The dispersal of sewage across agricultural land’s surface is another system. This has also been widely tried, but it has almost always failed. The sewage has very little fertilising effect, its disposal requires a sizable area, labour costs make the system expensive, and the crops are unsafe for human consumption due to the presence of disease germs. If a health official criticises a surface disposal system due to cost and health risks, he is doing the correct thing.

Discharging sewage into a lake, river, bay, or another body of water is a third method of sewage disposal. This is a risky way to dispose of waste, particularly if the body of water is utilised as a water supply source. The oxidising bacteria is mostly responsible for the water’s natural cleansing actions of the water’s naturally dissolved oxygen. If the sewage percentage to the amount of water it discharges is between 1 and 200, the amount of oxygen in the water will be diminished to the point where some fish species can no longer survive in the water.

The amount of oxygen will be reduced to the point that putrefaction may occur if the sewage to water ratio is 1 to 50. However, even if the water does not become unpleasant to the senses, illness germs may still be present. Preventing sewage from polluting bodies of water is one of the major issues that health departments must deal with. Almost all sewage disposal systems that a health officer must deal with rely on bacterial decomposition for their action, followed by an additional purification step such as oxidation or soil filtering.

The organic materials in the sewage will either be eliminated or completely oxidised into carbon dioxide, water, and other minerals that are naturally present in ground water. Additionally, the water that flows away will be free of bacteria. This indicates that the purification process has been successful. Sewage can be cleaned up to the point where it can be used as drinking water.

The following tools are frequently used for sewage purification: a collecting tank, subsurface irrigation pipelines, a contact bed, sprinkler filters, sand filters, and chlorinating equipment. These tools are frequently combined in different ways, such as a collecting tank, a sprinkler filter, and a chlorinating system.

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Two types of flushing operations are normally used

(1)Flushing operation using automatic flushing tank

(2) Hand operated flushing operation

Automatic flushing tanks

This kind of flushing tank performs the flushing process automatically and on a schedule. The water entry is controlled in such a way that it fills the tank to the discharge point in a time that is equivalent to the flushing interval. In the event that the tank does not discharge properly and overflows, water can be drained away using an overflow pipe. Following is a description of how an automated flushing tank functions: The water level in the U-tube is initially between A and B when the tank is empty. The water level in the tank gradually increases as the water arrives through the entrance pipe. Until the water level in the tank stays below the level of the sniff hole, the water level in the U-tube stays at this level, or A-B. But the air is trapped and squeezed in the bell part as the water level in the tank rises over the level of the sniff hole. The water level in this along arm of U-tube is lowered as a result of the pressure that this compressed air exerts on surface A.

As the tank continues to fill up more and more, the water level continues to drop. A point is eventually reached when this occurs, a little amount of compressed air is released through the shorter arm of the u-tube, and an equivalent amount of water enters the bell. The adjustment is such that at this point the discharge line has just about been achieved, and the head of water above the bell exceeds that in the shorter arm of U-tube. When the compressed air is abruptly removed from the longer arm of the U-tube, a syphoning movement begins, allowing the water in the tank to flow into the bigger pipe and into the sewer. Up until the water level in the tank reaches the sniff hole, the siphonic activity is still in motion. The siphonic process is subsequently broken when the air enters the bell part through the sniff hole. The water level in the U-tow tube’s arms once more assumes positions A and B. the cycle continues, releasing water into the sewer on a regular basis.

Hand Operated Flushing Operations

In one way, the sludge entering the manhole from the inlet end will begin to gather in the manhole after the exit end of the manhole is closed by a sluice valve, etc. When enough sewage builds up, the manhole’s outlet end is quickly opened, allowing the sewage to enter the sewer and starting the flushing process.

Another approach allows water from the outside to enter the manhole by closing both the intake and outflow ends of the manhole with sluice valves, etc. The outputs and inlet ends can then be opened to perform the sewer flushing.

In a different technique, a nearby fire hydrant is attached to one end of a hose pipe, and the other end is then inserted into the manhole to perform the flushing action.

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1. Bell and spigot joint:

For stoneware pipes, each connection must be caulked with tarred gasket that is one length for each joint and long enough to completely round the pipe’s spigot end. The seal

shall then be partially dried, filled with a 1:2 cement sand mortar, and a fillet shall be applied made a 45° angle with the pipe’s barrel around the seam using a trowel per IS 4217. For jointing, rubber gasket can also be employed.

2. Collar joints

The plain ends of the following pipe lengths are kept close to one another for this type of junction, and a collar with a slightly larger diameter is positioned all around it. Then, a 1:1 amount of cement mortar is added to the annular space between the collar and the pipe ends. Larger diameter concrete pipes are used with these joints.

