LECTURE NOTES ON

ENVIRONMENTAL ENGINEERING

Department of Civil Engineering

INSTITUTE OF AERONAUTICAL ENGINEERING Dundigal, Hyderabad - 500 043

CIVIL ENGINEERING

ENVIRONMENTAL ENGINEERING

The chief sources of all water supplies are rainfall. This water after getting

proper treatment we get from municipal corporation/water supply department i.e.

public health engg. Department.

Other source of water is underground water. Water that has percolated into the

ground is brought on the surface.

The upper surface of free water in the top soil is termed as ground water level/

table.

Form in which underground sources are found infiltration galleries. Infiltration

wells are sunk in series on the bank of river. Other source is spring an outcrops

of water. A ground well is defined as an artificial hole/pit made in the ground for

the purpose of tapping of water. Following are types of wells-

(a) Shallow wells.

(b) Deep wells

(c) Tube wells

(d) Artesian wells.

Tube Wells -

Tube wells are of type-

(a) Strainer type

(b) Cavity type

(c) Slotted type

(d) Perforated type.

Tube Wells:

Bores are made into the ground by hand & mechanically operated augers,

percussion equipment or drilled by coring rigs.

The most common bores are made by augers in which a pipe is inserted on a

hand pump with a suction pipe is installed. Hand pumps are for local use and the

wells are exposed to the same pollution risks as the dug wells.

A more scientific deep-bore hand pump called Mark IV, for drawing safe water

from deeper strata, has been developed by Indian Scientists, and is now being

extensively used in rural water supply schemes in India,.

Tubewells deeper than 30 m or so have a lesser chance of being polluted. The

possibility of contamination in any Tubewell should never be discounted and

water should be tested often to ensure safety.

Tube well is deep well having diameter 50 to 200 mm.

A bore is drilled in the ground (Percussion core rotary drilling m/c.) For testing

the yields of a well recuperation and constant pumping test is done, pipe for tube

well is then inserted in the bore hole.

It consists, of strainer and blind sections. A strainer is a perforated pipe which is

provided with an arrangement such as that only water will be admitted to inside

of the pipe. Pumping is then started.

Maintenance of a Tube Well:

Use in the grounds and gardens, then it is essential to ensure that there is no

possibility of the contamination of potable water supplies with these lower-qual-

ity supplies, The two systems must be physically isolated and outlet points with

non-potable' supplies must be clearly labeled as not suitable for drinking.

(i) Cleaning of screen with hydro sulfuric acid. Hydrochloric acid.

(ii) Removal of lime particles - clogging of screen.

(iii) Replacement of parts. Failure of tube well is due to

(i) Corrosion

(ii) Incrustation - deposition of alkali salts on the inside walls of the tube well.

Types of Well Construction:

(a) Dug well - Shallow well

(b) Driven well - Deep well in unconsolidated solid

(c) Bored/Drilled well.

Sanitary Protection Of Well:

(a) Water tight connection of pump

(b) Covered top

(c) Casing depth 3m below

the ground water table.

(d) Distance from the source of contamination, minimum 90 m

(e) No presence of trees

(f) Priming of pump by safe water

(g) Washing of cloth should be prohibited

Open Streams/Springs Etc:

(a) Whenever no other water source is available, it may be necessary to tap a

local water-stream or river. However, the quantity, quality and dependability of

the source have to be investigated. The methods of treatment e.g. filtration

disinfection and storage must be decided on the basis of the results of these

investigations.

(b) When the source of water is far away from its area of consumption a detailed

survey of the area, route of pipe line has to be made for laying the water mains.

Rain Water Harvesting:

Conditions for Rain Water Harvesting

Many area endowed with a fair amount of natural precipitation do not have

geographical or subsoil conditions to absorb and impound the rain water.

Rivers:

Rivers are commonly used as a source of water but normally require treatment

before use particularly in downstream sections, rivers are often contaminated

with waste materials from industry, agriculture and communities. Rivers are

classified in terms of their quality:-

» Class 1a, Good Quality: water of high quality suitable for potable supply

abstractions; game or other high-class fisheries; high amenity value.

» Class 2b, Fair Quality waters suitable for potable supply after advanced treat-

ment supporting reasonably good coarse fisheries, moderate amenity value.

» Class 3, Poor Quality; waters which are polluted to an extent that fish are

absent or only sporadically present; may be used for low-grade industrial

abstraction purposes; considerable potential for further use if cleaned up.

» Class 4, Bad Quality; waters which are grossly polluted and likely to cause a

nuisance.

Lakes (Natural and Artificial):

Where there is a shortage of underground water, lakes or artificial reservoirs

may be used to provide water supplies but this water usually needs some form of

treatment prior to use recently, there has been an increase in the occurrence of

algae blooms caused by the growth of blue-green algae.

Some of these algae produce toxins which are poisonous to fish and mammals.

The same classification scheme is used for rivers and lakes.

Oceans:

The oceans represent the most abundant source of water on the planet, but the

cost of desalination is usually prohibitively high and therefore sea water is not

often used as a source of water. Coastal waters are often contaminated with

sewage and heavy metals.

INTAKES:

The main function of the intakes works is to collect the water from various

sources. The sources may be lakes, rivers, reservoirs and canals. The intake

work for each type of source is designed separately according to its requirements

and situations.

Intakes are structures which essentially consist of opening,

grating through which the raw water from source and is carried to a sump-well

by means of conduits.

Water from the sump well is pumped through the rising mains to

the treatment plant.

The following points should be considered while selecting a site for intake

works:

The best quality of water should be available at the site so that it can be easily

and economically purified in less time to the treatment plants.

The site should be such that intake work can draw more quantity of water if

required in the future, there should be sufficient scope for future.

The site of intake should be easily approachable without any obstruction.

As far as possible the selection of the site should be near the treatment works, it

will reduce the conveyance cost from the source of the water-works.

At the site sufficient quantity should be available for the future expansion of the

water-works.

As far as possible the selection the intake should not be located in the vicinity of

the point of sewage disposal.

TYPES OF INTAKES:

The intake work for each type of source is designed separately

according to the requirements and situations, Depending on the source of water

in intake works are classified as follows:

1. Lake intake

2. River intake

3. Reservoir intake

4. Canal intake

1. LAKE INTAKE:

For obtaining water from lakes mostly submersible intakes are used.

These intakes are constructed in the bed of the lake below the slow water level

so as to draw water in dry season also.

It essentially consists of a pipe laid in the bed of the river at one end, which is in

the middle of the lake is fitted with bell mouth opening covered with mesh and

protected by concrete blocks.

The water enters in the pipe through the bell mouth opening and flows under

gravity to the bank where it is collected in sump-well and then pumped to

treatment plant.

If one pipe is not sufficient two or more pipes may be laid to get the required

quantity of water.

As these intakes draw small quantity of water, these are not used on big water

supply schemes like rivers or reservoirs.

2. RIVER INTAKE:

Water from the rivers is always drawn from the upstream side, because it is free

from the contamination caused by the disposal of sewage in it.

It has circular masonary tower 4 to 7m in dia constructed along the bank of the

river at such place from where required quantity of water can be obtained even

in the dry period.

The water enters in the lower portion of the intake known as sump-well from

penstocks.

The penstocked are fitted with screens to check the entry of floating solids.

