An Overview of Sewerage Systems: Types, Functions, and Maintenance

What Is Sewerage System?

Sewerage is a system which expresses sewerage, a soil drainage by means of a sewer. It includes elements such as receptacle drains, manholes, pumping stations, collection overflows, and inspection chambers for mixed sewage or sanitary sewers.

Sewerage reaches the wastewater treatment system or the injection point into the area. It is a series of pipes, chambers, manholes, etc. that conveys sewerage and stormwater.

Types of Sewerage System:

1. Combined system.
2. Separate system.
3. Partial Separate System.

1. Combined Sewage System-

In a combined system, the very same sewer is meant to convey all household sewage, commercial waste as well as surface and flood water.

Situation of Adoption for Combined Sewage System:

1. Rainfall has been going on all year.
2. Both the sanitary sewage and the rainwater must be pumped.
3. The region to be torn down is densely built-up and there is not enough space for laying pipes.
4. Efficient or faster flows need to be given.
5. If the sewers are placed together with the general construction of the city, a mixed system is desired.

Advantages of Combined Sewage System:

1. Rainwater holds the waste fresh, providing a way and more affordable for disposal purposes.
2. Dilution also benefits, as this is in itself a form of treatment.
3. Automatic flushing is supplied with water.
4. This is the fastest way to collect and house plumbing economies.

Disadvantages of Combined Sewage System:

1. The greater sewer size would require bigger excavations.
2. Overflowing under the worst circumstances could endanger human safety.
3. The cost of pumping and disposal will rise due to the high amount of sewage to be treated.
4. The dry conditions stream is a tiny portion of the overall flow, the large size of the sewer will also allow silting to increase due to the low flow rate of the sewer during the dry period of the year.

2. Separate Sewage System-

In a separate system, residential and agricultural waste is transported with one system of sewers, while flood and surface water is transported in another set of sewers.

Situation of Adoption for Separate Sewage System:

1. Where there is uneven rainfall.
2. Sanitary waste shall have one outlet and other outlets for disposal or surface water shall be available.
3. The sanitary sewage must be pumped.
4. Separate sewers need to be deepened, and the stormwater drains lower to the surface than the excavation economy.
5. If the soil has steep slopes, it is easier to turn floodwater from an open drain into a natural stream.
6. The funding available is limited, but sanitary drainage is crucial.
7. If the subsoil is rough, it is challenging and expensive to lay a wide combined sewer.
8. If the sewers are placed before the construction of the city, it is advisable to follow a separate system.

Advantages of Separate Sewage System:

1. Although shorter in length, the sewers are very economical. Surface water can be taken in open or closed ducts or drains at or near the surface and drained at sufficient sources, making the construction of stormwater sewers much simpler.
2. There is no chance of runoff from lakes since no overflow of storms is to be given.
3. The amount of waste to be treated is limited and the drainage or treatment works may be economically planned.
4. If the pumping of the waste at the treatment plant were required, the cost of pumping will be much smaller, since there is no need to drain the floodwater.

Disadvantages of Separate Sewage System:

1. Only if it is placed at a steep gradient, the self-cleaning rate in the sewer cannot be ensured and the flushing must be carried out. This will prove unsatisfactory and costly.
2. There could be a chance of interference by an illegal accumulation of rainwater as well as the consequent leakage of sewage.
3. Multiple housing plumbing is another drawback. 2 sewers or drains in the street leading to a larger disruption of transportation, which restores every one of them, have been taken out.
4. Maintenance costs for two systems are higher than for one system.

3. Partial Separate Sewage System-

A partly separate system is a variation of a separate system in which separate sewers that discharge domestic sewage and commercial waste often comprise a portion of the surface drained from the backyards and roofs of the property.

Why We Need a Partially Separate System?

It can be claimed that a combined sewerage scheme was not considered to be sufficient within tropical Soil conditions for the reasons described herein.

1. Insufficient volumes of sewage water accessing the sewers due to a large variety of unwatered areas or because of other factors, the dry weather flow (DWF) is usually a limited proportion of the overall flow.
2. Low economy with minimal funding available.
3. Difficulties in the management and repair of the infrastructure attributable to the lack of oversight of fewer trained employees. Local authorities responsible for the job do not typically pay any attention to the maintenance of skilled and competent workers.

In fact, on the basis of the factors mentioned above, it has been considered necessary to provide a balance between the separate and combined systems and to follow, as far as possible, a partly combined as well as partially separate sewage scheme.

The underground sewage system holds either sanitary or residential sewers from which rainwater can also be discharged from the backyard and roofs of the homes.

In the other side, the stormwater from the front of the house and the surface wash of the streets and roads may, at some distance, divide into the watercourse flowing close or to the same low-lying area.

Advantages of Partial Separate System:

1. It optimizes the drainage of the property.
2. It has fair sewage sizes and is inexpensive.
3. Rainwater gives some protection from silting in the sewer.

Disadvantages of Partial Separate System:

1. Low pace during the dry season.
2. Storm overflows can be deemed appropriate.

How Does a Sewage Treatment Plant Work?

The sewage treatment plant uses internal processes to break down solid waste to create safer, more environmentally friendly effluent.

