Horizon Net Zero Dawn – keynote slides by Ben Abraham
Report water treatment for domestic water supplies (2) (1)
1. SCHOOL OF ARCHITECTURAL, BUILDING & DESIGN
BACHELOR OF QUANTITY SURVEYING (HONOURS)
BUILDING SERVICES 1
( BLD60403 )
TOPIC : WATER TREATMENT FOR DOMESTIC WATER
SUPPLIES
LECTURER : MR LEONG BOON TIK
SUBMISSION DATE : 6TH
JULY 2017
STUDENT NAME STUDENT ID
Foo Van Jean 0330017
Juan Roy Collie 0329004
Nur Firzana Binti Muhammad Hasmi 0324838
Penny Leung Ling Yee 0328245
Tan Shen Sin 0324602
2. CONTENT
1.0 Introduction 3
1.1 Conventional Method 4-5
1.2 Multi Media Filtration System (MMF) 6
1.3 Reverse Osmosis (RO) 7
2.0 Installation Process of Conventional Water Treatment 8
2.1 Chemical Mixing Chamber 11
2.2 Flocculation Tank & Clarifier Tank 11
2.3 Filtration Plant 12
2.4 Compressed Air System 13
2.5 Service Water Main Ring 13
2.6 Drainage System 13
3.0 Management Systems 14
3.1 Optimal Water Usage 14
4.0 The Advantages & Disadvantages 15
4.1 Disadvantages 15
4.2 Advantages 15
5.0 Case Study: Finding & Explanation 16
5.1 Source of Water – Muda River & Raw Water Balancing Pond 17
5.2 System Integrity 19
5.3 Hydraulic System (Flows & Pressures) 20
5.4 Water Quality Parameter 23
5.4.1 Physical Drinking Water Parameter 23
1
3. 5.4.1.1 Turbidity 24
5.4.1.2 Suspended Solid 25
5.5 Sampling Water 25
5.5.1 System Component 25
6.0 Possible Problems To The System 26
6.1 Ineffective Backwashing 27
6.2 Machinery Breakdown 27
6.3 Overdose of Chemical 27
6.4 Contamination of Source Water 28
7.0 Recommendation for Future Improvements 30
7.1 Physical Integrity 31
7.1.1 Operation & Maintenance Consideration 32
7.2 Hydraulic Integrity 33
7.2.1 Operations & Maintenance Consideration 33
7.3 Hazardous Chemicals 34
7.4 Air Quality 34
7.5 Staff Training 34
7.6 Renewable energy 34
8.0 Learning Outcome 35
9.0 References 36
10.0 Bibliography 37
11.0 Appendices 38
2
4. 1.0 Introduction
Water is a colourless, odourless and tasteless substance that is vital for every inhabitant
on earth. It is an important resource and a basic necessity for fresh drinking water, proper
hygiene, as well as providing productivity towards an individual and the population to
perform at their optimum level.
Access to clean water is very important and the majority of the people around the world
have poor access to clean water supplies. Polluted water is a health hazard and should not
be taken lightly. We purify water to get rid of contaminants that can be detrimental to our
health and other living things. Most of the water pollution is caused by man, possibly due to
the increase in the population and lack of education on the effects of polluting. Common
pollutants found in contaminated water are poisonous acids, chemicals, bacteria and waste
materials that are difficult to disintegrate. In addition, organic matter can be found within our
waters as it occurs naturally as a result of soil erosion and animal waste which has led to the
deterioration of water quality and can greatly affect the raw freshwater.
Malaysia receives water from an abundance of sources namely, surface water such as
lakes, reservoirs, rivers which originates and flows from the highlands and groundwater
which is stored underneath the earth’s surface. With this abundance of water, all that is
required is effective treatment so that it can be supplied to the public. Various methods of
water treatment have been developed throughout the years and all of them have their
benefits and drawbacks.
Water quality standards plays a role in these processes. Different levels of water purity is
required depending on the intended use, whether its purpose is for human consumption,
agriculture, industrial, domestic or recreational. The water quality guidelines must be
attained specified by the Ministry of Health Malaysia under the Drinking Water Quality
Surveillance Unit, Engineering Services Division.
3
5. In this report, three different water treatment process will be briefly introduced and we will
focus on the most commonly used process which is known as the conventional water
treatment process.
● Conventional Method Treatment Process
(Coagulation-Sedimentation-Filtration-Disinfection)
● Multi Media Filtration System (MMF)
● Reverse Osmosis (RO)
1.1 Conventional Method
For many years, the combined process of mixing, flocculation, sedimentation, filtration
and chlorine disinfection are known as conventional treatment that effectively removes
practically any range of raw water turbidity, along with harmful bacteria. The figures below
describes conventional water treatment process.