Number of penstock opening are provided in the intake tower to admit water at

different levels.

The opening and closing of penstock valves is done with the help of wheels

provided at the pump-house floor.

In case of emergency and temporary works , movable intakes can be used .

The water is directly pumped from the river and sent for the treatment and

distribution.

3. RESERVOIR INTAKE:

Reservoir intakes which mostly used to draw the water from earthern dam

reservoir. It essentially consists of an intake tower constructed on the slope of

the dam at such place from where intake can draw sufficient quantity of water

even in the driest period.

Intake pipes are fixed at different levels, so as to draw water near the surface in

all variations of water level.

These all inlet pipes are connected to one vertical pipe inside the intake well.

Screens are provided at the mouth of all intakes pipes to prevent the entrance of

floating and suspended mstter in them.

The water which enters the vertical pipe is taken to the other side of the dam by

means of outlet pipe.

At the top of the intake tower sluice valves are provided to control the flow of

water.

4. CANAL INTAKE

Canal intake is a very simple structure constructed on the bank.

It essentially consists of a pipe placed in a brick masonry chamber constructed

partly in the canal bank.

Other side of chambers as opening is provided with coarse screen for the

entrance of water.

The pipe in side chamber is provided with a bell-mouth fitted with a a

hemispherical fine screen,

The out-let pipe carries the water to the other side of the canal bank from where

it is taken to the treatment plants.

One sluice valve which is operated by a wheel from the top of the masonry

chamber is provided to control the flow of water in pipe.

LAYOUT OF WATER TREATMENT

Uniform settling velocity:

Settling is the process by which particulates settle to the bottom of a liquid and

form a sediment.

Particles that experience a force, either due to gravity or due to centrifugal

motion will tend to move in a uniform manner in the direction exerted by that

force.

Discrete particle settling - Particles settle individually without interaction with

neighboring particles.

Flocculent Particles – Flocculation causes the particles to increase in mass and

settle at a faster rate.

Hindered or Zone settling –The mass of particles tends to settle as a unit with

individual particles remaining in fixed positions with respect to each other.

The purpose of a Water Treatment Plant is to remove particulates and

pathogens from water that may pose a health threat to consumers.

PRINCIPLES OF WATER TREATMENT:

The Principles of Water and Wastewater Treatment

Processes has been divided into the following Units:

PHYSICAL PROCESSES:

Microbes and other colloidal particles can be physically removed from water

by various processes. The sizes of the microbes are especially important for their

removal by sedimentation and filtration.

CHEMICAL PROCESSES:

Calcium hydroxide (hydrated lime) (Ca(OH)2):

Is dosed at the start and end of the treatment process.

The pre-dose increases the alkalinity for optimal coagulation as well as the

hardness and buffering capacity of water (resistance to change in pH).

The post-dose is to raise the pH to within drinking water guidelines and the

optimum level for the residual disinfectant.

SLUDGE TREATMENT:

Sludge is produced from the treatment of wastewater in on-site (e.g.

septic tank) and off-site (e.g. activated sludge) systems. The primary aim of

wastewater treatment is removing solids from the wastewater.

ODOUR MANAGEMENT:

Wastewater treatment plant odours are common. Perimeter odour neutralizing

spray systems can be used to great effect to control wastewater treatment plant

odours.

( Biofiltration systems can treat several contaminants

simultaneously, without the use of chemicals. With 95% odour removal

efficiency, our biofiltration systems can treat a wide range of contaminants )

SURFACE LOADING

Calculating the surface loading gives a guide to how much water can be

processed each day per area of sedimentation tank.

Surface loading is one of the most important factors affecting the effectiveness

of the sedimentation process. The surface loading rate is used to determine if the

sedimentation tanks and clarifiers are under loaded or over loaded.

If actual surface loading is > the design values then this indicates the tanks are

overloaded.

If actual surface loading is < the design values then this indicates the tanks are

underloaded.

The surface loading test calculates the volume of water being treated over a

period of time over surface area of the tank.

surface loading (kL per day per m2) = flow rate (kL per day)

surface area of tank (m2)

AERATION:

Aeration (also called Aerification) is the process by which air is circulated

through, mixed with or dissolved in a liquid or substance.

Passing the liquid through air by means of fountains, cascades, paddle-wheels or

cones.

USES:

Production of aerated water for drinking purposes.

Secondary treatment of sewage or industrial wastewater through use of aerating

mixers/diffusers.

To increase the oxygen content of water used to house animals, such

as aquarium fish or fish farm.

In chemistry, to oxidize a compound dissolved or suspended in water.

WATER QUALITY TESTING

As the quality of source water varies daily in every season, it is necessary that

the water samples for analysis should be collected frequently.

According to the quality of water it should be treated.

The following are the tests which are done

During water quality test:

a) Physical test.

b) Chemical test.

c) Biological test.

a) PHYSICAL TEST:

1.TEMPERATURE: The temperature of water is measured by means of

ordinary thermometers.

From the temperature the MASS density(P=m/v), viscosity, vapour pressure

and surface tension of water can be determined.

The temperature of surface water is generally same to the atmospheric

temperature, while that of ground water may be more or less than atmospheric

temperature.

The most desirable temperature for public supply is between 4.4 °c to 10 °c.

Temperature above 28 °c are undesirable and above 35 °c are unfit for public

supply, because it is NOT PALATABLE(NOT ACCECTABLE TO TASTE).

2.COLOUR: The color of water is usually due to presence of organic matter,

but sometimes it is also due to mineral and dissolved organic and inorganic

impurities.

Before testing the color of the water, first of all total suspended matter should be

removed from the water by centrifugal force in a special apparatus.

After this the color of water is compared with standard color solution.

The permissible color for domestic water is 20p.p.m on platinium cobalt scale.

The color in water is not harmful but it is objectionable.

3. TURBIDITY: It is caused due to presence of suspended and colloidal matter

in the water.

The character and amount of turbidity depends on the type of soil over which the

water has moved.

There are two types of turbidimeters:

1) Based on visual method( through naked eye).

2) Based on direct (meter reading ) method.

b) CHEMICAL TEST:

In the chemical testing of water those test are done that will reveal the sanitary

quality of the water.

The chemical test involve the determination of total solids, hardness, chlorides,

iron and manganese etc.

1)Total solids:

• Total solids is a measure of the suspended and dissolved solids in water.

• The quantity of suspended solids is determined by filtering the sample of water

through a fine filter, drying and weighing.

• The quantity of dissolved and colloidal solids is determined by evaporating the

filtered water(obtained from the suspended solid test) and weighing the water.

• The total solids in a water sample can be directly determined by evaporating the

water and weighing it.

• By weighing we can determine the inorganic solids and deducting it from total

solids.

2)HARDNESS:

• It is the property of water which prevents the lathering (form ) of the soap.

• It is caused due to the presence of carbonates and sulphates of calcium and

magnesium in the water.

• Also in the presence of chlorides and nitrates of calcium and magnesium cause

hardness in the water.

• Hardness is usually expressed in mg/lit or p.p.m of calcium carbonate in water.

• In the past the hardness was determined by soap test, in which the standard soap

sol was added in the water and it was shaked to see the formation of lather for 5

min. The hardness of water was calculated on the basis of soap solution added

and lather factor.

