We would have continuous access to clean water that is fit for human consumption right out of the tap, similar to the most developed nations in the world, if our rivers and lakes were never polluted in the first place and if each of us cleaned up our own mess instead of dumping it on the planet and its precious water source. Metropolitan cities’ water management and treatment systems are a dystopian nightmare.Untreated sewage, which makes up a startling 70–80% of all sewage in this nation of 135 billion people, is the main cause of water pollution in India. Knowing the importance of sewage treatment plant, one is curios to know about its working. This article is all about the working of sewage treatment plant and also the introduction of several related terms. So, let’s begin…

What is waste water?

Water that has been utilised for home, commercial, and industrial purposes is referred to as wastewater. Since the makeup of all wastewaters is continually shifting and extremely changeable, it is challenging to give a clear-cut definition of the term effluent. 99.9% of wastewater is made up of water, while the remaining 0.1% is eliminated. Organic material, bacteria, and inorganic substances are all present in this 0.1%. Various habitats, including lakes, ponds, rivers, estuaries, streams, and seas, are exposed to wastewater effluents. Storm runoff also counts as wastewater since it contains dangerous compounds that are washed off of parking lots, rooftops, and highways.

Sewage treatment plant

Why are sewage treatment plants necessary?

Environmental conservation

The ecological impact of dumping untreated sewage back into the ecosystem is catastrophic. The pollutants in sewage may harm plants and animals, render ecosystems dangerous for them to live in, and make drinking water unhealthy. These negative effects may result from contaminated wastewater from several industries, including the oil and gas sector. The spread of hazardous algal blooms is another frequent environmental impact linked to wastewater. When wastewater containing high quantities of fertilisers like nitrogen or phosphorus enters freshwater sources, these blooms frequently develop. Eutrophication is a process where the nutrients build up in freshwater.

Nitrogen and phosphorus are essential for the growth of algae, therefore when they are consumed, the algae start to outgrow their environment. They frequently include toxic substances and use up a lot of the oxygen that is there. In the end, they often destroy aquatic species like fish and shellfish and choke out the local flora.

Human health

Untreated wastewater discharge into the environment has a number of detrimental implications on human health. For instance, a significant portion of the nearly 1.6 million diarrhea-related fatalities that occur each year are caused by untreated sewage outflow. 1.8 billion people use polluted water sources worldwide, and unsafe water, inadequate sanitation, and poor hygiene habits are to blame for 88% of diarrheal fatalities. Crops grown on farmland that is watered with untreated wastewater may also be harmful to human health.

Typhoid, dysentery, cholera, and schistosomiasis are just a few of the diseases that are prevalent in many areas of the world when sewage is not properly treated. Compared to malaria, measles, and AIDS put together, these illnesses claim the lives of more children.

Water shortage

In many parts of the world, a major issue with water scarcity exists. It is believed that water shortage affects two-thirds of the world’s population at least once a year, and by 2030, severe water scarcity might force up to 700 million people from their homes.

Processes for storing and reusing water are necessary for reducing water shortage. The treatment of wastewater is a crucial component of these procedures. If the treatment techniques are rigorous enough, thorough, effective wastewater treatment frequently makes wastewater appropriate for reuse in industrial operations or even occasionally as drinking water.

Phases of a sewage treatment plant

Primary, secondary, and tertiary treatment are the three main phases of wastewater treatment. Before the primary treatment procedure, many plants additionally include a pretreatment stage.

The wastewater enters pretreatment tanks in a typical municipal sewage treatment plant model before going through primary and secondary treatment. Tertiary treatment is not used by all plants; however, it is frequently used when wastewater must reach a specific standard.


Larger solid particles are typically removed from the wastewater using physical procedures like filtering and settling during pretreatment. Wastewater enters the treatment tanks and basins as an influent during pretreatment. Larger objects like tree branches, leaves, and plastic trash are filtered out by massive bar screens. Grit chambers allow for the precipitation of minute particles including dirt, gravel, sand, coffee grinds, and eggshells, while equalisation tanks (EQ tanks) moderate water flow to encourage settling.

The kind of wastewater is typically a factor in pretreatment. If the wastewater contains a lot of oil and fat, the treatment facility may utilise blowers to generate an easily-removable greasy froth or treatments to skim those contaminants from the water’s surface. Other plants could postpone these actions until the initial treatment.

