Evaluation of Shiraz wastewater treatment plant effluent quality for agricultural irrigation by Canadian Water Quality Index (CWQI)

Background: using treated wastewater in agriculture irrigation could be a realistic solution for the shortage offresh water in iran, however, it is associated with environmental and health threats; therefore, effluent qualityassessment is quite necessary before use. the present study aimed to evaluate the physicochemical and microbialquality of shiraz wastewater treatment plant effluent for being used in agricultural irrigation. in this study, 20physicochemical and 3 microbial parameters were measured during warm (april to september) and cold months(october to march). using the measured parameters and the canadian water quality index, the quality of theeffluent was determined in both warm and cold seasons and in all the seasons together.results: the calculated index for the physicochemical parameters in the effluent was equal (87) in warm and coldmonths and it was obtained as 85 for the seasons all together. when the microbial parameters were used in orderto calculate the index, it declined to 67 in warm and cold seasons and 64 in all the seasons together. also, it wasfound that three physicochemical parameters (tds, ec, and no3) and three microbial parameters (fecal coliform,helminthes egg, and total coliform) had the most contribution to the reduction of the index value.conclusions: the results showed that the physicochemical quality of shiraz wastewater treatment plant effluentwas good for irrigation in the warm, cold, and total of the two kinds of seasons. however, by applying themicrobial parameter, the index value declined dramatically and the quality of the effluent was marginal.