1. INDIAN OIL CORPORATION LIMITED , DIGBOI
A TRAINING REPORT
SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS OF THE
AWARD OF
THE DEGREE OF
BACHELOR OF TECHNOLOGY
(CIVIL ENGINEERING)
SUBMITTED BY :
SHUBHADEEP DEY
DURATION OF TRAINING PERIOD: 01/05/2015 TO 30/05/2015
MANOJ CHAUDHARY
Indian Institute of Technology, Roorkee

4. INTRODUCTION: DIGBOI REFINERY
The Digboi Refinery was set up at Digboi in 1901 by Assam
Oil Company Ltd.. The Indian Oil Corporation Ltd (IOC) took
over the refinery and marketing management of Assam Oil
Company Ltd. with effect from 1981 and created a separate
division. This division has both refinery and marketing
operations. The refinery at Digboi had an installed capacity
0.50 MMTPA (million metric tonnes per annum). The refining
capacity of the refinery was increased to 0.65 MMTPA by
modernization of refinery in July, 1996. A new
delayedCoking Unit of 1,70,000 TPA capacity was
commissioned in 1999. A new Solvent Dewaxing Unit for
maximizing production of microcrystalline wax was installed
and commissioned in 2003. The refinery has also
installed Hydrotreater-UOP in 2002 to improve the quality
of diesel.

5. REFINERY CIVIL CORE MAINTENANCE JOBS ARE AS FOLLOWS:
1. Painting of structures , buildings , pipelines and steel storage tanks.
2. Insulation and cladding of industry specific.
3. Housekeeping (garbage disposal , cleaning of premises)
4. Sewage cleaning and drain cleaning.
5. Horticulture jobs.(gardening ,landscaping etc.)
6. Repair and maintenance of buildings inside refinery.

6. PAINTING SPECIFICATION FOR CARBON STEEL STORAGE TANKS ,
PIPELINES AND STRUCTURAL
A. GENERAL:
1. This specification covers requirements for surface preparation and application of
primer and paint for carbon steel storage tanks ,pipelines and structures.
2. Wherever it is stated in the specification that a specific material is to be supplied or a
specific work is to be done ,it shall be dimmed that the same shall be supplied ,or
carried out by the contractor with the best quality of material and workmanship at
his own cost.
3. All required tools ,brushes ,blast materials ,steel scaffolding,shot blasting equipment
,air compressor etc. shall be arrainged by the contractor at site in sufficient quantity.
4. The paint manufacturers instruction shall be followed as far as practicable at all
times. Particular attention shall be paid to the following:
a) Proper storage to avoid exposure and extreme temperatures.
b) Surface preparation prior to painting.
c) Temperature ,dew point temperature ,relative humidity during application.
d) Mixing and thinning.
e) Application of paint and the recommended limits of time intervals between the
coat.
5. Mechanical mixing shall be used for paint mixing operations in case of 2-pack paint
system except that the engineer in-charge may allow hand mixing of small mixing at
his discretion.
B. SCOPE:
1. Scope of work covered in the specification shall include ,without being limited to
, painting of the following:
a) Painting of external surfaces of carbon steel CR,FR and AG Hoz. Tanks ,Horton
spheres and bullets of MS ,HSD ,SKO ,ATF ,naptha ,NGL and also black oils and
water sevice tanks.
b) Painting of internal surfaces of carbon steel CR ,AG-hoz. Tanks of HSD and
SKO service.
c) Painting of internal surfaces of carbon steel CR ,AG-hoz. Tanks of ATF service.
d) Painting of internal surface of FR tanks ,UG-hoz. Tanks of MS ,naptha ,NGL
services.
e) Painting of internal surface of cone roof carbon steel water tanks.
f) Painting of above ground product pipelines ,water lines and fittings.

