Agronomic aspects and environmental impact of reusing marginal water in irrigation: a case study from Egypt

Abstract

Egypt produces approximately 2.4 million m3 of secondary treated wastewater (TWW) annually, used for irrigation directly or indirectly by blending with agricultural drainage water (BDW). The annual re-use of (BDW) is approximately 4 million m3. The safe and efficient use of marginal water (BDW and TWW) is a core objective of this study which has been operating from 1997 to date. After six growing seasons the main results can be summarized as follows: MAXIMIZING CROP PRODUCTION: TWW can be used for high production of oil crops (canola, soybean sunflower or maize) compared to fresh water, while BDW can be used for high production of tolerant crops (cotton and sugar beet). CROP QUALITY: using marginal water increases the concentration of elements (Pb, B, Ni, Co) in all crops but these elements were under critical levels (there were no toxicity hazards). It is better to use alternative irrigation with fresh water under a drip irrigation system to maximise crop production and minimise the adverse effects of such water in field crops quality. SOIL POLLUTION AND SALINITY BUILD UP: A drip irrigation system under alternative irrigation by fresh with TWW or BDW reduces salinity build up risks and the levels of elements (Pb, B, Ni, Co) in soil compared to re-use marginal water. SOIL PATHOGENS: Using marginal water slightly contaminated the soil with total faecal coliform (TFC), mites, shigella and salmonella. PLANT ANATOMY: No great changes in anatomical disturbance where induced in different structures of plants which were reduced at maturity stage. PRIMARY GUIDELINES FOR RE-USING MARGINAL WATER: From obtained results it can be recommended to use marginal water with salinity content ranged between 1.1 to 3.64dS/m, and elemental contents (Pb 3.0-3.51 ppm), (B 0.05-1.67 ppm), (Co 0.04-0.07 ppm), (Ni 0.08-0.15 ppm) for safe (field, vegetable and medicinal) crops production. REUSE BIO SOLIDS FOR CROP PRODUCTION: Sewage sludge produced from treated wastewater can be safely used by mixing with rice straw (1:1 w/w) for economic crop production and saving mineral fertilisers. GENERAL CONCLUSION: In the North Nile Delta, marginal water (especially BDW) can be safely used without significant negative impact on the environment, but there is a need for multi-disciplinary, long-term research to investigate irrigation with marginal water in terms of the environment, public health and agricultural productivity.

Profiles and Risk Assessment of Heavy Metals in Great Rift Lakes, Kenya

“…Higher As and Hg concentrations may be from agricultural chemicals, industrial discharge and automobile emissions . Nickel was also to be found in all major types of commercial fertilizer products and in reusing marginal water for irrigation in Africa . Therefore, PC1 was noted as anthropogenic factor.…”

Microbiological Safety of Strawberries and Lettuce for Domestic Consumption in Egypt

“…Especially the sanitary quality of the manure and the irrigation and washing water influences the microbiological quality and safety of the fresh produce [26][27][28][29]. Also in Egypt, farmers are reported to re-use waste and agricultural water from drainage canals, despite the official prohibition of such practices, due to the limited availability water for irrigation [30].…”

Global Bibliometric Analysis of Research on the Application of Unconventional Water in Agricultural Irrigation

“…Wastewater irrigation also affects heavy metal content in crops due to crop absorption. A multi-year study in Egypt found that the use of marginal water irrigation increased the concentration of elements (Pb, B, Ni, Co) in all crops [50]. Xue, Zhan-Jun et al [51] found that the concentrations of the elements Cd, Zn, and Ni in vegetables collected from wastewater-irrigated soil exceeded the maximum allowable limits, which increased the daily intake of metals in food.…”