الفهرس 
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Abstract
The present study aimed to detect the problem of the early seasonal clogging of water filters which increase during autumn and when the level of the Nile River reduce and to find solutions to avoid such a problem, which causes a lot of damages (for example lose a lot of water during back washings process).
Also to show the relationship between the algal groups and some physico-chemical parameters.
Water samples were collected seasonally (June 2017-May 2018) from El-Fostat water plant .The purification run through 7 Stages for the water treatment plant .The first stage is the water Nile samples (raw water), second stage is chlorination stage, third stage is the clarifier, 4, 5 and 6 stages are the different filters (3 ordinary sand filters) and the last stage is the reservoir.
Consequently, many experiments were carried out using active carbon and sterilized rice straw as a layer above sand filters to find the effect of both of them on algal removal, resulting in solving the problem of clogging. Physico-chemical Parameters
Physical parameter Water Temperature (°C)
The water temperature was relatively low during winter months 17.4°C at stage 1 and 17.5oC at stage2 and stage7 while it were slightly warmer during autumn and spring months (22°C and 23.5°C) for all stages. But it is slightly high during summer for all stages, it is ranged from 29oC at stage 1to 30.4°C at stage7.
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Hydrogen ion concentration (pH)
The present results revealed that the seasonal variations for pH values ranged between 8.12 - 8.28 for stage1, 7.46 - 7.75 for stage 2 , 7.28 – 7.41 for stage 3, 7.13 - 7.4 stage 4, 7.11 -7.33 for stage 5 , 7.27-7.3 for stage 6 and 7.26-7.29 for stage 7 which were always in the alkaline side.
Electrical Conductivity [EC (μS/cm)]
Values of electrical conduction in the most valuable recorded seasonal variations of EC ranged from 336.6 to 494.4 for stage1, from 355.3 to 501 for stage2, from 340 to 505 for stage3,from 344 to 504 for stage4, from 345 to 505 for stage 5, from 351 to 508 for stage6 and from 359 to 513 for stage 7.
Total Dissolved Solids [TDS (mg/L)]
The seasonal average of TDS recorded 332 mg/L as a maximum value during winter, while the minimum value of 221 mg/L was determined during spring.
Dissolved Oxygen [DO (mg/L)]
In the present results revealed that the seasonal variations of DO ranged between 7.27 mg/L during summer(where the lowest phytoplankton biomass exited) and 9.06 mg/L during winter (where the highist phytoplankton biomass exited) for stage1. While ranged between 7.4 mg/L and 9.06 mg/L during summer and winter for stage 2and between 7.78 and 9 mg/L during summer and winter for stage3, 7.96 mg/L and 9.12 mg/L during autumn and winter for stage 4 , between 7.95 mg/L and 9.1 mg/L during autumn and winter for stage5, between 7.84 mg/L and 9.1 mg/L during summer and winter for stage 6 between 7.7 mg/L and 9.09 mg/L during summer and winter for stage7.
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Turbidity (NTU)
The minimum value of 0.38 NTU during winter in stage 7, while its maximum value was 12.8 NTU during autumn in the stage 1. The seasonal average values of turbidity ranged between 2.7 NTU during summer and 3.9 NTU during autumn.
Chemical parameters
Total alkalinity [CaCO3 (mg/L)]
The values of alkalinity ranged from 134.6- 151.3 for stage1, from 125.3-145.3 for stage2, from 113.5 - 126 for stage3, from 112-126.6 for stage4 , from 114.6 – 126.6 for stage 5, from 114 – 128.3 for stage 6 and from 112-126 stage 7. The maximum value of 151.3 mg/L was during winter, while the minimum value of 112 mg/L was during spring.
Nitrite [NO2 (ppm)]
The maximum value of 0.064 ppm was determined in stage 1 during autumn and a minimum value of 0 ppm was detected in stages 4, 5, 6 and 7 during seasonal changes. The seasonal average value reached 0.029 ppm as a maximum value during summer, while the minimum value of 0.005 ppm during winter.
Phosphate [PO4 (ppm)]
The maximum value of 0 .056 ppm was recorded in stage 3 during winter, while the minimum value of 0 ppm was determined in all stages during summer, spring and winter. The maximum seasonal average value of 0.032 ppm was recorded during autumn, while the minimum value of 0.0038 ppm during spring.
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Chlorides (Cl) mg/L
The chloride contents increased at different sites during autumn, it reached its maximum value of 39.3 mg/L at stage 3 during autumn, while it s minimum value of 24.5mg/L was recorded at stage 1 during spring. The maximum seasonal average value of 37.28 mg/L was recorded during autumn, while the minimum average value of 26.1 mg/L during spring. The distribution pattern of seasonal variation values could be arranged in the descending order: autumn > winter > summer > spring.
Fluoride (ppm)
The maximum value of 0.63 ppm was determined at stage 4 during winter and a minimum value of 0.074 ppm was detected at stage 3 during summer. The seasonal average value reached 0.48 ppm as a maximum value during spring, while the minimum value of 0.164 mg/L during summer. The distribution pattern of seasonal variation values could be arranged in the descending order: spring > winter > autumn > summer .
Silicate (ppm)
The maximum value of 5.44 ppm was determined at stage 1 during summer and a minimum value of 0.15 ppm was detected at stage 7 during autumn. The seasonal average value reached 3.5 ppm as a maximum value during summer, while the minimum value of 0.26 ppm was recorded during autumn. The distribution pattern of seasonal variation values could be arranged in the descending order: summer > spring > winter> autumn.
Biological parameters
The phytoplankton community was presented in the investigated area by a total of 44 species belonging to 26 genera
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and 3 groups namely; Bacillariophyceae, Cyanophyceae and Chlorophyceae.
Bacillariophyta:
The results revealed that stage 1 there was in 4740 X103unit/L during autumn, 4514 x103unit/L during winter, 2259 X103unit/L during summer and 2183 x103unit/L during spring. In this investigation the total of 8 Bacillariophyta species were recorded belonging to 3 genera.
Cyanophyta
In this investigation a total of 11 Cyanophyta specie where recorded .The results revealed that in stage 1 there was 1099.7 x103 unit/L during autumn, 499.9 x103 unit/L during winter, 66.5 x103 unit/L during summer and 249.9 x103 unit/L during spring.
Chlorophyta
The results revealed that in stage 1 there was 149.6 x103unit/L during autumn, 481.7 x103unit/L during winter, 99.6 x103unit/L during summer and 383.2 x103unit/L during spring. In this investigation a total of 25 Chlorophyceae species were identified.
Sand Analysis
The Effective Size (ES)
Stage 4 has an appropriate an effective size of 0.916 mm, stage 5 was found to have an suitable an effective size of 0.983 mm and stage 6 was found to have an suitable an effective size of 0.95mm.