Different Types of Sewerage System and Their Advantages and Disadvantages

Looking for types of sewerage system and their advantages and disadvantages of them? Then here I have explained in detail for you.

The spectacular growth of cities in recent years would not have occurred without the development  of sewerage systems.

Before the development of these systems, urban concentrations were more inhospitable places than now, since the lack of sanitation in the streets was a source of infections and even fatal diseases. 

There was no way to evacuate the various types of sewage. 

In response to this demand for more hygienic cities, in the 19th century the main urban concentrations of the European continent began to install sewage systems.

Since then, sewage systems have been refined and evolved to achieve greater comfort in cities.

However, despite the improvement of the current sewerage system in the main European cities, their maintenance is necessary to avoid incidents. In this sense, Hidrotec presents itself as an expert in urban network sanitation and the best ally to keep the urban supply network in perfect condition.

Our knowledge of the sector and our accumulated experience over the years allow us to comment in this article on the main types of sewage systems and explain what differentiates the different systems from each other.

What types of sewer systems are there?


There are different types of public sanitation system that we will explain to you in the following list:

Unitary system

They are those systems formed by a single conduit for the evacuation of the different types of domestic and industrial wastewater and rainwater discharged in the area.

Separative system

They are the system that have two separate channels independently for domestic and industrial wastewater and for rainwater.

Pseudo-separative system

Pseudo-separative systems are halfway between unitary systems and separative systems. They are those that have separate conduits to isolate wastewater and rainwater in the street, but not in the homes of individuals and companies.

Doubly separative system

The systems that are included within this typology are those that have a network for domestic wastewater, another for commercial and industrial wastewater and another for rainwater.

How are the different sewer systems different?

The typologies of sanitation systems that currently exist differ in their function and constitution.

While the unit system is a unique construction to evacuate both wastewater and rainwater, the function of the separative system is to evacuate wastewater and rainwater separately, through two different pipes.

On the other hand, in a pseudo-separative system the street sanitation network includes two conduits to separate waste and rainwater and a single one in the network of private homes and companies.

The doubly separative systems are distinguished from the rest of the system because they assign a different evacuation channel for the wastewater that is channeled through the system of individuals and those of the companies and that have a different evacuation channel for rainwater.

Advantages of unit system


Unitary systems present an important economic benefit , since they only involve the installation of a conduit. In addition, the maintenance of this type of system is cheaper than in the case of other systems. In this type of network, the rainwater cleans the pipes as they carry the accumulated dirt in the sewers.

Corrosion due to the action of hydrogen sulfide (corona effect) is lower, since the ducts have larger dimensions than in the case of other types of network that favor their ventilation. In addition, as the action of rainwater cleans the pipes, this corrosion has less incidence.

Disadvantages of unit system

The main drawback is that since the treatment plants cannot handle the rainwater flows, they must be separated before reaching the treatment plant. This makes the urban sanitation process more expensive.

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In addition, these stormwater is separated into spillways. This is where we find the second disadvantage of this type of sewer system. And is that the spillway spill is polluting. The costs of purification increase.

Advantages of separative system

In this type of network, the purification regime acts more regularly , since it is not altered by the rains.

In addition, as in this type of network the wastewater is not mixed and the rainwater does not produce polluted water discharges . This implies a reduction in purification costs , compared to the water coming from the unit system.

Disadvantages of separative system


The main drawback of this type of network is the initial investment. It involves a high initial cost , compared to the unit system.

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In addition, this type of network also implies higher cleaning and maintenance costs. If the ducts are not cleaned well, the corona effect becomes very intense.

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