drinking water treatment process

Drinking Water Treatment
El-Hassan A. El-Sadek
2018

Agenda
This Presentation will cover :
• Water in Egypt
• Multiple Barrier Approach
• Current situation of water in Egypt
• Drinking Water Treatment Process

Do You Know…????
How long can humans live without
water?
How much of the human body is
made of water?
We can live 30+ days without food, but
only 4-7 days without water
The human body is about 60% water
We must drink at least 6-8 glasses of
water each day
How much water should humans
drink each day?

SDWA PROTECTING AMERICA’S PUBLIC HEALTH
Comprehensive Source Water Protection
MULTIPLE RISKS REQUIRE MULTIPLE BARRIERS
RISK
RISK
PREVENTION
RISK
MANAGEMENT
INDIVIDUAL
ACTION
PROTECTION
BARRIERS
RISK RISK RISK
RISK
MONITORING/
COMPLIANCE
RISK
RISK
PREVENTION
RISK
MANAGEMENT
INDIVIDUAL
ACTION
PROTECTION
BARRIERS
RISK RISK RISK
RISK
MONITORING/
COMPLIANCE
RISK
RISK
PREVENTION
RISK
MANAGEMENT
INDIVIDUAL
ACTION
PROTECTION
BARRIERS
RISK RISK RISK
RISK
MONITORING/
COMPLIANCE
RISK
RISK
PREVENTION
RISK
MANAGEMENT
INDIVIDUAL
ACTION
PROTECTION
BARRIERS
RISK RISK RISK
RISK
MONITORING/
COMPLIANCE
RISK RISK RISK RISK
RISK
PREVENTION
RISK
MANAGEMENT
RISK
MONITORING/
COMPLIANCE
User
Information
Multiple Barrier Approach to Public Health Protection
Goal: Protect Current &
Future Sources of
Drinking Water

‫بالجمهورية‬ ‫الشرب‬ ‫مياه‬ ‫جودة‬ ‫مراقبة‬ ‫منظومة‬

‫مستوى‬ ‫على‬ ‫الشرب‬ ‫مياه‬ ‫جودة‬ ‫منظومة‬‫شركات‬‫المياه‬

Water shortage in Egypt
• The current water shortage in Egypt is 13.5 Billion cubic meter per year (BCM/yr) and
is expected to continuously increase.
• water shortage in 2025 would be 26 BCM/yr in case of continuation of current
policies.

=Treatment
Source
Water +
Contaminants:
Particles (clay, silt)
Natural organic matter
Microcontaminants
(e.g., pharmaceuticals)
Bacteria , Protozoa.
Tap Water
Surface water
or groundwater
10

Water Teratment
Process
Water Treatment Process
5/15/2018 11

Water Teratment Process
1. Screening ‫الفحص‬(‫المأخذ‬)
2. Clarification ‫الترويق‬
3. Filtration ‫الترشيح‬
4. Disinfection ‫التطهير‬
5/15/2018 13
Screening
Clarification
Filtration
Disinfection

Screening
• Removes large solids
– logs
– branches
– rags
– fish
• Protects pumps and pipes in WTP

Screening
•Screens should be easily removable
or have automatic cleaning devices
• Steel or metal screens should be
corrosion resistant.

‫الخام‬ ‫المياه‬ ‫رفع‬ ‫طلمبات‬ ‫عنبر‬(‫النيل‬)
21

Maintenance of Screens
1. Clean and validity of screens
2. Clogging and corrosion are biggest problem
3. All screens must be inspected
4. Periodic maintains of pumps

‫؟‬ ‫المياه‬ ‫عكارة‬ ‫تأتى‬ ‫اين‬ ‫من‬
‫؟‬
Do You Know…????
24

Nature of Particles:
Particles in water are a result of :
• soil
• decay of plant material
• industrial contamination
• animal wastes, etc.