Figure 1.1 Conventional Water Treatment for Domestic Use
4
6. In coagulation, a positively charged coagulant (usually an aluminum or iron salt) is added to
raw water and mixed in the rapid mix chamber. The coagulant alters or destabilizes
negatively charged particulate, dissolved, and colloidal contaminants. Coagulant aid
polymers and/or acid may also be added to enhance the coagulation process. Now that the
particles have a neutral charge and can stick together. The water flows into a tank that
provide slow mixing and bring the small particles together to form larger particles called
flocs. Mixing is done quite slowly and gently in the flocculation step. If the mixing is too fast,
the flocs will break apart into small particles that are difficult to remove by sedimentation or
filtration. In the sedimentation process, the majority of the solids are removed by
gravitational settling; particles that do not settle and are still suspended are removed during
the filtration process. Sedimentation is generally accomplished in rectangular or circular
basins and is often enhanced by the addition of inclined plates or tubes which increase
effectiveness of the process by effectively increasing the surface area of the sedimentation
basin.
The filtration step removes particulate matter from water by forcing the water to pass
through porous media. The filtration system consists of filters with varying sizes of pores,
and is often made up of sand, gravel and charcoal. There are two basic types of sand
filtration; slow sand filtration and rapid sand filtration. Slow sand filtration is a biological
process, because it uses bacteria to treat the water. The bacteria establish a community on
the top layer of sand and clean the water as it passes through, by digesting the
contaminants in the water. Rapid sand filtration is a physical process that removes
suspended solids from the water. Rapid sand filtration is much more common than flow sand
filtration, because rapid sand filters have fairly high flow rates and require relatively little
space to operate.
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7. 1.2 Multi Media Filtration System (MMF)
Multi Media filtration (MMF) refers to a pressure filter vessel which utilizes three or more
different media as opposed to a "sand filter" that typically uses one grade of sand alone as
the filtration media. In a single media filter, the finest or smallest media particles remain on
top of the media bed while the larger, and heavier particles, stratify proportional to their mass
lower in the filter. The idea behind using media with differing masses. The filter media
arrangement allows the largest dirt particles to be removed near the top of the media bed
with the smaller dirt particles being retained deeper and deeper in the media. This allows the
entire bed to act as a filter allowing much longer filter run times between backwash and more
efficient particulate removal.
Figure 1.2
A well operated MMF can remove particulates down to 15-20 microns. In addition, an
MMF that uses a coagulant can induce tiny particles to amalgamate together to form
particles large enough to be filtered and remove particulates down to 5-10 microns.
Flocculants or coagulants may be used upstream of the filter to induce the tiny dirt particles
to join together to form particles large enough to be removed by the filter. This process is
called "agglomeration" and, with proper chemical dosage, adequate mixing and adequate
contact time, it will enable the filter to remove particles below 10 microns in average
diameter.
(Microns: A unit of length equal to one millionth of a meter)
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8. 1.3 Reverse Osmosis (RO)
Reverse Osmosis (RO) is a water treatment process that removes contaminants from
water by using pressure to force water molecules through a semipermeable membrane. It is
the process of osmosis in reverse. Osmosis occurs naturally without energy required, to
reverse the process of osmosis you need to apply energy to the more saline solution. A
reverse osmosis membrane is a semi-permeable membrane that allows the passage of
water molecules but not the majority of dissolved salts, organics, bacteria and pyrogens.
However, you need to 'push' the water through the reverse osmosis membrane by applying
pressure that is greater than the naturally occurring osmotic pressure in order to desalinate
(demineralize or deionized) water in the process, allowing pure water through while holding
back a majority of contaminants. During this process, the contaminants are filtered out and
flushed away, leaving clean, delicious drinking water. Reverse osmosis is capable of
removing up to 99 percent of contaminants, including lead, fluoride, chlorine, dissolved salts,
and more.
Figure 1.3
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9. 2.0 Installation Process of Conventional Water Treatment
The water treatment process may vary slightly on the area of location setup by the
standards and requirements of the local community but the basic principles are typically the
same. The factors to consider in the treatment process is the withdrawal, transportation,
treatment and dispersal of clean potable water.
Advanced modern technologies have provided with remarkable capabilities to achieve
these goals. For this reason, another concept to take into consideration is the sustainability
and energy consumption. Incorporating the two components into the process and design
practices, it will offset the trend of poor quality water resources and allow higher levels of
water treatment without the negative impacts along with assisting the water treatment
industry to develop ways and be more efficient while conserving resources.
The installation process for the conventional water treatment is observed from the Sungai
Dua Water Treatment Plant located on an 18.2-hectare site in Seberang Prai Utara, Pulau
Pinang. The raw water is delivered from the Sungai Muda river to the plant via a 14km canal.
Image 2.1 Overview of Sungai Dua Water Treatment Plant
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12. 2.1 Chemical Mixing Chamber
Chemical mixing point begins with instilling controlled amounts of chemicals into the body
of water flow. The chemical mixing chamber is equipped with two sets of electrically motor
driven flash mixers that provides strong mixing to give the required energy for the materials
in the water to stick together, also known as floc, in the coagulation process. The mixing is
able to cater for flow rates between the minimum and maximum plant flows.
