الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Generally, studies on drinking water aimed at provision of safe, hygienic and affordable instant drinking water to the consumers. However, protozoa are often encountered in water; they include ; Cryptosporidium spp., Giardia spp. , Entamoeba histolytica, Cyclospora spp. , Microsporidia spp. , and Isospora spp. All of these organisms produce environmentally resistant cysts or oocysts. These organisms are potential pathogens associated with water related diarrhea outbreaks.
Raw water supply system in Alexandria is derived from El-Mahmoudia Canal and El- Noubaria Canal , both receiving flows from the Rosetta Branch of the Nile River. The raw water quality system is influenced by non point, and point pollution discharges along all its rural and urban reaches including Alexandria.
Alexandria Water Company (AWCO’s) raw water supply system conveys water to the intakes for all water treatment plants (WTPs) in Alexandria. The Drinking Water Canal a special branch from El- Mahmoudia Canal is owned and operated by AWCO solely for drinking supply purposes, it supplies Sharky WTP.
The treatment process of raw water in the Sharky WTP includes, chemical clarification using alum , followed by rapid sand filtration, and disinfection by chlorine in reservoirs. Coagulation , sedimentation , and filtration are the most commonly employed methods for physical removal of parasites.
The aim of the present study was to detect protozoal contamination in ; surface water, in different steps of treatment in Sharky WTP, and in the distribution system network in Alexandria. This included tracing the sources of pollution in El-Noubaria Canal , El-Mahmoudia Canal , and the Drinking Water Canal ; study of the physico-chemical parameters, and detection of protozoa in the various parts of the drinking water system during the four seasons. Using different staining techniques for evaluation and identification of protozoa in water samples.
To fulfil the aim of the present study, water samples were collected seasonally for one year as follows ; for Raw water supply system : eight sites for water collection were chosen at each of the three raw water canals , taking in consideration distance and probable sites of contamination , for Sharky WTP : water samples were collected from the steps of water treatment process; clarification, filtration, and the disinfection process in reservoirs, for Distribution network : 30 houses were chosen randomly, representing three districts supplied by drinking water from the Sharky WTP : Sidi-Gaber, El-Shatby, and Bahary (10 houses from each zone). Samples were taken from first floor tap water, and from roof tank in the same house.
The following physicochemical parameters were measured in each sample: colour , odour, temperature, pH , turbidity , conductivity , total alkalinity , chloride , total hardness , nitrates , nitrites , ammonia , total dissolved solids, organic load , and residual chlorine.
All samples were examined for protozoa, there were counted when found. Identification of protozoa cysts and / or oocysts were performed as follows: Ten liters samples were collected , filtered through a special membrane filter apparatus , collected from the membrane filter and sedimented by concentration. Protozoa were identified using three stain techniques : Lugol’s iodine , Trichrome stain and Modified Ziehl – Neelsen , microscopic examination was carried out , after staining , to identify and determine the presence of protozoa.
Sources of pollution in the vicinity of each canal were studied. It was noticed that the main sources of pollution in El- Mahmoudia Canal were ; contamination by agricultural as well as industrial wastes. Irrigated agriculture is the main activity for most of the rural population. Sewage in the system, polluted water from domestic and household needs add to the contamination of the canal. Domestic wastes from the settlement of inhabitants living along the banks of the canal, animal wastes from barnyard, refuse that is disposed of along the stretch of the canal, drain carrying irrigation drainage water mixed with domes¬tic waste water into the canal , were all observed in El- Mahmoudia Canal. In El-Noubaria Canal , the main source of pollution was through pouring of four agricultural drains , in addition to waste loads from industrial effluent .
Study of the physical and chemical parameters of raw water in the three canals was carried out to estimate the effect of pollution in the different seasons. All samples were analyzed according to the Standard methods for the examination of water and wastewater.
Colour and odour of water in the three canals was normal during the different seasons. It was noticed that no sources of thermal pollution existed in the three canals and slight differences were attributed to the normal seasonal variation in temperature. The pH values were almost in the normal range which is slightly alkaline due to the presence of the silt alkaline metals in water. Turbidity was found to vary in the different canals and seasons. The lowest value was recorded in the Drinking water canal during spring, and the highest value was recorded in El-Noubaria canal during winter followed by summer. The highest value may be due to the low water level in the canal during winter which is centrally determined by the Irrigation Sector, and is due in summer to the presence of high phytoplankton density. Electrical conductivity of raw water in the three canals agreed with Egyptian Standards for drinking water.
The values of the chemical parameters ; chlorides, total hardness and total dissolved solids were within the normal range in the different seasons. High Alkalinity values were recorded in almost all locations during the whole year and exceeded the standard limits of the Egyptian law for the raw water; this indicated the presence of pollutants in the raw water, and increase in carbonates and bicarbonates. Nitrate and nitrite in the different seasons agreed with the Egyptian Standards, but increased during winter in the three canals. Ammonia results indicated the presence of organic pollution in the three canals. Organic pollutants may be due to the discharge of human wastes and relatively high concentrations of organic compounds in the canals, or might be due to the decaying aquatic vegetation. The highest value of ammonia was detected during winter, because of the low water level in the canals, and consequently the contaminant level was raised.