Wastewater and sewage are supplied to the main tank where the solids and liquids are distributed. The resultant liquor runs into the chamber of the bio-zone. The pump airs the waste in the chamber and allows friendly bacteria to condense organic matter. It breaks down and purifies the result.

As it exits the final waste chamber, 95 percent of the waste left over is safe and ready for dispersion into local ditches or soaking schemes, according to the approval of the appropriate environmental body.

Sewage System Includes The Following:

1. House Service Connections Link the house to the sewers on the lane.
2. Sewers These are pipes or ducts designed for the transport of sewage that is laid around the roads and flow by gravity.
3. Lift stations When the sewers are at a deeper level, lift stations are used to help transfer the sewage from the lower elevations below the ground to the higher elevation needed.
4. Pumping stations The sewage is moved from one site to another.
5. Water Treatment Plants Treatment of sewage to meet the allowable discharge quality.
6. Safe final effluent drainage The sewers are the most critical component of the sewage system. They are laid down underneath the ground and are impossible to restore.
7. A great deal of consideration is also required in their O&M and the following concerns are discussed.
8. Quality Maintenance of sewerage system.
9. Type of Maintenance of Sewerage System.

Quality Maintenance of Sewerage System:

The efficiency of the maintenance of the wastewater system consists of the optimal use of manpower, machinery and resources to maintain the system in good order so that it can successfully fulfill its intended function for the processing of wastewater.

Type of Maintenance of Sewerage System:

There have been three types of maintenance of the drainage system –

1. Preventive.
2. Routine.
3. Emergency.

Preventive or routine repairs should be carried out in order to deter any deterioration of the infrastructure and to stop emergency operations to cope with clogged drainage pipes or overflowing manholes or back-up of water into the house or systemic collapse of the system.

Preventive maintenance is more efficient and guarantees efficiency in the service of the sewer services.  Emergency corrections, which can be very unlikely if adequate servicing is carried out well, must also be accounted for. Proper inspection and preventive maintenance are required.

Frequently Asked Questions (FAQ) About Sewerage Systems

What is a sewerage system?

A sewerage system is a network designed to transport sewage and stormwater through a series of pipes, chambers, manholes, and other elements to a wastewater treatment facility or disposal point.

What are the main components of a sewerage system?

The main components include receptacle drains, manholes, pumping stations, collection overflows, and inspection chambers for mixed or sanitary sewers.

What types of sewerage systems are there?

There are three primary types:

1. Combined Sewage System
2. Separate Sewage System
3. Partial Separate Sewage System

What is a combined sewage system?

A combined sewage system uses the same sewers to transport household sewage, commercial waste, and stormwater.

When is a combined sewage system typically used?

It is used in areas with consistent rainfall throughout the year, densely built-up regions with limited space for laying pipes, and where a faster flow and efficient transport are needed.

What are the advantages of a combined sewage system?

1. Keeps waste fresh with rainwater, aiding in easier disposal.
2. Provides dilution, which is a form of treatment.
3. Allows for automatic flushing.
4. Enables faster collection and reduces plumbing costs.

What are the disadvantages of a combined sewage system?

1. Requires larger sewer sizes, leading to bigger excavations.
2. Can overflow, endangering human safety.
3. Higher costs for pumping and treatment.
4. Risk of silting during dry periods due to low flow rates.

What is a separate sewage system?

A separate sewage system uses different sewers for residential and commercial waste and for stormwater.

When is a separate sewage system typically used?

It is used in areas with uneven rainfall, where sanitary waste and stormwater need separate outlets, and in regions with limited funding but critical sanitary drainage needs.

What are the advantages of a separate sewage system?

1. Economical and simpler construction.
2. No risk of runoff from lakes.
3. Reduced amount of waste to be treated.
4. Lower pumping costs as there is no need to handle floodwater.

What are the disadvantages of a separate sewage system?

1. Requires steep gradients to ensure self-cleaning rates.
2. Potential for illegal rainwater connections and leakage.
3. Higher maintenance costs for two systems.

What is a partial separate sewage system?

A partial separate system combines features of both combined and separate systems, using separate sewers for household sewage and a portion of the surface water, while the rest of the stormwater is handled by separate channels.

Why might a partial separate sewage system be used?

It is often used in tropical areas where combined systems are insufficient due to low dry weather flow and economic constraints.

How does a sewage treatment plant work?

A sewage treatment plant breaks down solid waste using biological processes to produce safer effluent, which is then dispersed into local ditches or soakaway systems.

What are the key elements of a sewage treatment plant?

1. House service connections
2. Sewers
3. Lift stations
4. Pumping stations
5. Water treatment plants
6. Safe final effluent drainage

What types of maintenance are required for a sewerage system?

There are three types of maintenance:

1. Preventive maintenance
2. Routine maintenance
3. Emergency maintenance

Why is preventive maintenance important for sewerage systems?

Preventive maintenance helps avoid system deterioration, prevents clogged pipes and overflowing manholes, and reduces the likelihood of emergency repairs.

What does quality maintenance of a sewerage system involve?

It involves the optimal use of manpower, machinery, and resources to keep the system in good condition for effective wastewater processing.