Approximately 10% of the world water resources are used for domestic purpose. Reuse of waste water for irrigation is in many regions since hundreds of years a common practice to supplement water resources with additional supply. With regard to the rising water shortage in the context of climate change, waste water reuse offers an additional opportunity to address imbalances between water demand and supply. Mainly in semi-arid regions with a large population rate, water scarcity and a high agricultural activity, waste water reuse should be considered as an adequate adaptation method to climate change.
Concern for human health and the environment are the most important constraints in the reuse of wastewater, which can be overcome with effective treatment methods completed with educational advertising.
Wastewater reuse for irrigation
Waste water reuse or recycling comprises the use of treated and untreated domestic and non-domestic waste water by different techniques for further purpose such as irrigation and fertilization.
Benefits of waste water treatment
The benefits of waste water treatment are in general:
- Use of a reliable water source for irrigation
- Fertilisation of land
- Substitution of scarce water resources
- Safe disposal of waste water to avoid surface or groundwater contamination
- Groundwater recharge
The wide number of treatment techniques offers mostly developing countries additional opportunities to reduce the risk of pathogens through waste water by a cost-effective and practical manner.
Preconditions of waste water treatment
To ensure cost-effectiveness of waste water treatment measures some preconditions should be considered. A functional waste water collection and distribution system is elementary for its further purpose. Trained human capacity for implementation and maintenance are a key aspect to ensure an adequate and sustainable use of waste water and to reduce the human health risk through pathogens. Moreover the acceptance by the users is a key factor for success of waste water reuse initiatives and should be secured. In some regions people are forces to accept this additional water source due to economic pressure. But a constant and patient awareness raising is needed to change step by step the behavioural patterns of the users.
To reduce or eliminate the health risks of using waste water by pathogens several control measures and reducing methods are offered:
- primary and secondary treatment: to eliminate or reduce concentration of pathogens and other potentially toxic elements to acceptable level
- improved occupational health of sewage farm workers and farmers through protective clothing and measures
- agronomic techniques: restriction on the type of crops grown and control of irrigation techniques
- disinfection of waste water contaminated crops by consumers
A range of treatment methods are already worked out implement the adequate technical process of waste water recycling. The basic structure of this method is illustrated by the figure 1.
Figure 1: General sanitation components for waste water reuse
Related to the number of established treatment steps different levels on human health risk are expected.
| Sludge drying
|| Secondary treatment
|| Sand filtration
| High health risk
|| Health risk existing
|| Low health risk
|| Low health risk
Figure 2: Workflow of the rural sanitation system, with a Small Bore Sewer System connected to a treatment plant (GIZ 2006)
In regard of an intensifying cultivation practice which needs to produce food for a rapidly raising number of world population with limited water and land resources, waste water treatment systems offer a suitable response for such conditions. The expansion of reuse of waste water is already raising in agriculture and it is expected that this development will continue in the future. To establish these systems effectively and sustainable in more regions, a promotion of changes in behavioural patterns are required. To gain acceptance the introduction should also be made stepwise so immediate benefits can be observed by the users.
- ↑ 1.0 1.1 DWA (2008): Aufbereitungsstufen für die Wasserwiederverwertung, Hennef. http://www.dwa.de/dwa/shop/produkte.nsf/FB80640612B95B80C1257539004DA953/$file/vorschau_BIZ-11-04_2008-05.pdf [accessed 17 April 2013]
DWA (2008). Water Reuse arabic.pdf
DWA (2008). Water Reuse chinese.pdf
DWA (2008). Water Reuse english.pdf
GIZ (1993): Irrigation and the Environment – A review of Environmental Issues. Eschborn.
GIZ (2002): Use of Reclaimed Water in the Jordan Valley. Appraisal Mission. Final Report. http://www2.gtz.de/Dokumente/oe44/ecosan/en-use-of-reclaimed-water-in-the-Jordan-Valley-2002.pdf [accessed 17 April 2013]
GIZ (2009) Wasser in der Landwirtschaft, Eschborn.
GIZ (2009): Use of treated wastewater in agriculture Jordan Valley, Jordan http://www.susana.org/docs_ccbk/susana_download/2-78-en-susana-cs-jordan-treated-wastewater-reuse-2009.pdf [accessed 17 April 2013]
WHO (2006) Quality guideline for waste water and excreta for agricultural use http://www.who.int/water_sanitation_health/wastewater/gsuweg3/en/index.html