Waste Water re-use Projects for Agricultural Irrigation in Yemen [Archives:2000/24/Health]

June 12 2000

By: Abdulkadir M. Al-Ariqi
Environment/Development Consultant
In response to environmental and economic needs many developing countries in the Middle East and Latin America introduced since long time the development of re-use system for agricultural irrigation in order to decrease the pressure of population growth, increasing urbanization, industries and agricultural requirements, considering the wastewater reuse in the framework of water resources.
In fact, there are many economic benefits resulting from re-using waste water safely such as: recovering arid lands for agricultural purposes, creation of employment opportunities; increasing food production and improving nutrition and above all finding an alternative to sewage disposal and their corresponding pollution and public health problem. In other words by re-using the treated sewage, the polluting effect of discharging it into the environment, will be avoided.
However the following problem arose: many countries started reusing untreated domestic sewage for irrigation in response to the pressure of water shortages and protein shortfalls. Thus these have posed some health risks for the farm worker and for the general population consuming agricultural products from sewage re-use sites (CEPIS). AS an example, in Latin America in Chile, Mexico City and Peru, problems of health hazards appeared after re-using waste water containing heavy pathogens; in fact in Chile, 57% of the population have been infected with Salmonella, and 30% with typhoid and antibodies.
According to the epidemiological data collected by the researchers in the area, (campus)1 for the populations in the district producing the sewage (at Sanjuan)1 and those consuming the produce from the re-use site, it appeared that the most prevalent infectious diseases in the area are: acute diarrhea diseases (principal agents are rotavirus, entro toxigenic and entropathogenic E coli, Salmonella, and shigella) typhoid and paratyphoid fever; viral hepatitis polio; and intestinal parasites such as Entameba histolyica and giard’a Lamblia. The mortality and morbidity associated with these diseases in line is shown in table I.
The above mentioned example indicates that the greater public health risk contains in “NOT Anticipating re-using projects” and planning for it appropriately and accurately, but what so ever the need might be it should not be at the cost of harmful effects on human health that might be caused by exposing to pathogen and toxic substances contained in untreated wastewater. Thus the main objective in re-use project should be to minimize the exposure and reduce the potential health risk without unnecessary discouraging wastewater reclamations.

Wastewater re-use for irrigation
The practices for wastewater re-use for agricultural irrigation proved successfully in many parts of the world especially in developing countries with water resources scarcity such as: Jordan, Saudi Arabia, Peru. On the other hand agricultural use of sewage sludge (night soil) has been applied particularly in the Far East countries for many centuries.
In fact, in many countries of Middle East with severe water scarcity such as: the Republic of Yemen the main source of water for agriculture is groundwater and due to the limitations and over exploitation of that source, many countries in the region looked or are looking for other alternatives to be used for agriculture irrigation. As a matter of fact re-use of wastewater became a fact and a means of water conservation and pollution control. Many private farmers by their own initiative, especially in Yemen, started using waste water for irrigating their farms. This is a clear indication of the high demand for agricultural re-use in respect to the extreme shortage of water resources and high pumping costs. In doing so equal quantities of fresh water can be made available for potable water supply. this practice of re-using might encourage to re-consider waste water as an essential part of a water resource plan or to include it in the national water policy.

In addition to the sewage sludge, agriculturally there is an obvious benefit of waste water-reuse through conserving water resources, and using it as a fertilizer especially providing nitrogen to the soil. The recovery of the nutrients will help in reducing the direct cost to the farmer and his dependency upon inorganic fertilizer often imported from outside. If the irrigation operation is managed appropriately the water-resources (surface and ground water) could be protected from pollution such as high nitrate concentration due to the use of fertilizers on irrigated land.

The treated waste water re-use in irrigation will contribute significantly in improving or controlling the ground water resources which are the main sources (especially in Yemen) for agricultural irrigation provided that irrigation management system would be based on:-
– High frequency irrigation without increasing the applied treated effluent.
– Application of the needed effluent in amount just sufficient for plant growth having almost no excess effluent to percolate into the ground water basin.
– Application of the needed effluent with low pressure orifices or close as possible to plant roots.