7. g) Painting of steel structures.
C. SURFACE PREPARATION:
1. In order to achieve maximum durability ,one or more of the following methods of surface
preparation shall be followed ,depending on the condition of the steel surface and as given
in the engineering data sheet or as instructed by engineer in-charge.
a) Blast cleaning
surfaces shall be blast cleaned using abrasives and moisture/oil free air. On completion
of blasting operation ,the blasted surface shall be cleaned and made free from any scale
or rust and must show a grey white metallic lustre. Primer or first coat of paint shall be
applied within 2 hours and be finished within 4 hours of surface preparation. Blast
cleaning shall not be done outdoor in bad weather when the relative humidity is more
than 80%. The surface profile shall be uniform to provide good key to the paint.
Following points are to be noted for blast cleaning:
i. Minimum air supply pressure shall be maintained at 7Kg per sq. cm during
blasting opertation.
ii. Compressor should be moisture and air trap.
iii. At least 25mm ID hose is to be used if the distance between compressor
and blaster is 15 metre or more.
iv. The grit size for blasting shall be 16-30 mesh size i.e. abrasives below 16
mesh and above 30 mesh shall not be used.
v. The nozzles should be discarded when the crevice is worn outto a diameter
50% greater than original i.e. ¼ nozzle should be discarded whwn the crevice
is worn out to 3/8 diameter.
b) Manual or hand tool cleaning
It normally consists of hand de-scaling and hammering ,hand scrapping and hand wire
brushing .Rust mill scales ,spatter ,old coatings and others foreign matters shall be
removed by hammering ,scrapping tools ,emery paper ,wire brushing or combination of
the above methods . On completion of cleaning loose materials shall be removed from
the surface by cleaning rags and the surface shall be brushed ,swept,de-dusted and
blown off with dry compressed air to remove all loose matter.the surface cleaning shall
correspond to SSPC SP2 if not otherwise specified.
c) Mechanical or Power Tool cleaning:
Power tool cleaning shall be done by mechanical striking tools ,chipping hammers
,grinding wheels ,or rotating steel wire brushes. On completion of cleaning ,the
detached rust ,mill scales etc. shall be removed by cleaning rags and washed by water or
steam and thoroughly dried with dry compessed air jet before application of paint .The
surface cleaning shall correspond to SSPC SP3 if not otherwise specified.

8. D. APPLICATION OF PRIMER AND PAINT:
1. Before application of primer ,the surface shall be cleaned of dust etc.
2. All paints shall be stirred up thoroughly prior to and during application . To follow manufacturer s
data sheet . Straining is to be carried out if the contents are settled down at bottom of the
container.
3. Application of coats shall be carried out at least 5 degree celcius above dew point temperature
and shall not be applied above 50 degree celcius of surface temperature . Paint shall not be applied
when RH is more than 85%.
4. Coating media shall be of uniform thickness.All slots ,recesses ,grooves ,corners ,angles and
interstices shall be covered by paint . Sag & runs shall be distributed or removed and new paint shall
be applied uniformly.
5. All paint containers shall only be prior to utilization and shall be carefully closed immediately after
withdrawal of material. Materials which become unserviceable during storage shall not be applied .
All painting materials shall be kept weather proof barracks and shall be kept cool and dry.
6. Application of primer , intermediate coats and finish coats shall be done as per the given
instructions given in the manufacturer s data sheet.
7. For spray application the compressor should be capable of supplying of25 CFT/min. of free air at
1000 psig for each gun.
8. All filters ,moisture traps & air regulators shall be as close as possible to the painter.
9. The spray gun shall be around 250 mm away from the surface and shall be perpendicular to it.
10. Painting shall be done in day hours only.
11. Successive coats in a paint system should be slightly different in shade for easy identification
.shades of each coat shall be decided by E-I-C.
E.INSPECTION AND TESTING:
1. All painting materials including primers and thinners brought to the site by
contractors shall be procured directly from manufacturer as per the specification
and shall be accompanied by manufacturer s test certificates . Paint formulation
without certificates are not acceptable under any circumstances.
2. The paint work shall be subject to inspection by engineer in-charge . The quality
assurance plan is strictly followed at all times.