3)CHLORIDES:

• The natural water near the sea or mines have dissolve sodium chloride(Nacl).

• The presence of chlorides may be due to the mixing of saline water (Saline

water is water that contains a significant concentration of dissolved salts

(mainly NaCl) and is commonly known as saltwater) and sewage in the water.

• Excess of chlorides is dangerous and unfit for use. The chloride can be reduced

by diluting the a water.

• Chlorides above 250p.p.m are not permissible(not allowed) in water.

The chloride can be determined by titrating the water with silver

nitrate(Agno3) and potassium chromate(k2cro4), in that titration process reddish

colour will be formed if chlorides are present.

4) IRON AND MANGANESE

• These are generally found in ground water. If these are present less than 0.3

p.p.m. it is not objectionable . But it exceeds 0.3p.p.m the water is not suitable

for domestic and laundering purposes.

• The presence of iron and manganese in water makes brownish red colour in it,

leads to growth of micro-organisms. Iron and manganese also cause taste and

odour in the water.

• The quality of iron and manganese is determined by colorimetric methods.

• In these methods some colouring agents are added in the water and compared

with standard colour solutions.

5)PH VALVE

• In general, a water with a pH < 7 is considered acidic and with a pH > 7 is

considered basic.

• The normal range for pH in surface water systems is 6.5 to 8.5 and for

groundwater systems 6 to 8.5.

• Alkalinity is a measure of the capacity of the water to resists a change in pH that

would tend to make the water more acidic.

PH SCALE

0 TO 7 7 Slightly above 7 to 14

(Acidic range) (Alkaline range)

3) BIOLOGICAL TEST:-

In a biological test the following two tests are done:-

a) TOTAL COUNT OF BACTERIA:- In this method total number of bacteria

present in millimeter of water is counted. The sample of water is taken, 1 ml of

sample water is diluted in 99ml of sterilized water.

1. Sterilized Water (absence of any bacteria in the water).

2. Distilled water (that has many of its impurities removed through distillation.

Distillation involves boiling the water and then condensing the steam into a

clean container).

• This mixture is kept in incubator at 37°c for 24hrs.

• After it the sample will be taken out from incubator and counted by means of

microscope.

b) BACTERIA COLI(B-COLI)TEST:

• There are 2 tests B-coli first is presumptive and second confirmative.

• In the presumptive test definite amount of diluted sample of the water in

standard fermentation tubes is kept in inclubator at 37°c for 24hrs. If some gas is

produced in the fermentation tube , indicates the presence of B-coli.

• And it again kept in incubator at 37°c for 48 hrs, if there is formation of gas in

the tube , it confirms the presence of B-coli and the water is unsafe to use.

This method is known as “MEMBRANE FILTER TECHNIQUE”.

WATER TREATMENT

Defination:

• A wastewater treatment plant is a physical plant where various physical,

biological or chemical processes are used to change the properties of

the wastewater (e.g. by removing harmful substances) in order to turn it into a

type of water (also called effluent) that can be safely discharged into

the environment or that is usable for a certain reuse purpose.

• By-products from wastewater treatment plants, such as screenings, sewage

sludge, odorous gases are also treated in a wastewater treatment plant.

1.Preliminary treatment:

The purpose of preliminary treatment is to protect the operation of the

wastewater treatment plant which can damage pumps, or interfere with

subsequent treatment processes.

Preliminary treatment devices are, therefore, designed to:

1.Remove or to reduce in size the large, entrained, suspended or floating solids.

These solids consist of pieces of wood, cloth, paper, plastics, garbage, etc.

together with some fecal matter.

Pre- chlorination:

• Pre-chlorination is a process that involves adding chlorine to the collection

system of industrial plants and other Treatment plant, mainly for corrosion and

odor control.

• It is also applied for the purpose of disinfection and for the removal of oil

particles.

• It is also used in water treatment to control aquatic growth as well as taste, and

as aid in settling and coagulation.

• In pre-chlorination, chlorine is added to the raw water prior to flash mixing and

post screening.

The excess chlorine is beneficial in the various stages of treatment by:

1. Aiding coagulation

2. Controlling of algae problems

3. Reducing odor and mud ball formation

Actual chlorination process:

2.Coagulation:

Coagulation removes dirt and other particles suspended in water. Alum and

other chemicals are added to water to form tiny sticky particles called "floc"

which attract the dirt particles.

The combined weight of the dirt and the alum become heavy enough to sink to

the bottom during sedimentation.

Solids are removed by sedimentation (settling) followed by filtration. Small

particles are not removed efficiently by sedimentation because they settle too

slowly; they may also pass through filters. They would be easier to remove if

they clumped together (coagulated) to form larger particles, but they don't

because they have a negative charge and repel each other (like two north poles

of a magnet).

In coagulation, we add a chemical such as alum which produces positive charges

to neutralize the negative charges on the particles. Then the particles can stick

together, forming larger particles which are more easily removed.

The coagulation process involves the addition of the chemical (e.g. alum) and

then a rapid mixing to dissolve the chemical and distribute it evenly throughout

the water.

3.Floccuation:

Flocculants are used in water treatment processes to improve the sedimentation

or filterability of small particles.

Floc:

A soft or fluffy particle suspended in a liquid or the fluffy mass of suspended

particles so formed. Floc may be mineral as for clay, chemical as in water

treatment or biological as in sewage treatment.

4.Sedimentation process:

• Sedimentation is a physical water treatment process using gravity to

remove suspended solids from water.

• The particles that settle out from the suspension become sediment, and in water

treatment is known as sludge. When a thick layer of sediment continues to settle,

this is known as consolidation.

• Solid particles entrained by the turbulence of moving water may be removed

naturally by sedimentation in the stilwater of lakes and oceans.

5.Sand purification:

• Sand filters are used for water purification. There are three main types;

• Rapid (gravity) sand filters.

• Sand filtration is a frequently used very strong method to remove suspended

solids from water.

6. Post chlorination:

• Post Chlorination is the final process in water treatment.

• The chlorine will kill any bacteria or viruses remaining in the water and it is

important that a minimum level of chlorination remains in the water through the

storage and distribution.

• If needed, additional chorine is added to the finished water that leaves the water

plants. Low levels of chlorine (approximately 0.2 to 1.0 part per million) must

be maintained in the distribution systems pipes and home plumbing to prevent

the growth of microorganisms.

7.flouridation:

• Water fluoridation is the controlled addition of fluoride to a public water

supply to reduce tooth decay.

• Water fluoridation is the addition of the chemical fluoride to public water

supplies, for the purpose of reducing cavities.`

Advantages:

• Water purification is the removal of contaminants from untreated water to

produce drinking water that is pure enough for the most critical of its intended

uses, usually for human consumption.

• Measures taken to ensure water quality not only relate to the treatment of the

water, but to its conveyance and distribution after treatment as well.

AQUIFERS

What is an aquifer???

• An aquifer is an underground layer of water-bearing permeable rock or

unconsolidated materials (gravel, sand, or silt) from which groundwater can be

extracted using a water well.

• The study of water flow in aquifers and the characterization of aquifers is

called hydrogeology.

What is confining layer (aquitard)?

Geological material through which significant quantities of water can not move,

located below unconfined aquifers, above and below confined aquifers. Also

known as a confining bed.