Type of Particles
Particles
Particles
NOT Able to perception
‫غير‬‫للترسب‬ ‫قابلة‬
Particles
Able to perception
‫للترسب‬ ‫قابلة‬

‫المياه‬ ‫في‬ ‫الجسيمات‬ ‫ترسيب‬ ‫قابلية‬
‫الحبيبات‬ ‫قطر‬(‫مم‬)‫النوع‬‫الترسيب‬ ‫زمن‬*‫للترسيب‬ ‫القابلية‬
10‫حصي‬1‫ثانية‬‫قابلة‬
1‫رمل‬10‫ثواني‬‫قابلة‬
0.1‫ناعم‬ ‫رمل‬2‫دقيقة‬‫قابلة‬
0.01‫طمي‬/‫طحالب‬2‫ساعة‬‫قابلة‬ ‫غير‬
0.001‫بكتريا‬8‫يوم‬‫قابلة‬ ‫غير‬
0.0002‫غروية‬ ‫مواد‬‫سنتين‬‫قابلة‬ ‫غير‬
0.00002‫فيروسات‬20‫سنة‬‫قابلة‬ ‫غير‬
*‫زمن‬‫الترسيب‬‫هو‬‫القدرة‬‫التقريبية‬‫للرسوب‬‫لمسافة‬1‫م‬‫في‬‫المياه‬‫تحت‬‫تأثير‬‫الجاذبية‬‫فقط‬
.

Coagulation
‫ترويب‬
Flocculation
‫تنديف‬
Sedimentation
‫ترسيب‬
Clarification stages

Microsand ballasted technology

‫لشكل‬ ‫نموذج‬‫الدائرية‬ ‫المروقات‬

‫لشكل‬ ‫نموذج‬‫الدائرية‬ ‫المروقات‬
15.05.201
8

5/15/2018 water treatment
‫لشكل‬ ‫نموذج‬‫المروقات‬‫المستطيلة‬

1. Coagulation
Coagulation Flocculation Sedimentation Filtration Disinfection

Coagulation
Surface water usually has a lot of suspended and
dissolved matter
These solids must be removed to ensure that the
water is safe for consumption
The coag/floc process facilitates the removal of
small, suspended and dissolved matter

Natural Forces Between Particles
1- Zeta potential
Preventing force between any two particles of like Charge
2- Van der Waals force
Attraction force between particles pulling them together
Particles will stay in suspension :
zeta potential > van der Waals force

Coagulant agent
Alum Magnesium chloride
Polyacrylamide
Moringa oleifera

Flash Mixers
Provide agitation to evenly mix coagulant through
water
Add chemicals to center of mixing chamber
Coagulation occurs in less than 1-2 seconds
This stage determines the success of coagulation
Detention time should not exceed 30 seconds
(Design Criteria)

Flash Mixers
Types of Flash Mixers
Mechanical mixers
Static mixers
Pumps and conduits
Baffled chambers

Baffled chambers
5/15/2018
Plan view (horizontal flow)
L
Isometric View (vertical flow)
L
W
H
• Horizontally baffled tank
The water flows horizontally.
The baffle walls help to create
turbulence and thus facilitate mixing
• Vertically baffled tank
The water flows vertically.
The baffle walls help
to create turbulence and
thus facilitate mixing

2. Flocculation

Flocculation
Follows coagulation
Provides gentle agitation to build floc
Mixing energy must be low so floc will not be sheared
Floc should not be allowed to settle in floc basin
Detention time must be at least 30 minutes,
with 45 minutes recommended (Design Criteria)

Flocculation
Operating Factors That Affect Floc Development
• Inadequate flash mixing
• Improper flocculation mixing
• Inadequate flocculation time
• Incorrect chemical dose

Choosing a Coagulant
Begin by using the jar test with various chemicals
• Dose
• Mixing speed
• Chemical combination
• Full-scale plant operation may not match jar test results
• Indication of improper flash mixing, coagulant
• Pinpoint floc
• High settled turbidity
• Frequent filter backwash

