Greywater, or sullage, is defined as any form of wastewater, such as shower, sink, or dishwasher water, that does not include the wastewater from toilets. Therefore, greywater may not contain feces, but it can contain grease, dirt, and food. Being able to reuse the daily several dozens of gallons of greywater from your home rather than allowing it to go to waste is one of the most frugal and beneficial things that you can do.
We will learn about four different smart systems that you can utilize for reusing greywater, and the pros and cons of each system.
But before we go into what these different systems are, first ask yourself what you will be using the recycled water for, and then determine if that purpose requires you to first treat and clean the water.
You need to consider greywater differently than you would fresh water, as it is “contaminated” with organic matter. On the plus side, this means you have great fertiliser for your plants, but on the downside those nutrients are a potential biohazard for natural waterways, so be responsible in where you chose to irrigate and avoid runoff.
All that organic material in sullage also makes it an ideal breeding ground for bacteria, so it shouldn’t be stored for more than 24 hours or allowed to pool. If you plan on using the recycled water for agriculture, it’s important to filter it correctly first to avoid getting raw greywater on the edible parts of your crops.
Fortunately, safely recycling greywater is not a difficult process so long as you set up the proper equipment. It can be used for direct irrigation, or there are an abundance of different purification methods out there for filtering greywater.
Kitchen sinks use a lot of water. However kitchen sink greywater typically contains a lot of organic material including solid food waste and grease, meaning it is not suited for many filtration methods. For this reason, it is not permitted to be domestically recycled in many areas, so do check local regulations.
The best system for reusing greywater from kitchen sinks is to send it through a branched drain system, meaning the grey water travels through a pipe on a downward slope that repeatedly branches off into smaller pipes, where each branch ends in a mulch basin.
A properly constructed mulch basin traps any food particles, effectively acting like a woodchip-based biofilter. This method is well suited for watering trees or large shrubs, including fruit trees/bushes.
Branched drains and mulch basins may be a drag to set up, but they both require very little maintenance.
Showers and bathtubs are another excellent source of greywater because, like kitchen sinks, they provide a lot of it! These can also be diverted into a branched pipe system that carries your greywater downstream, however this water can be used directly rather than via a mulch basin. Another option is to create a wetlands area.
The principle of constructed wetlands is simple: it is essentially an eco-filter of vegetation, soil and associated microbes. In addition, you can also grow a variety of beautiful plants in your wetlands that will absorb the nutrients of the greywater.
However, a wetlands area is a long term project that needs to be carefully researched and engineered in order to utilize the natural processes that will make your greywater safe for use and storage. This system is not well suited to arid environments.
The beauty of using grey water from washing machines is that it can be collected without having to make any changes to your plumbing system.
Instead, you simply install a diverter valve on your washing machine outlet hose which allows you to switch between sending the water to your irrigation system or the sewer (or septic tank). It really is that simple, and once installed, is practically hassle free.
If setting up irrigation piping doesn’t suit your needs, you can just direct the laundry outlet straight into a container and use a watering can or hose to decant the water to precisely where you want it on that day.
A rain barrel or even an old laundry drum will do just fine, as laundry drums are little more than simple barrels that will collect the water.
There are a number of manufactured greywater filtration systems on the market, available in manual cleaning and self-cleaning varieties. In general, they collect greywater in a tank from where it passes through a filter or system of filters, and in some cases the water is also disinfected.
The treated water is then used for irrigation or is pumped to the header tank for toilet flushing. Cleaning the filters on these is either a gross job (manual cleaning) or in some designs uses potable water (self-cleaning). The most common cause of failure in manufactured systems is lack of maintenance by the users.
However you choose to do it, remember that human contact with greywater should be kept to a minimum when designing your purification system. It’s essential to only use plant-friendly and non-toxic products if you plan to domestically recycle your sullage (anything labeled “suitable for septic tanks” is a good bet).
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