1.CONFINED AQUIFER(ARTESIAN) :-

Confined aquifers are those in which an impermeable dirt/rock layer exists that

prevents water from seeping into the aquifer from the ground surface located

directly above.

2.Unconfined aquifer (water table aquifer):-

Unconfined aquifers are those into which water seeps from the ground surface

directly above the aquifer.

UNCONFINED AQUIFERS:

Natural recharge of the unconfined aquifers is mainly due to the downward

seepage (or percolation) through the unsaturated zone of the excess water over

passing the field capacity of the soil. Recharge can also occur through upward

seepage (leakage) from underlying aquifers.

CONFINED AQUIFERS:

A regional confined aquifer is directly recharged by precipitation in the area

where the aquifer crops out, having the same characteristics as an unconfined

aquifer.

INFILTRATION GALLERIES:

• Infiltration galleries is a conduit,

• built in permeable earth, for collecting ground water.

• We have seen earlier that ground water travels towards lakes, rivers or streams.

This water which is travelling can be intercepted by digging a trench or by

constructing a tunnel with holes on sides at right angle to the direction of flow.

• These underground tunnel used for tapping underground water near rivers, lakes

or streams are called “INFILTRATION GALLERIES”.

• These are also known as Horizontal walls.

Example:-

• Infiltration galleries can be used to collect sub-surface flow from rivers. Water is

taken to a collective well, or sump, and then pumped to a storage tank.

• Infiltration galleries vary in size, from a few meters feeding into spring box, to

many kilometers forming an integral part of unban water supply.

• Construction of galleries:

• To ensure a continuous supply of water , infiltration galleries should be built in

the end of dry season and should be at least one meter under the dry season

water table.

• Excavate a trench to at least 1 m below the water table,

• Lay graded gravel on the base of the trench.

• Lay the pipe or drain blocks on top of the gravel. Cover the top and sides with

more graded gravel.

• Cap the gravel with an impermeable layer of clay to prevent surface water

entering the gallery.

DISTRIBUTION SYSTEM

What is Distribution System?

• Distribution system is the part of the water works which receives the water from

the pumping station in the form of gravity flow or pumping system and delivers

it throughout the town which is to be served.

• The distribution system consists of pipes of various sizes, valves, meters, pumps,

distribution reservoirs, hydrants etc.

Requirements of distribution system?

• The pipe lines carry the water to each and every street, road.

• Valves control the flow of water through the pipes.

• Meters are provided to measure the quantity of water consumed by the town.

• Hydrants are provided to connect the water to the fire fighting equipments

during fire.

• Service connections are done to connect the individual building with the water

line passing through the streets.

• Pumps are provided to pump the water to the elevated service reservoirs or

directly in the water mains to obtain the required pressure in the pipe lines.

Requirement for good distribution system?

• It should convey the treated water up to the consumers with the same degree of

purity.

• The water should reach to every consumer with the required pressure head.

• Sufficient quantity of treated water should reach for the domestic and industrial

use.

• It should be able to transport sufficient quantity of water during emergency such

as fire- fighting.

• It should be reliable so that even during breakdown or repairs of one line water

should reach that locality from other line.

LAYOUT OF DISTRIBUTION SYSTEM:

Generally there are four different systems of distribution which are used,

Depending upon their layout and direction of supply, they are classified as

follows:

1. Dead end or tree system.

2. Grid Iron system.

3. Circular or ring system.

4. Radial system.

TYPES OF DISTRIBUTION SYSTEM:

Depending upon the methods of distribution , the distribution system is

classified as follows:

1. Gravity system

2. Pumping system

3. Dual system or combined gravity and pumping system.

1) GRAVITY SYSTEM:

• This method is much suitable when source of supply such as lake, river or

impounding reservoir is at sufficient height than city.

• The water flows in the mains due to gravitational force, as no pumping is

required, therefore it is most reliable system for the distribution of water.

• In this system usually pumping is not required at any stage, in case the source of

water supply is lake situated at the hill, low lifting pumping is required to lift the

water up to water treatment plant.

ADVANTAGES:

• This will reduce the

• Leakage and waste to the

• Minimum.

DISADVANTAGES:

But in case of fire attack the water had to be pumped.

2)PUMPING SYSTEM:

• In this system water is directly pumped in the mains

• Since the pumps have to work at different rates of the day, the maintenance cost

increases.

• High lift pumps are required and their operations are continuously watched.

• If power fails, the whole supply of the town will be stopped, therefore it is better

to have diesel pumps also in addition to the electric pumps as stand bye.

ADVANTAGE:

During fires, the water can be pumped in the required quantity by the stand-bye

units also.

3)DUAL SYSTEM:

• This is the combination of both gravity and pumping system.

• The pump is connected to the mains as well as to an elevated reservoir.

• In the beginning when water demand is small the water is stored in the elevated

reservoir, but when demand increases the rate of pumping, the flow in the

distribution system comes from the both the pumping station as well as from

elevated reservoir.

ADVANTAGES:

• This system is more reliable and economical.

• The water stored in elevated reservoir meets the requirements of demand during

breakdown of pumps and for fire fighting.

• The balance reserve in the storage reservoir will be utilized during fire. In case

the fire demand is more, and if required the water supply of few localities may

be closed.

Factors to be considered in the design of distribution system:

• Type of flow- whether continuous or intermittent.

• Method of distribution- whether by gravity or by pumping.

• Probable future demand based on increase in population. This also includes the

industrial demand as well as fire –fighting requirements.

• Period to be considered in with life of pipes used. The system should be

designed anticipating the future of the town or city.

HYDRAULIC GRADIENT:

A line joining the points of highest elevation of water in a series of vertical pipes

rising from a pipeline in which water flows under pressure.

According to HAZEN- WILLIAMS the flow-formula is written as:

V=velocity of flow in pipe m/sec.

M= radius of the pipe in m.

I= Hydraulic gradient.

C=friction coefficient whose valve depends on type of pipe used.

FORMULA:

The design procedure as been outlined as below:

a) Prepare a contoured plan of the city or town, locating the positions of districts

or distribution zones with their population, service reservoirs, pumping stations,

main roads and streets and other small features. A small scale (1/10,000) may be

used.

b) Estimating the rate of demand for all purposes including fire demand and

determining the quantity flowing in each section of pipe length. This gives the

average daily flow in the pipe. The max flow will be 3 times.

c) Assuming the pipe sizes, The velocity of flow varies 0.9-1.2 m/sec.

JOINTS:

A point at which parts of an artificial structure are joined.

TYPES:

1. Butt-welded Joints

2. Socket-welded Joints

3. Threaded or Screwed Joints

4. Grooved Joints

5. Flanged Joints

6. Compression Joints

1.BUTT WELDED JOINTS:

• Butt-welding is the most common method of joining piping used in large

commercial, institutional, and industrial piping systems.

• Material costs are low, but labor costs are moderate to high due to the need for

specialized welders and fitters.

2. SOCKET-WELDED JOINTS

• Socket-welded construction is a good choice wherever the benefits of high

leakage integrity and great structural strength are important design

considerations.

• Construction costs are somewhat lower than with butt-welded joints due to the

lack of exacting fit-up requirements and elimination of special machining for

butt weld end preparation.

3. THREADED OR SCREWED JOINTS:

• Threaded or screwed piping is commonly used in low-cost, noncritical

applications

such as domestic water, fire protection, and industrial cooling water systems.