Primary treatment

Primary treatment is the next step in the wastewater treatment process. Its major objective is to remove particles from wastewater using gravity and ongoing physical processes. The pretreated water gathers in primary clarifiers during basic wastewater treatment. The effluent is allowed to rest for some time to allow more contaminants to precipitate out. Some of the solid stuff may be collected by mechanical scraping equipment, which will then transfer it to the sludge treatment equipment to be used in the activated sludge process. Oil and grease will be skimmed off the surface during primary treatment if the facility didn’t remove them during pretreatment. In a procedure called as saponification, certain plants combine the skimmed lipids with alkali materials.

Secondary treatment

Bacterial methods are used in secondary wastewater treatment rather than physical ones. To break down more of the solid pollutants in the wastewater, it employs advantageous microorganisms.

There are several primary modalities of secondary therapy.

Anoxic Treatment

Although some oxygen may be present in the form of nitrates, nitrites, or sulphates, free molecular oxygen is not available throughout the anoxic therapy. The denitrification of wastewater with a high nitrogen concentration frequently usesthis method. It makes use of bacteria whose metabolic activities don’t require oxygen.

Anaerobic Treatment

In the lack of oxygen, anaerobic therapy is also used. Anaerobic therapy takes place in the absence of all forms of oxygen, unlike anoxic treatment, which happens when molecular oxygen is absent but bound oxygen may be present in other compounds. In covered digestion lagoons, anaerobic bacteria may break down organic waste during anaerobic treatment.

Wastewater having a high concentration of biodegradable materials, such as concentrated municipal wastewater, slurry from animal dung, and wastewater from food processing, benefits from aerobic treatment. Because there is no equipment needed to combine oxygen with the wastewater, it is less energy-intensive than anoxic treatment.

Aerobic Treatment

Because the microorganisms involved need oxygen for their metabolic functions, aerobic treatment takes place in the presence of oxygen. The wastewater treatment facility must contain machinery that can deliver oxygen and integrate it into the wastewater in a process known as aeration for aerobic treatment to occur. Lagoons with surface aerators to mix air into the water may be present at the facility. Or it may employ aeration tanks filled with ceramic or rubber membrane diffusers, frequently in the form of discs or tubes. Air enters the diffusers through pipes on the tank’s floor and passes through a variety of tiny apertures. These holes let out little bubbles of air. Aerobic digestion and the transport of oxygen are made easier by the bubbles as they ascend through the water column.

Tertiary treatment

Additional filtration and disinfection are provided by the tertiary treatment. Tertiary treatment is often optional, in contrast to primary and secondary treatment, which are carried out in the majority of wastewater treatment facilities. When their effluent needs to fulfil exceptionally strict specifications, plants frequently employ it.

Filtration is the initial step in tertiary treatment, followed by some sort of disinfection:


To eliminate residual pollutants from the wastewater, tertiary treatment frequently employs filters like sand filters or carbon adsorption filters. These filters might come in the form of discs, bags, drums, or granulated activated fibre (GAC).


To sanitise the water, chlorine is frequently added at wastewater treatment facilities. Since using chlorine is inexpensive, many municipal plants use this technique.

UV disinfection:

During the last stages of treatment, any leftover bacteria in the wastewater may be sterilised or destroyed using UV light, rendering them harmless.

Ozone treatment:

Some wastewater treatment facilities disinfect by using ozone. Although ozone treatment is more efficient than chlorine, it is costly, necessitates specialised corrosion-resistant equipment, and emits harmful gases, therefore plants must carefully consider the advantages and disadvantages of this treatment.

Ion exchange:

A tertiary treatment method that substitutes neutral ions for harmful ones, much as how a household water softener exchanges out harmful calcium and magnesium ions with neutral sodium ions.

Other plans

The burden on sewage treatment systems and industrial wastewater treatment facilities is growing as a result of pollution issues. Water now contains far more pollutants, heavy metals, and hazardous compounds. To obtain the purified water, modern waste treatment methods and improved wastewater systems that separate pollutants, absorb carbons, and filter the water are employed.

Why choose compactstpplant for your sewage treatment plant?

Make Compactstpplant your go-to supplier for dependable machinery and goods to enhance your wastewater treatment processes. Diffusers, and MBBR systems are available from compactstpplants whether you want to upgrade an existing facility or build a new one. And our qualified engineering teams are delighted to speak with you about your requirements, respond to your inquiries, assist you in troubleshooting, and improve the effectiveness and efficiency of your wastewater treatment.

To order equipment for wastewater treatment or to find out more, contact us right now.Call us at +91-9650608473 for any questions you may have about commercial or industrial RO plant, or you can send an email to enquiry@netsolwater.com  

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