Reuse of agricultural drainage water and wastewater for crop irrigation in southeastern Algeria

Abstract

Water resources are regarded as the primary impediment to proper human development in arid and desert regions, and the situation has been exacerbated by current climate change. The same phenomenon can be observed in the Ziban region of the Biskra wilaya, where agriculture consumes the most water resources. It is due to the increase in the size of reclaimed agricultural areas from year to year as the region’s urban centres expand, causing wastewater to be discharged into agricultural sewers and discharged into the Oued Djedi. However, during our field survey, we discovered that some farmers water their crops with drainage water mixed with wastewater. This study aims to determine how climate change is affecting the region, as well as the damage caused by watering crops with agricultural and sanitary drainage water. A statistical analysis of climatic parameters (mainly rainfall) and physiochemical parameters of drainage water at six sampling points in the Occidental Zab region was carried out. We measured nitrates, calcium hardness, chloride ions, nitrates, chemical oxygen demand (COD) and biochemical oxygen demand (BOD5). The results show a reduction in the total annual rainfall rate, from 208.6 mm in 1996 to 19 mm in 2017. As for drainage water analysis, the following results were noted: SO₄ ²⁻ (mg/l) [545.45–3436.36], NO₃ ⁻ (mg/l) [0.75–3.94], BOD5 (mg/l) [10–50], COD (mgO₂/l) [14.12–72.25], Cl⁻ (mg/l) [331.33–1692.16], Ca²⁺ (mg/l) [352.68–643.23], Mg²⁺ (mg/l) [120]. The study emphasises the importance of a comprehensive assessment of wastewater for agriculture, particularly because some farmers use it to water their crops, as well as the need for targeted interventions to mitigate potential challenges associated with potential damage. As a result, these findings can help decision-makers and local stakeholders establish wastewater filtration plants, improve farmers’ water use, and protect this valuable resource.