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WATER TREATMENT TECHNOLOGY (TAS 3010) LECTURE NOTESUNIVERSITY MALAYSIA TERENGGANU 2009Disclaimer: I don't own this file. If you believe you do, and you don't want it to be published here, please let me know. I will remove it immediately
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Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
© SHAHRUL ISMAIL, DESc.University College of Science and Technology Malaysia
CHAPTER 3:Environmental Microbiology
CHAPTER 9d : CHAPTER 9d : CHAPTER 9d : CHAPTER 9d :
TAS 3101 : WATER TREATMENT TECHNOLOGY
Water Water
Treatment Treatment
Process :Process :
FiltrationFiltration
Water Water
Treatment Treatment
Process :Process :
FiltrationFiltration
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
Menu
1) Introduction
2) Filtration Methods
3) Filtration Types:
- Gravity Filter
- Pressure Filter
4) Percentage of filtered water
5) Filter Sand
6) Filter Gravel
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
Introduction
- Water management begins with knowing the quantity of water
available
- Basic information on water measurement units and convenient
conversion factors.
- Conversion factors simplify changing from one unit of measurement to
another.
- There are two conditions under which water is measured—water at
rest and water in motion. Water at rest is measured in units of volume.
Water in motion is measured in units of flow— unit of volume for a
convenient time unit. It is important that the difference between a unit of
volume and a unit of flow be kept in mind.
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
- Passage of water through a porous medium to remove remaining flocs or suspended solids.
- Needed for most surface waters in order to provide a second barrier against the transmission of water borne disease
1) Suspended matter and colloidal matter are removed
2) Chemical characteristic of water are changed
3) Number of bacteria materially reduced.
- Assist significantly by reducing the load on the disinfections process, increasing disinfection efficiency.
Filtration
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
METHODSMETHODS
MECHANICAL MECHANICAL STRAININGSTRAINING
SEDIMENTATION & SEDIMENTATION & ADSORPTIONADSORPTION
BIOLOGICAL BIOLOGICAL METABOLISMMETABOLISM
ELECTROLYTIC ELECTROLYTIC ACTIONACTION
Filtration - Mechanism
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
- Size of suspended solid is bigger than size of porous medium
- Removing such particles of suspended matter as are too large to pass through the interstices between size grains
-
Mechanical Straining
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
1. The interstices between the sand grains act as sedimentation
basins in which the suspended particles smaller than the
voids in the filter-bed settle upon the sides of the sand grains
2. The particles stick on the grains because the physical
attraction between the two particles of matter and because of
the presence of the gelatinous coating formed on the sand
grains by the previously deposited bacteria and colloidal
matter.
Sedimentation & Absorption
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
1. “ The growth and life process of the living cells”
2. The surface layer gets coated with a zoogleal film in which the
bacterial activities are the highest and which feed on the organic
impurities.
3. The coated converts organic impurities by a complex biochemical
action into simple, harmless compounds – purification of water.
Biological Metabolism
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
1. Due to the friction between medium and suspended solids
2. A certain amount of dissolved and suspended matter is
ionized.
3. Suspended matter in water is ionized, carries charge of one polarity
and the particles of sand in filter which are also ionized, possess
electrical charges of opposite polarity.
4. These neutralize each other; change the chemical character of water
Electrolytic Action
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
1) PRESSURE FILTER SYSTEM
2) GRAVITY FILTER SYSTEM
- Commonly used
- Two (2) general categories
1. Slow Sand Filter (SSF)
- 0.1 – 0.5 m/h ~ 0.2 m/h
2. Rapid Sand Filter (RSF)
- 3 – 12.5 m/h ~ 5 - 7.5m/h
Filtration - Types
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
1) Action at the surface of the sand bed
2) Surface gets coated with a skin or layer formed due to the
bacterial action of finely suspended matter, plankton and other
organic matter present in raw water, with algae, bacteria etc.
previously coated on the surface of the sand-bed by the water
itself – “ schmutzdecke”.
3) Below this layer and up to 30 cm, present other bacterial zones-
completely oxidize the organic matter, destroy most of the
bacteria present and let only simple and unobjectionable
inorganic salts to pass through the filter bed into the effluent.
Slow Sand Filter
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
- Straining action – Throughout the depth of the filter sand rather than on
the surface or to a small distance below this.
- Other action – complex biological and chemical changes as water passes
through the sand-bed as SSF.
- Previously coated material is important - Necessary for waters to be
coagulated before they are allowed to pass through the rapid sand filter.
- Other factors : Proper thickness of sand-bed, size of the sand grains.