Control Tests
Tests that are used to optimize the coagulation and flocculation processes:
Jar test
• allows you to test different chemicals or dosages before you
try them in your plant

Control Tests
pH
• ensures proper pH range for coag/floc process
Turbidity (settled)
• success of sedimentation process
Turbidity (finished)
• overall process success

Control Tests
Zeta potential meter
measures charge of water
Streaming current monitor
measures overall charge after coagulant is added
Particle counter
measures size and concentration of particles in finished water

Control Tests
Visual inspection of floc in floc basins:
• size and distribution of floc
• Visual inspection of how floc settles in sedimentation Basin
• Calibrate feeder equipment at least once per shift
• Use in-line monitors to measure water quality

Common Operating Problems
Low water temperature
• As temp drops, water becomes more viscous
• Solutions: operate near optimal pH, increase coagulant dose,
add weighting agent or coagulant aid
Weak floc
• Passes through filters
• Slow floc formation
• Often caused by low turbidity or insufficient alkalinity
• Solutions: add weighting agent or increase alkalinity

3. Sedimentation

Sedimentation
Rachel Casiday, Greg Noelken, and Regina Frey, Washington University

Sedimentation
Occurs following flocculation and before filtration
Decreases the solids loading on filters and other
treatment processes
The decreased loading can result in
• longer filter runs
• reduced filter maintenance

SEDIMENTATION BASIN OPERATION
Goals of Sedimentation
• To produce settled water with the lowest possible
Turbidity
• To reduce the concentration of organics which can
cause color or form DBP’s (disinfection by products)

→
Inlet
Water
→
Outlet
Water
‫الراسى‬ ‫االتجاه‬ ‫سرعة‬
(‫الجاذبية‬)
‫االفقى‬ ‫االتجاه‬ ‫سرعة‬
(‫الطفو‬)

‫الترسيب‬ ‫عند‬ ‫الجزئيات‬ ‫سلوك‬
[‫ل‬]‫الترسيب‬ ‫حوض‬ ‫طول‬(‫م‬)
[‫ض‬]‫الترسيب‬ ‫حوض‬ ‫عرض‬(‫م‬)
[‫ق‬]‫الترسيب‬ ‫حوض‬ ‫عمق‬(‫م‬)
[‫أ‬ ‫ع‬]‫االفقية‬ ‫الطفو‬ ‫سرعة‬(‫م‬/‫س‬)
[‫ع‬‫هـ‬]‫رأسية‬ ‫هبوط‬ ‫سرعة‬(‫م‬/‫س‬)
(‫عمق‬‫الترسيب‬ ‫حوض‬(‫ق‬))
‫التدفق‬ ‫معدل‬(‫المياه‬ ‫تصرف‬)
________________________
‫المقطع‬ ‫مساحة‬(‫العرض‬ x ‫القاع‬)
‫الطول‬
________
‫العمق‬
‫الطول‬x ‫العرض‬
‫الطفو‬ ‫سرعة‬
________
‫الهبوط‬ ‫سرعة‬

