Recycling water through greywater systems

The author of this post is Angela Tipp, a senior Biology major at the University of St. Thomas.

Currently irrigated agriculture around the world is estimated at using 70% of the worlds freshwater, however, with the growing population, food yields will have to double by 2050 increasing the demand for water drastically (Ray et al., 2013). It is calculated that by 2025 around 800 million people will live in water scarcity (Greenwood et al., 2009). There has also been an increase in megadroughts and other severe storm patterns due to global warming and changing climates. This raises a problem in urban areas where there is an increase in impermeable surfaces due to concrete and compacted soil (Lye et al., 2009). In order to help combat a shortage in water new practices need to be implemented. It only makes sense that these practices start in urban areas where populations are high and the need for water is at its greatest.

Although rainwater catchment systems have been created for cities with the ability to collect ample amounts of water that can be used for watering gardens and potentially for drinking water, I will not focus on it. Rainwater catchment systems are a great way to collect water and save it, but there seem to be problems with rooftop runoff (i.e. heavy metals and bacteria). More research needs to be conducted to find a user-friendly way of collecting healthy rainwater in urban areas. Being so, I believe there is a better and bigger option available for saving and recycling water. Recently the topic of greywater has caught the attention at a large-scale and small-scale level; again I will focus on small scale in urban environments. Generally greywater (waste water from washer machines, dishwashers, and showers) is mixed with wastewater (from toilets) and is brought to a treatment plant. The wastewater/greywater mixture is then sent through four treatments before it is later transported and used for irrigation (Matos et al., 2014). The option that has been brought forth by Matos et al. looks into a simpler greywater treatment system that can be done at your own house (Matos et al., 2014). This system would potentially collect greywater straight from your house (or only from your laundry machine or a combination of other greywater sources) to the treatment area, which would need two to three treatments and then could be used for garden and grass irrigation in your lawn. This system can also be implemented at places like golf courses that use a large amount of water to irrigate their lands.Angela 1 2

When looking into energy consumption and CO2 emissions, Matos et al. found that the centralized wastewater system (WWCRS) tends to use more energy and generally releases more CO2 to the environment than a decentralized greywater treatment system (GWDRS) (Matos et al., 2014).

Not only does this reduce environmental impacts and recycle water at your own house, it can protect you from future droughts, drastically reduce the amount of overall water you are using at your house, and reduce the costs you have to pay for water usage.

Due to California’s drought and drastic water restrictions reaching a current 20% reduction of water usage, CA has been leading in finding ways to reduce and reuse water with the help of greywater activist Laura Allen. Allen has made easy and cheap systems for urban families to use and collect water from showers and laundry at their own house. More on the greywater activist Allen can be found at:
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Greywater treatment is a system that can be easily implemented today with the right tools. It will help reduce the use of energy and release of CO2 as compared to the traditional wastewater treatment plan and reduce the amount of water used in a house by recycling a large quantity of water. In the future it would greatly help with water shortage if this greywater system were implemented on a large-scale (i.e. wastewater treatment plants split waste water and greywater with different filtration systems reducing energy use and CO2 emissions among other benefits) for rural agriculture. This implementation would need a large sum of money, though, in order to split the greywater and wastewater treatments.

More information on CA municipal recycled water:


About Adam Kay

I study urban ecology and urban agriculture
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