3. Simplex joint.

Similar to collar joints, simplex joints, also known as ring tie coupling, are used for asbestos cement pipes. The joint is made up of two rubber rings that are compressed between the interior of the sleeve and the interior of the pipes, as well as a pip sleeve or coupling made of asbestos cement. Such a joint is very adaptable.

4. Flexible or bituminous joint.

The collar joint using cement mortars is relatively rigid. Such joints crack. These joints are made flexible by using bitumen or bituminous compounds instead of cement mortar.

5. Joints in machines.

To hold the two ends of these joints together, mechanical devices such flanged rings, bolts, screwed ends, etc. are used. Cast iron, steel, and other metallic sewers are utilised with them.

6. Open joint

Unclosed joints Open joints are used if there is no objection to infiltration. Without adding any filler to the annular area, the bell and spigot ends are simply joined. To preserve alignment, a gasket can be placed. To stop soil from entering the sewer, the joint is simply coated with tar paper.

The post Joints in sewers first appeared on Student Projects.

The centre line of a sewer is indicated on the roads and streets according to the designs, moving upward from the lowest point or outfall of the main. Chain and a theodolite or compass is used to lay out the work. In order to check the centre line during construction, wooden pegs or steel spikes are typically driven at intervals of 10 metres on a line parallel to the centre where installing sewers won’t disturb them. Temporary benchmarks are set up at 200–400 metre intervals to monitor the levels and alignment of sewer lines. These benchmarks’ reduced level (R.L.) should be determined in relation to G.T.S benchmarks. Sewer appurtenance positions are also shown on the centre line.

EXCAVATION TRENCHES

The first phase is the removal of pavement, which begins at the lower end of the sewers and moves upward after noting the arrangement of the sewer lines on the ground. Concrete pavement removal tools include pickaxes, spades, and pneumatic drills. Trench digging is done either manually or with the use of machinery after pavement removal. The sewer line’s diameter and depth below ground determine the trench’s width.

For ease of lowering and altering the sewer pipe, the sewer line’s breadth is 15 cm wider than its exterior diameter. Even extremely tiny size sewers can be laid and joined conveniently with a minimum trench width of 60 to 100 cm. The need for trench side excavation require shoring and shuttering and also dewatering is done by gravity method or pumping method.

PREPARATION OF BEDDING:

In order for sewage to exclusively flow into sewers owing to gravitational flow, trenches are dug with the right grade. Sewers’ centre line and grades are transferred from the using a boning rod and a sight rail, the ground. If a sewer needs to be installed in a soil, the trench must be dug deeper than what is necessary, whether it is in reclaimed land or subsurface strata. Typically requires rock or trench bottom. When the soil is really poor, the trench bottom should be filled in with grade-appropriate cement concrete. Where there is a risk of subsidence. The pipe sewer must be installed on a pile- or platform-supported concrete cradle or platform made of wood. In the case of casting-site sewers and R.C.C section with reinforcement, bearing capacity is encountered and soil stabilization shall be done either by rubber, concrete or wooden crib.

LAYING:

Only the pipe layers themselves can directly lay smaller pipes by hand. However, thicker and heavier pipes are dropped into the trenches by being roped around and supported through the hock. To make joining easier, it is customary to lay pipes with upgraded socket ends. After carefully positioning and arranging the pipes, they are linked by bringing them close and inserting the spigot end of one pipe into the socketed end of the other. Carefully curing the joints for an appropriate amount of time

JOINTING OF SEWERS

The C.I Pipes must be checked for line and level, and any empty space in the socket must be filled with molten piglead of the highest quality in accordance with IS:782 and IS 3114. For concrete pipes, the collars must be symmetrically positioned over the ends of the pipes. The annual space between the inside of the collar and the outside of the pipe must be filled with hemp yarn soaked in tar or cement slurry that has been thoroughly packed and rammed with caulking tools before being filled with cement mortar 1:2. The joints must be completed with a fillet that slopes at 45 degrees to the pipe’s surface and is cured for 24 hours.

For stoneware pipes, each connection must be caulked with tarred gasket that is one length for each joint and long enough to completely round the pipe’s spigot end. The seal shall then be partially dried, filled with a 1:2 cement sand mortar, and a fillet shall be applied made a 45° angle with the pipe’s barrel around the seam using a trowel per IS 4217. For jointing, rubber gasket can also be employed.

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When choosing sewage materials, the following elements should be carefully taken into account.

1. Price: The price should be fair and reasonable.
2. Sturdiness: The substance should be sturdy.
3. Imperviousness: The sewer’s construction material must possess this property.
4. Abrasion Resistance: The material must be sufficiently resistant to abrasion brought on by grit moving at a high speed.
5. Corrosion resistance: Due to the sewage’s corrosive properties, the material should be able to offer corrosion resistance.
6. Weight: To facilitate handling and transportation, the material should be moderate in weight.