Figure 2.1 Diagram section of the mixing chamber
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13. 2.2 Flocculation Tank & Clarifier Tank
The clarification plant consists of flocculation tanks and lamella clarifier tanks. The plants
is divided into two basic sections:
1. The flocculation zone
2. The lamella settling zone
The raw water conditioned with coagulant enters the flocculation tank flowing to the
lamella clarifier tank. The clarification plant is designed to perform satisfactorily to treat water
with turbidity loading between 20 and 500 NTU and between minimum to the nominal design
flows to produce the specified clarified water quality. Mixing for flocculation generally lasts
for 20 to 40 min.
The lamella plate clarifier is a settlement device that provides maximum efficient settling
surface for particles and removes up to 90% more footprint than standard clarifiers. As the
liquid flows upward through the unit, it allows the suspended material to settle on the inclined
parallel plate before they enter the next stage of a process or discharged to a receiving
water course. The sludge that settles on the plates slides to the bottom of the tank at the
base of the unit and removed through the sludge outlet.
Figure 2.2 Diagram of a stainless steel lamella plate settling tank used at the SDWTP
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14. 2.3 Filtration Plant
The filtration plant (fig 2.1) consists of six filter tanks within each filter tank has a total of
105m² media surface area. It is important to note the filters performances do not depend
only on the filter design and proper operating procedure but also on the water quality
incoming from the sedimentation process. Filters are designed as downflow open rapid
gravity type, operating at a constant rate with flow divided equally between the filters by
means of adjustable weirs at the filter inlets.
For collection of filtrate, the nozzles are set in a reinforced concrete false floor; the
nozzles are robust and designed to provide control of the distribution of air and wash water
during the backwashing of the filters.
Image 2.3 Filtered water tank at Sungai Dua Water Treatment Plant
2.4 Compressed Air System
Compressed air supply is used for the operation of pneumatic actuators for penstocks
and valves, as well as for flushing of choked pipelines. It takes out the dirt, water and oil to
be swept along in the air and deposited in the inner surfaces of the pipes and fittings.
The compressed air system of this water treatment plant consists of two numbers of
stand-alone air receiver sized for minimum four cycles of all valves and penstocks operation.
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15. 2.5 Service Water Ring Main
The service water ring main is designed to supply water to the treatment plant and
supernatant recovery plant. The supply is taken to 2 sources; one is the treated water
delivery pipelines near to the surge vessel of the newly constructed contact and clear water
tanks and the other is from the existing high lift pump house.
Figure 2.5 A diagram comparison showing the difference of flow rates
2.6 Drainage System
Drainage systems to drain waste from the drainage and scum gallery. It pumps the waste
to the perimeter drain which will lead into the common sludge / wash water/ overflow
channel. Drainage pump can be controlled from either the Motor Control Centre (MCC) or at
the Push Button Station (PBS) depending on the selection switch minimising the amount of
material that must ultimately be disposed of by recovering the recyclable material and
reducing water content.
Image 2.6 (Left to right) Motor Control Centre (MCC) & Push Button Station (PBS)
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16. 3.0 Management Systems
3.1 Optimal Water Usage
Optimum usage of water resources is becoming more and more essential as water
demand increases everyday with the increasing population on earth. Only 0.08 percent of
the world’s fresh water is exploited by mankind,thus developing or improving more efficient
methods to reuse water is a continuous effort
worldwide. Numerous water management systems are already being practiced globally and
many of them are proving to be a success.
Most water management systems at this present time aim to find ways to recycle water.
In places with uncertain climates smart use of drinking water is essential. As a result many
countries have methods of recycling wastewater for non drinking purposes such as:
● Agriculture irrigation
● Watering public parks and gardens
● Toilet flushing
● Carwashing
● Garden watering
Below is an example of wastewater being recycled and used for Agriculture irrigation:
Figure 3.1 Lindstrom, Carl, Grey water System
In addition to water recycling there are other systems that concentrate on setting
regulations aimed at promoting efficient use of water. Conformance marks such as the
(Water Regulations Advisory Scheme 1999) in the United kingdom are placed for the
specific purpose of preventing misuse, waste, undue consumption or enormous
measurement water.
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17. 4.0 The Advantages & Disadvantages
The conventional method of water treatment has become more complex over the years.
As explained previously a series of treatment processes are set before the water is certified
clean enough for supply to the public. This is the result of higher demand for better water
quality which has caused implementation of stricter regulations in water treatment. The extra
treatment procedures have definitely improved water quality however there are a few
drawbacks leaving room for improvement.
4.1 Disadvantages
● Much precaution is required in the chemical dosing of coagulants as it may be toxic.
Only highly trained people should perform dosage of coagulants.
