الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
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Abstract
Water is a unique substance. It is one of the most essential component. of the human environment. Man needs it for his physical existence as well as for his civil activities. In Alexandria governorate. many water purification plants were installed. Bab-Sharky water purification plant IS one of the largest plants. Water filtration process In Bab-Sharky water purification plant is essential and controls the produced water quality. In Bab-Sharky plant, the rapid sand filters are in operation. This work intend to evaluate the efficiency of the rapid sand filters In removIng biological and suspended matter and to determine the quality of filtered water. , A sanitary survey was carried out for the differe~~ types of filters of Bab-Sharky purification plant. The present state of the filters were evaluated by taking samples from influent. effluen~ and effluent water samples after 4 k ~) minutes of the backwash process. Also sand samples werp taken from the filter at different depths (at surfacE:, 15. 30. SC. and 80 cm). ~ r Collected water and sand samples were analysed for physical, chemical and biological parameters according to the standard methods for analysis of water and wastewater. from the results of the sanitary survey, Italba filters No. 1 and No. 12 were chosen for this study and 10 runs were carried out for one year from October 1988 to September 1989. Wi th respect to Degremont type, filters No. 52 and No. 54 were chosen for this study and 10 runs were performed for one year from February 1990 to January 1991. The results of the previous analysis of the two types of filters are summarized as follows: The physical and chemical quality of the influent water entering the filte~ were relatively constant through out the whole study. Italba filter remove a part of the turbidity present in the influent water which was found to be 6.2 percent. The bad condition of Degremont sand had increased the turbidity in the effluent water by 60 percent. Regarding the biological parametel. Italba filter had low efficiency ln removing total bacterial count from influent water, the percentage of removal was 5.3 percent, wh i 1 e Degremont filter had increased the total count of bacteria by 1.7 percent in the effluent water. Algal removal in Italba filter was up to 80 percent and in Degremont filter was 92 percent. Fungi were removed by 88 percent by Italba filters and were increased by 80 percent in the effluent water of Degremont filters. High percentages were found for removing yeast from influent water by Italba and Degremont filters. The percentages were 88 and 85 percent for the two filters respectively. The results of experiments carried out for evaluating the efficiency of the backwash process exhibited the following: , Aftel~ 45 minutes of backwash process either Italba or Degremont filters had no influence in improving the quality of influent water due to incomplete formation of the biofilm at the sand surface of the filters. Regarding the effect of the backwash process on the sand media. Suspended particles measured as turbidity present on the sand layers were decrease~ by bad:wash process to 65 anc 67 percent for Italba and Degremon~ filters respectively. Total bacterial counts present on sand layers were removed by backwpsh process of Italba and Degremont filters by 80 and 90 percent for the two filter respectively. ThE backwash process removed also algae accumulated at the sand layers of Italba and Degremont filters by 97 and 96 percent respectively. Fungi and yeast were removed from sand layers by the backwash process of Italba filter up to 62 and 65 percent for fungi and yeast respectively. while the backwash process of Degremont filters removed the fungi and yeast existed on the sand layers by 71 and 61 percent f Ol~ fungi and Y ”””’’’”’ ~u._ respectively. . , Parasltes was removed from the sand layer of Italba and Degremont filters not only by backwash but a Ise. by disinfection process of the filters themselves. According to the previous results, the followings are recommended to improve the efficiency of rapid sand filters in Bab-Sharky purification plant: 1- The purification process (coagulation and flocculation) before the filtration process must be performed perfectly to prevent suspended matter such as algae to reach the filter. because this suspended matter cause the clogging 0: the filters. 2- The backwash process of the filters using air and water to remove the dirty substances accumulated on the sand surface IS necessary for preventing the cracks, mud balls formation and filter clogging. 3- The time of bac~ash process must be enough to remove all the undesirable matters present in the filters. 4- The backwash process of the filter must be carried out every 24 hours or as the recommended design to avoid the increase of total bacterial count Inside the fi 1 te~’ and E the effluent water. 5- The effluent water after the backwash process of the fi I teJ mus” r:L b~ collected dire~tly into storag tanks because th~ filter in this case has no influence in removing substance~ till the biofilm is formed on the sand surface. So. it is recommended to collect filtered water after 20 minutes from the backwash process. 6- The disinfection process of the filter by bleaching powder (Calcium hypochloride) every si:,: especially months durIng summer IS essential for removing of parasites from the filter and hence increases the efficiency of the filter in removing of microorganisms. 7- It is recommended to use rapid sand filters only those having more than 60 cm depth of sand media to obtain a good quality of filtered water. , 8- Study on the effect of the algae species retained by the sand f i I ter and those go i ng wi th ef fluent water after the bac)~wash process on the water quality. Also. the effect of the disinfection process of the filters on these species of algae