الفهرس 
Chapter (1) IntroductionOnly 14 pages are availabe for public view
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Abstract
Improving the efficiency of nitrogen removal from wastewater is a very important process in order to preserve the ecological life and avoid eutrophication in surface water. Hence, the development of different systems in biological treatment has attracted the researcher’s attention to enhance the removal of nitrogen from wastewater. Among the best of these methods are simulations nitrification denitrification system (SND). In this study, a novel system namely of dual flow nitrification denitrification (DFND) system was developed based on the (SND) technology mentioned earlier. Its methodology is to divide the untreated wastewater entering the reactor into two parts, the first one enters the aeration zone of the reactor and the nitrification process takes place to transform NH4 to NO3. The other part of the raw wastewater enters directly into the anoxic zone of the reactor. where the NO3 is used as a source of oxygen for bacteria and the raw wastewater as a carbon source, thus improving the removal of nitrogen. A pilot plant was manufactured and installed in the wastewater treatment plant of Talkha city. The experimental work program was designed to investigate the biological removal of nitrogen from wastewater. Furthermore, a mathematical model was derived using the response surface methodology to reach the optimal values of HRT and COD/N. In order to accurately know the types of bacteria found in the aerobic and anoxic zones, a bacterial analysis was carried out to identify the types of bacteria present using the universal primers method (PCR). The results showed the high efficiency of this system in removing nitrogen from wastewater. It was also found that the system was able to partially sudden changes of nitrogen and the organic load in the water entering the reactor. It was noted that the best nitrogen removal was when 80% of the water enters the reactor to the aerobic zone, and a ratio of 20% to the anoxic zone. Finally, the microbiological analysis of bacteria revealed a great diversity in the types of bacteria that were active in the aerobic zone and other different types in the anoxic zone. The microbial analysis showed that several bacterial species coexisted in the aerobic zone such as Alcaligenes, Achromobacter, Bordetella, Caenimicrobium, Pusillimonas, and Saccharedens. Only Bordetella, Achromobacter, and Alcaligenes thrived in the anoxic zone suggesting a nitrate respiration mechanism.