Why does the use of waterwater matter?
The use of nightsoil or human excreta in agriculture has been practiced for decades in China and South-East Asia, while wastewater use is a more recent practice in Latin America, Western and Southern-Asia and Africa. Use of both treated and untreated wastewater is widespread globally but especially in arid and semi-arid countries where fresh water is increasingly becoming scarce and planners are forced to consider marginal quality sources as alternatives. The exact extent of wastewater use for urban agriculture is, however, not known due to a lack of data the varying definitions of wastewater. The use of wastewater in agriculture has the potential to raise both agricultural productivity and the living standards of the poor. Wastewater provides alternatives to scarce freshwater sources as water scarcity and stress increases. The proper use of wastewater can also help in recharging aquifers through infiltration, or in reducing surface water pollution as the wastewater gets ‘treated’ in the vadose region of soil before reaching the water bodies. It also helps alleviate environmental health problems. Again the beneficial use of the nutrients and water in agriculture could reduce the amounts of untreated wastewater discharged into aquatic bodies like rivers and lakes.
Despite the numerous benefits associated with wastewater use, its use in agriculture also holds clear risk to agricultural workers and consumers of wastewater irrigated produce. These risks normally originate from pathogens and chemicals dissolved in the wastewater. The health risks are predominantly helminth infections and diarrhoeal diseases (bacterial and enteric viral infections). The use of wastewater exposes farmers (and their families) to faecal matter through direct contact with wastewater and irrigated soil, whilst consumers are exposed through the consumption of raw produce irrigated with wastewater. However, there are relatively few studies that have provided evidence on the excess risk of pathogen infection for both farmers and consumers of uncooked vegetables. Furthermore there are limited studies which document how risk from wastewater use in agriculture compares to risk of disease from faecal contamination in the different domains (occupational, domestic and public domains). Risk estimations (especially for low and middle income countries) have often been underestimated or overestimated due to lack of primary input data. The above research limitations provide a basis for more research to provide more evidence on the excess risk attributed to wastewater use and to also systematically assess the risk factors for produce along the food chain.
Key research and contributions to this area:
Contributions to the WHO’s wastewater use guidlines
Most of the earlier studies related to wastewater use have been compiled by the World Health Organisation (WHO) in their book: “WHO Guidelines for the safe use of wastewater, excreta and greywater. Volume II-Wastewater Use in Agriculture (2006)”. A major global contributor to research in this area is the International Water Management Institute (IWMI). Dr Jeroen Ensink worked with IWMI from 1998 to 2006 in Pakistan, Sri Lanka, Vietnam and India on projects investigating the impact of (agricultural) water management on human health. Some of his research included Livelihoods from wastewater in Faisalabad – Pakistan, Giardia duodenalis infection and wastewater irrigation in Pakistan, High risk of hookworm infections among wastewater farmers in Pakistan and a nationwide assessment of wastewater use in Pakistan.
Current research in this area:
Currently, Prince Antwi-Agyei (a PhD student) is undertaking a research in Ghana to assess the risk of faecal disease transmission in the occupational, public and domestic domains and to provide policy implications for the safe use of wastewater in agriculture in Ghana. Specifically, he assesses how the microbial quality of produce changes from wastewater irrigated farms to markets, street vending sites, hotels and restaurants. He also assesses the critical risk behaviours at the farm associated with faecal disease transmission to agricultural workers. Other components of his study include quantifying the health risk to both farmers and consumers of wastewater irrigated produce and to determine how awareness of wastewater use and risk influence farmers and consumers health exposure patterns. The final objective of the research is to use the research findings to assess the adequacy of the current WHO guidelines on the use of wastewater for urban agriculture.
Publications related to Wastewater Use
- Faecal contamination and hygiene aspect associated with the use of treated wastewater and canal water for irrigation of potatoes (Solanum tuberosum)Forslund, A.; Ensink, J.H.J.; Battilani, A.; Kljujev, I.; Gola, S.; Raicevic, V.; Jovanovic, Z.; Stikic, R.; Sandei, L.; Fletcher, T.; Dalsgaard, A.Agricultural Water Management, 2010; 98(3):440-450
- Escherichia coli contamination and health aspects of soil and tomatoes (Solanum lycopersicum L.) subsurface drip irrigated with on-site treated domestic wastewater.Forslund, A. ; Ensink, J.H. ; Markussen, B. ; Battilani, A. ; Psarras, G. ; Gola, S. ; Sandei, L. ; Fletcher, T. ; Dalsgaard, A. Water Res, 2012; 46(18):5917-34
- Safe and high quality food production using low quality waters and improved irrigation systems and management: Safir Plauborg, F.; Andersen, M.N.; Liu, F.L.; Ensink, J.; Ragab, R. Agricultural Water Management, 2010; 98(3):377-384
- Implementation of the WHO guidelines for the safe use of wastewater in Pakistan: balancing risks and benefits. Ensink, J.H.; van der Hoek, W. J Water Health, 2009; 7(3):464-8
- Wastewater use in agriculture Editorial: New international guidelines for wastewater use in agriculture. Tropical Medicine and International Health, Ensink, J. H. J. & van der Hoek, W. (2007).12 (5), 575- 577.
