How Does A Wastewater Treatment Plant Work?

Wastewater treatment is essential for minimizing water pollution that can disrupt delicate ecosystems, interfere with food chains, and transmit diseases. As the urban population continues to rise, this increasing population density can generate more organic waste and wastewater, which calls for proper treatment and more efficient wastewater treatment plants.

A dwindling supply of clean water necessitates more cost-efficient, high-quality wastewater treatment systems. These modern treatment plants employ the latest technologies to decontaminate dirty water before funneling the water back into these ecosystems.

What pollutants wastewater treatment removes?

A wastewater treatment system harnesses the power of technology to facilitate wastewater treatment and BOD compliance. Common pollutants include Biochemical Oxygen Demand (BOD), phosphates and nitrates, pathogens, metals, Total Suspended Solids (TSS), Total Dissolved Solids (TDS), and synthetic chemicals. High BOD levels indicate an elevated biodegradable material concentration, resulting from the presence of pollutants like fertilizer runoff, fecal waste, or food processing wash-down or cleaning.

Releasing phosphates and nitrates to the environment may cause extensive algae, phytoplankton, and weed growth and high BOD. It can also result in eutrophication or water body deoxygenation, which kills aquatic life and potentially causes hypoxia. Pathogens like viruses, bacteria, and fungi, which transmit through polluted water, cause various illnesses such as hepatitis A, cholera, giardiasis, dysentery, botulism, and salmonellosis.

Harmful metals end up in wastewater due to various industrial processes. These metals can threaten human health and environmental well-being alike. Much like the rest of the contaminants, TSS (inorganic and organic suspended solid materials) and TDS (metals, anions, salts, cations, or minerals) damage the crops, kill aquatic life, humans, and may affect irrigation. The typical synthetic chemicals in wastewater are DDT, diethylstilbestrol, PCBs, and dioxin.

The wastewater treatment process

Wastewater treatment plants oversee three main stages: primary, secondary, and tertiary. However, some pollutants require advanced treatment, such as the quaternary, which involves fine filtration or oxidation processes to lower emergent pollutants dissemination.

Every stage targets different pollutants, so the water becomes cleaner as the process advances. Depending on the original water’s quality and the intended purpose for the treated water, certain or a combination of treatment stages are initiated.

Primary wastewater treatment

Primary wastewater treatment involves momentarily holding the wastewater in a tank to allow the settlement of heavy solids at the bottom and lighter solids, grease, and oil to float. Water treatment experts contain these loose materials while the water moves to the next step or discharges. Sedimentation occurs after the filtration of larger substances. During this process, wastewater goes through multiple filters and tanks to separate contaminants from water.

Secondary wastewater treatment

Secondary wastewater treatment operates on a more profound level than the primary stage and eliminates suspended and dissolved biological matter. It usually involves the use of native water-borne microorganisms released in a controlled habitat.

Treatment plants may have to eradicate organisms through a separation process upon completing the treatment before discharging or advancing to the tertiary stage. The secondary step will involve performing biological content degradation through aeration, biofiltration, and oxidation ponds.

1. Aeration

Aeration is a timely process that can last for 30 hours and is equally instrumental, as it involves combining wastewater with a microorganism solution. Aeration gives the bacteria oxygen to stabilize and treats the wastewater by biodegrading the organic substance containing carbon to create carbon (IV) oxide and water. Without sufficient oxygen, breakdown has to occur under slow and odorous septic conditions, resulting in an incomplete transformation of pollutants.=

2. Oxidation Ponds

The large stabilization ponds or lagoons are mainly used in warmer areas to treat wastewater through bacteria, algae, and sunlight interaction. Algae relies on energy from the sun, inorganic compounds, and carbon (IV) oxide released into the water by bacteria to grow. Through photosynthesis, algae release the oxygen required by aerobic bacteria. Sometimes, experts introduce mechanical aerators to provide more oxygen.

3. Biofiltration

Biofiltration is a standard method in greywater recycling, wastewater treatment, and aquaculture, as it helps raise the water quality while lowering water replacement. Biological filters eliminate contaminants through biodegrading natural components, filtering suspended solids, and absorbing micro-pollutants. Biofiltration processes are typically aerobic, so the microorganisms need oxygen for metabolism.


The biofilm receives oxygen counter-currently or concurrently with the water flow. Biofilters have low operating expenses, a simple structure, a robust process, and resistance to shock loads.

Tertiary wastewater treatment

Its primary purpose is to increase the water quality to meet industrial and domestic standards or the specific safe discharge requirements while also removing nitrates and phosphates. For municipal wastewater treatment, this stage also involves eliminating pathogens, making the water safe to drink. The tertiary treatment process is usually performed using substances such as sand and activated carbon.


Successful wastewater treatment requires reliable and high-quality equipment, as the living organisms’ well-being and the environment may depend on it. Wastewater treatment plants can achieve proper wastewater management change by understanding the process and components found in their local water sources.

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About Salman Zafar

Salman Zafar is the Founder of EcoMENA, and an international consultant, advisor, ecopreneur and journalist with expertise in waste management, waste-to-energy, renewable energy, environment protection and sustainable development. His geographical areas of focus include Middle East, Africa, Asia and Europe. Salman has successfully accomplished a wide range of projects in the areas of biomass energy, biogas, waste-to-energy, recycling and waste management. He has participated in numerous conferences and workshops as chairman, session chair, keynote speaker and panelist. Salman is the Editor-in-Chief of EcoMENA, and is a professional environmental writer with more than 300 popular articles to his credit. He is proactively engaged in creating mass awareness on renewable energy, waste management and environmental sustainability in different parts of the world. Salman Zafar can be reached at or

4 Responses to How Does A Wastewater Treatment Plant Work?

  1. Pingback: Microbial Biodiversity and Sustainable Development | EcoMENA

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  3. Henry Killingsworth says:

    It was interesting to learn more about the wastewater treatment process. I would imagine that it would be important to use the right process in areas of a high population. It would be important to be able to provide clean water for the residents in an area.

  4. Pingback: As Goes the Air Goes the Effluent - Coalition for the West Credit River

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