● Time is required for preparation of coagulants as natural coagulants are not available
in usable form.
For maximum effectiveness in coagulation, three factors need to be carefully monitored:
1. Uniformity of the coagulant flow (ideal dose in a steady stream)
2. The vigor of coagulant mixing
3. The PH and alkalinity
Any slight errors or misjudgments in any of these three factors could affect the
effectiveness of the process. Therefore, regular maintenance on machinery like Flocculators,
Coagulators and Clarifiers need to be undertaken and this could be costly and time
consuming.
● Using chlorine gas or sodium hypochlorite in the disinfection stage is always risky as
they are toxic and could react with organic compounds in the water to form potentially
harmful levels of chemical by-products.
● Chlorine has limited effectiveness against protozoans that form cysts in water.
4.2 Advantages
● The series of procedures eliminates most of the solids and bacteria from the water
before being supplied to the public.
● Natural coagulants can be obtained at low costs or even for free.
● With a very good filtration system cysts that chlorine cannot get rid of can be
eliminated from the water
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18. ● 5.0 Case Study: Finding & Explanation
The research is conducted through interviewing the consulting engineers in Teknoserv
Engineering Sdn Bhd, the utility division of GUH Holdings Berhad. It is an engineering and
contracting company specialised in the design and build of water treatment plants. Their
office operates in Shah Alam.
In order to gain a deeper understanding of the entire system of water treatment plant, the
engineer, Mr. Khu has kindly used one of their past projects as a reference. It’s a
construction of Sungai Dua 25MGD water treatment plant for the client named Perbadanan
Bekalan Air Pulau Pinang Sdn. Bhd.
Millions of gallons per day (MGD) is a measurement unit of a plant’s capacity. It
represents the ability of facilities to move or process water. Therefore, the amount of this
water treatment plant owned by PBA is able to supply 25 millions of gallons of clean water
for domestic use in Penang per day.
Figure 5.0.1 Penang State Water Supply Statistic
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19. 5.1 Source of Water – Muda River & Raw Water Balancing Pond
Water sources can be from ground water (deep wells/shallow wells), surface water
(lake/rivers), ocean water (desalination reverse osmosis) and spring water. It is not possible
for a single treatment plant to treat all the different types of raw water as every of them is
built specifically to produce the required quality of water
The raw water source for this treatment process unit is abstracted from the existing raw
water balancing pond and its water flows from the Muda river; the longest river in Kedah,
Malaysia. The Beris Dam is used to regulate the flow of water along the Muda River basin.
The Muda River in Malaysia experiences oods every year hence the existing raw water
balancing pond is designed to control flow rates by storing floodwater and releasing it slowly
once the risk of flooding has passed. During dry season, the pond contains water. The
stored water will change the water level, thus serving its purpose in both dry and wet
weather.
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21. 5.2 System Integrity
System integrity is defined as the state that a water distribution system has to be in to
ensure that it fulfils its purpose. Three types of integrity can be identified:
● Physical integrity means that the system components are able to function as
intended and provide a barrier between the water in the system and external threats.
● Hydraulic integrity means that the system is able to provide the flows and pressures
required for the required level of service.
● Water quality integrity means that the system is able to deliver water of acceptable
quality to all its users (assuming that it receives source water of acceptable quality).
The different types of system integrity are not independent since they influence each
other. For instance, a loss of physical integrity due to cracks in pipe may lead to a loss of
hydraulic integrity through increased friction losses, and a loss of water quality integrity if
polluted water outside is able to enter the pipes through cracks.
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22. 5.3 Hydraulic System (Flows & Pressures)
Sungai Dua water treatment plant runs based on the earth gravity force, the water flows
from a high entry point to the lower outlets (basin at the bottom) under the pressure of the
hydraulic head.
During the treatment process, the raw water flows in one direction from the pump station
to the clear water tank at the end. Whereas, it pumps water backwards during backwash,
sometimes including intermittent use of compressed air during the process. Backwash is a
form of preventive maintenance so to remove trapped particles and the filter media can be
reused. Thus, compressed air system and washwater pump only operate for backwashing in
this system.
By understanding how pressure works in treatment units, two situations can be identified;
an open system and closed system. As the water fills in a closed system, the static pressure
is up to the level of the entrance point. Whereas, open system allows the water continuously
flow and the dynamic pressure is the maximum pressure. The total available head at the
treatment plant is the difference in water surface elevations in the inflow of first treatment
unit and that in the outflow of last treatment unit. If the total available head is less than the
head loss through the plant, flow by gravity cannot be achieved. In such cases pumping is
needed to raise the head so that flow by gravity can occur.
Preventing spillage over the channel and tanks walls are also taken into consideration
while determining the hydraulic profile. Hence there are level electrodes to indicate the fluid
level at filter and tanks. Alarms are also set at every segment of unit to be triggered in case
the water level exceeds the height limit.