9. 3. Any defect noticed during various stages of inspection shall be rectified by
thecontractor to the entire satisfaction of engineer in charge before proceeding
further.
4. Irrespective of the inspection repair and approval at immediate stages of work
,contractor shall be responsible for making good any defect found during the final
inspection period liability period as defined in general condition of contract .Dry Film
Thickness shall be checked and recorded after application of each coat and extra
coat of paint shall be applied to make up the DFT specified without the extra cost of
owner.
5. The contactor must approve following standart measuring instrument required as
per the QA plan :
a) Surface measuring thermometer.
b) Dew point measuring thermometer.
c) Relative humidity tester.
d) Profile measuring meter.
e) Wet film thickness meter.
f) Dry film thickness meter.
THERMAL INSULATION:
1. The provision made to retard heat flow from a hot surface to a cold
environment and from a worm environment to a cold surface.
2. This simple system in industry had acquired enormous importance in recent
times for what it can do for us if we give a very little extra attention.
3. Major tools for energy conservation.
Todays need is for currectly designed and well installed insulation system-
i. Which is easy on the purse.
ii. Speedy to erect.
iii. Stays maintenance-free & efficient in survice.
An efficient insulation in place serves our best interests in todays context-
i. Economy , safety , smoother process control at plant level.
ii. Substancial reduction of fuel cost & enhanced profitability at the
corporate level.
iii. Reduction of green house gas emission at the larger global level.
iv. Prefab insulation.

10. POTENTIAL ENERGY LOSS FROM A HOT SURFACE
Difference between heat loss Kcal/m2.hr
ambient and surface
temperature.
25 185
40 329
100 1029
150 1625
225 2486
From a metallic surface at 40 degree celcius ambient temperature and wind
velocity 1m/sec.
Properly designed insulation can restrict heat loss to 85 Kcal/m2.hr. with 0
m/sec. wind velocity & 150 kcal/m2.hr with 1m/sec. Wind velocity.
THERMAL INSULATION DESIGN
Design of an insulation broadly covers the following :-
1. Defining operating condition.
2. Defining environment condition.
3. Type of surface
4. Desired surface temperature
5. Type of cladding
6. Insulation material
7. Heat loss over cladding
INSULATION IN REFINERY CIVIL DIGBOI IS MAINLY OF TWO
TYPES :-
a) Hot insulation
b) Cold insulation

11. HOT INSULATION
Commonly used hot insulation materials :-
1. Mineral wool : Rockloyd range
a) Rockloyd mattress
b) Rockloyd slab
c) Rockloyd pipe section
2. Calcium silicate
a) Density 200-250 kg/m3
b) Conformity : IS 8154/9428 & ASTM C-533.
c) Stability : upto 950 degree celcius as per IS 9428
d) Non combustible
e) Hygroscopic product

12. 3. Moulded perlite Block and pipe thermal insulation
a) 27 to 1649 deg. C
b) Expanded perlite and silicate binders.
c) Site moulded sections
d) Water absorption (48 hrs.) : 50%
e) Non combustible
4. Supercera blankets
a) Double needled soft refractory fibres to form a blanket.
b) Zirconia stabilized , suitable for use upto 1260 to 1425 deg. C
c) Thickness 6 , 12 , 25 & 50 mm.
d) Size 7620 X 610 mm

13. 5. Cladding materials
a) Aluminium
b) Galvanised steel
c) HDPE
d) Stainless steel
e) Galvalume steel
f) Aluminised steel
g) PVC
h) Cementaceous plasters
PURPOSE :-
a) For water prone areas cladding plays important role
b) Impervious cover over insulation
c) Vapour barrier
d) Completely sealed cladding
e) Hard cover
f) Protect insulation from environment abuses like
i. Dust
ii. Water
iii. Foot traffic
iv. Extended life of insulation

14. COLD INSULATION
Commercial cold insulation materials :-
1. Polyurethane Foam (PUF)
2. Polyisocynurate Foam (PIR)
3. Foam Glass
4. Phenolic Foam
5. Expanded Polystyrene (EPS)
COLD INSULATION PIPING
1. Execution concept
a) Cast in-situ PUF system
b) Pre foam PUF segments
c) Combination of pre foam and cast in-situ.
CAST IN-SITU PUF SYSTEM
i. For faster erection
ii. System is monolithic and joint free
iii. Best suited for temperature upto -50 degree celcius