• Installation productivity is moderately high, and specialized installation skill

requirements are not extensive.

• Rapid temperature changes may lead to leaks due to differential thermal

expansion between the pipe and fittings.

4. GROOVED JOINTS:

• The main advantages of the grooved joints are their ease of assembly, which

results in low labor cost, and generally good leakage integrity.

• They allow a moderate amount of axial movement due to thermal expansion, and

they can accommodate some axial misalignment.

• The grooved construction prevents the joint from separating under pressure.

5. FLANGED JOINTS:

• Flanged connections are used extensively in modern piping systems due to their

ease of assembly and disassembly; however, they are costly.

• Contributing to the high cost are the material costs of the flanges themselves

and the labor costs for attaching the flanges to the pipe and then bolting the

flanges to each other.

• Flanges are normally attached to the pipe by threading or welding, although in

some special cases a flange-type joint known as a lap joint may be made by

forging and machining the pipe end.

6. COMPRESSION JOINTS:

• Compression sleeve-type joints are used to join plain end pipe without special

end

preparations.

• These joints require very little installation labor and as such result

in an economical overall installation. Advantages include the ability to absorb a

limited amount of thermal expansion and angular misalignment and the ability

to join dissimilar piping materials, even if their outside diameters are slightly

different.

SCREENS

The primary treatment incorporates unit operations for

removal of floating and suspended solids from the wastewater. They are also

referred as the physical unit operations. The unit operations used are screening

for removing floating papers, rages, cloths, plastics, cans stoppers, labels, etc.;

grit chambers or detritus tanks for removing grit and sand; skimming tanks for

removing oils and grease; and primary settling tank for removal of residual

settleable suspended matter.

Designs of these primary treatment units are discussed

in this chapter. Screen is the first unit operation in wastewater treatment plant.

This is used to remove larger particles of floating and suspended matter by

coarse screening. This is accomplished by a set of inclined parallel bars, fixed at

certain distance apart in a channel.

The screen can be of circular or rectangular opening.

The screen composed of parallel bars or rods is called a rack. The screens are

used to protect pumps, valves, pipelines, and other appurtenances from damage

or clogging by rags and large objects. Industrial wastewater treatment plant may

or may not need the screens.

However, when packing of the product and cleaning of packing bottles/

containers is carried out, it is necessary to provide screens even for industrial

wastewater treatment plant to separate labels, stopper, cardboard, and other

packing materials. The cross section of the screen chamber is always greater

(about 200 to 300 %) than the incoming sewer. The length of this channel should

be sufficiently long to prevent eddies around the screen.

Types of Screens:

Screens can be broadly classified depending upon the opening size provided as

coarse screen (bar screens) and fine screens. Based on the cleaning operation

they are classified as manually cleaned screens or mechanically cleaned screens.

Due to need of more and more compact treatment facilities many advancement

in the screen design.

COARSE SCREEN:

It is used primarily as protective devices and hence used as first treatment unit.

Common type of these screens are bar racks (or bar screen), coarse woven-wire

screens, and comminutors. Bar screens are used ahead of the pumps and grit

removal facility.

This screen can be manually cleaned or mechanically cleaned. Manually cleaned

screens are used in small treatment plants. Clear spacing between the bars in

these screens may be in the range of 15 mm to 40 mm. It is used in conjunction

with coarse screens to grind or cut the screenings. They utilize cutting teeth (or

shredding device) on a rotating or oscillating drum that passes through stationary

combs (or disks). Object of large size are shredded when it will pass through the

thin opening of size 0.6 to 1.0 cm. Provision of bye pass to this device should

always be made.

FINE SCREEN:

Fine screens are mechanically cleaned screens using perforated plates, woven

wire cloths, or very closely spaced bars with clear openings of less than 20 mm,

less than 6 mm typical. Commonly these are available in the opening size

ranging from 0.035 to 6 mm. Fine screens are used for pretreatment of industrial

wastewaters and are not suitable for sewage due to clogging problems, but can

be used after coarse screening. Fine screens are also used to remove solids from

primary effluent to reduce clogging problem of trickling filters. Various types of

microscreens have been developed that are used to upgrade effluent quality from

secondary treatment plant. Fine screen can be fixed or static wedge-wire type,

drum type, step type and centrifugal screens. Fixed or static screens are

permanently set in vertical, inclined, or horizontal position and must be cleaned

by rakes, teeth or brushes. Movable screens are cleaned continuously while in

operation. Centrifugal screens utilize the rotating screens that separate effluent

and solids are concentrated.

Types of Medium and Fine Screens Inclined (fixed):

These are flat, cage, or disk type screens meant for removal of smaller particles.

These are provided with opening of 0.25 to 2.5 mm.

They are used for primary treatment of industrial effluents. Band: It consists of

an endless perforated band that passes over upper and lower sprocket. Brushes

are installed to remove that material retained over the screen. Water jet can be

used to flush the debris. Opening size of 0.8 to 2.5 mm is provided in this screen.

They are used for primary treatment of industrial effluents.

DRUM SCREEN OR STRAINER: It consists of rotating cylinder that has

screen covering the circumferential area of the drum. The liquid enters the drum

and moves radially out.

The solids deposited are removed by a jet of water from the top and discharged

into a trough.

The micro-strainers have very fine size screens and are used to polish secondary

effluent or remove algae from the effluent of stabilization ponds. Opening size

of 1 to 5 mm and 0.25 to 2.5 mm is used for primary treatment and opening size

of 6 to 40 µm is used for polishing treatment of secondary effluents. It consists

of rectangular channel. Floor of the channel is normally 7 to 15 cm lower than

the invert of the incoming sewer. Bed of the channel may be flat or made with

desired slope.

This channel is design to avoid deposition of grit and other materials in to it.

Sufficient straight approach length should be provided to assure uniform

distribution of screenings over the entire screen area. At least two bar racks, each

designed to carry peak flow, must be provided. Arrangement of stopping the

flow and draining the channel should be made for routine maintenance. The

entrance structure should have a smooth transition or divergence to avoid

excessive head loss and deposition of solids . Effluent structure should be having

uniform convergence. The effluent from the individual rack may be combined or

kept separate as necessary.

WASTEWATER MANAGEMENT

Double chamber bar screen and influent and effluent arrangement

Requirements and Specifications:

1. The velocity of flow ahead of and through a screen varies materially and affects

its operation. Lower the velocity through the screen, the greater is the amount of

screening that would be removed.

2. However, at lower velocity greater amount of solids would be deposited at the

bottom of the screen channel.

3. Approach velocity of wastewater in the screening channel shall not fall below a

self cleansing velocity of 0.375 m/sec or rise to a magnitude at which screenings

will be dislodged from the bars (Rao and Dutta, 2007).

4. The suggested approach velocity is 0.6 to 0.75 m/sec for the grit bearing

wastewaters. Accordingly the bed slope of the channel should be adjusted to

develop this velocity.

5. The suggested maximum velocity through the screen is 0.3 m/sec at average

flow for hand cleaned bar screens and 0.75 m/sec at the normal maximum flow

for Effluent Gate closed Gate closed Gate closed

6. Mechanically cleaned bar screen Velocity of 0.6 to 1.2 m/sec through the screen

opening for the peak flow gives satisfactory result.