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23. With the example of filter operation and backwash system, the system components are
designed to control the hydraulic pressure as shown below:
Equipment Capacity Location Function
Washwater
Pump
840m³/hr at 9m
each
Filter Plant
Control Building
Provide water during filter
backwashed.
Washwater
Pump
Delivery
Valve
400mm
diameter
To control the flow of wash water
by opening during pumping
sequence and closing when pump
is stopped.
Modulating
Valve
600mm
diameter
To modulate the wash water flow
through PLC controlled during
combined air-water wash and
rinsing.
Air Scour
Valve
300mm
diameter
Filter Pipe
Gallery
To allow air from blower to enter to
the filter during backwashing.
Air Release
Valve
50mm diameter To allow excess air to escape after
the air scour.
Filter Loss Of
Head
· To measure the loss of head for
each filter.
· To initiate the automatic backwash
system when the level reaching to
pre-set value.
· To determine the filter drain down
level.
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25. 5.4 Water Quality Parameter
The Department of Environment (DOE) uses Water Quality Index (WQI) and National
Water Quality Standards for Malaysia (NWQS) to evaluate the status of the river water
quality. The WQI introduced by DOE is being practiced in Malaysia for about 25 years and
serves as the basis for the assessment of environment water quality, while NWQS classifies
the beneficial uses of the watercourse based on WQI.
5.4.1 Physical Drinking Water Parameter
Physical parameters define those characteristics of water that respond to the senses of
sight, touch, taste or smell.
Figure 5.4.1.1 Physical or general water parameters
Based on Sg. Dua water treatment plant, the clarification plant is designed to produce the
specified clarified water quality as indicated as below. Therefore, we will discuss more on
parameter of turbidity and suspended solids in water treatment:
Turbidity Not exceeding 5NTU
Suspended Solids Not exceeding 5mg/l
Aluminium as Al Not exceeding 0.4mg/l
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26. 5.4.1.1 Turbidity
Turbidity is the cloudiness or haziness of a fluid caused by large numbers of individual
particles that are generally invisible to the naked eye.
Material that causes water to be turbid include clay, silt, finely divided inorganic and
organic matter, algae, soluble coloured organic compounds, and other microscopic
organisms.The relative clarity of fluid is a key measurement of water quality.
Excessive turbidity, or cloudiness, in drinking water is aesthetically unappealing, and may
also represent a health concern. Turbidity can provide food and shelter for pathogens. If not
removed, turbidity can promote regrowth of pathogens in the distribution system, leading to
waterborne disease outbreaks.
Figure 5.4.1.1.1 Samples of water being tested for turbidity and solids
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27. 5.4.1.2 Suspended Solid
Solids are classified as settleable solids, suspended solids and filterable solids.
Settleable solids (silt and heavy organic solids) are the one that settle under the influence of
gravity. Suspended solids and filterable solids are classified based on particle size.
Total suspended solids (TSS) are particles that are larger than 2 microns found in the
water column. Anything smaller than 2 microns (average filter size) is considered a dissolved
solid.
These solids include anything drifting or floating in the water, from sediment, silt,and sand
to plankton and algae. Organic particles from decomposing materials can also contribute to
the TSS concentration. As algae, plants and animals decay, the decomposition process
allows small organic particles to break away and enter the water column as suspended
solids.
5.5 Sampling Water
Continuous samples of water at various stages in the treatment plant process are
required for monitoring water quality. Stainless steel deep well sampling pumps are provided
for the sampling of water from the settled water channel as well as the filtered water channel.
Two pumps will be provided at each point – one for duty and one on standby. The sampling
pump will be running for 24/7. Operator are to alternate duty and standby pump preferably
once a week.
5.5.1 System Component
Equipment Quantity Capacity / Size Location Function
Sampling
Pump
4 1.08m3/ hr Settled Water
Channel And
Filtered Water
Channel.
Pumps the
settled/filtered water
to the analyzer rack.
Analyzer
Rack
1 - Clarifier Control
Building.
Monitors the quality
of water.
Turbidity
Meter
2 · 0-5 for filtered
water
· 0-10 for settled
water
Clarifier Control
Building.
To measure the
turbidity of the
sampled water.
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28. 6.0 Possible Problems To The System
For mixing chamber, flocculation tank, and clarifier tank, these are the usual problems
that affects the process or the settled water quality.
Problem : Settled water turbidity > 5
Step 1 : Check to see if the raw water quality is out of range, eg : NTU > 500
Step 2 : If yes, then the plant might have to be shut down to prevent contamination of the
clear water tank.
Step 3 : If not, check to see if chemical are indeed dosed the correct amount.
Step 4 : If the chemical dosing is not the problem, check visually at the chemical dosing
point to ensure chemical is reaching the point. Make sure all valves are in their correct
position.
Step 5 : If not, then check to make sure all flash mixer and flocculators are running and are
at the correct speed.