15. iv. Neat and clean finish
v. Requires no mastic vapour barriers as metal cladding does all required
duties.
vi. Ideal for pipe dia above 350 mm nb , underground pipelines.
SUPERFOAM :-
East fit polyurethane foam for low temperature applications and chilled water pipelines
insulation :-
SUPER FOAM MOULDED INSULATION
Like other urethane foam insulants , superfoam has low thermal conductivity low smoke
emission and low water vapour permeability . Superfoam can be factory moulded to any
shape and for most applications , the need for a facing material is completely eliminated as
the product comes out of a factory with self skin formation.
LATEST DEVELOPMENT
NEW GENERATION SHIPLAP PIPE SECTION WITH ALUMINIUM FOIL LAMINATION
POLYURETHANE/POLYISOCYANURATE FOAM PIPE SECTION FOR ENERGY EFFICIENCY AND
FAST APPLICATION

16. SCAFFOLDING
Scaffolding is temporary framework used to support people and material in construction
,inspection ,repair of building or equipment and piping and structure .The purpose of a word
scaffold is to provide a safe place of work with safe access suitable for the work being done
. In a recent study 72% of worker injured in a scaffold accident attributed the accident either
to the planking or support giving way or to the employee slipping from the scaffold .This
document set out performance requirement and method for erection and dismantling of
scaffold to provide safe place of work with safety.
Types of scaffolds :-
Following are the types of scaffolds , depending upon materials being used
a) Wooden (bamboo or balli)
b) Tubular metal
c) Metal frame
d) Mobile platform
In Refinery mostly the tubular metal scaffold are in use .
i. Free standing scaffolds.
ii. Independent tied scaffolds
iii. Putlog scaffolds

17. PART II : CIVIL TOWNSHIP DEPARTMENT

18. INDEX
1. INTRODUCTION
2. VETIVER PLANTATION
3. RAIN WATER HARVESTING
4. WATER TREATMENT PROCESS

19. INTRODUCTION : CIVIL TOWNSHIP
Civil township is the other half of the civil engineering works in Indian Oil
Corporation Ltd. (A.O.D.) , Digboi . It performs all the works in the Digboi area
except the refinery area. The civil works in the in the Digboi refinery are under
the refinery civil department . All the maintenance jobs , construction works
both small and big , repair works etc. are the specific works that the civil
township has to perform . Civil township is operated in a consistent manner
and tend to be well organised . The maintenance jobs include road
construction undertaken by the civil township department. The recent jobs
under the department were rain water harvesting in the general office ,
vertiver plantation , tiling jobs , construction of school toilets in remote
areas,construction of fountain. Construction of a ramp at A.O.D. hospital ,
construction of retaing wall at Nazirating near the river Dibru , creating a water
harvesting system at the digboi golf club are some of the undergoing major
works under Civil Township Department.
VETIVER PLANTATION
The Vetiver System (VS) is a system of soil and water conservation whose main component is
the use of the vetiver plant in hedgerows. It is promoted by the Vetiver Network
International (TVNI), an international non-governmental organization.
The Vetiver System is used in more than 100 countries for soil and water conservation,
infrastructure stabilization, pollution control, waste water treatment, mitigation and
rehabilitation, sediment control, prevention of storm damage, and many other environmental
protection applications (through bioengineering and phytoremediation).

