Treated Wastewater Irrigation—A Review

Abstract

As the most important resource for life, water has been a central issue on the international agenda for several decades. Yet, the world’s supply of clean freshwater is steadily decreasing due to extensive agricultural demand for irrigated lands. Therefore, water resources should be used with greater efficiency, and the use of non-traditional water resources, such as Treated Wastewater (TW), should be increased. Reusing TW could be an alternative option to increase water resources. Thus, many countries have decided to turn wastewater into an irrigation resource to help meet urban demand and address water shortages. However, because of the nature of that water, there are potential problems associated with its use in irrigation. Some of the major concerns are health hazards, salinity build-up, and toxicity hazards. The objectives of this comprehensive literature review are to illuminate the importance of using TW in irrigation as an alternative freshwater source and to assess the effects of its use on soil fertility and other soil properties, plants, and public health. The literature review reveals that TW reuse has become part of the extension program for boosting water resource utilization. However, the uncontrolled application of such waters has many unfavorable effects on both soils and plants, especially in the long-term. To reduce these unfavorable effects when using TW in irrigation, proper guidelines for wastewater reuse and management should be followed to limit negative effects significantly.

Suitability of the Decentralised Wastewater Treatment Effluent for Agricultural Use: Decision Support System Approach

“…However, the AF effluent proved to be unfit for maize production with regards to contribution to N and P uptake. This is contrary to reports given by some authors [30,31] that treated wastewater can supply nutrients to increase crop yields, which is not always the case. Overapplication of nutrients such as N is likely to cause delayed flowering and uneven ripening.…”

Integrative Effects of Treated Wastewater and Synthetic Fertilizers on Productivity, Energy Characteristics, and Elements Uptake of Potential Energy Crops in an Arid Agro-Ecosystem

“…It activates various enzymes involved in the metabolism of plants. Studies have shown that in soils that receive TWW for irrigation, the availability of total N, K, and available P increase considerably [52][53][54][55][56]. Similarly, Abd-Elwahed [57] and Xu et al [58] observed increased total N, available K, and P contents in the top layer of soil for irrigated plants with wastewater.…”

“…Therefore, the continuous availability of essential nutrients present in TWW enhanced total chlorophyll, photosynthesis rate, and plant growth, which then results in higher maximum leaf area, plant height, and total biomass. TTW also contains the trace-elements (Mn, Zn, Fe, and Cu) and organic matter necessary for plant growth [56,59]. This makes TTW rich in fertilizers that can increase the fertility of soil and enhance crop yield [60][61][62], since trace-elements have critical importance and play significant roles in plant growth and development.…”

“…Cu acts as a component of metalloenzymes, involved in regulation of enzyme activity and acceleration of oxidative reactions [70,71]. Thus, the nutrient elements present in TWW can be used as fertilizer for enhancing the fertility of soil and the growth and production of crops [6,8,16,56]. Therefore, the growing of crops on soil with an adequate amount of nutrients results in the faster and more vigorous growth of plants and, consequently, a higher economic yield [7].…”

“…As a result, the 100% NPK dose did not present important differences in growth, productivity, or energy traits in the tested crops. As already mentioned, TWW contains various nutrient elements such as N, P, K, B, Fe, Mn, Zn, and Cu, as well as a significant amount of OM [8,56,59]. This makes TWW rich in fertilizer, which can increase soil fertility and enhance the dry biomass of plants when irrigated with TWW, as well as reduce the use of synthetic fertilizers [8,78,87,88].…”