What is the sewage treatment process?

What is the sewage treatment process, and how does it work exactly? That’s a question we answer often here at OMDI, so our experts put together this article to explain the process in more detail.

The sewage treatment process is a method employed to break down wastewater. It happens within a sewage treatment plant, and can be employed on an industrial scale or a smaller one in the backyard of homes that can’t be connected to the main sewerage systems.Sewage treatment plants are a popular way to dispose of wastewater, and they are kind to the environment too. 

What is sewage?

To understand how the sewage treatment process works, you first must understand what actually constitutes sewage. 

Sewage is the wastewater that’s produced by a household, or a business, which is then ordinarily pumped into a main sewer system. It’s important to note sewage is liquid, and not solid. 

This liquid wastewater can also be treated on-site by a sewage treatment plant, which can be constructed in your back garden or where you work. They operate according to the same principles regardless of the volume of sewage they are expected to process.

What does the sewage treatment process do?

The sewage treatment process is a way to turn wastewater into an environmentally-friendly product. While sewage treatment plants are similar to septic tanks, this is where they differ.

Septic tanks produce wastewater which is released into the ground. Meanwhile a sewage treatment plant creates wastewater that is treated, essentially by separating solid and liquid waste. 

The liquid waste, or wastewater, is is subjected to the sewage treatment process; a combination of physical, chemical and biological mechanics that we describe in greater detail below.Together they break down harmful bacteria, purifying the wastewater and then releasing it into waterways without risking harm to the environment. The discharge can be made into areas where you would not normally be allowed to build a septic tank. Because the sewage is effectively treated and decontaminated, it can be released directly into waterways. This makes a sewage treatment plant a popular choice for homes in the countryside, where they might not have direct access to the main public system and might also be surrounded by waterways or areas of environmental concern. 

Physical, chemical and biological elements of the sewage treatment process

The sewage treatment process involves several distinct stages that conclude with a wastewater product that can safely be discharged. They include:

Pre-Treatment

When household waste begins the sewage treatment process, it will first enter the pre-treatment stage. This is essential to the process because pre-treatment removes any large objects. That includes rubbish such as plastics, or food waste like eggshells, that have made their way into the waste.That is important because it prevents the sewage treatment plant from becoming blocked.

Primary treatment

The primary treatment stage involves waste being pumped into a settlement zone. There, other large solids are separated from liquid. A settlement tank allows heavier solids to rest at the bottom, while liquid and lighter solids remain at the top. Bacteria is present in the settlement tank, which works anaerobically or without oxygen. It begins the process of breaking down harmful substances.

Secondary treatment

The liquid and lighter solids that collect in the primary treatment process are siphoned off for a secondary treatment stage. Aerobic bacteria in the plant – using an oxygen-fuelled process – deconstructs harmful substances in the wastewater. It attacks harmful substances such as ammonia which would otherwise be a cause for environmental concern if released.It essentially digests them, leaving behind only water.This is known as the biological treatment zone. 

Tertiary treatment

The final stage is tertiary treatment. By now the most harmful substances will have already been broken down and removed. Next the wastewater needs to be as clean as possible, and bacteria or chemicals account for any remaining substances that could damage the environment. Afterwards, the wastewater ought to be clean enough to be discharged into nearby watercourses without causing any harm. 

What about all that sludge?

At the end of the sewage treatment process, only the wastewater is safe to be discharged. You’ll still left with solids, or what’s simply known as sludge. It isn’t treated, and it can’t be discharged. 

Over time, sludge will build up inside a sewage treatment plant. At some point, it needs to be emptied. We recommend that should be done at least every 12 months, preferably by a trained professional do this. At the same time, they can also service your sewage treatment plant to ensure it can continue to run efficiently.

If you don’t remove the sludge, the sewage treatment process will begin to suffer. It can cause blockages, and also stop the discharge of wastewater. If you pick up a foul odour coming from your plant, then you know it’s time to call for a service.

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OMDI are leading experts in the field of waste removal. 

If you’re looking to install, or need to service, a sewage treatment plant or septic tank then give us a call today.Contact our experts at OMDI for a free, no-obligation quote.