If you were asked to write down everything you could recycle, your list would probably include the majority of the most commonly recycled materials, like metal and glass, and perhaps a few items that are somewhat more unusual. But chances are that one very important thing would be missing from your list: water.
Water recycling is not something that people tend to think much about; in fact, many consumers might not be aware that water is actually something you can recycle. But recycling water is not only possible, it’s currently benefitting many communities across the globe. Read on to learn more about what water recycling is all about, and why it’s a good thing.
What is water recycling?
Water recycling involves reusing treated wastewater—water that carries waste from homes, businesses, and industrial operations—for other purposes. The type and degree of treatment for the wastewater depends on the purpose the recycled water is intended for.
For the most part, people use recycled water for non-potable purposes; some common applications include watering crops or landscapes, flushing toilets, cooling facilities like power plants and oil refineries, processing materials in mills and plants, mixing concrete, and filling artificial lakes. In general, recycled water applications with a limited chance of human exposure, like concrete mixing, require less treatment than applications where the chance of human exposure is higher, like landscape irrigation.
Is gray water the same thing as waste water?
If you have renovated your home or built a new home recently, you may have heard the term “gray water,” specifically with reference to the installation of a gray water system. Gray water is a particular type of reusable wastewater that comes from sources like domestic baths, kitchens, and laundries. When you wash your dishes, for example, the leftover water is a form of gray water.
One of the distinguishing characteristics of gray water is that it can be directly reused onsite with minimal or no treatment; if you have a gray water system in your home, for example, the water that you drain from your bath might be used to flush your toilets or water your lawn.
Note that not all domestic wastewater falls into the category of gray water. When water contains human, animal, or food waste, it is known as “black water.”
Do people ever use recycled water for potable purposes?
Most water recycling projects are intended for non-potable purposes, but there are a smaller number of situations in which people use recycled water indirectly for potable purposes. One such example is the recharging of groundwater aquifers with recycled water.
An aquifer is an underground layer of rock that is permeable and water-bearing; drilling wells into these aquifers gives us one of our main sources of fresh water. But when aquifers are heavily drilled, the amount of accessible water in them gradually decreases over time. To mitigate this, people inject recycled water into these aquifers to help augment, or “recharge,” the supply of groundwater. Eventually, municipal water systems use this groundwater, which is why its use as potable water is said to be indirect.
What are some of the benefits of water recycling?
As is the case with all other forms of recycling, there are many important benefits associated with water recycling. These include the following:
Protecting sensitive ecosystems—Water recycling can help protect sensitive ecosystems in several ways. First, it can limit the amount of water that communities divert from plants, wildlife, and fish to serve agricultural, urban, or industrial purposes; when people can use recycled water to supplement demand instead of fresh water, water flows can be freed up to serve vital ecosystems. In addition, water recycling can help prevent wastewater from being discharged into oceans or streams, thus protecting plants and wildlife and their habitats.
Preventing pollution—Wastewater can be a strong pollutant, so when wastewater is sent to a recycling facility instead of being discharged into the environment, the risk of pollution is decreased. In addition, some applications for recycled water can actually make use of compounds in the water that are pollutants in other contexts; for example, recycled water may contain high levels of nitrogen, which is harmful to wildlife and naturally occurring vegetation but highly useful as a fertilizer when used for agricultural irrigation.
Saving energy—Extracting, treating, and transporting fresh water from sources like groundwater aquifers is an extremely energy-intensive process. The lower the level of water in a groundwater aquifer, for example, the more energy is needed to pump the existing water out. Likewise, if the aquifer is far away from the municipalities or communities that make use of it, transporting the water can consume significant amounts of fuel. Recycling water on site helps reduce both the energy needed to move water longer distances and the energy needed for aquifer pumping. In addition, when the quality of recycled water is tailored to a specific use, the amount of energy required for treatment purposes can also be decreased.