Step 6 : If not, check the turbidity analyser to make sure the reading is accurate. Clean and
re-calibrate the analyser if necessary.
Step 7 : If all these does not solve the problem, then the operator should consult his superior
to do more detailed troubleshooting.
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29. For filtration plant,
Problem : Filtered water turbidity > 0.4
Step 1 : Check to see if the raw water quality is out of range, eg : NTU > 200
Step 2 : If yes, then the plant might have to be shut down to prevent contamination of the
clear water tank.
Step 3 : If not, check to see if chemical are indeed dosed the correct amount.
Step 4 : If the chemical dosing is not the problem, check visually at the chemical dosing
point to ensure chemical is reaching the point. Make sure all valves are in their correct
position.
Step 5 : If not, then check to make sure all flash mixer and flocculators are running and are
at the correct speed.
Step 6 : If not, check the turbidity analyser to make sure the reading is accurate. Clean and
re-calibrate the analyser if necessary.
Step 7 : Make sure all of the filter tanks are in service.
Step 8 : Make sure all the filters have been recently backwashed and if there’s any filter
nearing it’s preset backwash time, backwash that tank.
Step 9 : Check the turbidity of filtered water from each filter tank manually to identify which
tank contributes to the problem.
Step 10 : If all these does not solve the problem, then the operator should consult his
superior to do more detailed troubleshooting.
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30. 6.1 Ineffective Backwashing
Ineffective backwashing is one of the main reasons that water treatment filters fail.
Backwashing refers to pumping water backwards through the filters media, sometimes
including intermittent use of compressed air during the process. Backwashing is a form of
preventive maintenance so to remove trapped particles and the filter media can be reused.
Filter backwashing run automatically and back to normal operation automatically by local
programmable logic controllers (PLCs). Not more than 1 filter will be washed concurrently.
The backwash cycle is triggered upon following criteria : -
● The filter running hour reach to preset time (48 hours).
● The differential pressure across the filter reaches to preset level (1.8m)
● When the filter effluent turbidity is greater than a treatment guideline.
Failure of a backwash treatment process and reintroduction of the resulting poor quality
water into the main water purification plant flow stream can cause overall process upsets
and result in the production of poor quality treated drinking water.
6.2 Machinery Breakdown
There are different components in each process unit. They serve different purposes yet
interlinked in a way that malfunction of an individual part may indirectly affect the rest. For
instance, if the compressor does not provide enough air supply, backwashing will not be
done properly. And the clogging of filter bed increases in time. Consequently the required
pressure will drop and water will not be flowing from one process unit to the other at
maximum efficiency.
In the event of weak pump or cracked pipe at the raw water station, there will be
insufficient flow intake to the treatment plant. Without enough raw water flowing in, it will not
be able to produce clean water to meet the user's’ demand.
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31. 6.3 Overdose of Chemical
Disinfectants kill present unwanted microorganisms in water. Typically drinking water has
0.5mg of chlorine per litre, compared to pools that have up to 3mg. However, supplying
water that is unfit for human consumption can be hazardous.
Scientists discovered that when chlorine is added to water, it forms Trihalomethanes
(THMs), one of which is chloroform. THMs increase the production of free radicals in the
body and are highly carcinogenic. “Cancer risk among people using chlorinated water is as
much as 93 percent higher than among those whose water does not contain chlorine,”
according to the U.S. Council of Environmental Quality.
Besides issues of affecting human health, the impact of chemical caused to environment
has also evoke serious concern. In the case of draining the water with high content of
aluminium sulphate back to the soil or wastewater, soil underneath may undergo aluminium
toxicity. Plant growth and development can be disrupted as it is an growth limiting factors.
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32. 6.4 Contamination of Source Water
According to the United Nations World Water Development Report 2015, every day, 2
million tons of sewage, industrial and agricultural waste are discharged into the world’s
water, the equivalent of the weight of the entire human population of 6.8 billion people.
Besides the number of threats mentioned, air pollution has also caused increased acidity
in rainwater and stormwater runoff can pollute rivers, streams and lakes. Therefore, it is
known that having clean water source is essential for treatment plant. Drinking water that is
not properly treated or disinfected, may impose outbreaks and health risk.
The most recent scenario of contaminated source water in Malaysia occurred in
Kuantan. The impact of bauxite mining has caused the streams and rivers nearby turned
red. Traces of aluminium in the treated water supply is found in Felda Bukit Goh and Felda
Bukit Sagu, and lead, in Semambu. It is believed that the bauxite sediments resulted from
the anthropogenic activities is channelled into nearby water catchment area. Such
contaminants have seeped into water supply especially during the rainy season as more
runoff is generated. Even though aluminium was used as a coagulant in the treatment of
water, it was unusual to have such high levels of it in drinking or potable water.
Figure 6.4 Online news articles on the Kuantan River contamination.
