Irrigation III: Reusing Your Graywater
People in Jordan have always been careful about how much water they use. There is simply no other choice. From the times of the Nabataeans, Romans, Byzantines, and Umayyads, there is evidence of the use of rainfall harvesting and of water conservation practices. Many Jordanians will remember how - until very recently - households reused water from sinks or basins by pouring it over plants. Such a small-scale, simple practice will save a little on the household water bills, and may mean a few additional trees or shrubs for the household. Of course, the bigger picture is that every bucket of water reused in the house is a bucket less that the Jordan Water Authority needs to find from our ever-decreasing store of underground water.
This idea of recycling household water is common today in many areas of the world where water is scarce. The term‘graywater’ has been coined to distinguish used household water from toilet water (known as ‘blackwater’), which naturally is too contaminated for use at home. Graywater is the water that goes down baths, showers, and sinks, and even can include laundry water. Legislation in a number of countries does not allow the kitchen sink water to be reused as graywater, as it is laden with food material. However, it remains to be seen whether this is also the case in Jordan.
Graywater generally is not as ‘dirty’ as we would expect. If we use it to irrigate plants, then it needs little or no treatment. In fact, a healthy topsoil layer provides a very effective treatment environment for most of the substances contained in graywater. Also, plants love the nitrates in the soil that result from the breakdown of organic material found in graywater in the soil.
When we come to the use of graywater, however, care should be taken as to what we put into it. Putting chemicals down the drains – bleaches, paint removers, … etc. – or anything that plants would not like should be avoided. Also, care should be taken not to use water that was used to wash diapers, clothes with a lot of blood or vomit on them, or anything else that is dirtier than normal. In order to keep such contaminants from entering your graywater system, simply keep one sink that goes to the municipal wastewater system or the septic tank. Anything that should not be going onto your plants should be disposed of down this sink. Of course, many of these items should not be put into the municipal drain anyway. Also, some detergents are high in sodium, which many plants and some soils do not like. Consequently, if you wish to use laundry water as a source of graywater, you could switch to a non-sodium-based detergent, or simply ensure adequate dilution of your laundry water before using it to irrigate plants.
To go about reusing graywater, at the simplest level just cut a hole in your sink drain, use it to fill out buckets of graywater, and pour this on your plants. However, it may be easier to get your plumber in to lay some new pipes to take your graywater to a central point in your garden. A small surge tank would receive this water and allow you to place a simple filter in it (a window screen or even a sock would suffice for most cases). This water can then be used in a simple drip irrigation system and distributed to your trees or shrubs. Of course, take care that the water is not too hot for your plants. If it is, then allow it to cool down. Do not use a hose or a sprinkler, as it is important to avoid human contact with the graywater before it reaches the soil. Also, you should not irrigate food plants where the fruit or vegetable comes into contact with the ground (potatoes, carrots, onions, herbs, …). Fruit trees (olives, dates, apples, oranges, …) are fine, and so are ornamentals. However, since it is important to avoid human contact with the graywater, do not use graywater to irrigate grass or to wash cars or your yard.
The Center for the Study of the Built Environment (CSBE) currently is running a small project through support from the Enhanced Productivity Program at the Ministry of Planning to investigate how people use graywater in other countries. The project also aims at setting up a number of test schemes in Jordan to find out exactly which practices work best in Jordan and which do not. All results will be placed on the CSBE web site. In addition, CSBE will be producing a set of guidelines for graywater use in Jordan. Right now, some provisional guidelines already can be viewed on the CSBE web site. So go ahead, read the guidelines, call in your plumber, and have a go at it.
This article is part of a series of articles prepared by the Center for the Study of the Built Environment (CSBE) on water conserving landscapes.
For additional information on water conserving gardens, visit the CSBE web site at www.csbe.org
Support for the CSBE project on water conserving landscapes is provided by WEPIA (Water Efficiency and Public Information for Action), a program being implemented in collaboration with the Ministry of Water and Irrigation and funded by the United States Agency for International Development (USAID).