20. The vetiver plant, Chrysopogon zizanioides, is the main component to all Vetiver System
bioengineering and conservation applications. It can be used in the tropics and semi-tropics, and
areas that have a Mediterranean climate where there are hot summers, and winters are
temperate.
When Vetiver is planted as a hedgerow across a slope, it forms a very dense vegetative barrier
that slows down and spreads rainfall runoff. Combined with a deep and strong root system, a
wide range of pH tolerance from about pH 3 to pH 11, a high tolerance to most heavy metals, an
ability to remove from soil and water large quantities of excess nitrates, phosphates and farm
chemicals, the vetiver plant can be used for soil and water conservation, engineered construction
site stabilization, pollution control (constructed wetlands), and other uses where soil and water
come together.
The variety of vetiver that is promoted for VS applications originates in south India, is non-fertile,
non-invasive, and has to be propagated by clump subdivision. Its massive, finely structured root
system can grow very fast - in some applications, rooting depth can reach 10

21. The variety of vetiver used in the Vetiver System does not have stolons or rhizomes, does not
produce fertile seed, and stays where it was planted. In some countries vetiver has even been
used to define property lines. Hedgerows will not invade other areas of the property.
The Vetiver System is a developing technology. As a soil conservation technique and, more
recently, a bioengineering tool, the effective application of the Vetiver System in large-scale
projects that involve significant engineering design and construction requires an understanding of
biology, soil science, hydraulics, hydrology, and geotechnical principles.
RAIN WATER HARVESTING
Rainwater harvesting refers to structures like homes or schools, which catch rainwater and store
it in underground or above-ground tanks for later use. One way to collect water is rooftop
rainwater harvesting, where any suitable roof surface

22. underground storage tank, serving a whole community, or it might be just a bucket, standing
underneath a roof without a gutter. Rainwater harvesting systems have been used since
antiquity, and examples abound in all the great civilizations throughout history.
Introduction
In many cases, groundwater or surface water may be unavailable for drinking water. The
groundwater level may be too deep, groundwater may be contaminated with minerals and
chemicals such as arsenic or salt, surface water may be contaminated with faeces or chemicals.
In these cases, rainwater harvesting can be an effective and low-cost solution.
The good thing about rainwater is that it falls on your own roof, and is almost always of excellent
quality. Several studies have shown that water from well-maintained and covered rooftop tanks
generally meets drinking water quality standards. It enables households as well as community
buildings, schools and clinics to manage their own water supply for drinking water, domestic use,
and income generating activities.
It provides the luxury of

23. the outlet of the tank so that there is no dead storage; Ensure the catchment itself is efficient
(e.g. gutters); Improve access to micro-finance; Support the capacity of the government or
private sector to be able to provide (for payment) a tankering scheme.
Drought effects on cement tanks
Effects of drought: Badly made concrete and cracked linings (e.g. in tanks, dams, waterways,
wells, and other structures).
Underlying causes of effects: Less water used for curing; Impure water used for mixing.
To increase resiliency of WASH system: Ensure adequate mixing, ratios, purity of ingredients;
Minimize water content in mixture; Ensure adequate curing.
More information on managing drought: Resilient WASH systems in drought-prone areas.
Making cement in regards to drought: Concrete production and drought.
Construction, operations & maintenance
Catchment & storage tanks
The flow of water can be intercepted in different ways. Different catchment types are used, such
as roof catchment, paved surface catchment, surface catchment and riverbed catchment. The
cheapest storage of all is to use the ground as storage area, a technique called groundwater
recharge. It is accomplished by letting rainwater infiltrate in the ground. The recharge will locally
lead to a higher water table, from which water can be pumped up when needed. Whether the
infiltrated water raises the water table in a local area or is spread across a wider area depends
on soil conditions.
If using storage tanks, structures made with ferrocement or brick-cement are the best and
cheapest options, and they can be made locally. When a water tank is below ground, it is called
a cistern. Among the different storage types are the underground tank, ferrocement tank,plastic-
lined tank, etc. The size of the tank is a compromise between cost, the volume of water used, the
length of the dry season, etc. It is advisable to first construct a small tank before attempting a
large one. Storage tanks can additionally be filled up using pumps. Several pump systems can
be used to lift the water from underground tanks, for example with a rope pump or with a deep
well pump, which can elevate water up to a height of 30 m.
Keeping the water clean
Roof rainwater is usually of good quality and does not require treatment before consumption. If
the house has a chimney, however, it is possible that the water becomes smoky. High chimneys
are therefore preferred. Water is collected through roof gutters made of PVC, bamboo, etc. and
stored. The most important thing to ensure water quality is a good lid, keeping out light and
insects, and a filter, keeping out all kinds of dirt. A concrete lid protects the tank from pollution.
Small fishes can be kept in the tank to keep it free from insects.
A foul-flush device or detachable down-pipe can be fitted that allows the first 20 litres of runoff
from a storm to be diverted from the storage tanks. This is because runoff is contaminated with
dust, leaves, insects and bird droppings. To prevent the use of dirty water, the runoff is then led