5/15/201879
‫؟‬
‫افضل‬ ‫الترسيب‬ ‫احواض‬ ‫اى‬‫؟‬

‫؟‬ ‫افضل‬ ‫الترسيب‬ ‫احواض‬ ‫اى‬!!
‫من‬ ‫يتضح‬‫السابقة‬ ‫المعادلة‬‫هب‬ ‫سرعة‬ ‫لها‬ ‫التى‬ ‫العالقة‬ ‫المواد‬ ‫أن‬‫وط‬
‫مساوية‬ ‫رأسية‬‫من‬ ‫أكثر‬ ‫أو‬"‫ع‬‫هـ‬"‫الحوض‬ ‫فى‬ ‫ترسيبها‬ ‫يتم‬.
‫أقل‬ ‫الرأسية‬ ‫سرعتها‬ ‫كانت‬ ‫إذا‬ ‫المواد‬ ‫ترسب‬ ‫ال‬ ‫العكس‬ ‫وعلى‬‫من‬
"‫ع‬‫هـ‬”.
‫الترسيب‬ ‫لحوض‬ ‫السطحية‬ ‫المساحة‬ ‫أن‬ ‫نرى‬ ‫ذلك‬ ‫ومن‬(‫الطول‬×
‫العرض‬)‫الترسيب‬ ‫كفاءة‬ ‫على‬ ‫مباشر‬ ‫تأثير‬ ‫لها‬
‫السطحية‬ ‫المساحة‬ ‫زادت‬ ‫فكلما‬‫قلت‬"‫ع‬‫هـ‬"‫عمق‬ ‫تقابل‬ ‫والتى‬
‫الترسيب‬ ‫حوض‬(‫ق‬)‫الحوض‬ ‫كفاءة‬ ‫زادت‬.
‫و‬‫تسمى‬"‫ع‬‫هـ‬"‫الترسيب‬ ‫لحوض‬ ‫السطحى‬ ‫التحميل‬ ‫بمعدل‬‫ت‬ُ‫ت‬‫و‬‫خذ‬
‫األحواض‬ ‫لهذه‬ ‫التصميم‬ ‫أسس‬ ‫من‬ ‫كأساس‬‫وحدتها‬ ‫وتكون‬‫م‬3/‫م‬2
/‫س‬.
‫التدفق‬ ‫معدل‬(‫تصرف‬
‫المياه‬)
‫للجزئيات‬ ‫الرأسية‬ ‫الهبوط‬ ‫سرعة‬=________________________
‫المقطع‬ ‫مساحة‬(‫الطول‬ x
‫العرض‬)

Ideal sedimentation tanks
The conditions must be done to be an ideal sedimentation tank:
1.The flow is laminar flow.
2.There are no dead zones.
3.The horizontal velocity is constant.
4.Good arrangement of inlet and outlet weirs.

ZONES OF A SEDIMENTATION BASIN

ZONES OF A SEDIMENTATION BASIN
Influent Zone (inlet)
• Decreases the velocity of incoming water from flocculation
• basin
• Distributes it evenly across the basin
Settling Zone
• Provides the calm area for the suspended material to settle
• Largest zone
• Effluent Zone
Provides smooth transition from settling zone to effluent
flow area
V-notch weirs enable flow to be evenly distributed
Sludge Zone
Area where solids collect as they settle

SEDIMENTATION BASIN OPERATION
Factors Affecting Sedimentation
• Temperature
• Colder water = slower settling
• Particle size, shape, and weight
• Electrical charge of particles
• Wind and rain
• Coagulant dose and type
• Basin hydraulics

Water coming from
flocculation basin.
Water goes to
filter.
Floc (sludge) collected
in hopperSludge to solids
treatment
Sludge removal

OPERATING PROBLEMS
Poorly Formed Floc
Doesn’t settle properly
Characterized by smaller loosely held particles that
do not settle & are carried out of the settling basin
Can be caused by
• improper mixing
• dosage
• type of coagulant
• changes in raw water
• Solutions
• increase mixing energy
• perform jar tests
• use coagulant aid

OPERATING PROBLEMS
Short Circuiting :
Water bypasses normal flow and reaches outlet
without proper amount of DT
Can be caused by
• poor inlet baffling (main cause)
• wind driven currents
• density currents
• when the influent contains more suspended solids
than the water in the basin
• when the influent is colder than the water in the basin

OPERATING PROBLEMS
Algae and Slime Growth
Outdoor, uncovered basins
Causes taste and odors
Can detach and clog filters or weirs
Can create slick, hazardous surfaces
Solutions
can be controlled with a mixture of copper
sulfate and lime or other chemicals
drain basin and apply mixture to
problem areas with a brush

