Wastewater Treatment

Know About Wastewater and its Treatment Process

The wastewater treatment is required for removing waste and other unwanted material from sewage. The process involves several stages for removing harmful water substances and producing safe water that is not a threat to the environment. In the wastewater treatment process systems, effluent from factories, homes, and businesses drains into pipes. The effluent then leads to a treatment center, and then it passes through the wastewater treatment process.

Source: Sahuarita Official Website

What is Wastewater?

Water is discharged after use from various locations such as households, industries, medical labs, and other agricultural and transport activities. This used water becomes wastewater due to changes in its quality, composition, and temperature with time.

Types of wastewater

Broadly, wastewater can be categorized into :

  1. Sewage waste: originating from all surrounding households and industrial toilets and sinks.
  2. Industrial waste: originates due to various construction, industrial and commercial activities, but is different from sewage waste. 
  3. Municipal waste: wastewater originating from localities and municipalities that have mixed sewage waste, other water sources mixed into it and flowing through sewers.

Why wastewater treatment is important?

A very important but often ignored question. Why do we need to recycle and reuse wastewater? Water, being a scarce natural resource, is very important for the survival of all species on this planet. By wastewater treatment, it can be recycled and reused for various processes and applications, depending on the water quality and parameters of the recycled water. There are different pollutants in the wastewater that need to be treated and removed to make it reusable. 

  1. Biochemical Oxygen Demand (BOD): It refers to the amount of dissolved oxygen needed by aerobic organisms to decompose organic matter into smaller molecules. High levels of BOD due to fecal or fertilizer waste can reduce the amount of oxygen in the water thereby leading to algae blooms and severely affecting aquatic life.
  2. Nitrates and Phosphates: These enter the wastewater through human waste, food waste, detergents, and pesticides, which also affect oxygen levels in the water.
  3. Metals: Various metals such as lead, cadmium, copper, mercury, and manganese are commonly found in wastewater and are very toxic to human health and the environment.
  4. Pathogens: Bacteria, fungi, algae, and other microorganisms have the potential to cause various health issues mainly digestion relative problems. 

Wastewater Treatment Process

The wastewater treatment process generally involves four noteworthy stages. These four states are preliminary treatment, primary treatment, auxiliary or secondary treatment, and sterilization.

Continue reading this blog to get insights into these four states.

Preliminary treatment

Preliminary treatment is the screening stage of the treatment process. At this stage, the wastewater is pumped through screens that comprise bars a few inches apart. The screens eject bits of junk such as wood, clothes, paper, glass, plastics, and other comparable things. These items are removed from the water for the safety of the pumps and other gear in the next stages. After the successful removal of the materials, the wastewater is pumped into the sedimentation tanks.

Primary treatment

In this stage, the wastewater comes to the sedimentation tanks. The water remains in the tank for two to three hours. This lets the lighter junk such as oil and small plastic material to float. On the other hand, heavier solids reach the base of the tank. This way, the floating junk is skimmed from the highest point of the tanks.

The filtration methods that are applied to the industrial application include oils waste removal, ultra-filtration, Nano-filtration, pulp, and paper removal – paper industry, color removal – textile factories, laundry effluent removal, and ultra-filtration.

After the filtration of small junk, primary sludge (also known as heavier solids) is pumped through gadgets that are pumped through devices that use radiating power for isolating granules of different sizes which are then expelled. The treated wastewater (to some extent) from this stage streams to the secondary treatment framework.

Auxiliary treatment

In the auxiliary treatment stage, sludge and air are pumped into the tanks for further wastewater separation. The air pump blends the muck and wastewater by fortifying the growth of oxygen-utilizing microbes and other bacteria that are usually found in the sewage.

These bacteria or microorganisms ingest much of the organic substance that still contaminates the water. This stage of the Wastewater Treatment Process Systems may usually consume five to seven hours.

After this, the last sedimentation tanks that are much like the ones in the primary stage are used to settle relatively bigger particles at the base as auxiliary much. The rest of the auxiliary muck is removed from the sedimentation tanks.


Sterilization is the fourth stage of the wastewater treatment process. It is typically the use of a chemical or physical procedure for eliminating all microorganisms. It also includes the infusion of a chlorine process into the wastewater in a contact that lasts around half an hour. Despite connecting propelled wastewater treatment necessities, a chlorine contact time may span two hours to remove high levels of solids. It is now again required for employing a specific water system for wastewater. The chlorine measurement depends on the quality of the wastewater and the different variables, yet doses of 6 to 20 mg/l are basic.

These are the four stages of the wastewater treatment process.