7. Head losses due to installation of screens must be controlled so that back water

will not cause the entrant sewer to operate under pressure.

Head loss through a bar rack can be calculated by using Kirchmer’s equation:

h = β (W/b)4/3 hv Sin θ where,

h = head loss,

m β = Bar shape factor = 2.42 for sharp edge rectangular bars = 1.83 for

rectangular bars with semicircular upstream = 1.79 for circular bars = 1.67 for

rectangular bars with both u/s and d/s faces as semicircular.

W = Width of bars facing the flow,

m b = Clear spacing between the bars,

m hv = Velocity head of flow approaching the bars,

m = V2 /2g

V = geometric mean of the approach velocity,

m/sec θ = Angle of inclination of the bars with horizontal.

Usually accepted practice is to provide loss of head of 0.15 m but the maximum

loss of head with the clogged hand cleaned screen should not exceed 0.3 m. For

mechanically cleaned screen, the head loss is specified by the manufacturer, and

it can be between 150 to 600 mm.

The head loss through the cleaned or partially clogged flat bar screen can also be

calculated using following formula:

h = 0.0729 (V2 – v 2 ) Where,

h = loss of head, m

V = velocity through the screen,

m/sec v = velocity before the screen, m/sec

The head loss through the fine screen can be calculated as:

h = (1/(2g.Cd))(Q/A)2

g = gravity acceleration (m/sec2 );

Cd is coefficient of discharge = 0.6 for clean rack;

Q is discharge through screen (m3 /sec); and

A is effective open submerged area (m2 ).

1. The slope of the hand cleaned screen should be in between 30 to 60o with

horizontal. The mechanically cleaned bar screens are generally erected almost

vertical;

2. However the angle with the horizontal can be in the range 45 to 85o .

3. The submerged area of the surface of the screen, including bars and opening

should be about 200% of the cross sectional area of the incoming sewer for

separate system, and 300% for the combined system.

4. The clear spacing between the bars may be in the range of 15 mm to 75 mm in

case of mechanically cleaned bar screen. However, for the manually cleaned bar

screen the clear spacing used is in the range 25 mm to 50 mm. Bar Screens with

opening between 75 to 150 mm are used ahead of raw sewage pumping. For

industrial wastewater treatment the spacing between the bars could be between 6

mm and 20 mm.

5. The width of bars facing the flow may vary from 5 mm to 15 mm, and the depth

may very from 25 mm to 75 mm. Generally bars with size less than 5 mm x 25

mm are not used. These bars are welded together with plate from downstream

side to avoid deformation.

6. Quantities of Screening ¾ The quantity of screening varies depending on the

type of rack or screen used as well as sewer system (combined or separate) and

geographic location. ¾ Quantity of screening removed by bar screen is 0.0035 to

0.0375 m3 / 1000 m3 of wastewater treated.

(Typical value = 0.015 m3 /1000 m3 of wastewater)

(Metcalf & Eddy, 2003) ¾

In combined system, the quantity of screening increases during storm and can be

as high as 0.225 m3 /1000 m3 of wastewater.

¾ For industrial wastewaters quantity of the screening depends on the

characteristics of the wastewater being treated.

Disposal of Screenings ¾ Screening can be discharged to grinders or

disintegrator pumps, where they are ground and returned to the wastewater. ¾

Screenings can be disposed along with municipal solid waste on sanitary

landfill. ¾ In large sewage treatment plant, screenings can be incinerated.

7 ¾ For small wastewater treatment plant, screenings may be disposed off .

Aeration

Aeration (also called aerification) is the process by which air is circulated

through, mixed with or dissolved in a liquid or substance.

Methods

Aeration of liquids (usually water) is achieved by:

Passing the liquid through air by means of fountains, cascades, paddle-wheels

or cones.

Passing air through the liquid by means of the Venturi tube, aeration

turbines or compressed air which can be combined with diffuser(s) air stone(s),

as well asfine bubble diffusers, coarse bubble diffusers or linear aeration

tubing.

Ceramics are suitable for this purpose, often involving dispersion of fine air or

gas bubbles through the porous ceramic into a liquid.

The smaller the bubbles, the more gas is exposed to the liquid increasing the

gas transfer efficiency.

Diffusers or spargers can also be designed into the system to cause turbulence

or mixing if desired.

Porous ceramic diffusers are made by fusing aluminum oxide grains using

porcelain bonds to form a strong, uniformly porous and homogeneous structure.

The naturally hydrophilic material is easily wetted resulting in the production

of fine, uniform bubbles.

On a given volume of air or liquid, the surface area changes proportionally with

drop or bubble size, the very surface area where exchange can occur. Utilizing

extremely small bubbles or drops increases the rate of gas transfer (aeration) due to

the higher contact surface area. The pores which these bubbles pass through are

generally micrometre-size.

USES OF AERATION OF LIQUIDS:

To smooth (laminate) the flow of tap water at the faucet.

Production of aerated water or cola for drinking purposes.

Secondary treatment of sewage or industrial wastewater through use of aerating

mixers/diffusers.

To increase the oxygen content of water used to house animals, such

as aquarium fish or fish farm

To increase oxygen content of wort (unfermented beer) or must (unfermented

wine) to allow yeast to propagate and begin fermentation.

To dispel other dissolved gases such as carbon dioxide or chlorine.

In chemistry, to oxidize a compound dissolved or suspended in water.

To induce mixing of a body of otherwise still water.

Pond aeration.

Introduction Several techniques are used to treat domestic wastewater. These can

be classified into two groups: conventional and non-conventional treatment

plants. The former has high-energy requirements. The later is solely dependent

on natural purification processes. The conventional systems of wastewater

treatment includes trickling filters, activated sludge systems, biodisc rotators and

aerated lagoons. The non-conventional systems, which European Scientific

Journal May 2013 edition vol.9, No.14 ISSN: 1857 – 7881 (Print) e - ISSN

1857- 7431 279 are also called eco-technologies include constructed wetlands

and waste stabilization ponds (WSPs). Among these technologies, the widely

recommended ones for developing countries are the WSPs (Awuah, 2006).

Oxidation ponds are also called stabilization ponds or lagoons and serve mostly

small rural areas, where land is readily available at relatively low cost (Bitton,

2005). Waste stabilization ponds are biological treatment systems, which

processes and operations are highly dependent on the environmental conditions

such as temperature, wind speeds and light intensity which highly variable and

any given combination of these environmental parameters is usually unique to a

given location (Gray, 2004). There are many advantages of using this kind of

biological treatment like easy to operate, low energy required, less equipment

maintenance, and better sludge thickening. However, the effluent quality from

fixed- film system are relatively poorer than suspended growth systems in terms

of biochemical oxygen demand (BOD) and suspended solid (SS) (Metcalf &

Eddy, 2003). If pond systems are correctly designed and managed in order to

cultivate anaerobic and aerobic bacteria and green micro-algae, then such

systems would decompose waterborne organic wastes effectively and efficiently,

and would help in reducing some of the problems associated with the treatment

and disposal of wastewater. In addition, about 90% of the ponds in the United

States are used in small communities with less than 10,000 residents and are to

be very effective in wastewater treatment (Gray, 2004). This study was

conducted to establish proper design guidelines for installation of WSP in Al-

dewaniyah province to provide a solution for the problem of the wastewater

generated from hundreds of villages and small towns in the province. For this

purpose a typical representative communities of 10000 population was selected

by making a model depending on a scale. Wastewater treatment in WSPs

Louisiana Administrative Code (2004) defines that an oxidation pond is a

shallow pond designed specifically to treat sewage by natural purification

processes under the influence of air and sunlight. The stabilization process

consists largely of the interactions of bacteria and algae. Bacteria digest and

oxidize the constituents of sewage and render it harmless and odor free. Algae

utilize carbon dioxide and other substances resulting from bacterial action and

through photosynthesis produce the oxygen needed to sustain the bacteria in the

treatment process. During the detention period, the objectionable characteristics

of the sewage largely disappear (Louisiana Administrative Code, 2004).

