bacteria, viruses, and a wide range of parasitic organisms. Generally, indicator organisms are used to reflect the sanitary quality and suitability of particular water reuse or consumption. Typical indicators are fecal coliform content measured as CFU/100mL (colony forming units) and the number of helminth eggs or ova (Ascaris and Trichuris species and hookworms) in a water sample.
Waste water can also contains large amounts of dissolved and suspended organic matter that has the potential to clog soil pores and irrigation equipment emitters. Clogged soils have a decrease in permeability resulting in poor irrigation efficiencies and water logging due to poor drainage. Irrigation emitters of various types (drip, microsprayers, etc) can become clogged by particulate matter and the development of biogrowth or biofouling. Wastewater effluent applied through a drip irrigation system typically requires sand filtration as a pretreatment to avoid problems with clogging. The organic content of the wastewater is expressed as Total Suspended Solids (TSS) and as Biochemical Oxygen Demand (BOD) both reported as mg/L.
In agriculture, treated wastewater has been applied mainly to field crop but Gideon Oron et al. (1999) demonstrated that sweet corn (zea maize), Saccharatum and sweet pepper (paprika) could be irrigated using treated wastewater through subsurface drip irrigation systems without detection of fecal coliform in plant parts and with minimal bacteria concentrations in the soil surface. Maximum bacterial concentrations was detected at a soil depth of 30-50 cm. Oron’s study supports previous work by Gerba et al. (1975).
Wastewater reuse rules for agricultural lands in the Middle East countries either follow the rules developed by the World Health Organization (WHO, 1989) or they follow more stringent rules developed in the United States by the State of California. In the Middle East, federal agencies are in charge of wastewater management (Table 1).
Table 1. Federal Agency in Middle East Countries responsible for wastewater regulations.
Country
|
Federal Agency
|
Jurisdiction
|
| Jordan | Ministry of Water and Irrigation | Regulates and manages both the drinking and wastewater treatment plantsRegulates the crop and conditions under which wastewater can be used in agriculture |
| Palestinian Authority | Ministry of Environmental Affairs | Wastewater management |
| Israel | Ministry of Health (Jerusalem, the Chief Health Engineer) | Wastewater management |
| Egypt | Ministry of Agriculture | Regulates the application of wastewater |
WHO standards for the use of wastewater in agricultural production for export generally require a level of treatment that ensures that the fecal coliform content of the wastewater is less than 103 cfu per 100 ml (WHO, 1989). WHO also sets standards for helminth eggs and intestinal nematodes that may be a problem for agricultural workers, consumers, and the public when the wastewater is surface applied or flood irrigated. The wastewater effluent should contain less than 1 heliminth egg per liter. The WHO recommended treatment methodology to achieve this standard is a series of stabilization ponds (aerobic, facultative, and polishing lagoons) with a hydraulic retention time (HRT) of not less than 8-10 days. This health problem only exists where intestinal nematodes are prevalent These standards do not address the risks if the wastewater is applied through a subsurface drip irrigation system.
WHO standards do not take into consideration the technology for application of wastewater that may help reduce health risks. If subsurface drip irrigation is used to apply the irrigation water, the health risks are negligible (Oron et al., 1999). When using subsurface drip irrigation, the treatment of wastewaters to levels less strict than that generally required by WHO may, in fact, still produce food products that are completely safe for human consumption and export. Therefore, it is important to investigate the use of subsurface drip irrigation as an alternative to surface irrigation and as a preferred method of application of wastewater.
Currently in the Middle East, wastewater treatment levels for application to agricultural land range from zero—discharge of raw sewage—to highly treated water produced from newly constructed wastewater treatment plants. Trained operators who carefully monitor the wastewater stream for health risk levels run these plants. The long-term goal of all Middle East countries is to treat wastewater used in agriculture to minimum WHO standards. The minimum levels defined by WHO as acceptable, however, they might be made less strict if the products remain safe and meet required standards when using subsurface drip methods for applying the water. The biggest problem facing policy makers and end users of treated wastewater in agriculture production is a lack of understanding of the standards, acceptable levels of treatment, methods of application and the maintenance of wastewater treatment systems.
Understanding all of the issues and problems associated with the use of treated wastewater in agriculture is a global concern. There is no central data bank for reference. However, there are several groups that have been formed to research and compile information on the topic.
In the United States, the Consortium of Institutes for Decentralized Wastewater Treatment was established with the purpose of compiling information and promoting standardized education and training of new approaches and tools for wastewater treatment. The consortium is made up of representatives from educational institutions, special interest groups, regulatory agencies and private industry. The Internet web site is used as the method of disseminating information about wastewater treatment and application (CIDWT, 2000), http://www.dal.ca/~cwrs/cdwt/.
The National Small Flows Clearinghouse (NSFC, 2000) is another web-based site that maintains several databases on regulations, technologies, and people who have experience in small wastewater treatment systems. The purpose of the clearinghouse is to provide information on wastewater issues to homeowners, government officials, operators, manufacturers, contractors, and related professionals, http://www.estd.wvu.edu/nsfc/NSFC_homepage.html.
In the Middle East an Appropriate Technology Consortium (ATC) was formed to develop low-cost, efficient, and replicable wastewater treatment and reuse systems in rural areas of the Middle East. The consortium consists of the following Institutions: The Galilee Society (Israel), The Palestinian Hydrology Group (West Bank), The Egyptian Center of Organic Agriculture (Egypt), The Technion, Israel Institute of Technology (Israel) (ATC, 2000).
Each country in the Middle East has a unique system of rules and regulations to protect the quality of their water resources and to regulate wastewater use and application. Each country system has some similarities to its neighbors’ system but also some differences. To improve and coordinate the clean water policies of each country it is essential to understand the similarities and differences in water regulatory systems and wastewater use and application.
1. Appropriate Technology Consortium (ATC). (2000). Online. Available: http://www.gal-soc.org/atc.html.
2. Asano, T., & Mills, R.A. (1990, January). Planning and analysis for water reuse projects. Journal American Water Works Association, 38-47.
3. Gerba, C.P., Wallis, C., & Melnick, J.L. (1975). Fate of wastewater bacteria and viruses in soil. J. Irrig. Drainage Div., ASCE 101 (IR3), 157-174.
4. The Consortium of Institutes for Decentralized Wastewater Treatment (CIDWT). (2000). Online. Available: http://www.dal.ca/~cwrs/cdwt/.
5. National Small Flows Clearinghouse (NSFC). (2000). Online. Available: http://www.estd.wvu.edu/nsfc/NSFC_homepage.html.
6. Oron, G., Campos, C., Gillerman, L., & Salgotm M. (1999). Wastewater treatment, renovation and reuse for agricultural irrigation in small communities. Ag. Water Management, 38, 223-224.
7. World Health Organization. (1989). Health guidelines for the use of wastewater in agriculture and aquaculture (Technical Report Series 778, pp. 1-74). Geneva: Author.
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