The treatment process of surface water in WTP includes , clarification , filtration and disinfection. Clarification and filtration are the most important steps for removal of turbidity and microorganisms. The water effluent of the clarifiers showed that the decreased turbidity was high by clarification process. The annual mean value of turbidity decreased by 75% from influent of the clarifiers. Compared with raw water , the values of pH , alkalinity , total hardness, NO3 , NO2 , NH3 , and organic load were lowered ; while the E.C , Cl- were higher. Studying the turbidity of the effluents of the filters, showed that it is a good performance and satisfactory operation. The annual reduction of turbidity after filtration was 72% from that of clarified water.
Filtered water samples showed further lowering in the values of pH , alkalinity, total hardness, NO3 , NO2 , NH3 , and organic load , while the E.C , and Cl- values were still relatively high.
Disinfection process is performed in the reservoirs, by injection of a dose of chlorine to the filtered water. Postchlorination process affects the turbidity to very small extent. Compared with filtered water the samples from reservoirs showed decrease in pH , alkalinity, total hardness, NO3 , NO2 , NH3 , and organic load values , while the E.C , and Cl- values were higher. Regarding the mean values of the residual chlorine during the four seasons, the highest level was noticed in summer, as chlorine is added in reservoirs at higher values during summer.
Regarding the results of physical and chemical parameters, they were in compliance with the Egyptian Standards except for a slight increase in ammonia level in winter. It was noticed that the values of physical and chemical parameters of taps and tanks differed slightly from that of the outlet of the treatment plant. This may be due to deterioration that occurred during transportation of water through the pipe lines and the sites distance from the source, some times supplied by other WTPs. All chemical constituents in both tap and tanks were higher than that of outlet of the WTP, but the values were within normal range except for slightly elevation in turbidity, and ammonia in winter. There was another difference between water from the taps and that from tanks, the latter being higher in turbidity, and nitrite while residual chlorine was lower in tanks.
Considering the parasitological results, it was observed that all protozoa studied were found in the three canals; Cryptosporidium spp., Giardia spp., and E.histolytica showed the highest numbers followed by Cyclospora spp., Microsporidia spp., and Isospora spp.
Comparing the mean numbers of different parasites in the three canals, the numbers of protozoa recognized in El-Mahmoudia canal in all seasons , was more than those counted from El-Noubaria canal, this was explained by high population density on the banks of the canal causing increased pollution. The count was lower in the Drinking water canal, compared to El-Mahmoudia canal, this reduction is due to less local direct pollution sources due to the specific structure of the canal, and the effect of presence of sieves and addition of activated carbon.
The present study showed that the number of all protozoa (oo)cysts counts fluctuated significantly between seasons in the three canals. Lower numbers were found in winter , and autumn , then the number showed increase in spring to attain the highest counts of protozoa in summer. The highest counts of protozoa were in El-Mahmoudia Canal in summer due to the presence of many sources of pollution in this season in view of the greater activities of the population. It is known that temperature increases outdoor human activities and accordingly pollution, so occurrence of protozoa becomes higher in summer. Moreover, parasite levels may fluctuate significantly due to weather events that influence agricultural practices, wastewater type, and operational practices.
The different protozoa were detected in the steps of the water treatment plant in the different seasons. In every step, it was observed that the mean numbers of all protozoa studied showed a decrease in winter as compared to autumn , the values then increased successively in spring, reached a maximum in summer. Regarding the different steps of treatment, there was significant decrease in the number of protozoa between each step and the next one during all seasons.
Sharky WTP has high removal efficiencies of parasites, in spite of the presence of few counts of protozoa in finished water samples. Outlet of WTP showed that the treatment process is working properly, and that high load of protozoa in the raw water has been significantly reduced. Sharky WTP has succeeded in removal of 87% of protozoa.
Considering the protozoal investigation of the water samples collected from the three zones in the network of sharky WTP, slight elevation in the number of protozoa was found in tanks more than taps in all seasons. Protozoa load in taps samples of El-Shatby, the nearest zone from the WTP, was nearly the same as that of the plant outlet.
Comparing the outlet of WTP and water taps from the three distribution zones, it was found that; E. histolytica, Giardia spp., Cryptosporidium spp., and Microsporidia spp. showed significant increase. While Cyclospora spp., and Isospora spp. showed no significant difference. All protozoa showed significant difference between treated water and tanks samples from the three distribution areas. A significant difference is observed with all protozoa except Isospora. There were significant difference between taps and tanks samples in the different zones. The difference was found between all parasites in all sites except Isospora .
The highest numbers of protozoa (oo)cysts detected in tanks of Bahary whereas the lowest one was found in tanks of El-Shatby, as the majority of the high buildings were newly constructed and hence their roof tanks were covered and cleaned periodically.
The mean number of protozoa detected in summer was higher than those in other seasons.
The mean numbers of protozoa detected in taps and tanks ranged between 0-2 / L.
Parasitic protozoa were identified using different staining techniques : Lugol’s iodine , Trichrome and Modified Ziehl – Neelsen .
Lugol’s iodine helped for identification of Giardia spp., and E. histolytica only. Trichrome showed higher number of positive for Giardia spp., E. histolytica, and was with modification the only stain that showed Microsporidia spp.
Only Ziehl-Neelsen stain showed Cryptosporidium, Cyclospora, and Isospora.
Samples considered negative by one stain proved positive by other stain.