Harnessing Greywater in Urban Residences

How can urban residents benefit from the use of grey water

With each passing away, the water crisis is getting worse. This necessitates that we consider our water usage and find ways to reduce waste. One of the most common ways of doing this is, of course, by being more thrifty in our daily habits. For instance, using a mug after brushing our teeth, instead of leaving the tap open, or switching from the shower to a bucket while taking a bath.

Another approach, which can be used in tandem, is reusing the water. Water from bathroom sinks, showers, tubs and washing machines outlets is known as greywater. (It is important to note that water from toilets is not greywater. Because of the presence of faeces, it is categorised as blackwater.) Greywater may contain traces of dirt, food, grease, hair, and certain household cleaning products.

Recycling greywater is a simple and easy way of minimising water use. It's estimated that just over half of household water used could be recycled as greywater, saving potentially hundreds of litres of water per day. The application of greywater reuse in urban water systems provides two major benefits:

i. It reduces the demand for fresh clean water; and
ii. It reduces the amount of wastewater required to be conveyed and treated

Treated greywater has many uses. In a closed system, the water can simply be redirected to the toilets. Or it can (with minimal treatment) be used to water backyard gardens and vegetable patches. Treated greywater can be used to irrigate both food and non-food-producing plants. The nutrients in the greywater (such as phosphorus and nitrogen) provide an excellent food source for these plants. While greywater may look “dirty,” it is a beneficial source of irrigation water. (It must be kept in mind, however, that if greywater is released into water bodies like ponds, rivers and lakes, it becomes a pollutant.)

Reusing greywater for irrigation reconnects urban residents and backyard gardens to the natural water cycle. Many plants benefit more from watering with greywater than tap water. Since greywater has waste and detergent residues, such as phosphorus, plants can use it as nourishment. Some plants that benefit from gray water are roses, bougainvilleas, agapanthus and honeysuckle.

Certain precautions need to be kept in mind when recycling greywater:

1. Greywater should not be stored for more than 24 hours. Storing greywater for longer can make it stink.

2. Greywater could contain pathogens (from washing meat in the kitchen sink, for instance), so the system should be designed for the water to soak into the ground and not be available for people or animals to drink.

3. If used for irrigation purposes, it must ensured that greywater doesn’t pool. Pooling greywater can become breeding grounds for mosquitoes.

4. A simple system (like a three-way valve) needs to be in place to redirect excess greywater to the sewers to prevent overflowing or clogging.

Some simple systems to incorporate greywater reuse are given below:

1. Closed-loop systems: For most people, especially in the cities, it is not possible to reuse water for purposes such as gardening or irrigation. In such cases, designs such as the SinkPositive might be employed, which redirect greywater to toilets in the house.

2. Laundry drums: One of the cheapest setups involves installing a laundry drum. Greywater is pumped into a barrel called a surge tank. At the bottom of the barrel is a hose, through which the water drains out into the yard for irrigation purposes.

3. Laundry-to-landscape: Invented by Art Ludwig, in this greywater system, the greywater hose is attached directly to the irrigation system. The greywater irrigation system directs water through 1″ tubing with 1/2″ outlets directing water to specific plants. This system is low cost, easy to install, and gives flexibility for irrigation.

Greywater provides an effective and viable method of repurposing what would otherwise become wastewater. Recycling greywater not only helps us create our own personal water system for our daily needs, it also provides us with a simple and affordable way of doing our bit for the environment.