Application of Secondary Treated Municipal Wastewater for Irrigation of Agricultural Lands: Quantitative Microbial Risk Assessment of Legionella

Water scarcity is a main issue in most countries in the worldwide. Nowadays, irrigation with treated wastewater is becoming a necessary alternative to addressing issues of water shortage, especially in arid and semiarid countries.The potential health risks and environmental impacts resulting from inadequate microbial quality of treated wastewater have been well known and is a challenge for developing countries. In this study 25 effluent samples were collected from Isfahan wastewater treatment plant and presence of Legionella in STWW samples were monitored using nested real time PCR. As well as using the quantitative microbial risk assessment model, Legionella risk due to the use of secondary effluent for spray irrigation of agricultural lands for farmers was determined. Legionella was detected in %84 of STWW samples. The mean annual Legionella disease risk ranged from 7.7 × 10-8 to 1.5 × 10-5 pppy which was lower than the reference level of 10-3 pppy has been recommended by WHO.  The results of this study showed that use of STWW for irrigation, dose note significant health risk associated with Legionella for farmers. Also, STWW could be used as an alternative source for agricultural irrigation in semiarid areas.