Assessing Backwash Water Quality from Rapid Sand Filters in Order to Reuse in Agriculture and Irrigation of Green Space (Case Study of Sanandaj Water Treatment Plant)

The effluent from the backwashing of the filters used in water treatment can be considered as one of the potential functions for reuse for various applications, provided that it has the required quality. The purpose of this study was to determine the quality of effluent from backwashing of rapid sand filters in Sanandaj water treatment plant for reuse. For this purpose, in two high and low water seasons, the effluent of phases 1 and 2 of the water treatment plant was sampled and the physical, chemical and microbial properties of the samples were studied using standard methods for drinking water, agriculture and green space uses. The data were analyzed using SPSS software and one-sample t-test and independent t-test. The results showed that the mean value of all the studied parameters in the effluent from the backwashing of the filters of the phases No. 1 and 2 of the treatment plant was less than the standard of agricultural and green space use. Compared with the drinking water standard, only the mean values of turbidity (48 NTU in phase 1 and 45 NTU in phase 2), total coliform (4 MPN for phase 1 and 6 MPN for phase 2) and fecal coliforms (1 MPN for both phases) parameters in the effluent were significantly higher than the standard (p <0.05). The results also showed that there was no significant difference between the mean of the studied parameters in the treatment plant effluent in the two phases and the autumn and winter seasons (p <0.05). Finally, it was found that it is possible to use the effluent for agricultural and green space use, but it could be reused for drinking purpose only after treatment.