European Scientific Journal May 2013 edition vol.9, No.14 ISSN: 1857 – 7881

(Print) e - ISSN 1857- 7431 280 Pena and Mara (2004) indicates that the

arrangement of WSPs, wastewater is first subjected to preliminary treatment -

screening and grit removal - to remove large and heavy solids. The design of this

preliminary treatment stage is the same as that used for conventional electro

mechanic WWTP, but for WSPs the simplest systems are generally used

(manually raked screens and manually cleaned constant-velocity grit channels).

Basically, primary treatment is carried out in anaerobic ponds, secondary

treatment in facultative ponds, and tertiary treatment in maturation ponds.

Anaerobic and facultative ponds are for the removal of organic matter (normally

expressed as BOD) and maturation ponds for the removal of faecal viruses,

faecal bacteria (for example, Salmonella spp., Shigella spp., Campylobacter spp.

and pathogenic strains of Escherichia coli), and nutrients (nitrogen and

phosphorus) (Pena and Mara, 2004). Types of WSPs and Their Specific Uses

Kayombo et al.(1998) refers that WSP systems comprise a single string of

anaerobic, facultative and maturation ponds in series, or several such series in

parallel. In essence, anaerobic and facultative ponds are designed for removal of

BOD, and maturation ponds for pathogen removal, although some BOD removal

also occurs in maturation ponds and some pathogen are removed in anaerobic

and facultative ponds. In most cases, only anaerobic and facultative ponds will

be needed for BOD removal when the effluent is to be used for restricted crop

irrigation and fish pond fertilization, as well as when weak sewage is to be

treated prior to its discharge to surface waters. The types of waste stabilization

pond are :- Aerobic ponds An aerobic stabilization pond contains bacteria and

algae in suspension; aerobic conditions (the presence of DO) prevail throughout

its depth. There are two types of aerobic ponds, shallow ponds and aerated

ponds(AFM, 1988). • Shallow ponds Shallow oxidation ponds obtain their DO

via two phenomena, oxygen transfer between air and water surface, and that

produced by photosynthetic algae. (AFM, 1988). • Aerated ponds An aerated

pond is similar to an oxidation pond except that it is deeper and mechanical

aeration devices are used to transfer oxygen into the wastewater. The aeration

devices also mix the wastewater and bacteria. On the other hand, the

disadvantage is that the mechanical aeration devices require maintenance and

use energy (Shilton, 2001). Its European Scientific Journal May 2013 edition

vol.9, No.14 ISSN: 1857 – 7881 (Print) e - ISSN 1857- 7431 281 detention

times are in the order of 1 to 10 days, depending on organic loading rate,

temperature, and the degree of treatment required (Liu, 2007). Aerobic-

anaerobic (facultative) ponds Facultative ponds (FPs) are characterized by

having an upper aerobic and lower anaerobic zone, with active purification

occurring in both. Facultative pond designed for BOD removal and sized on the

basis of volumetric BOD loading (g BOD/m2 .d) (Hassan, 2011). Facultative

ponds are often categorized as either primary or secondary ponds, treating raw or

settled wastewaters respectively. As organic matter enters the basin, the

settleable and flocculated colloidal matter settles to the bottom to form a sludge

layer where organic matter is decomposed anaerobically. The remainder of the

organic matter, which is either soluble or suspended, passes into the body of the

water where decomposition is mainly aerobic or facultative, although it is

occasionally anaerobic (Gray, 2004). Three zones exist facultative pond : (AFM,

1988) • A surface zone where aerobic bacteria and algae exist in a symbiotic

relationship. • An anaerobic bottom zone in which accumulated solids are

actively decomposed by anaerobic bacteria. • An intermediate zone that is partly

aerobic and partly anaerobic in which the decomposition of organic wastes is

carried out by facultative bacteria. Because of this, these ponds are often referred

to as facultative pond. Gawasiri (2003) indicates that the facultative ponds

normally follow anaerobic ponds in a WSP system. Facultative ponds usually

have a depth of 1.5-2.0 meter . (Earnest F. Gloyna, 1971; Mara, D. D., Mills, S.

W., Pearson, H. W., & Alabaster, G. P. ,2007) while Liu (2007) referred that

facultative pond depth ranges between 1.2 to 1.5m. Maturation ponds

Maturation ponds are widely used throughout the world as a tertiary treatment

process for improving the effluent quality from secondary biological processes,

including facultative ponds. (Gray, 2004). Pena and Mara (2004) indicated that

maturation ponds receive the effluent from the facultative ponds and their size

and number depends on the required bacteriological quality of the final effluent.

They are shallower than facultative ponds with a depth in the range 1−1.5 m,

with 1 m being optimal (depths of less than 1 m encourages rooted macrophytes

to grow in the pond and so permites mosquitoes to breed). European Scientific

Journal May 2013 edition vol.9, No.14 ISSN: 1857 – 7881 (Print) e - ISSN

1857- 7431 282 Anaerobic ponds Anaerobic ponds are commonly 2 – 5 m deep

and receive wastewater with high organic loads (usually greater than 100 g

BOD/m3 .day, equivalent to more than 3000 kg/ha.day for a depth of 3 m)

(Kayombo et al., 1998, ). They normally do not contain dissolved oxygen (DO)

or algae. In anaerobic ponds, BOD removal is achieved by sedimentation of

solids, and subsequent anaerobic digestion in the resulting sludge. The process

of anaerobic digestion is more intense at temperatures above 15 o C. designed

for BOD removal and sized on the basis of volumetric BOD loading (g BOD/m3

.d) (Hassan, 2011). Sazbo and Engle (2010) found when no oxygen is available,

anaerobic degradation may occur by anaerobic microorganisms. The benefit of

anaerobic digestion is that it can deal with highly concentrated waste water and

can achieve good purification results within short retention times. The anaerobic

pond should be installed as the first treatment step, when the load of waste water

is the highest. Controlled discharge ponds Controlled discharge ponds have long

hydraulic detention times and effluent is discharged when receiving water

quality will not be adversely affected by the discharge. Controlled discharge

ponds are designed to hold the wastewater until the effluent and receiving water

quality are compatible. Complete retention ponds Complete retention ponds rely

on evaporation and/or percolation to reduce the liquid volume at a rate equal to

or greater than the influent accumulation. Favorable geologic or climatic

conditions are prerequisite. Experimental Work and data collection The

experimental work of this study was performed in Aldewaniyah sewage

treatment plant to study the adequating of using waste stabilization pond for

wastewater treatment for many towns where using of wastewater treatment

plants by conventional methods are very expensive and needing very long times

for construction and operation . The experimental work was conducted in the

period from 20.11.2011 to 1.07.2012. All test in the experimental work were

done in the laboratory of WWTP of Aldewaniyah and the laboratory of the

engineering collage in AlQadissiyah university. According to references on this

study like basic principles available in Aldewaniyah sewage directorate,

previous tests for recent years, and other of scientific references. Experimental

work in this search included the following tests :- 1- Biochemical oxygen

demand (BOD) test. European Scientific Journal May 2013 edition vol.9, No.14

ISSN: 1857 – 7881 (Print) e - ISSN 1857- 7431 283 2- Chemical oxygen

demand (COD) test. 3- Total suspended solid TSS. 4- PH. 5- Nitrate and nitrite.

