Exploring the use of wastewater in agriculture
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Exploring the use of wastewater in agriculture
Once seen as a problem to be disposed of , municipal liquid waste is now being eyed as an option for addressing water scarcity
19 January 2017 , Berlin / Rome - With food demand and water scarcity on the uptick , it ’ s time to stop treating wastewater like garbage and instead manage it as a resource that can be used to grow crops and help address water scarcity in agriculture .
Properly managed , wastewater can be used safely to support crop production — directly through irrigation or indirectly by recharging aquifers — but doing so requires diligent management of health risks through adequate treatment or appropriate use .
How countries are approaching this challenge and the latest trends in the use of wastewater in agriculture production will be the focus of discussions by a group of experts taking place today in Berlin during the annual Global Forum for Food and Agriculture ( 19-21 January ). The event has been convened by FAO along with the United Nations University , Institute for Water , Environment and Health ( UNU-INWEH ), the UN ’ s Educational , Scientific and Cultural Organization and the Leibniz Research Alliance Food and Nutrition .
“ Although more detailed data on the practice is lacking , we can say that , globally , only a small proportion of treated wastewater is being used for agriculture , most of it municipal wastewater . But increasing numbers of countries — Egypt , Jordan ,, Mexico , Spain and the United States , for example — have been exploring the possibilities as they wrestle with mounting water scarcity ,” says Marlos De Souza , a senior officer with FAO ’ s Land and Water Division .
“ So far , the reuse of wastewater for irrigation has been most successful near cities , where it is widely available and usually freeof-charge or at low cost , and where there is a market for agricultural produce , including non-food crops . But the practice can be used in rural areas as well — indeed it has long been employed by many smallholder farmers ,” notes De Souza . The important thing is that wastewater be managed adequately and safely used in a way that is appropriate to local conditions , he adds .
An alternative source of a critical resource
Water is of course fundamental for food production , and the intensifying scarcity of this important natural resource — likely to be more intense in a context of climate change — has very significant implications for humanity ’ s ability to feed itself .
Globally , population growth and economic expansion are placing increasing pressure on freshwater resources , with the overall rate of groundwater withdrawals steadily increasingly by 1 percent per year since the 1980s . And those pressures are now increasingly being exacerbated by climate change .
Already , agriculture accounts for 70 percent of global freshwater withdrawals — with demand for food estimated to grow by at least 50 percent by 2050 , agriculture ’ s water needs are poised to expand . Yet demand from cities and by industries is on the rise as well .
Greater use of non-conventional , alternative sources of water — including the urban effluent and farm-runoff — can help mitigate this competition , if properly treated .
In addition to helping cope with water scarcity , wastewater often has a high nutrient load , making it a good fertilizer . “ When safely used and managed to avoid health and environmental risks , wastewater can be converted from a burden to an asset ,” De Souza says .
Managing risks
Untreated wastewater often contains microbes and pathogens , chemical pollution , antibiotic residues , and other threats to the health of farmers , food chain workers , and consumers — and it also poses environmental concerns .
A number of technologies and approaches exist that are being utilized around the globe to treat , manage , and use wastewater in agriculture , many of them specific to the local natural resource base , the farming systems in which they are being used , and the crops that are being produced .
In Egypt , for example , where water supplies are limited and wastewater tends to be highly contaminated , constructed wetlands are proving to be a promising , economically viable approach to treatment . In Egypt and also in Tunisia wastewater is being widely used in agroforestry projects , supporting both wood production as well as anti-desertification efforts .
In Central Mexico , municipal wastewater has long been used to irrigate crops . In the past , ecological processes helped reduce health risks . More recently , crop restrictions — some crops can be safely grown with the wastewater , while others cannot — and the installation of water treatment facilities have been added to the system .
In Jordan , reclaimed water represents an impressive 25 percent of all total water use in the country . In the United States , treatment and managed aquifer recharge is a common practice , especially in the West .
Beyond helping tackle the problem of water scarcity , reducing environmental contamination , and supporting food production , infrastructure and management systems for reclaiming , treating , and re-using wastewater can be job creators , according to De Souza . The Global Forum for Food and Agriculture , organized by the German Federal Ministry for Food and Agriculture ( BMEL ) takes place every year , bringing together high-level decision makers , technical experts , researchers and farmers to discuss pressing issues affecting agriculture worldwide .
The Forum ’ s theme this year is “ Agriculture and Water - Key to Feeding the World .” An organizing partner of the event , FAO is taking the lead on a number of events at the Forum .
Source : FAO
2 Africa Water , Sanitation & Hygiene • March - April 2017