‫الشرب‬ ‫مياه‬ ‫تنقية‬ ‫محطات‬ ‫الداء‬ ‫المبدئى‬ ‫التقييم‬
‫المروقات‬:
•‫الخروج‬ ‫ومياه‬ ‫المأخذ‬ ‫لمياه‬ ‫والعكارة‬ ‫الشفافية‬ ‫مقارنة‬.
•‫كبيرة‬ ‫ندف‬ ‫وجود‬ ‫مالحظة‬Flocks‫للمحطة‬ ‫عالية‬ ‫كفاءة‬ ‫على‬ ‫لتدل‬
•‫الشبة‬ ‫وتركيز‬ ‫الطلمبة‬ ‫دفع‬ ‫مالحظة‬10%‫الشبة‬ ‫وحقن‬
(‫المضاف‬ ‫الشبة‬ ‫جرعة‬(25–30‫جرام‬/‫م‬3)
•‫المبدئية‬ ‫الكلور‬ ‫جرعة‬ ‫مالحظة‬(3-5‫كيلو‬/1000‫م‬3)‫صيفا‬
‫و‬(2-3‫كيلو‬/1000‫م‬3)‫شتاءا‬
•‫المطلوب‬ ‫للمعدل‬ ً‫ا‬‫طبق‬ ‫الروبة‬ ‫مخرج‬ ‫ومالحظة‬ ‫مراقبة‬

PURPOSE OF FILTRATION
Removal of particulate impurities and floc
• Aesthetics – minor reason
• Rremoves microorganisms - main reason

‫لمرشح‬ ‫نموذج‬ ‫فيديو‬

‫مرشح‬ ‫من‬ ‫مقطع‬ ‫صور‬
97

‫طبقات‬ ‫عن‬ ‫عبارة‬ ‫المرشح‬
‫من‬:
• ‫الرمل‬
• ‫الزلط‬
5/15/2018 99

‫الترشيح‬ ‫رمل‬
‫البالطات‬‫الخرسانية‬‫ذات‬‫الفواني‬:
‫تصنع‬‫البالطات‬‫عادة‬‫من‬‫الخرسانة‬‫وتحتوي‬‫علي‬‫فتحات‬‫تركب‬‫في‬‫ها‬
‫الفواني‬‫وتصنع‬‫الفواني‬‫من‬‫الصلب‬‫الذي‬‫ال‬‫يصدأ‬‫أو‬‫من‬‫البالستيك‬‫وتحت‬‫وي‬‫علي‬
‫مشقبيات‬‫رفيعة‬‫ال‬‫تسمح‬‫بمرور‬‫الرمل‬‫الخشن‬‫فيها‬.
‫ماء‬

PURPOSE OF FILTRATION
Sedimentation on media (very important) :
Adsorption
stick to surface, adhere
Absorption
penetration of substance into structure of another
substance, like a sponge
Straining

BACKWASHING
Solids trapped by adsorption and straining :
• Solids clog openings through the filter
• turbidity can occur

‫المرشح‬ ‫انسداد‬
5/15/2018 112

‫المرشحات‬ ‫غسيل‬ ‫عملية‬
15.05.2018
‫المرحلة‬‫في‬ ‫المستخدمة‬ ‫المادة‬
‫الغسيل‬
‫الهدف‬
1‫هواء‬‫أو‬‫ماء‬‫في‬ ‫المستخدمة‬ ‫المادة‬ ‫دخول‬ ‫بدء‬‫الغسيل‬
‫المعاكس‬ ‫االتجاه‬ ‫في‬
2‫هواء‬+‫ماء‬‫الجزيئات‬ ‫لفصل‬ ‫احتكاك‬ ‫عمل‬‫العالقة‬
3‫ماء‬‫يزداد‬‫تصرفة‬‫تدريج‬‫يا‬‫الترشيحي‬ ‫الوسط‬ ‫من‬ ‫الهواء‬ ‫طرد‬
4‫ماء‬‫فقط‬‫العالقة‬ ‫المواد‬ ‫طرد‬
5‫ماء‬‫يقل‬‫تصرفه‬‫تدريج‬‫يا‬‫كل‬ ‫الجزيئات‬ ‫لتعود‬‫الي‬‫الحجم‬ ‫حسب‬ ‫مكانة‬
‫والكثافة‬

