2.3. Experimental setup and digesters start-upIn this study, a series of lab scale digesters were operated inbatch mode to study the biogas production from the medical cottonmixed wastes. Basically, the apparatus used to carry out the processesof the anaerobic co-digestion comprised of 500-mL Pyrexborosilicate heatproof code glass bottles act as the digesters. Thecomponents of each digester were maintained at 1:10 which isequivalent to 40 g solid waste material: 400 mL (inoculum slurry ordistilled water). Each digester was tightly plugged with rubberstopper contains 2 holes each of 4 mm diameter through which apiece of glass tube was submersed into the digester and the otherend of the glass tube was connected with rubber tube for theproduced biogas transfer to the gas measuring section. The rubberstoppers were tightly wrapped with parafilm to prevent any releaseof the produced gas. In order to achieve anaerobic conditions in thedigesters, they were flushed with nitrogen for 10 min to provideanaerobic environment conditions. Digesters were immersed in athermostatic water bath to maintain the required temperatureconditions. Manual shaking of digesters was performed daily toinsure that substrate molecules and bacteria come into close. Sodiumbicarbonate (NaHCO3) was used for pH adjustment andphenolphthalein was used to color the water in the displacementbottle. Table 1 describes the experimental conditions for eachdigester taking into consideration that each digester was preparedin triplicate resulted in preparing a total of 12 digesters.
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