The present study was carried out in EL-Fostat water plant in order to find out the problem of early seasonal clogging of the sand filters during Autumn season and during the low level of the Nile River. This problem causes a lot of damages, e.g. losing of water during the back washing process and increasing of the used chemical doses used in the process of drinking water treatment (chlorine and aluminum sulphate). Also the study provides proper information on the phytoplankton communities, turbidity and phenol. The phenol experiment is very important to insure that the produced filtered water from the sterilized rice straw doesn't contain any phenolic compounds. Water samples were collected from stage1 (the raw water), stage 2 (after pre-chlorination), stage 3 (the clarifier) and stage 4 (the ordinary filters, sand only).
The results revealed that the algae, especially diatoms (Synedra ulna) were the main cause of the early clogging of filters. In order to find a solution for this problem, several experiments were done by using two types of filters (activated carbon and sterilized rice straw beside the ordinary sand filters). These treatments proved the solving of this problem and helped to extend the filtration period to about 24 hours instead of 8 hours. So that this reduction of the washing time of the sand filter for one time, instead of three times leads to a provision of large quantities of water at El- Fostat water plant and reduce the doses of the used chemicals.