Back to: MICROBIOLOGY 400 LEVEL
Welcome to class!
Hi superstar! It’s wonderful to see you in class again. You’re truly doing great things with your learning, and today’s topic is one that matters to every community in Nigeria and beyond. Have you ever wondered how dirty water becomes clean again before it’s released into rivers or reused? That’s exactly what we’ll be talking about—Primary, Secondary, and Tertiary Treatment of wastewater. This process is like giving water a full beauty treatment—step by step—so it can be safe for people and the environment.
Primary, Secondary, And Tertiary Treatment
Wastewater treatment is a stepwise process used to remove physical, biological, and chemical pollutants from used water. These treatment stages ensure that harmful substances are taken out before the water is released back into the environment.
1. Primary Treatment
This is the first step. It focuses on removing large solid materials and particles that can settle or float.
Screening: Large items like plastics, sticks, and rags are removed using metal screens.
Sedimentation: The water is allowed to sit in large tanks, so heavy particles like sand and faeces settle at the bottom as sludge, while lighter materials float and are skimmed off.
At this stage, most of the physical waste is removed, but the water still contains harmful microorganisms and dissolved substances.
2. Secondary Treatment
This stage removes organic matter and microorganisms that can cause diseases.
It uses biological processes, mostly involving beneficial microbes (like bacteria), which feed on the organic waste in the water.
A common method is the activated sludge process, where air is pumped into the water to encourage microbial activity.
The microbes break down the waste, and then the mixture is allowed to settle again. The clean water moves on, while the remaining sludge is removed.
This stage removes up to 85% of harmful organic matter, making the water much safer.
3. Tertiary Treatment
This is the final and most advanced stage. It removes any remaining chemical pollutants, nutrients, and pathogens.
Techniques used include filtration, chlorination, UV treatment, or using chemicals like ozone.
It removes things like nitrogen, phosphorus, heavy metals, and harmful bacteria or viruses.
After this, the water is clean enough to be released into rivers or even reused for farming or industrial purposes.
In big cities like Abuja or Port Harcourt, tertiary treatment helps protect water bodies from pollution and supports reuse during water shortages.
Summary
- Wastewater treatment is divided into three main stages.
- Primary treatment removes large physical particles through screening and sedimentation.
- It prepares the water for biological cleaning by removing solids.
- Secondary treatment uses microbes to break down organic waste.
- The activated sludge process is a common method in this stage.
- This step removes most disease-causing organisms and organic matter.
- Tertiary treatment removes chemical pollutants and remaining pathogens.
- It involves filtration, chlorination, or UV and ozone treatment.
- After tertiary treatment, water is clean enough for discharge or reuse.
Evaluation
- What is the purpose of primary wastewater treatment?
- How does secondary treatment make use of microorganisms?
- List two methods used in tertiary treatment and what they remove.
Learning how water is treated shows how science solves real problems. You are building the knowledge to protect your environment and help your community. Stay curious and consistent—Afrilearn is right here with you every step of the way. See you in the next class!