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Water Turbidity is important from three aspects, desirability, filterability and disinfection. Also because of the relationship between turbidity and some microbial parameters, turbidity can be used as indirect indicator to estimate removing efficiency and rate f presence of these parameters.
In this study a statistical relation between turbidity of filtered water and removing logarithm of Giardia Cysts was also found. This relation was shown by a polominial (power law) model. Based on the model results, to achieve 99.9 percent efficiency for Giardia Cysts removing, turbidity of filtered water must be less than 0.5 N. T. U. where as on the base of national standards this value is less than one T. U and must be reviewed.