الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Nile is the only main source of water for drinking in Egypt. It reaches Alexandria through both of Mahmoudia and Noubaria canal. Eight water purification plants in Alexandria; namely: Maamoura, Sharki, Manshia, Forn ELgraia, Nozha, Siouf, Borg Alarab and Noubaria.
Noubaria Water purification Plant, (NWPP), is located in North El Tahrir province at 46km of desert road. Noubaria canal is the source of raw water supply to the NWPP. The daily average of water production is 510, 000 m3 / day.
Although chlorine is widely used for disinfection, it has several major disadvantages. Chlorine reacts with natural organic material found in water to produce strange tastes, objectionable odor, and other by-product such as THMs. Then there was an apparent association between THMs and different types of cancer.
This study aims to evaluate of pre-chlorination, post-chlorination, residual chlorine and assessment of Trihalomethane in Noubaria Water Purification Plant, and its distribution system, this study started on January 2010 through December 2010 to cover the seasonal differences in this study.
It has been proved that temperature, pH, Algal count, bacterial count, total and fecal coliform, Ammonia free, COD, BOD, TOC and prechlorination dose are dependent parameters that have directly effect on THMs formation in treated water.
The results of the thesis can be summarized as follows:
Temperature variation in Raw water, NWPP and its sites; was affected with the seasonal changes, the highest temperature recorded during summer which ranged from 28.3 to 32.4 oC with mean 30 oC, the lowest temperature recorded during winter which ranged from 17.5 to 23.6 oC with mean 19.6 oC, annually the temperature ranged from17.5 to 32.4 oC with mean 24.9 oC; there is no significant difference in temperature in the same season for raw water, NWPP and the 6 sites.
Turbidity for raw water ranged from 10.5 to 60 NTU with mean 30.12 NTU all over the year, for treated water ranged from 0.2 to 0.4 NTU with mean 0.33 NTU for the whole year and for 6 sites ranged between 0.3 to 0.9 NTU with mean 0.57 NTU for all year with mean for all year.
pH of raw water ranged from 8.01 to 8.35 with mean 8.19 along the year through all the tested samples. The pH decreased in the water treatment process by the addition of chemicals during treatment such as alum and chlorine. So the pH ranged from 7.63 to 7.81 with mean 7.73 and for (6) sites from 7.63 to 7.89 with mean 7.77 yearly.
WHO Standards and Egypt Guidelines for EC value for drinking water is 1700 μs/cm, present study results show that all water samples EC value in the permissible limits of WHO Standards. EC has closed relationship with total dissolved solids, thus high EC value indicate that there is a high concentration of dissolved solids in water.
Total Organic Carbon is often used as a non-specific indicator of water quality. Contaminations of TOC can origin from not only natural organic substances, but also anthropogenic ones such as insecticides, herbicides, and other agricultural chemicals, which enter the water body via rivers, streams or from rainfall runoff. Domestic and industrial waste waters also contribute with organic material in various amounts.
A high organic content means an increase in the growth of microorganisms, which contribute to the depletion of oxygen supplies. Generally, the content of organic material in surface waters is 5-30 mg/l; also TOC has an important influence on the pH value in raw waters.
TOC for raw water recorded for the whole year range from 6.4 to16 mg/l with mean 10.08 mg/l, treated and sites are almost close to each other ranged from 1.3 to 4.8 mg/ l.
Currently, coliforms and E. coli are of great importance among bacterial indicators used in water quality definition and health risk, the annual range value of total coliforms in raw water detected from 560 to 1200 CFU / 100 ml with mean 889 CFU / 100 ml, it was noticed that the maximum value recorded during spring and summer, it ranged from 650 to 1200 CFU / 100 ml with mean 1133 CFU / 100 ml, while the minimum values recorded during autumn and winter, it ranged between 560 – 1050 CFU / 100 ml with mean 840 CFU / 100 ml.
Algal count is a particular concern in drinking resources due to the release of harmful toxins, taste and odour into water supplies, as well as their negative impact on treatment process performance these organisms can cause serious problems in treatment plant basins by the accumulation of growths on walls, clogging of filters, algal growth controlled by using high shock doses of chlorine during times of algal abundance. Prechlorination reduces all microbiological contaminants and keeps the treatment plant practically free of algae, but cause a potentially worse problem of THMs formation, total algal count during the whole year ranged from (750 to 2982) x103 U/L with mean 1392.9 x103 U/L, the maximum value recorded during spring and summer, it ranged between (920 – 2982) x103 U/L with mean 1994 x103 U/L, while the minimum values recorded during autumn and winter, it ranged between (755- 1800) x103U/L with mean 1055 x103 U/L.
The disinfection step by chlorine, eliminate the pathogenic microorganisms, prechlorination dose for raw water was detected by breakpoint chlorination.
The dose of chlorine in raw water ranged from 5.5 to7.5 mg/l with mean 6.5 mg/l, the highest dose recorded during summer and spring which ranged from 6.5 to 7.5 mg/l with mean 7.3 mg/l, The lowest dose recorded during winter and autumn which ranged from 5.5 to 6.5 mg/l with mean 6.0 mg/l. Post chlorination dose was fixed 1.5 mg/l annually.
Residual chlorine for treated water ranged from 2.4 to 3.3 mg/l with mean 2.9 mg/l the highest value was recorded during summer and spring which ranged from 2.9 to 3.3 mg/l with mean 3.2 mg/l, and residual chlorine for the six sites ranged from 0.6 to 2.6 mg/l with mean 1.5 mg/l the highest value was recorded during summer and spring while the lowest value recorded during winter and Autumn.
The predominant chlorine disinfection by-product is the THMs. THMs formation in NWPP was in compliance generally with Egyptian Standard (100 µg/l) and WHO Guideline (80 µg/l) in winter and autumn from 46.2 to 71 µg/l with mean 63.0 µg/l. while it was not in compliance with Egyptian Standard and WHO Guideline in spring and summer, THMs levels tend to be highest during the warmest months of the year (April through August) from 80 to 103.2 µg/l with mean 89.4 µg/l, Also for six sites network in winter and autumn from 55 to 78 µg/l with mean 68.2 µg/l, in spring and summer from 85 to 120 µg/l with mean 98.67 µg/l.
Reaction time is one of the most important factors in determining THM concentrations, when the time of residual chlorine increases, the THM concentrations increase.
According to the results, the followings are recommended to reduce the THMs:
Alternative pre-disinfection could be used such as ultraviolet light, potassium permanganate, per acetic acid, ozone, or a combination of chlorine dioxide and chloramines. Chloramines or chlorine are recommended to be used to provide the required disinfection residual effect in the distribution system.
Recommendation should be considered as minimizing organic matter from raw water and maintaining the network to avoid cross contamination with any organic substance.
Reducing the primary and secondary disinfection dosages and having booster chlorination later in the distribution system can help to reduce disinfection loads.