6- phosphate Description of oxidation ponds and the arrangement of the ponds in

the model The experimental model contains three ponds: anaerobic pond,

faculatative pond and aerobic pond. Also there is collecting basin at the end of

the series. Anaerobic pond The first pond in the series is anaerobic pond which

made with dimensions (5.75*2*2)m and detention time (8) days. Anaerobic

pond was used because of the high organic load in the influent wastewater enters

the ponds as shown in the results of the tests. Facultative pond It is the second

pond receives wastewater from anaerobic pond. It was made with dimensions

(5.75*2*1.5) m and detention time (6) days. Aerobic pond The third pond of the

series of ponds is the aerobic pond. It was made with dimensions (5.75*2*0.75)

m with detention time (3) days. This pond was supplied with two mixing pumps

operate as aerators in the pond.

SEWAGE FARMS:

Sewage farms comprise agricultural land irrigated and fertilised with sewage.

The product being "farmed" at such a works is actually the combination of

microbes and bacteria used to break down the sewage.

As a predecessor to modern sewage treatment systems, household sewage was

collected from towns and cities and transported to nearby farm lands.

During the Middle Ages this was accomplished with hand-carried buckets, but as

local populations grew, during the Industrial Revolution sanitary sewer systems

were built.

These used a network of pipes and pumps to transport sewage beyond the city

boundaries to large rented grasslands, into which the sewage trickled down. Berlin

once rented 20 sewage farms occupying about 10,000 hectares.[1]

Some of these farms remained in use until the end of the 20th century, at which

point it became apparent that as it was usually contaminated with industrial waste,

sewage was unsuitable for use as a fertiliser.

Therefore, sewage plants began to replace sewage farms. Modern sewage farms are

usually combined with such plant, so that they irrigate the land with reclaimed

water. Some types of untreated sewage can be used on a sewage farm, or filtered

through a constructed wetland.

A small-scale example of a sewage farm exists at Chester Zoo, where water fouled

with elephant droppings and urine is filtered through a reedbed.

SOAKAGE PIT FOR PROPER DISPOSAL OF WASTE WATER:

Note:

Do not use your soak pit for disposing of waste water from latrines.

Day-to-day household tasks, such as cleaning, bathing, and washing clothes,

produce waste water. Stagnant pools of water around houses, in the streets,

and in choked drains are a health hazard.

Besides producing bad odour and making areas muddy, stagnant pools

become breeding places for mosquitoes.

Kitchen gardens are a good place to dispose of waste water. However, if you

don't have space for a garden, building a soak pit is a practical, effective

alternative.

Soak pits work like this: waste water gets dispersed in the specially designed

pit and is absorbed in the subsoil, while pieces of solid waste naturally

decompose.

Since decomposition takes place in a sealed pit, no foul smell is produced.

Materials required Stones (large, medium, small): 1 cart load Plastic or metal

perforated plate (15 cm diameter): 1 PVC pipe (30 mm diameter) 75 cm - 1

m Cement: 2 kg Bricks: 12 Polythene or gunny bags: 4 Sand: 2 cubic ft

Masonry and labour charges (digging, fitting, and finishing construction of

the pit): 1 day

CONSTRUCTION:

Select a 1 sq m area close to the drain outlet, and 30 to 60 cm away from the

nearest wall of the house.

- Dig a pit 1m x 1m x 1m x.

- Fill the pit with big stones (coconut size) up to 30 cm, followed by medium

stones (guava size), from 30 to 60 cm, and small stones (wainut size) from 60 to 90

cm.

Note

In case the distance between the drain outlet and the soak pit is greater than the

recommended distance of 30 to 60 cm, the length of the drain pipe has to be

increased accordingly.

Note

During heavy rains, cover the trap with a plastic sheet to stop the rainwater

from draining in.

Choose a drain pipe (PVC, bamboo or any used rubber tube or hose) 5 mm

in diameter. Cut it to a length of about 75 cm

Make a hole 3 cm in diameter at one end of this pipe.

Construct a brick-lined trap below the drain outlet of the house, install a

perforated plate and a drain pipe running down to the soak pit.

Construct a brick-lined trap

The principal/function of the trap is to keep solid deposits, rainwater, and

mud out of the soak pit. You can also use a clay pot with holes in the

bottom as a trap.

Install the drain pipe so that the end with the 3 cm hole reaches the centre

of the pit and the perforation faces downwards.

Cover the pit with a polythene sheet (fertilizer bags or cement bags).

Make sure that the cover stretches at least 15 cm beyond the sides of the

pit. Spread earth on this cover and pack it until the surface of the pit is

level with the ground. Make the finished surface look the same as the

surrounding area.

Maintenance

Daily-Remove solid deposits held in the trap and flush a litre of water

through the trap to clear any blockage.

Periodic-In time, your soak pit might become choked. Excess moisture on

top of the soak pit is - an indication of choking. When choking occurs, dig

out the soak pit and remove the stones and debris. Wash the stones and refill

them in the pit.

For an average family, a well maintained soak pit will last for at least five

years.

SEWAGE SLUDGE TREATMENT

Sewage sludge treatment describes the processes used to manage and dispose

of sewage sludge produced during sewage treatment.

Sludge is mostly water with lesser amounts of solid material removed from

liquid sewage.

Primary sludge includes settleable solids removed during primary treatment

in primary clarifiers.

Secondary sludge separated in secondary clarifiers includes treated sewage

sludge from secondary treatment bioreactors.

Sludge treatment is focused on reducing sludge weight and volume to reduce

disposal costs, and on reducing potential health risks of disposal options.

Water removal is the primary means of weight and volume reduction,

while pathogen destruction is frequently accomplished through heating

during thermophilic digestion, composting, or incineration.

The choice of a sludge treatment method depends on the volume of sludge

generated, and comparison of treatment costs required for available disposal

options.

Air-drying and composting may be attractive to rural communities, while

limited land availability may make aerobic digestion and mechanical

dewatering preferable for cities, and economies of scale may encourage

energy recovery alternatives in metropolitan areas.

Energy may be recovered from sludge through methane gas production

during anaerobic digestion or through incineration of dried sludge, but

energy yield is often insufficient to evaporate sludge water content or to

power blowers, pumps, or centrifuges required for dewatering.

Coarse primary solids and secondary sewage sludge may include toxic

chemicals removed from liquid sewage by sorption onto solid particles in

clarifier sludge.

Reducing sludge volume may increase theconcentration of some of these

toxic chemicals in the sludge.