Abnormal Conditions
Mudball in media

Abnormal Conditions
Media cracked or shrinkage

Abnormal Conditions
Media boils during backwashing

‫المرشحات‬:
•‫رؤية‬‫رمل‬‫الترشيح‬‫بوضوح‬(‫شفافية‬‫المياه‬)
•‫مالحظة‬‫الطفو‬‫الزائد‬over flow
•‫مالحظة‬‫نظافة‬‫الحوض‬
•‫مالحظة‬‫ندرة‬‫كور‬‫الطمى‬mud ball
•‫مالحظة‬‫قلة‬‫الندف‬‫حيث‬‫ان‬90%‫منها‬‫يجب‬‫أن‬‫يكون‬‫بالمروقات‬.
•‫انتظام‬‫الغسيل‬‫العكسى‬‫للمرشح‬

Disinfection or
Sterilization !!
121

Disinfection
Disinfection – the
destruction of pathogenic organisms
• To prevent waterborne disease
outbreaks
• Destroys only disease-causing
organisms

Sterilization
Sterilization :
• the destruction of all organisms
in the water
• Not all microorganisms are bad!

How to express the strength of chlorine
•Chlorine gas typically contains pure chlorine
•Chlorine powder and liquid do not contain pure chlorine
- are mixed with other substances (e.g., calcium, sodium or water)
•The strength of chlorine in chlorine powder or chlorine liquid is referred to:
• as the Concentration of chlorine in that substances.
(percentage (%) of active chlorine present)

Chlorine (Gas)
Chlorine Gas (Cl2):
• Greenish-yellow color
• 2.5 times as dense as air
• Pungent, noxious odor
• Highly irritating to eyes,nasal passages,
and respiratory tract
• Strength: Approx. 100 % active chlorine
• Stability: Most stable

Chlorine (Liquid)
Hypochlorite (Liquid)
Sodiuim hypochlorite (NaOCl)
Bleach
Clear, light-yellow color
Costs 3 times as much as chlorine gas
Shelf life of 60-90 days
• 5.25% chlorine : Clorox
• 12.5% chlorine : Pool bleach

Chlorine (Solid)
Hypochlorite (Solid) :
• Calcium hypochlorite [Ca(OCl)2]
• Solid, granular or tablet
• White or yellow-white in color
• Most dangerous – fire hazard
• 65% pure – High Test Hypochlorite (HTH)
• Strength: Typically 30 to 70 % active chlorine
•Stability: May lose strength over time;

Preparing chlorine liquid from chlorine powder

Powder & liquid chlorine may lose strength
over time
Chlorine liquid solutions are generally less stable than chlorine powder (i.e.,
lose strength more quickly)

How to calculate the required amount of
chlorine powder

Chlorine dose rate
‘Chlorine dose rate’ means how much chlorine liquid solution you are adding to the water
over time .
May be measured in various ways
⇒ mL per second
⇒ mL per minute
⇒ L per hour

How to calculate the chlorine dose rate

How to calculate the actual chlorine dose

Chlorine dose
•Usually expressed as milligrams per litre (mg/L).
•for example,
• if drinking water has a chlorine concentration of 1 mg/L,
• this means that there is 1 milligram of chlorine present in 1 litre of water

Chlorine chemical reactions
Under normal water conditions, hypochlorous acid will also chemically react and
break down into a hypochlorite ion (OCl-):
The hypochlorite ion is a much weaker than hypochlorous acid, about 100
times less effective.