24. through a small filter of gravel, sand and charcoal before entering the storage tank, or a filter is
placed between the catchment structure and the storage tank. Where there is no foul-flush
device, the user or caretaker has to divert away the first 20 litres at the start of every rainstorm.
The EMAS filtration system
The EMAS system for rainfall collection uses various EMAS technologies as well as simple tools
to convert rainwater into usable drinking water. If roof rainwater is being used, it is collected
through a regular gutter. To filter the water, at the bottom of the gutter, a pitcher or ferrocement
tank is placed, with an outlet pipe. A synthetic cloth bag is attached to the rim of the pitcher using
an iron ring or wire, which fits around the edge. The bag should be cleaned every 3 months.
As water begins to collect, to avoid too much garbage collecting here, first some amount of water
is deflected, along with most of the garbage. Hereafter, water can be directly sent to an EMAS
Cistern. It is advisable for multiple cisterns to be available for storage, depending on the size of
the roof. Connect one cistern at a time to the outlet pipe. From here water can be pumped and
distributed using a regular EMAS pump. The pump can also be connected to faucets and tanks
around the house.
Maintenance
The system should be also checked and cleaned after every dry period of more than one month.
The outsides of metal tanks may need to be painted about once a year. Leaks have to be
repaired throughout the year, especially from leaking tanks and taps, as they present health
risks. Chlorination of the water may be necessary.
Removal of debris and overhanging vegetation from gutters and the roof is important to prevent
the gutter being clogged. Tank maintenance consists of physical inspection and repairing cracks
with cement. Several studies have shown that water from well maintained and covered rooftop
tanks generally meets drinking water quality standards if maintained rightfully.
Basic water quality testing is recommended during the first year, with further testing when water
quality is in doubt. A low cost water test is the

25. was first demonstrated.
After this, concerns about the quality of drinking water focused on disease-causing
microorganisms (pathogens) in public
water supplies. Scientists discovered that visible cloudiness, or turbidity, not only made the water
look unappealing,
it could also indicate a health risk. The turbidity was caused by particles in water that could
harbor pathogens.
Most urban communities collect water from a natural water body in the catchment, whether a
stream, river, or
underground aquifer. The water collected may then be stored in a reservoir for some time.
Unless it is already of very
high quality, it then undergoes various water treatment processes that remove any chemicals,
organic substances or
organisms that could be harmful to human health. The water is then delivered to the community
through a network of
mains and pipes called a distribution system.
Brief History of Drinking Water Treatment
The importance of good drinking water in maintaining human health was recognised early in
history. However, it took
centuries before people understood that their senses alone were not adequate judges of water
quality. The earliest water
treatments were based on filtering and driven by the desire to remove the taste and As a result,
drinking water treatment
systems were designed to reduce turbidity, thereby removing pathogens that were causing
typhoid, dysentery and
cholera.
By the early twentieth century, better protection of water supplies from sewage pollution and
simple but effective methods
of water treatment (chlorination, sand filtration) had greatly reduced rates of waterborne disease
in developed nations.
Since then, scientists and engineers have been developing ways of processing water more
quickly, more effectively, in a
more controlled way and at lower cost.
Water Treatment Processes
The processes and technologies used to remove contaminants from water and to improve and
protect water quality are
similar all around the world. The choice of which treatment to use from the great variety of
available processes depends
on the characteristics of the water, the types of water quality problems likely to be present, and
the costs of different
treatments.
Coagulation/Flocculation

