We introduce pollutants and contamination to our environment whenever we use water. Even if nature has its way of coping with these pollutants, it can still get overwhelming.
That's where sewage treatment comes in.
Here's everything you need to know about sewage treatment plants and their processes.
What Is Sewage Treatment?
Sewage treatment is the man-made process of removing any impurities in wastewater.
It's how we ensure the water quality is safe enough to mix with natural bodies of water or aquifers.
We base water pollution on the concentration of these impurities in the water.
These can come from natural conditions and human activities. Knowing these conditions prevents us from returning polluted water to our water supply and nature.
These wastewater treatment plants help reduce the levels of pollution. The process makes it safe enough to mix in with nature's supply.
Why Should You Treat Waste Water?
In the past, a sewer system was more low-tech. People would directly return wastewater to nature. However, this has led to waterborne diseases and pollution.
Over time, we've experienced a lack of fresh water. A wastewater treatment system allows us to use domestic wastewater for our homes.
Bigger communities have started to use their industrial wastewater to supply their water shortage.
FUN FACT: Treated wastewater is also used as drinking water. It is common in parts of the world where there is a shortage of potable water.
The wastewater generated by our everyday activities also affects our other resources. We're helping ourselves and our environment with active wastewater treatment plants.
What Is an Onsite Sewage Facility?
An onsite sewage facility is a multi-stage wastewater treatment. It includes multiple systems, from collecting and treating to releasing treated water.
Homes and businesses can use these to better recycle their wastewater.
Rather than transporting waste water to a plant, water is treated and released into soils.
What Are the Three Stages of Sewage Treatment?
As soon as wastewater enters the sewer system, it undergoes preliminary treatment. This process removes any large and solid material using bar screens.
What about the smaller particles?
The primary and secondary treatment systems filter out about 90% of these particles. The remaining 10% are then cleaned out in the tertiary treatment.
Here are the specifics of what happens in a wastewater treatment plant.
Primary Treatment
During primary treatment, the water flows into the primary settling tanks. It allows solids to settle at the bottom of the tank, gathering as primary sludge.
Lighter solids, such as feces and grease, would float to the top. These suspended solids are then scraped off, leaving clarified water.
The primary treatment removes about 60% of the solids by stirring the waste water in settling tanks. This step reintroduces oxygen into the water.
Secondary Treatment
The secondary treatment allows biological processes to help clean wastewater.
The matter is removed biologically by using specific bacteria and sludge in a controlled environment.
The oxygen encourages bacterial growth. It also allows for anaerobic bacteria to feed on organic material.
Some suspended growth systems also use activated sludge. It combines decomposing bacteria from the sludge with wastewater to consume the biological matter.
Some use fixed film systems for secondary treatment. It gives the bacteria a place to grow as water passes through it.
The secondary sludge is then separated into a sand-drying bed for sludge treatment. This treatment is called sludge digestion.
The sewage sludge is later used to generate electricity.
The secondary treatment removes more than 90% of the suspended solids from the remaining liquid.
Tertiary Treatment
The final step of the treatment system is tertiary treatment. It can involve many chemical processes that make the water safer for the environment.
It's also the step that has nutrient removal, preventing contamination of natural conditions.
One is effluent polishing. It is where we release partially treated water into a natural body. It helps the water adapt to the local conditions of the environment.
If the water has large quantities of nutrients, it may undergo more processes. These nutrients can disrupt the local conditions by encouraging algae growth.
We can remove nutrients, such as nitrogen and phosphorus, through chemicals or bacteria. It allows the effluent water safe to mix in with clean water.
Some also store water in lagoons. It allows aquatic organisms, algae, and bacteria to filter out the nutrients.
After the tertiary treatment, we get clean water safe for reuse for any human activity.
What Are the Different Types of Sewage Water
Wastewater comes from various human activities and nature.
Domestic sewage is any liquid waste we dispose of in our own homes. Industrial sewage is liquid from businesses, factories, and commerce.
Rainwater runoff can also count as wastewater. These enter our sewage systems through our pipes.
These types of wastewater can be further categorized based on their contaminants, chemicals, and solids.
Storm Water
Rainwater runoff, or stormwater runoff, is all wastewater from rain or snow.
These may contain leaves, twigs, and other particles from nature. It may also contain harmful substances washed off roads, rooftops, and parking lots.
Substances are also collected during evaporation. It then rains down onto structures and joins our sewage systems.
There is an increasing amount of toxic chemicals in rainwater and our structures. Treating these waters before reusing or returning them to nature is best.
Grey Water
Grey water is any liquid that hasn't come from plumbing fixtures. These can come from domestic activities such as bathing, dishwashing, and laundry.
It requires little to no treatment, and you can reuse it immediately. However, if you store grey water for more than 24 hours, it's advised to treat it before use.
Black Water
Black water includes human waste, such as food scraps, grease, and feces.
It may also contain pathogenic organisms. They may contain biohazards which can be dangerous to living things.
This type of wastewater requires treatment before you can reuse it.
Frequently Asked Questions
You might have more questions about wastewater treatment and its processes.
We've gathered the most common questions to help you with your research.
The wastewater generated by nature and our activities has caused many problems for centuries.
Our wastewater has affected the life spans and reproduction of aquatic life. It also caused a shortage of drinking water for both humans and wildlife.
Industrial waste in surface water has also resulted in contaminated waterways and soil degradation.
There are also centralized sewage treatment plants. This combined sewer system mixes both industrial and domestic wastewater.
However, differing levels of contaminants in a combined sewer may still be dangerous.
With a proper treatment process in place, we are reducing these effects to make them more manageable for nature.
You can generally use wastewater for various things that don't need potable water.
You can use grey water for domestic needs because it has less toxic materials. It includes gardening, flushing toilets, or washing clothes.
Black water is best used for subsurface irrigation of gardens.
Products of sludge digestion are filled with nutrients. These can be used as fertilizers or energy sources.
Aerobic processes need the presence of oxygen for them to work. You would need large treatment ponds or aeration tanks to introduce oxygen to biomass.
This system would need to circulate or aerate wastewater.
On the other hand, anaerobic processes don't need oxygen to treat wastewater.
You'll only need to put wastewater in an enclosed, airtight digester. It prevents the sludge from getting exposed to air.
Anaerobic processes have lower operational costs and energy demands compared to aerobic processes. Yet, they are a lot slower and would need upfront capital.
Conclusion
Something as simple as a sewage treatment plant can greatly impact our environment and water supply.
Water isn't as infinite as we think. We are actively finding ways to reuse our wastewater to make ends meet.
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