants/secondarystandards.cfm

http://books.google.com.my/books?

id=NeTmfhOfdAwC&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=one

page&q&f=false

https://www.linkedin.com/groups/hi-how-fix-negative-pressure-3780529.S.111621301

EPANET MANUAL

EPANET 2.0

https://www.youtube.com/watch?

v=RyxOjo7siNg&index=8&list=PLB2780D59FE4D2065

https://www.linkedin.com/groups/hi-how-fix-negative-pressure-3780529.S.111621301

http://books.google.com.my/books?id=NeTmfhOfdAwC&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false



http://water.epa.gov/drink/contaminants/secondarystandards.cfm

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