Rapid Sand Filter (RSF)
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
Gravity Flow
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
Rapid Sand Filter (RSF)
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
Percentage of filtered water :
i) Quantity of filtered water every 24 hours operation, f = Qfto
ii) Filter area, As = Qf / Vof
iii) Quantity of wash water, i) QBW = As x VOBW (ii) BW = QBW x t
iv) Percentage of filtered water = BW / f x 100%
Where;
f = Quantity, m3 QBW = Flow of wash water, m3/min
to = 24 VOBW = Rate of washing
Qf = flow rate As = filter area, m2
Vof = Rate of filtration BW = Quantity of wash water, m3
Filtered Water Percentage
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
ITEMS SSF RSF
Filtration rate (m3/m2/hr) 0.1 – 0.2 3 – 12.5
Area (m2) 50 – 2000 (more area) < 400 (less area)
Size of sand (mm) 0.3 – 0.35 > 0.55
Distribution of medium size
Not stratum Stratum
Washing method Replace the upper layer of sand
Backwash
Operation Cost Low High
Efficiency of disinfections
99% 60%
Supervision Simple Skilled
Gravity Filter System
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
ITEMS SSF RSF
Loss of head Very small – 0.6 – 0.9 m
More – 2.5 – 3m
Coagulation Not required Required – satisfactory filtration
Period of cleaning Once every 2 – 3 months
24 – 48 hours
Amount of wash water 0.2 – 0.6 percent of filtered water
2 – 4 percent of filtered
Maintenance cost Small More because of maintenance of
pumps for pumping up wash-water and a compressor unit for
obtaining compressed air.
Gravity Filter System
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
Pressure Filter
1) Water is allowed to pass under a pressure greater than
atmospheric pressure through a closed cylinder. The force
gravity has no function.
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
1) Free from clay, loam, vegetable or organic matter
2) Uniform and proper size
i. If the sand is too fine, it tends to quickly clog causing a greater loss
of head in the filter
ii. If the sand is too coarse, it will permit suspended solids and bacteria
passes through the voids between the sand grains.
3) Filter sand classification :
- Effective size, Uniformity coefficient, Percent size
Filter Sand
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
1) No function in the actual purification of water
2) Slow sand filter :
Simply supports the sand-bed
3) Rapid sand filter :
Serve to distribute the wash water evenly throughout the sand
4) Usually placed in five or six layers; finest layer on top
5) Hard, rounded and durable.
Filter Gravel
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
1) PRESSURE FILTER
2) DOUBLE FILTRATION
3) MICROSTRAINING
4) DIATOMACEOUS EARTH FILTERS
5) IN-DEPTH FILTRATION
6) DUAL MEDIA FILTERS
i) Dual media filters ii) Mixed Media Filters
Filtration – Other types
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
Determine the percentage of filtered water
required for washwater based on the following
criteria :
Flow, Qf = 300 L/s
Rate of filtration, Vof = 170m3/m2.day
Time of washing = 10 min
Rate of washing, VoBW = 15 mm/s
Problems!!!!
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
1) Effective size :
i. The seize size in mm, permits 10 percent of the sand,
which permits 10 percent of the sand, by weight to pass - size
of the grain that is larger than 10 percent by weight of all the
particles comprising the sand.
ii. Indicate the minimum size of 90 percent by weight of
the sand.
iii. Consideration of variable in individual grain size.
[NEXT]
Filter Sand – Effective Size
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
2) Uniformity coefficient :
i. Expression of the degree of variation
ii. The ratio between the size, that will pass 60 percent by
weight to the effective size – the ratio of the particle
size which is coarser than 60 percent by weight to the sand
to the effective size of sand.
iii. E.g. if sand has an effective size of 0.50 mm and 60
percent of sand passes a 0.80 mm, the uniformity
coefficient =
0.80 0.50
= 1.60
[NEXT]
Filter Sand – Uniformity Coefficient
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
3) Percent Size
i. The size of the grain that has the given percent, by
weight, of materials finer in size.
ii. Percent size specified = 1, 10, 60 and 90 percent
iii. E.g. A percent size of 10 means that 10 percent of the
sand is smaller than the grain size given.
[BACK]
Filter Sand – Percent Size
Izan Jaafar, Engineering Science, FST, UMTIzan Jaafar, Engineering Science, FST, UMT
THANKS FOR THANKS FOR
YOUR ATTENTION…..YOUR ATTENTION…..
THANKS FOR THANKS FOR
YOUR ATTENTION…..YOUR ATTENTION…..