Low quality water is essentially wastewater that has been treated using high-level technology so that it can be used (or more aptly reused) to irrigate agricultural and industrial crops and recharge aquifers. Why would we switch to using low quality water when we currently use fresh water for agricultural irrigation? Sources of freshwater are steadily decreasing across the globe, and agriculture accounts for approximately 70% of the world’s freshwater withdrawal. As the world’s population increases and the amount of available freshwater decreases, water scarcity and food security will soon become two major concerns.
The use of irrigation is also increasing to meet the food demands of a growing population. Already, there has been a net increase of 117% in irrigated land from 1961-2009, and in some countries, irrigation uses more than 40 percent of renewable water resources. Unfortunately, not all of this water reaches the crop; as much as 60% of water withdrawn for irrigation is lost through leakage, spillage, evaporation, or infiltration. How can we decrease the amount of freshwater withdrawn for irrigation? Well, first, technology, education and maintenance issues must be addressed to reduce lost water in
irrigation. One solution is also to reuse low quality water for irrigation to mitigate the global strain on freshwater.
One of the targets of the 6th World Water Forum is “to increase the use of treated wastewater and/or low quality water in agriculture in the Americas by 25% as compared to 2005-07 baseline” by 2020. Several sessions where held on this topic and ideas and suggestions were exchanged. Some projects are in the works to help accomplish this goal:
1. The Edward C. Little Water Recycling Facility (ELWRF) in California is one of the largest water recycling facilities in the world. The facility recycles 30 million gallons of water per day, in 5 different classes depending on intended use. The two classes of interest here are:
- Title 22 (Tertiary) Water, which is used for a wide variety of irrigation uses, including landscaping, and
- Softened Reverse Osmosis Water that has been purified by micro-filtration, reverse osmosis, and disinfection and used for groundwater recharge.
2. Mexico currently uses extensive irrigation practices due to its climate and agricultural practices. The city of San Luis Potosi, with a population of more than 1.3 million inhabitants, is one such example. The recent increase in water withdraws from population and development increase threatened the water supply of the local aquifer. In response, the city improved its water water treatment infrastructure so that it could use treated wastewater for agricultural uses, primarily irrigation of corn and other cereals.
3. On an even smaller scale, Fundación Simiente, an NGO in Honduras, works with local families to collect wastewater from the kitchen, bath and laundry. The wastewater is then sent through a locally-made filtration unit before being used on local crops.
The three projects listed above are just a few of many worldwide, and they good examples of the varying scales of these types of projects. While large scale projects such as the ELWRF in California contribute to national food security, even small projects that collect wastewater at the household level can help increase food security, only in this case at the local level. We must keep in mind that not all projects will work in every country. Different countries have different environmental and health laws that dictate the use of treated wastewater in agriculture. Developing countries tend to have fewer, more relaxed laws, while in the United States the Environmental Protection Agency and state and local laws can make it difficult to use wastewater on food crops.
What are your thoughts on using treated wastewater for agriculture? Do you think this idea will become popular as water scarcity increases?