6 Things You Need To Know About Wastewater
Water is essential for life. But all the water on Earth’s surface combined only makes up about 0.001% of all the water on our planet, and it’s not evenly distributed. Much of this precious resource is locked away in ice caps at the North and South Poles, while vast stretches of dry land are left without a drop to drink. The average person needs between 2-3 liters (6-9 cups) per day for basic hygiene and drinking alone – that’s around 150 gallons or 600 liters each month. And we’re using more every day: as populations grow and developing nations industrialize, demand is increasing by 1% per year.
What is wastewater?
Wastewater is the water that goes down our drains and toilets when we’re done with it. It includes both sewage – the black water humans excrete from sinks, bathtubs, toilets, etc. – and stormwater runoff, also known as gray water. While most of us don’t think about wastewater until it’s time to flush, it’s important to understand what happens to this water once we’re done using it. After all, wastewater is one of our most valuable resources as we use it in wastewater treatment plants and stormwater management, among many other ways. Around 32% of homes in the US are equipped with appliances that can be used with gray water, including washing machines, dishwashers, sinks, showerheads, and toilets. Gray water is also sometimes purified for reuse as irrigation water or even drinking water.
Where does wastewater come from?
Wastewater comes from every household in the world – rich or poor, urban or rural – and flows through a complex network of underground pipes on its way to a sewage treatment plant. In the U.S., homes usually have a septic tank or a connection to a municipal sewer system that carries wastewater from your house to a larger sewage treatment facility in your community. In developing countries, on the other hand, most people have no sanitation infrastructure and must rely on inexpensive latrines built above nearby waste-collecting ponds.
What happens to wastewater once it gets to the treatment plant?
At a sewage treatment plant, both sewage and stormwater are combined with oxygen, microorganisms, and sunlight to treat the water so it’s clean enough for humans to swim or fish in. The process is called wastewater treatment and it works by taking advantage of the fact that microorganisms love to eat pollution and other stuff we don’t want in our water. Wastewater goes through three main treatment processes: solids separation, liquid clarification (also called biological treatment), and liquid disinfection.
Sewage treatment plants include several different steps to remove most of the pollution from wastewater, including solid waste (like human excrement and unflushable toilet paper) and liquid waste (soaps, chemicals, oils).
How does wastewater get treated?
The first step is for sewage treatment plants is to separate solid waste from liquid waste. Solid waste (called sludge ) is thick and watery materials that are run through treatment screens or presses to remove as much solid waste as possible before the wastewater moves on to the next stage of treatment.
Liquid waste (called supernatant ) is then piped to huge tanks called basins where bacteria digest most of the organic matter in the wastewater. The liquid that’s leftover after this process – which can still look pretty mucky – gets mixed with microorganisms and exposed to oxygen, sunlight, and carbon dioxide so it becomes purified water.
What happens to wastewater after it leaves our homes?
After the sewage has gone through the first two processes, it’s ready for the last step, which is to clean the wastewater as much as possible before it’s released back into a nearby river or ocean. This stage is called disinfection because the wastewater gets treated with chlorine or another chemical to kill any remaining pollution. Before it enters the water, wastewater goes through a second round of solids separation and liquid clarification to get rid of all extra materials that could make the water murky.
The cleaned wastewater then typically goes into a holding tank where sediments settle at the bottom and oxygen from air bubbles helps remove ammonia from the water. Finally, after being treated with chlorine or another chemical to kill germs, wastewater is released into a nearby body of water like a river or ocean.
What happens to wastewater after it leaves our homes?
Now that the water is a more manageable 120 million liters each day, treatment plant operators need to make sure that bacteria levels are low enough that the water is safe for humans to come in contact with. The most common way to do this is chlorination, which kills bacteria by adding chlorine (Cl) to the wastewater. Finally, once the treatment plant is satisfied that all of the water is clean, it’s released into natural waterways like rivers or oceans.
The wastewater we produce each day is a valuable resource that’s used in many different ways. After going through a complex process of separation, clarification, and disinfection, the water is clean enough to be released back into our natural environment. We need to understand where our wastewater comes from and what happens to it after we’re done with it so that we can continue to use this valuable resource responsibly.