Have you ever considered reusing water that is wasted or that goes into sewage? 

No? 

Well, you’ll be surprised to know that the water we waste in domestic, industrial, and commercial places can be reused with the help of sewage treatment plants (STP). 

Yes, You read it right!

A sewage treatment plant is a complete process that purifies sewage water and makes it reusable. It collects the wastewater, treats it accordingly, removes harmful chemicals and other particles, and makes it reusable. 

If sewage remains untreated, its nitrogen and phosphorus will increase environmental and water pollution. So, to get rid of waste and reduce pollution, sewage treatment plants are what we need.  

According to WHO statistics, approximately 2.2 billion people lack access to safe drinking water, and untreated sewage is one reason for this. Proper sewage treatment plants can reduce the risk of water-borne diseases, protect human health, and ensure access to clean water. They remove contaminants from water before releasing it for reuse. 

There are a few stages involved in the treatment of sewage water:-

• Preliminary treatment 
• Primary treatment
• Tertiary treatment

When water undergoes Sewage treatment, it can be considered for reuse. Let’s discuss how STP (Sewage Treatment Plan) works in detail. 

How Does The Sewage Treatment Process Work?

Sewage treatment plants run wastewater through multiple stages and treat it accordingly to make it reusable.

The Preliminary Stage

Water from the sewage moves into the treatment plant and vents through multiple screens to separate the water from the solid waste. 

These screens remove objects like paper, bags, plastics, rags and metals. Some STP plants use rough and fine screens to remove waste material from water. 

Once the larger object is separated from the water, the remaining will be treated in the next step.

Primary Treatment

Water from the preliminary stage passes to the sedimentation tanks, where the solid substance present, known as sludge, settles. While the lighter particles form a layer above water known as scum. 

The water that gets filtered moves to another tank for secondary treatment, leaving the sludge behind. Sometimes, the collected sludge is treated correctly and used as fertilizers.

Secondary Treatment

Secondary sewage water treatment, also known as biological treatment, removes biodegradable organic matter (BOD) and suspended solid particles through filtration.  

This process is successful because microbes and biological agents consume and degrade the organic matter. As a result, the remaining smaller particles are removed from the water, making it purer than the primary water treatment. 

It is an important treatment method for sewage treatment plants. As it involves a physical primary treatment process and microorganisms for water waste. 

This treatment process uses three methods, which are

1. Anaerobic

Anaerobic water treatment removes the bulk of chemical oxygen demand (COD) from the wastewater and converts it into biogas (carbon dioxide and methane). 

The methane produced with anaerobic treatment is used to fuel Sewage treatment plants. This treatment is ideal for plants that treat water with biodegradable material such as food waste, animal waste, or other organic matter.

2. Aerobic

Aerobic treatment uses aeration and microorganisms, which are metabolic processes that all require oxygen. With the aeration process, the oxygen content is increased in water.   This allows microorganisms to break down and consume the water waste that is separated through sedimentation. 

Activated sludge treatment is most common in the aerobic process of secondary treatment (STP). During this STP, secondary clarifiers mix and settle the sewage with raw and primary sludge. 

After this, an air compressor is used in the aeration tank to allow sludge to break down. The different water treatment plants perform this process using equipment such as media filters or diffusers.

3. Anoxic

The anoxic process treats water using microbes that have metabolic processes that don’t need oxygen. However, it can happen in the form of nitrates and sulfates, which are all forms of oxygen.

This process helps to identify wastewater with high nitrogen, which is further converted to nitrates using trickling filters.

Tertiary Treatment

Tertiary treatment is an advanced method for treating water. It removes contaminants that remain after the secondary treatment.  

It involves physical-chemical separation techniques like the absorption of carbon, membranes for advanced filtration, reverse osmosis and more. 

This involves water treatment in various ways:-

1. UV Disinfection:

This treatment often uses UV lights to remove the harmful particles from the water and make it safer.

2. Ion Exchange:

Water-softener substitutes such as calcium and magnesium ions help treat water. 

3. Chlorination:

Several STPs apply chlorine to the water to disinfect and make it usable. Because chlorine is cost-effective, it can be used in large amounts to purify the water.

4. Ozone Treatment:

Ozone water treatment is a chemical-free process that acts as an oxidizing agent and disinfectant. This allows the water to be reusable for drinking and other purposes.

5. Membrane Filtration:

Membrane filtration uses a thin layer of semi-permeable membrane that has small pores to filter water. It uses ion diffusion in the osmosis process, helping to drive water away from the dissolved substance.

6. Activated Carbon Adsorption:

It helps remove organic compounds like odours and residual chemicals from water through adsorption. This makes the water cleaner and safer to release. 

Conclusion

Sewage treatment plants are important for transforming wastewater into reusable water through physical, chemical, and biological techniques. 

With 72,369 per million litres of sewage generated per day, only 31,841 million litres of water is treated by sewage treatment plants. This gap makes it more important to have more and more plants for treated sewage water.

Advancement in technology have brought modern STPs with advance automation. These plants remove water impurities and odour, resulting in protecting human health along with being environment-friendly.

Also Read More About: Water Recycling: Needs, Benefits And Uses