Impact of Treated Wastewater Reuse for Irrigation Purposes in Tunisia on Crops Growth, Human Health and Soil

Cherif Hayet^*, Saidi Hakima & Elfil Hamza

Laboratory of Natural Water Treatment, Water Researches and Technologies Center, Tunisia

Dr. Cherif Hayet, Laboratory of Natural Water Treatment, Water Researches and Technologies Center, Tunisia.

Keywords: Treated Wastewater; Irrigation; Yield Decrement; Water Quality; Crops

Abstract

This work analyzed several Tunisian researches about reused water quality and their effects on crops growth and soil properties as well as harmful substances content and human health risks. Five irrigation areas were selected (Nabeul-oued Souhil, Sfax-Elhajeb, Sousse-Zaouit, Borj Touil and Gabés-El Hamma). Results Showed a very higher TWW conductivities (3.5-5.6ms/cm). An important level of toxic compounds were observed; sodium from 4.87meq/L to 32meq/L, Chloride from 15.45 to 49.77meq/L and nitrate from 13.4 to 22.74mg/L compared to FAO guideline which recommended 3meq/L, 4meq/L and 5mg/L respectively. A medium sodium hazard was observed (SAR ranged from 1.33 to 10.74). Due to higher salinities TWW were classified according to Riverside as doubtful (C₄S₁) and unsuitable (C₅S₁ and C₅S₂) for irrigation purposes. Nutrients, trace of metals (cadmium, lead, iron and manganese), SS, biochemical and chemical oxygen demand exceeded sometimes the Tunisian restrictions 106.03 for water reuse. Pathogens and drug degradations were also detected in some Tunisian regions (Sapovirus, antibiotic resistance genes, polycyclic aromatic hydrocarbons and polychlorinated biphenyls). Reused wastewater in irrigation with current quality can reduce crops yield growth 50% for olive, citrus and pomegranate and 25% for sorghum, corn and bersim. To prevent human health risks, soil properties modification and damage, defoliation and desiccation of plants, desalination of treated wastewater with an adequate pretreatment steps and hybrid membrane systems combined reverse osmosis and nanofiltration was necessary.

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