الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Water is necessary for our life; Water covers about 70% of Earth’s surface, makes up about 70% of your mass, and is essential for life. Without it there will be no life on the earth’s surface.
Alexandria is in a doubly difficult position, geographically, with respect to its water supply. Being downstream of almost all other users of Nile means the raw water supply. AWGA withdraws for treatment is seriously threatened from both a water quality and quantity perspective. In Alexandria, the source of raw water to most water purification plants is Mahmodia canal. This canal runs most of its course from its origin at the Rosetta branch of the Nile river till its end at the Mediterranean sea through many industrial as well as water agricultural communities that discharge their wastes within the body of the canal. Its water often contaminated by industrial discharges and waste produce from water treatment plants. These practices are restricted by the law number 48 for the year 1982.
Untreated surface waters contain clays, minerals, inert solids, microbiolgical organisms, and other suspended materials. All of these materials can inhibit disinfections, cause problems in distribution system, and leave the water cloudy rather than clean.
Public drinking water systems use various methods of water treatment to provide safe drinking water for their communities. Today, the most common steps in water treatment used by community water systems (mainly surface water treatment) include Screening, Coagulation, flocculation, Sedimentation, Filtration, and Disinfection.
In surface water supplies, the excessive nutrient causes algae proliferation. Algae in water reservoirs cause numerous difficulties in water treatment plants and distribution systems: impairment of coagulation and flocculation processes, filter clogging or premature filter backwash, increased chlorine demand and disinfection by-product (DBP) concentrations, taste and odor problems, algal toxins, and increased microbial regrowth potential in distribution systems.
The best way to combat these problems is to remove algae before raw water is filtered and disinfected. The suitable treatment to remove algae without causing cell breakdown that can release toxins is the process of coagulation, flocculation, and sedimentation.
Chemical coagulation in the water treatment is the process of bringing suspended matter in untreated water together for the purpose of settling and for the preparation of the water for filtration. Typically, two major types of coagulants are added to water. These are aluminum salts and iron
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salts. The most common aluminum salt used in water treatment plant is aluminum sulfate. Optimum coagulation conditions are those that maximize pathogen removal, produce low turbidities and natural organic matter, and minimize residual aluminum.
Aluminum has been shown to be a neurotoxin compound if it is allowed to enter the bloodstream. Long-term exposure of patients to dialysis water high in aluminum may cause encephalopathy and/or bone mineralization disorders. The maximum limit of residual aluminum in drinking water according to the Egyptian Standards is 0.2 mg/l.
Enhanced coagulation technology is defined as the addition of excess coagulant for multiple objectives which are: 1) to maximize particulates and turbidity removal by downstream solid-liquid separation, 2) to maximize total organic carbon (TOC) and DBP precursor removal, 3) to minimize residual coagulant, 4) to minimize sludge volume, and 5) to minimize operating costs. In addition, enhanced coagulation increases the removal of suspended solids and large number of algae. Enhanced coagulation is a well-proven technology for the significant removal of colour and particulate matter including protozoa (e.g. Cryptosporidium oocysts and Giardia cysts), viruses, bacteria, and other micro-organisms. Iron, manganese, tastes and odours may also be removed from the water by these processes.
This study performed in EL-Nozha WTP, which located in the Eastern edge of El-Mahmoudia canal- since 1995 up to the year 2010, and on the pilot plant located in El-Nozha WTP. Alun costs 2000L.E/m3.
Activated silica process is disclosed for the production of acidic solutions of this material, activated silica is formed during the process of acidifying a sodium silicate solution to below pH 2 with sulfuric acid.
By using different doses of alum to determine the optimum dose during each season, taking the two doses just below the optimum dose, and determine the optimum enhancing coagulant dose from the four selected with alum through the jar-test, it was found that; all enhancing coagulants reduce turbidity, algae (all types), zooplankton, and bacteria.
Algae causing taste and odor were affected greatly by the addition of enhancing coagulants especially activated silica where the percent of reduction reached 72.5% in winter season and 67.5% in summer season.
Blue- Green algae which secretes toxins with bad effects on public health also affected by enhancing coagulants where the percent of reduction reached 43% in winter season by the enhancement of PAC and 61% in Summer season with activates silica as an enhancing coagulant.
Zooplankton especially protozoa had very large percent of reduction reached to 98% with optimum dose of alum and all enhancing coagulants especially activated silica.
Heteotrophic plate count, total coliforms, and fecal coliforms reduced by addition of enhancing coagulants especially polyaluminium chloride and activated silica.
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Iron derivatives were effective in reducing algae especially ferric sulphate were found to be effective in reducing all algal types. Ferric chloride costs 3614 L.E/ metric ton, and ferric sulphate costs 2259 L.E. / metric ton
Polyaluminium chlorides was effective, had many advantages; 1. PAC reacts faster than aluminium sulphate because of its polymeric structure which allows higher coagulation efficiency 2. The formed flocs are bigger which means a faster sedimentation. Moreover, PAC remains effective over a wider turbidity range and even at very low temperatures 3. Lower quantities of residual aluminium in water (compared with the analogous value with aluminium sulphate) reducing consequently health problems (Alzheimer) 4. Reduced cleaning frequency of the filters (longer runs in the sand filters), 5. PAC consumes less alkalinity than the other coagulants. In most cases, there is no need of alkalinity addition for an effective flocculation, so additional pH correction chemicals aren’t necessary 6. Lower doses are required for equivalent results in comparison with aluminium sulphate 7. PAC remains efficient over a larger pH range 8. Less sludge production compared to the other coagulants, but Aluminium is corrosive to metals, some articles proved that it produce health hazards on large scale. PAC costs 2349 L.E./ metric ton.
Activated silica was the best in removing algae especially blue green algae which produce neurotoxins, hepatotoxins, and cytotoxins all of them have adverse effects on public health. Also activated silica had no residuals with health hazards on public health, good TOC removal, no color residue, safe in handling, and it considered to be cheap compared with iron salts. So, the best enhancing coagulant was activated silica due to the cheap cost but the activation chemicals increase its cost to reach 5862 L.E. / metric ton, it produced from many companies so it is available, no bad residuals on public health, whether it needed closed preparation to obtain good result in stability.