الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
The main drinking water sources for Alexandria Metropolitan area are El-Mahmoudia and El-Nubaria canals. They supply water treatment plants (WTP), ran and managed by Alexandria Water Company with the raw water.
Sanitary drinking water supply from surface fresh water includes several steps; raw water collection, pre-chlorination, coagulation, sedimentation, filtration, disinfection, storage and distribution (using chlorine).
Filtration processes is one of the most important treatment process for reducing water turbidity. Filters can be classified into gravity filters {slow sand filter (SSF) and rapid sand filter (RSF)} and pressure filters (high rate filter)
The major advantage of RSF is that the coarser sand has relatively higher voids ratio which do not fills and seal off quickly. Rapid sand filters are effectively run when water contains variable and relatively high turbidities. The major disadvantage of the RSF is that only the top layer of the sand (15 to 25cm) does most of filtration, therefore about 80% of the bed is not being used effectively. The filtration rate of the dual media filter is around 3- 4 times the filtration rate of RSF. The major advantage of dual media filters is coarse to fine gradation of filter media. In operation, the coarse layer on the top removes the larger suspended particles, and then the finer particles pass through this layer and are removed by finer media below. As a result, most of filter bed is used to remove suspended particles, and allows for longer operation time before back wash (filter run) and higher filtration rates
This study was accomplished by using dual media filter (anthracite and sand) and conventional filter (sand filter).
The present study was performed in the pilot plant of Alexandria Water Company form April 2016 to December 2016, aimed to improve the water quality and increase productivity of the water purification
The present study was carried out to evaluate the performance of Anthracite -Sand dual media filter and conventional rapid sand filter and compare the produced water quality from the two different types of water purification technologies (conventional filter and dual filter).
Water samples were collected from two sites: Settled water (influent) and Filtered water (effluent) for each filter run, the following parameters were measured and recorded:
Physical water quality indicators: turbidity and Color, Chemical water quality indicators: TOC and Ammonia, Biological water quality indicators: THPC, TC, FC, Total Algal Count, Blue green algae and Protozoa and operation indicators: head loss, filtration rate, filter run time and amount of water Backwash.
The results of the present study showed that the pilot filter using Anthracite -Sand dual media filter had the greatest effect on improving water quality.
The mean value of turbidity for conventional filter was 0.92 NTU with percentage reduction 81.2%, while the mean value of dual filter was 0.3 NTU with percentage reduction 93.3%. The results of paired t-test show high significant difference (p<0.001) between the two filters types towards values of turbidity.
The mean value of color for conventional filter was 22.1 Hz with percentage reduction 39.73%, while the mean value of dual filter was 6.16 Hz with percentage reduction 82.93%. The results of paired t-test show high significant difference (p<0.001) between the two filters types towards values of color.
The results of paired t-test show high significant difference (p<0.001) between the two filters types towards values of TOC. Because the mean value of TOC for conventional filter was 2.99 mg/l with percentage reduction 35.32% while the mean value of dual filter was 1.26 mg/l with percentage reduction 75.14 %.
The results showed that dual filter more effective than conventional filter for removal ammonia where, the mean value of ammonia for conventional filter was 0.408 mg/l with percentage reduction 65.48 % while the mean value of dual filter was 0.05 mg/l with percentage reduction 95.32 %. The results of paired t-test show high significant difference (p<0.001) between the two filters types towards values of ammonia.
The results of THPC removal obtained by dual filter more effective than conventional filter where, the mean value of THPC for conventional filter was 22 CFU/ml with percentage reduction 80.6 %, while the mean value of dual filter was 8 CFU/ml with percentage reduction 92.3%. The results of paired t-test show high significant difference (p<0.001) between the two filters types towards values of THPC.
The Dual filter was better than conventional filter in TC removal, because the percentages of positive samples of TC collected from Conventional filter and Dual filter were 64.5% and 5.6 % respectively.
Also the results refer to Dual filter was better than conventional filter in FC removal, the percentages of positive samples of FC collected from Conventional filter and Dual filter were 5.6% and 0 % respectively.
The percentage reduction of total algal count for conventional filter and dual filter was 43.9% and 75.6% respectively. The results of paired t-test show high significant difference (p<0.001) between the two filters types towards values of total algal count.
The percentage reduction of blue green algae for conventional filter and dual filter was 25% and 78.2 % respectively. The results of paired t-test show high significant difference (p<0.001) between the two filters types towards values of blue green algae.
The Dual filter was better than conventional filter in protozoa removal, because the percentages of positive samples of protozoa collected from Conventional filter and Dual filter were 38.8 % and 5 % respectively.
The results of head loss mean for the Conventional filter was 77.25 cm. On the other hand, the mean value of the Dual filter was 58.8 cm. This mean that the dual - media (anthracite -Sand filter) had run time longer than Conventional filter and backwash frequently less than Conventional filter and then the amount of water consumed in backwash by dual - media anthracite -Sand filter was less than that consumed in mono-media sand filter.
The study recommended that:
1- Application of using dual filter (Anthracite and sand filter with depth 50 cm and 100 cm ) respectively in drinking water purification plants is recommended due to:
• Reduction the turbidity, colour, ammonia, TOC, THPC, TC, FC, total algal count ,blue green algae and protozoa.
• Increasing run time of filter and decrease loss of water amount which used in filter backwash.
• Avoid release of algal toxin to water.
• Reduction the cost of loss of water amount and electricity.
• Solve the taste and odor problems.
• Reduction of disinfectant dose.
2- High filtration rate should be used instead of constant rate controller to increase filtered water production.
3- Further researches are needed to evaluate the relationship between different Anthracite depths for completely removal of protozoa and blue green algae.