CEMENT CONCRETE SEWERS

The sewers made of cement concrete might be conventional or reinforced. Up to a diameter of 600 mm, ordinary cement concrete sewers are utilised; for diameters more than 600 mm, reinforcing is given.

ADVANTAGES:

1. These are robust and resistant.
2. A larger diameter is possible.
3. The sewer’s interior surface is smooth.
4. The interior surface of the structure should be lined with vitrified clay to protect it from chemical and erosive attacks.

DISADVANTAGES:

1. It is challenging to transport and handle heavy objects.
2. Carefully filled joints should be used

A.C.PIPES

Asbestos fibres and cement are combined to create these sewers. They come in sizes up to 900mm.

ADVANTAGES:

1. Easy to cut and join.
2. Durable and good resistance to corrosion.
3. The inside surface is smooth.
4. Light in weight and hence easy to handle

DISADVANTAGES:

1. Brittle and cannot stand impact forces during handling operations.
2. The structural strength is poor and hence cannot be laid to resist heavy external loads

The post Sewers first appeared on Student Projects.

1. BASKET HANDLE SECTION: In this type of sewer, the upper portion of sewer has got the shape of a basket-handle. The bottom portion is narrower and carries small discharges during monsoon and combined sewage is carried through the full section. This shape of sewer is not generally used at present
2. CATENARY-SHAPED SECTION: In this type of sewer, the shape of sewer is in the form of a catenary and only gravity force is acted upon this sewer. This is suitable for tunneling work
3. SECTION THAT IS EGG-SHAPED OR OVOID: This style of sewer is appropriate for transporting combined flow. The main benefit of this style of sewer is that, compared to a circular sewer with the same capacity, it provides a little higher velocity with low flow. However, this portion is more complex to manufacture and less stable than circular sections. Sewers in the shape of an inverted egg provide improved stability and can carry large discharges.
4. HORSE-SHOE SECTION: This kind of sewer is utilised to transport heavy discharges, including truck and outfall sewers, during tunnel construction. When there is little headroom available for sewer construction, this is also appropriate. The sewer’s invert may be flat, round, or paraboloid, with a semicircular-shaped top and vertical or inclined sides.
5. PARABOLIC SECTION: This type of sewers are suitable for carrying comparatively small quantities of sewage and economical in construction. The invert of sewer may be flat or parabolic and upper arch of the sewer takes the form of parabola
6. RECTANGULAR OR BOX TYPE SECTION: The sewage section is stable and simple to build in a rectangular or box shape. It is occasionally employed as a storage tank when it becomes essential to temporarily hold sewage due to the tide.
7. SEMI-CIRCULAR: This style of sewers has greater hydraulic qualities and is appropriate for building huge sewers with limited headroom.
8. SEMI-ELLIPTICAL SECTION: This type of section is used for soft soil since it is sturdier and can carry big discharges. Except at low depths, the sewer’s dia may exceed 1.8 metres and it has good hydraulic characteristics.
9. U-SHAPED SECTION: The shape of this section is the true shape of letter. Or small trench of U shape can be setup in the larger section of sewer. The trench is known as the cunette and adopted for a combined sewer having predominant flow of storm water.

BRIEF DESCRIPTION AND CHOICE OF TYPES OF SEWERS

When choosing sewage materials, the following elements should be carefully taken into account.

1. Price: The price should be fair and reasonable.
2. Sturdiness: The substance should be sturdy.
3. Imperviousness: The sewer’s construction material must possess this property.
4. Abrasion Resistance: The material must be sufficiently resistant to abrasion brought on by grit moving at a high speed.
5. Corrosion resistance: Due to the sewage’s corrosive properties, the material should be able to offer corrosion resistance.
6. Weight: To facilitate handling and transportation, the material should be moderate in weight.

The post Shapes of non-circular drain first appeared on Student Projects.

1. Rectangular surface drains
2. Semi-circular surface drains
3. U-shaped surface drains
4. V-shaped surface drains

1. Rectangular surface drains

Heavy discharge can be carried by these drains. However, when the depth of flow is shallow, they do not achieve the necessary velocity and easily deposit.

2. Semi-circular surface drains

These are appropriate for streets with a small amount of discharge that needs to be accommodated. These drains are prefabricated, semi-circular portions of asbestos cement, stoneware, or concrete pipes.

3. U-shaped surface drains

These drains are easy to construct and they combine the advantages of semi-circular drains and rectangular surface drains.

4. V-shaped surface drain

These drains are more effective hydraulically, but they are challenging to build. These drains will be constructed with fluctuating. These drains may generate a good velocity and can transport a variable discharge without depositing solids everywhere. These drains are built using cement mortar for stone or brick construction. Rich cement mortar has been used to neatly plaster the inside surface. In order to prevent either silting or scouring, the drains are equipped with adequate slopes that keep the velocity within the range.