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33. 7.0 Recommendation for Future Improvements
The purpose of a water treatment system is to provide an adequate and reliable supply of
safe water to its users. Operation and maintenance are those activities needed to
continuously fulfil this purpose which involves activities necessary to deliver the service,
while maintenance involves activities that keep the system in good operating condition.
Operation includes monitoring the system state, running the system and enforcing
policies and procedures. Maintenance entails condition assessment, servicing, repair and
replacement of system components. When maintenance is done before a system element
fails in order to prevent it from failing, this is called proactive maintenance. Maintenance
done after a component failure is called reactive maintenance.
Operation and maintenance of a water distribution system can be greatly affected by the
system design and construction practices used. For instance, a design that specifies
unsuitable pipe materials or pipes that are damaged during construction may lead to major
future operation and maintenance problems for the system. The system should be done in
such a way that consumers are provided with a high quality service in the most cost-effective
method.
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34. 7.1 Physical Integrity
A water distribution system consists of a complex combination of components, including
pipes, fittings, pumps, reservoirs, valves, hydrants, meters and backflow preventers that are
all critical in maintaining the physical integrity. At the same time, the distribution system is
constantly changing through aging, replacement of components and the addition of new
extensions. For that reason, having correctly functioning components and maintain a
physical barrier between the water in the network and the external environment is crucial.
Below is a table that provides a summary of the common components of a water
distribution system, what external threats they protect against, and the common materials
used in these components.:
Components External Threats The Components
Protects Against
Common Material
Used
Network pipes Soil, groundwater, sewage
contamination, surface run-off, human
activity, animals, plants and
pathogens.
Cast iron, ductile iron,
steel, asbestos cement,
PVC and polyethylene.
Plumbing Pipes Human activity, sewage and
non-potable water.
Copper, iron, steel,
PVC, poly- ethylene,
polybutylene.
Fittings (meters,
valves, hydrants,
etc)
Soil, groundwater, sewage
contamination, surface run-off, human
activity, animals, plants and
pathogens.
Cast iron, brass, steel,
rubber, plastics.
External Coating and
wraps for pipes and
fittings
Supporting role in that it preserves the
pipe integrity from external threats.
Zinc (galvanising),
polyethyl- ene, bitumen
coating, bitumen
wrapping,
cement-mortar.
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35. Internal linings for
pipes and fittings
Supporting role in that it preserves the
pipe integrity from internal threats.
Zinc (galvanising),
epoxy, urethanes,
bitumen, cement-
mortar, plastic inserts.
Storage facility
walls, roof covers
and vent hatches.
Air contamination, rain, algae, surface
runoff, human activity, animals, birds
and insects.
Concrete, steel, cast
iron, bitu- men, epoxy,
and plastics.
Backflow prevention
devices
Non-potable water. Brass, ductile iron,
plastics.
Gaskets and joints Soil, groundwater, sewage
contamination, surface run-off, human
activity, animals, plants and
pathogens.
Rubber, leadite,
bitumen, plastics.
7.1.1 Operation & Maintenance Consideration
It is important to do a proactive maintenance to keep the unplanned failures to a minimum
and resources can be used in the most effective way to ensure the integrity of the system.
However, proactive maintenance will never be possible as unexpected failures are bound to
occur even in the best maintained system. A general maintenance principal and operations
are important in this process.
● Condition monitoring is important to know the components condition and
performance histories. The components should be operated within their capabilities
and according to manufacturer instructions to ensure optimal benefit is obtained from
them.
● Timeous Repair & Earlier Detection of Problems; Refurbishing and replacement
of components. Most control systems have alarming features that detects and
notifies an operator of operation or process problems. Centralised control can
dramatically reduce the required time to make changes in water production during a
crisis. In addition, online instruments can detect many types of water quality
problems in real time as opposed to waiting for the result of grab sample analysis.
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36. ● Protecting the system environment ensuring that components are not exposed to
unnecessary risks. This includes protection against vandalism or accidental human
entry, prevention of external water from entering the system and protection against
organisms such as birds and insects.
● Corrosion control should be implemented to ensure that system components are
not damaged. It is necessary to analyse system to determine areas where pipes and
other components are vulnerable to corrosion, and then take appropriate steps to
prevent it.
Metal Pipes Soil Resistivity, pH, redox potential, the presence of sulphides,
and site drainage conditions
Concrete Pipes Soil chloride content and resistivity
External Corrosion Applying protective coatings and linings, installing and
maintaining cathodic protection systems and mitigating stray
currents.
Internal Corrosion Adding corrosion inhibitors, such as phosphates to water and
adjusting pH and alkalinity to appropriate levels.
● Backflow prevention; Water supplied to consumer installations should be protected
from being able to enter the system again through check valves or other measures
where appropriate.