HOCl
OCl-
100
90
80
70
60
50
40
30
20
10
0
Percentageoffreechlorinespecies
Hypochlorous acid (HOCl ) VS hypochlorite ion (OCl-)
50:50 equilibrium at
pH 7.5
Best disinfection pH 6 - 7
Acidic
HOCl Hypochlorous acid
Alkaline
OCl- Hypochlorite ion

Understanding
Chlorination Process

‫الحقيقة‬ ‫فى‬ ‫الماء‬:
Understanding Chlorination Process
Inorganic
Organic

Combined
Residual
Chlorine
Chlorine
Demand
Free
Residual
Chlorine
+
Inorganic
+
Organic
Kill
Chlorine Dosage ( total added )
1. Chlorine Demand (Inorganic)
2. Combined Residual Chlorine (Organic)
3. Free Residual Chlorine
Understanding Chlorination Process

The “Breakpoint”
Chlorine is
reduced to
chlorides by
easily oxidizable
stuff (H2S, Fe2+,
etc.)
Chloramines
broken down &
converted to
nitrogen gas which
leaves the system
(Breakpoint).
Cl2 consumed by
reaction with
organic matter. If
NH3 is present,
chloramine
formation begins.
At this point,THM
formation can
occur
inorganic organic Chloramines Free

The “Chloramines”
breakpoint
NH3 + HOCl → NH2Cl + H2O (4 < pH < 6) ….. (1)
NH2Cl (mono) + HOCl → NHCl2 + H2O (4 < pH < 6) ….. (2)
NHCl2 (di) + HOCl → NCl3 + H2O (pH < 3) ….. (3)
2NH2Cl (Tri) + HOCl → N2 (‫النتروجين‬ ‫غاز‬) + 3 HCl + H2O ….. (4)

‫الكلور‬ ‫مصطلحات‬Chlorine Terms
‫الكلى‬ ‫الكلور‬ ‫جرعة‬
Chlorine Dosage
‫مستهلك‬ ‫كلور‬
Chlorine Demand
‫متبقى‬ ‫كلور‬
Residual
Chlorine
‫متحد‬ ‫متبقى‬ ‫كلور‬
Combined Residual
Chlorine
‫حر‬ ‫متبقى‬ ‫كلور‬
Free Residual Chlorine

Relationship between :
chlorine demand & chlorine dose

Factors to
success of chlorination

Factors to success of chlorination
Chlorine concentration (C)
Contact time (T)
Water temperature
Water pH
Foreign substances in water

Ct concept for disinfection
“kill” is proportional to C x T
Destruction of organisms depends on the
concentration of chlorine added (C)
and
the contact time with the organisms (T)
If one is decreased, the other must be increased

Factors influencing the Ct value

Influence of chlorine concentration

Influence of water temperature

Influence of pH
• For effective chlorination, the pH of the water should be < pH 8.0
• Where water is >pH 8.0,
higher chlorine concentrations or More contact time will be required!

HOCl
OCl-
100
90
80
70
60
50
40
30
20
10
0
Percentageoffreechlorinespecies
Free Chlorine Distribution with pH
50:50 equilibrium at
pH 7.5
Best disinfection pH 6 - 7

Minimum required
contact time for effective disinfection
For effective disinfection, the WHO recommends
at least 30 minutes contact time,
where the residual chlorine concentration is
≥0.5 mg/L and the pH of the water is <pH 8.