26. The most widely applied water treatment technology, a combination of some or all of coagulation,
flocculation and
sedimentation, plus filtration, has been used routinely for water treatment since the early part of
the twentieth century.
Sedimentation, coagulation and flocculation Some particles will spontaneously settle out from
standing water (a process
called sedimentation). When particles are slow to settle or are non settling, chemicals
(coagulants), such as alum, are
added to the water. These react with the unwanted particles to form larger particles, called floc.
The larger size and
weight of the flocs then causes them to settle rapidly.
Coagulation and flocculation are very effective at removing fine suspended particles that attract
and hold bacteria and
viruses to their surface. They can remove up to 99.9 per cent of the bacteria and 99 per cent of
the viruses from water
supplies. They also remove some of the organic matter that gathers as water travels across the
landscape, from raindrop
to river. However, certain taste and odour problems may remain.
Filtration
Filtration occurs as the water passes through filters that help remove even smaller particles. One
of the oldest and
simplest processes used to treat water is to pass it through a bed of fine particles, generally
sand. This process of sand
filtration usually removes fine suspended solid matter as well as some other particles, such as
larger microorganisms.
Filters can also be made of layers of sand, gravel and charcoal. The development of new
synthetic materials has led
to a new range of filter materials and methods. Processes based on these new materials are
used increasingly to treat
water for urban and industrial purposes. In membrane filtration, water is filtered through tiny
holes (pores) in a membrane
wall rather than a bed of sand. The smaller the pore size, the more material is held by the
membrane as the water passes
through.
Of the different kinds of membrane filtration processes, micro filtration is the most widely used in
water treatment,
becoming increasingly popular for small-scale water treatment plants supplying smaller
communities. This is because it is
an effective treatment, is simpler to operate and requires less constant operational control. Two
other types of membrane
filtration, with even smaller pores

27. contaminants from water, these
processes do not usually remove all the material dissolved in the water. If the water contains
undesirable impurities,
additional treatment such as adsorption and oxidation may be required.
Adsorption is a form of chemical filtration that involves removing dissolved substances by
chemically or physically binding
them to the filter material. It is quite different from the similarly sounding process of absorption. In
water treatment,
specialised adsorbent materials such as activated carbon and ion exchange resins are used to
remove certain
soluble contaminants from water.
One way of using activated carbon is to percolate water through a bed of carbon granules. Once
the carbon is saturated
with the contaminants, it needs to be replaced or regenerated by heating it to a high temperature.
If water contamination
occurs only occasionally, but can be detected by a regular monitoring program, a better
approach is to add powdered
activated carbon to a conventional coagulation/flocculation process when a problem arises. The
saturated carbon
is collected in the filters and then discarded with the normal sludge from the water treatment
plant. This form of
intermittent dosing is widely used where there are occasional problems with blue-green algal
blooms, which can cause
taste and odour problems, and can also be toxic.
Oxidation
Oxidation with chemicals such as ozone or chlorine dioxide, a common treatment technology in
Europe, has appeared in
Australia only recently. Strongly reactive chemicals such as ozone are used to disinfect water
and to destroy soluble
contaminants such as algal toxins, taste and odour compounds and, particularly in Europe,
traces of pesticides.
Water Stabilisation
Some water supplies can become acidic or alkaline by dissolving or reacting with the material
they are in contact with.
This can cause piping systems and hot water services to corrode and cause dissolved metals to
appear in the water.
For example, a common sign of copper corrosion is a bluish stain where a tap drips onto a
surface. To prevent corrosion,
many waters are chemically stabilised to a particular pH before distribution by adding lime and
sometimes carbon dioxide.
Disinfection
Water is disinfected to kill any pathogens that may be present in the water supply and to prevent

28. them from regrowing in
the distribution systems. Without disinfection, the risk from waterborne disease is increased. The
two most common
methods to kill microorganisms in the water supply are oxidation with chemicals such as chlorine
or ozone or irradiation with ultra violet (UV) radiation.