- Giardia duodenalis infection and wastewater irrigation in Pakistan. Transactions of the Royal Society of Tropical Medicine and Hygiene, Ensink, J.H.J., van der Hoek, W & Amerasinghe, F. P. (2006). 100, 538-542
- Wastewater quality and the risk of intestinal nematode infection in sewage farming families in hyderabad, India. Ensink, J.H.; Blumenthal, U.J.; Brooker, S. Am J Trop Med Hyg, 2008; 79(4):561-7
- High risk of hookworm infection among wastewater farmers in Pakistan. Transactions of the Royal Society of Tropical Medicine and Hygiene, Ensink, J.H.J., van der Hoek, W., Mukhtar, M., Tahir, Z., & Amerasinghe, F.P. (2005). 99, 809-818.
- Editorial: New international guidelines for wastewater use in agriculture. Ensink, J.H.; Hoek, W. Trop Med Int Health, 2007; 12(5):575-7
- A nation-wide assessment of wastewater use in Pakistan: an obscure activity or a vitally important one? Water policy, Ensink, J.H.J., Mahmood, T., van der Hoek, W., Raschid-Sally, L. & Amerasinghe, F.P. (2004). 6, 197- 206.
- Wastewater-irrigated vegetables: market handling versus irrigation water quality. Tropical Medicine and International Health, 12 suppl. 2, 2-7 Ensink, J. H. J., T. Mahmood & A. Dalsgaard. (2007).
- Water management and vector breeding: the importance of waste stabilization ponds and wastewater irrigation in the generation of vector mosquitoes in Pakistan. Journal of Medical Entomology, Mukhtar, M., Ensink, J.H.J., van der Hoek, W., Amerasinghe, F.P. & Konradsen, F. (2006). 43 (5), 996-1003.
- Adult anopheline ecology and malaria transmission in an irrigated area of south Punjab, Pakistan. Medical and Veterinary Entomology, Herrel, N., Amerasinghe, F.P., Ensink, J., Mukhtar, M., van der Hoek, W., & Konradsen, F. (2004). 18, 141-152.
- Role of wastewater irrigation in mosquito breeding in South Punjab, Pakistan. Southeast Asian Journal of Tropical Medicine and Public Health, Mukhtar, M., Herrel, N., Amerasinghe, F.P., Ensink, J., van der Hoek, W., & Konradsen, F. (2002). 34 (1), 72-80.
- Breeding of Anopheles mosquitoes in irrigated areas of South Punjab, Pakistan. Medical and Veterinary Entomology, Herrel, N., Amerasinghe, F.P., Ensink, J., Mukhtar, M., van der Hoek, W., & Konradsen, F. (2001). 15 (3), 236-248.
- Ensink J, Scott C, Brooker S, Cairncross S. 2010. Sewage disposal in the Musi-River, India: water quality remediation through irrigation infrastructure. Irrigation and Drainage Systems 24:65–77. DOI 10.1007/s10795-009-9088-4
- Ensink JHJ, Hoek W vd, Mara DD, Cairncross S. 2007. Waste stabilization pond performance in Pakistan and its implications for wastewater use in agriculture. Urban Water Journal 4 (4): 261 – 267. DOI: 10.1080/15730620701427429
- Importance of waste stabilization ponds and wastewater irrigation in the generation of vector mosquitoes in Pakistan Mukhtar, M.; Ensink, J.; van der Hoek, W.; Amerasinghe, F.P.; Konradsen, F.Journal of Medical Entomology, 2006; 43(5):996-1003
- Ensink JHJ, Brooker S, Cairncross S and Scott CA 2006. Wastewater use in India, the impact of irrigation weirs on water quality and farmer health. Proc. 32nd WEDC International Conference, Colombo, Sri Lanka.
- Moraes L.R.S., Cancio J.A., Cairncross S., Huttly S.R.A. 2003. Impact of drainage and sewerage on diarrhoea in poor urban areas in Salvador, Brazil. Transactions of the Royal Society of Tropical Medicine and Hygiene 97: 153-158.
- Jensen P.K., Matsuno Y., van der Hoek W., Cairncross S. 2001 Limitations of irrigation water quality guidelines from a multiple use perspective. Irrigation and Drainage Systems 15 (2): 117-128.
- Kolsky P.J., Butler D., Cairncross S., Blumenthal U.J., Hosseini M. 1999. Modelling drainage performance in slums of developing ountries; how good is good enough? Water Science & Technology 39 (9) 285-292.
- Cairncross, S and Ouano EAR 1991. Surface Water Drainage for Low Income Communities. Geneva: World Health Organisation. (Also published in Spanish and French)
- Cairncross, S. 1990. Use of sewage and sludge in agriculture. Editorial, Lancet (i) 635‑636.]
- Mara, D.D. and Cairncross, S. 1989. Guidelines for the Safe Use of Wastewater and Excreta in Agriculture and Aquaculture. Geneva: World Health Organisation. (Also published in French and Spanish)
- Cairncross, S. 1986. Urban drainage in developing countries. Parasitology Today, 2: 7, 200‑202.
- Blumenthal, U.J., Strauss, M., Mara, D.D. and Cairncross, S. 1988. Generalised model of the effect of different control measures in reducing health risks from waste reuse. Water Science and Technology, 21: 567‑577.