DIFFERENT SHAPES OF CROSS-SECTIONS FOR SEWERS CIRCULAR AND NON CIRCULAR

Because of the following factors, circular sewers are typically used.

1. Construction costs for the same area of a circular form are lowest since it has the smallest perimeter.
2. Lack of corners minimises the deposition of organic materials.
3. They are simple to produce, assemble, and handle.
4. Because of their circular design, these are subject to hoop compression, requiring only a small amount of concrete and no reinforcing.
5. Because they offer the greatest hydraulic mean depth while running full or half full, they have exceptional hydraulic properties.

When the discharge does not vary significantly and there is less likelihood of sewers flowing at very shallow depths (less than half), circular sewers perform well. However, there are a few additional uses for sewers with non-circular geometries.

1. To decrease building costs
2. To increase flow velocity when sewage is present at shallow depths
3. To ensure greater structural stability
4. To streamline the construction procedure
5. Enlarge them to allow a man to enter for maintenance or cleaning

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Use of nomograms in accordance with IS 1742 to ascertain the gradient, diameter, discharge, and velocity’s unknown values.

In order to determine the necessary gradients, the provided self-cleansing velocities, and the estimated discharge, calculations must be made for each sewage line in a town’s sewerage system. This requires using a formula for each calculation, which makes designing the entire system a laborious task. The use of tables, nomograms, partial flow diagrams, etc. created using the appropriate formula simplifies this process.

The nomogram is frequently employed in sewer system planning. Based on Manning’s method, this nomogram uses 0.013 as the value of n. The Nomogram’s values are based on full, flowing sewers. The Nomogram can be used easily in accordance with IS 1742. A line is formed connecting these two numbers, for instance, if the required discharge of a sewer with n=0.013 is 224 lit/sec and the grade is 0.00125. The matching values are determined by where this line on the velocity scale and diameter scale intersect. Thus, for this case, the sewer’s diameter is determined to be 600 mm, and the required velocity is 0.765 m/sec. Therefore, if two numbers are known, the other two values can be obtained with ease.

Sewers are underground, closed channels used to transport waste from public and residential water closets as well as chemically mixed industrial water without causing a nuisance outside of the community. Sewer cross sections should be designed so that self-cleaning velocity develops even in dry weather flow. No deposit should under no circumstances should you lie down in the sewer bed. These ought to be spread out in the town at a slope that prevents water from manholes in the event of a river flood near the outflow and lead to unhygienic environments.

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Under the following circumstances, using the effluent irrigation method to dispose of sewage is recommended.

• When certain nearby natural rivers are not present.
• When irrigation water is in short supply, extensive irrigation can be carried out using sewage effluents.
• In places with little rainfall
• The presence of sandy, loamy, or alluvial soils
• In regions with a low water table.

Sewage Farming

The emphasis is placed on using sewage effluents to irrigate crops and improve the fertility of the land.

Ways to use sewage effluents on farms

• Broad irrigation, or surface irrigation
• Subsurface irrigation
• Irrigation via sprinklers or spray

Sewage sickness

The pores or voids in the soil may become filled with and clogged with the sewage matter trapped in them when sewage is applied constantly to an area of land. Of course, the type of soil will determine how long it takes for such a blockage to form.

Preventative actions

1. Sewage primary treatment
2. Land selection
3. Poor drainage of the soil
4.  Resting the land
5. Crop rotation
6. Making use of shallow depths

The post Disposal on land first appeared on Student Projects.

1. Organic substances are oxidised.

2. Encourages coagulation and flocculation while transforming dissolved and colloidal materials into settle able solids.

The flow diagram of activated sludge process is shown in the figure below:

The necessary quantity of activated sludge from S.S.T. is combined with the settled sewage from P.S.T. Mixed Liquor Suspended Solid (MLSS) is the name given to the resulting mixture.

MLSS is put through an aeration tank and mixed with air there for 4 to 8 hours. Bacteria oxidise the sewage in the presence of oxygen, reducing the sewage’s BOD. After being aerated, the MLSS is transported to S.S.T. where it can settle. After treatment, the settled sludge is disposed of and some of it is recalculated as activated sludge after the effluent is discharged.

The S.S.T’s effluent is crystal clear water with a very minimal quantity of organic debris, and it may be disposed of without further treatment other than the sporadically used chlorination.

Benefits of the Activated Sludge Process include

1.  Low installation costs
2. Good effluent
3. Requires little land.
4. Head loss is minimal
5. Elimination of odour and insect annoyance good standard of care

Activated sludge process drawbacks

1. Not very flexible method (If there is a rapid increase in sewage volume or if there is a quick change in sewage character, there are negative effects on the process’s operation and as a result, poor-quality effluent is produced).
2. High operational costs
3. Large-scale sludge disposal is necessary
4. This method is delicate to some industrial wastes. 5. To ensure that the returned sludge is still active, skilled observation is necessary.

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