In urban and peri-urban zones in developing countries, poor farmers commonly use nutrientenriched sewage and wastewater to irrigate high-value crops. In many places, this untreated wastewater is their only source of irrigation water-so their livelihoods depend on it. On the other hand, the unregulated use of wastewater also poses risks to human health and the environment. Wastewater irrigation can also significantly contribute to urban food security and nutrition. Recent studies in several Asian and African cities have revealed that wastewater agriculture has accounted for over 50% of urban vegetable supply. it is estimated that one tenth or more of the world’s population currently eats food produced on wastewater (but not always in a safe way).
The study focused on two study areas: the Kafue Lagoon area and along the Ngwerere river and Ngwerere is a small river whose origin is in the city of Lusaka and it stretches over a distance of approximately 30 kilometers. In Zambia despite the health hazards associated with crops grown in the Kafue Lagoon using wastewater from Nitrogen Chemicals of Zambia (NCZ), Shikoswe stream and Lee Yeast, trucks loaded with a variety of vegetables and sugar cane came from Kafue about 50 kilometres south-west of Lusaka to Kamwala and Soweto markets to sell these products. Similarly the Ngwerere River has its share of urban and peri-urban agricultural activities despite the river being biologically polluted. it was demonstrated that the river exhibited significant self-purification capacity along its stretch from Garden Compound to the confluence with the Chongwe River. The current study incorporated BOD, COD, and total nitrogen and flow measurements as recommended in previous studies. The current study also linked water analysis to the users of water, a link that was left out in previous studies.
The methods used during the study were both qualitative and quantitative in the generation of information as well as documenting the findings. Various documents were reviewed on the work done on utilization of wastewater or nutrient enriched water in Zambia and other parts of the world including various legislative articles from institutions such as the Environmental Council of Zambia, Department of Water Affairs and Ministry of Health were also reviewed. Other documents such as the WHO guidelines and ECZ wastewater standards on the safe use of water for irrigation were also reviewed.
The growing and selling of crops in both study areas was the main source of cash income and food for most of the peasant farmers; Using ECZ, WHO, EU, DWA, ZABS and other guidelines the suitability of the water for various uses especially irrigation was determined. It was found that the water in the Ngwerere River and Kafue Lagoon Area was suitable for restricted irrigation of folder crops, and fruit trees and but not for salad crops and vegetables except at Kasisi Mission (Ngwerere). The water at all sampling points was not suitable for drinking; There was no evidence of pollution by heavy metals that may pose a threat to the irrigated crop consumers during the study period; Health risks associated with the use of water in the Ngwerere and Kafue Lagoon Area could be reduced if the contaminants (especially pathogens) were reduced or eliminated at the source through improved treatment of wastewater; The main irrigation method practiced during the study was the use of containers; In both study areas the users considered the wastewater to be economically valuable for irrigating crops in spite of risks associated with using such water.
The Ministry of Agriculture and Cooperatives (MACO) should incorporate reuse of wastewater or nutrient enriched water in the irrigation strategy which aims at improving food security and poverty alleviation in the country. Further studies need to be undertaken to check the seasonal variation of the parameters and prevention of helminthes among irrigators and consumers from both study areas.