How to calculate the Ct value
1. calculate the detention time for a storage
2. calculate the Ct value

How to calculate the detention time for a storage

Application Points
Chlorine may be added:
1. Pre -chlorination (before water treatment plant)
2. Post-chlorination (after water treatment process)
3. Secondary chlorination (during distribution)
4. Groundwater systems

Application Points
Pre-chlorination (source water chlorination)
Begins process of killing or inactivating pathogens
Minimizes biological growth throughout process
Oxidizes minerals, gases, organics, etc.
Increases contact time
May improve coagulation
High potential for DBP production

Application Points
Post-chlorination (terminal disinfection)
Application of chlorine to treated water
Required to meet state and federal
requirements for residual
Applied at or immediately before clearwell
Clearwell must minimize short circuiting to
meet C x T values

Application Points
Distribution system (Secondary chlorination )
Some systems may require booster chlorination
Added at storage tank discharge
Additional application points
Feeding 2 or more types of disinfectants at different
points may help meet requirements
Oxidants other than chlorine can be used early in
treatment process to reduce DBPs

Application Points
Groundwater systems
Often require no treatment other than chlorination
Apply chlorine just past wellhead

trihalomethanes ( THMs )
Organic material + Cl2 = trihalomethanes (THMs) :
Organics found in all surface and groundwaters
Humic and fulvic acids from decomposing plant material
THMs are potential carcinogens
Current MCL for total THM = 0.08 mg/L

Control Tests
Chlorine residual
Presence of residual
Free or combined
Concentration
By amperometric titration (most accurate, not affected by color or
turbidity) or DPD method
Bacteriological test
Indicates fecal contamination

‫الخروج‬ ‫مياه‬
•‫عن‬ ‫الكلور‬ ‫جرعة‬ ‫زيادة‬ ‫عدم‬ ‫مالحظة‬1.5-3‫جرام‬/‫النهائى‬ ‫فى‬ ‫لتر‬.
•‫للـ‬ ‫تقييم‬ ‫عمل‬ ‫مع‬ ،‫المياه‬ ‫خزان‬ ‫في‬ ‫المياه‬ ‫مستوى‬ ‫طريق‬ ‫عن‬ ‫التالمس‬ ‫وقت‬ ‫راجع‬"C*T"
•‫الجرعة‬ ‫في‬ ‫التحكم‬(‫كجم‬/‫ساعة‬)‫الشهري‬ ‫واالستهالك‬
•‫المياه‬ ‫خزان‬ ‫مخرج‬ ‫عند‬ ‫المتبقي‬ ‫الحر‬ ‫الكلور‬.......‫الهدف‬:‫األدنى‬ ‫الحد‬0,5‫مليجرام‬/‫لتر‬-‫األقصى‬ ‫الحد‬1,5
‫مليجرام‬/‫الخط‬ ‫أول‬ ‫في‬ ‫الموجودين‬ ‫العمالء‬ ‫عند‬ ‫لتر‬
•‫الشبكة‬ ‫فى‬ ‫نقطة‬ ‫وأبعد‬ ‫الشبكة‬ ‫أول‬ ‫فى‬ ‫المتبقى‬ ‫الكلور‬ ‫يكون‬ ‫أن‬ ‫الفرق‬ ‫مالحظة‬‫حدود‬ ‫فى‬0.5‫ملليجرام‬/‫لتر‬.

Water Storage
Purpose
Equalizing supply and demand
Increasing operating convenience
Leveling out pumping requirements
Decreasing power costs

‫أقوال‬ ‫من‬‫ي‬‫البصر‬ ‫الحسن‬:
”‫يعلم‬ ‫لم‬ ‫ما‬ ‫علم‬ ‫هللا‬ ‫ورثه‬ ‫علم‬ ‫بما‬ ‫عمل‬ ‫من‬
‫حتى‬ ‫يعمل‬ ‫فيما‬ ‫ووفقه‬‫يستوجب‬، ‫الجنه‬
‫يعلم‬ ‫فيما‬ ‫تاه‬ ‫يعلم‬ ‫بما‬ ‫يعمل‬ ‫لم‬ ‫ومن‬
‫النار‬ ‫يستوجب‬ ‫حتى‬ ‫يعمل‬ ‫فيما‬ ‫يوفق‬ ‫ولم‬”.

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