Filtration process has an evident manner. Primarily, surface of the filter media is not ready to adsorb particles, therefore some of them would have the chance to pass through the filter, which causes the unsuitability in the quality of the effluent. After a few minutes, the surface media would obtain the capability to adsorb the particles and idiomatically would have the chance to get ripened. The ripening stage would improve the effluent quality up to a level, which stays approximately constant through the end of the operation time. The effect of filter ripening stage on the removal of giardia cysts is evaluated in this study by using a laboratory pilot consisting of raw water supplying system, coagulation unit, flocculation unit, single and triple media filters. The results obtained showed that the average number of cysts in the effluent related to the ripening stage is greater than the number of the average cysts in the effluent related to the whole operation time. It was also seen that addition of two milligrams of ferric chloride to the filter washing water during the rinsing period would enormously improves the quality of the effluent and shortens the ripening stage.
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