الفهرس 
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Abstract
Practically, anaerobic digestion of sewage added to enzymes and chemicals achieved good results. Those materials make c progress in digestion and nutrition of the germ cells, and are achieved a significant increase in the production of biogas in varying amounts in accordance with the operating conditions, by using of anaerobic reactor, capacity (2) and (5) liter, after connecting these components with rubber tubes airtight. The reactor is put in a thermal bath at 20°, 37.5° and 65° C, and the system is operated at each temperature of batch one and feeding system once, and then measure the amount of biogas emitted by using the displacement method of liquid at a specific time period. Biogas production rate is increased more than 80%, by adding the digestive enzymes to synthetic and natural sewage, under different circumstances. These enzymes have included pepsin and ox bile extract at concentrations (0.25, 0.5, 1, 2, and 4) mg/L and (20, 30, 40, 50, and 60) mg/L, respectively single and blended. Enzymes mixtures contain (lipase (L), amylase (AM) and protease (P)), with concentrations described by commenting on the fourth chapters. Samples are incubated at temperature of 20° and 37.5˚C and pH (6.5 to 7.2), and retention time 12 day. Laboratory examination of salinity and COD are also conducted, which is ranged between (1004 - 1475) maicromoz/cm and (2028 – 2510) mg/l, respectively. Results are confirmed that the addition of any enzyme digester to sewage increases the proportion of biogas production of at least 20% in a short survival time. In order to reach the highest productivity of biogas from sewage, it is necessary to add a mixture of enzymes rather than a single enzyme. For example, biogas production is increased by 20% with enzyme pepsin only to 80% using pepsin and ox bile extracts. Better productivity of biogas is recorded at 37.5° C compared to 20° C. Biogas production is increased by adding chemicals to simple percentages of not less than 10% at temperature of 37.5° C, and not more than 55% maximum. Productivity is reached a ratio of not less than 75% and not more than 157% at temperature of 65° C. It is appeared that the best degree optimal temperature for the production of biogas is 37.5°C followed by 65°C and finally 20°C. Using of the specific bacterial strain of the type (Methanobacterium) has no positive impact on biogas production, whether with/without the use of biological or chemical treatments. In addition, some experiences are done on reactor of large scale (80) liter, to make sure the results that are obtained of small scale (2 and 5) liter.