A plate and bowl float vertically atop water

When it comes to water conservation, the focus often falls on collecting and using rainwater. This technique is undoubtedly worthwhile in conserving water, but there are other ways to reduce water usage. 

For example, greywater filtration and treatment are essential to reducing your home’s water usage. 

When it comes to filtering and treating greywater, you should know what wastewater comprises, how a domestic system works, suitable materials for filtration, the treatment process, and safety concerns. There are many benefits to reusing greywater. Notably, it reduces the demand for freshwater.

Over the last few years, filtering and treating used water has become increasingly common in environmentally-conscious households. However, many homeowners are still unaware of what goes into this process. If you fall into this category, consider the following details on greywater filtration and contamination.

Details To Know About Filtering and Treating Greywater

Here are some of the most important considerations for treating and filtering greywater, in no particular order.

1.) Greywater Contaminants

Greywater is used water not considered to be hazardous waste. It can be used for a variety of purposes but is usually recycled for use in irrigation systems. 

A homemade harvest rainwater collector in use at an energy-efficient off-grid home

Used water is typically collected from the bathroom and kitchen. However, it is also possible to generate it from sources such as laundry, showers and bathtubs, dishwashers, and washing machines.

The water is called “grey” because it doesn’t contain human wasteand doesn’t need to be treated as hazardous. However, it isn’t safe to consume—certain chemicals and contaminants can render the water unsafe for consumption by humans and plants.

When you decide to filter or treat your greywater, you’ll want to know about the specific contaminants you need to remove before you start.

Some common contaminants include:

  • Food waste
  • Salts
  • Chemicals from household detergents and soaps
  • Bacteria

The most uncomplicated greywater treatment process uses a mesh bag to filter out larger solid objects such as food particles and hair. This method will remove debris from the water so you can safely use it for non-consumptive purposes like watering plants or lawns.

promo photo of a row of mesh bags for greywater treatment
Courtesy of Amazon

Although greywater is not considered safe for direct human consumption, homeowners can use it for other purposes with precautions.

2.) Benefits of Greywater Reuse

Water is an essential resource for all living beings and is necessary for maintaining human life. It helps maintain the ecosystem, creates jobs, and helps to keep the food chain going. 

With this in mind, various water management systems are formed to ensure that people get access to clean water at all times. Reusing wastewater is one of the most critical parts of a sustainable water management process.

While the practice has been common in arid areas like California for years, it has also become popular to save money and reduce environmental harm wherever a plumbing system is in place.

The benefits of this are significant on several levels, including:

  • Saving and reducing the need for freshwater 
  • Reduced energy consumption and chemical pollution from water purification
  • Nutritional recovery
  • Lowering the environmental impact of septic tanks and water treatment facilities
  • Groundwater replenishment
  • Higher quality of surface and groundwater is maintained when organic purification occurs in the topsoil layers than when artificial water treatment methods are used.

3.) Domestic Greywater Systems

In the past, greywater was a dirty word. Only recently has the general public become more aware of the benefits of using water from showers, sinks, and laundry for non-potable purposes instead of flushing it down the drain. 

It is now possible to filter out harmful pollutants and bacteria from household greywater using innovative filtration technology built into your home. This home feature makes it possible to use your house’s water supply more efficiently. 

In addition to helping reduce the amount of household water you use, you can also cut back on the amount of water you have to buy or otherwise get rid of. This reuse saves you money on your monthly water bill and reduces your environmental impact. 

The systems are easy to operate–they’re often automatic, requiring only a pump, filter, and collection tank. Compared to other plumbing systems, they can be cheap to install and relatively simple to maintain.

Ultimately, domestic these filtration systems are a great way to handle the wastewater from household activities and use them for agricultural purposes that would otherwise be draining into the sewer. 

4.) Using Natural Resources to Filter Greywater

Greywater is a tricky topic to tackle, as most people think of it in terms of filtration. While greywater needs to be filtered before it goes back into your garden’s plants, you can use natural resources to do this for you.

Diagram of a DIY Greywater System
This DIY greywater system uses wood and gravel as a filtration medium. Courtesy of Climate Biz.

For water to be considered “grey,” it must be sewage-free and free of chemical contaminants. This stipulation means that a shower with soap or a laundry load with bleach is an example of water-containing chemicals that shouldn’t go back into the soil. 

Soap and bleach produce biocides, which are dangerous for the plants in your garden. To ensure that your garden doesn’t get soaked in these chemicals, you should definitely have a filter on your system.

It’s important to note that water used for irrigation should have a pH between 5.0 and 7.0. The filters you can use are endless—natural materials, such as sand, gravel, and activated charcoal, are all feasible. These are effective, pocket-friendly methods for refining greywater properties to meet this standard. 

In fact, this study found that filtering greywater with activated charcoal successfully refines its properties to a pH of 5.0, making it suitable for agricultural purposes. 

5.) Treatment Process

Greywater is the second-largest source of water for many households. Though the idea of a wastewater system may seem daunting, it’s pretty simple. It’s just a matter of collecting water that would have gone down the drain, filtering it, and then using it for an appropriate purpose.

If approved by local ordinances, you can use the water for watering plants, flushing toilets, and other household uses. Filtering and treating greywater to make it safe for these uses is easy and affordable.

A homemade harvest rainwater collector in use at an energy-efficient off-grid home

One of the essential details about its filtration and treatment is that these systems should be designed for the amount of water you’re producing. 

A small system will work well for you if you have a modest household and don’t generate much water. However, a large-scale system will be necessary if your home is significant and creates plenty of wastewater.

While there are numerous ways to filter and treat greywater, they all adhere to the same general process:

  • Filtration
  • Sedimentation
  • Flotation of lighter solids
  • Disinfection by chemicals or UV

6.) Safety Concerns

As always, safety is paramount when dealing with household wastewater. 

If you’re recycling water in your house, it’s imperative to remember the difference between greywater and blackwater. 

Blackwater is used water that has come in contact with human waste, which is highly toxic and should never be reused or put back into the ground. Greywater is used water that doesn’t contain human waste – it’s wastewater from your bathroom sink, tub, and shower but not your toilet.

Final Thoughts 

While various methods of collecting and treating greywater exist, they all come with some risks

Before you start with a system of your own, you should understand the various aspects of greywater reuse – from best to worst-case scenarios – to make an informed decision about your home setup.


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