● Keeping records should be done on all maintenance actions. Extensive operational
information being collected and stored in a relational database can help staffs
analyse and report information in new ways. This allows decisions to be made based
upon the most accurate and up-to-date information possible. Historical operational
information can be done in evaluating long-term operational trends and answering
questions that require detailed historical information. Troubleshooting problems can
be instantaneously done with better alarm information and sequence of events
tracking.
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37. 7.2 Hydraulic Integrity
Hydraulic integrity is the ability of a distribution system to meet all user demands;
domestic, industrial, commercial, fire fighting etc. while ensuring desirable pressures,
velocities and water age in the system. Pressure is the most important indicator
of hydraulic integrity considering physical integrity is not enough in itself to provide water to
consumers.
7.2.1 Operations & Maintenance Consideration
To maintain the hydraulic integrity of water distribution systems as well as ensuring the
best possible water quality, the system should be kept as short as possible and large
fluctuations in flows and pressures. Low flows and pressures should be avoided. Various
operational and maintenance measures are important to maintain hydraulic integrity.
● Monitoring the operational parameters in a water distribution system should be done
as widely as possible.
● Positive water pressure should be maintained and the causes of low pressures
investigated and rectified without delay.
● Reservoirs levels can be reduced during low demand periods to ensure that the
retention time of water does not become excessive.
● Flushing or cleaning of pipes should be conducted systematically to ensure that
accumulated sediments are removed from pipes.
● Active leak detection should be conducted to find pipe leaks and reported or
discovered components failure should be repaired as soon as possible.
● Quality control measures on repairs are critical to ensure that repairs are done
properly and do not create new problems.
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38. 7.3 Hazardous Chemicals
Appropriate responsibility should be taken to measure as accidental release of gaseous
chemicals such as chlorine will present a significant health risk to adjacent communities.
Only highly trained staffs should be handling chemical dosing to coagulants. Safety concerns
should influence both site selection and mitigation process. Better control of the of the
process can minimise the chemical and energy use which leads to a much larger impact on
sustainability.
7.4 Air Quality
Water treatment plants typically do not generate strong odours. However, citizens are
wary from the familiar odours coming from the wastewater treatment plants and solid waste
facilities which may have fears about potential odours. The most common source of
unpleasant odours would be from the residual handling in the water treatment management.
For this reason, the clarifier tanks should be cleaned promptly to prevent the sludge to go
septic within the tank. Chemical storage should not generate odours if they are designed and
handled properly.
7.5 Staff Training
Training without a doubt should include new employee orientation and current employee
proficiency training as the water supply industry is a highly technical and ever changing,
every opportunity should be taken to send facility employees to attend seminars, workshops,
and conferences to upgrade their skills to initiate and maintain professional contacts. Online
training can be done as an additional option. Unauthorised and incompetent personnel are
not allowed to operate any equipment at the plant.
7.6 Renewable energy
Renewable energy source may result in life-cycle cost saving and may be a good
investment for a water utility. The most common renewable energy sources utilise at water
treatment plants are hydraulic turbines, wind and solar power. Electrical requirements are
similar for backup power supply.
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39. 8.0 Learning Outcome
After taking everything into account, we have realised that water treatment plants are
more complex than what meets the eye. It requires a tremendous amount of research and
analysis, extensive understanding of the various factors that must be considered, thorough
knowledge of the community’s values and interests, an inclination to cooperate with the
public and community officials with no small amount of good judgement and reasoning.
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40. References
Books
1. The Drinking Water Handbook. Frank R.Spellman and Joanne E.Drinan. CRC Press;
Second ed. (May 22, 2012)
2. Water and wastewater treatment : a guide for the non-engineering professional.
Joanne E. Drinan and Frank R. Spellman. (2013)
3. Water quality control handbook . E. Roberts Alley. (2007)
4. Drinking water : principles and practices. P.J. de Moel J.Q.J.C. Verberk, J.C. van
Dijk. New Jersey ; Hong Kong : World Scientific. (2006)
5. Water treatment plant design. Stephen J. Randtke, Michael B. Horsley. New York:
McGraw - Hill. (2012)
E-books
6. Water Treatment Plant Design, Fifth Edition.
https://accessengineeringlibrary.com/browse/water-treatment-plant-design-fifth-editio
n
7. Introducion to Operation and Maintenance of Water Distribution Systems.
http://www.wrc.org.za/Knowledge%20Hub%20Documents/Research%20Reports/TT
600-14.pdf
8. Principles of Water Treatment
http://outsidethesink.rtu.lv/documents/Principles%20of%20Water%20Treatment.pdf
E-Journal
9. http://iosrjournals.org/iosr-jestft/papers/vol8-issue12/Version-3/G081234044.pdf
10. http://umpir.ump.edu.my/3312/1/NUR_DIYANA_MOHD_SHAMSUDDIN.pdf
11. https://pdfs.semanticscholar.org/2dcd/965372f8ee9d7a3a347b64ff4240ddb6ccde.pdf
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