THESIS
2000
xiv, 88 leaves : ill. (some col.) ; 30 cm
Abstract
This research studies the utilization of dissolved organic matter and oxygen for sewage purification and to evaluate the feasibility of the application of the sewer as a pretreatment system for municipal sewage. The experiment was carried out in a 1.5-km section of a sanitary gravity sewer in a slope of 0.0075. This sewer is a cement pipe with an inner diameter of 450 mm. Continuous monitoring of dissolved organic carbon (DOC), suspended solids (SS), flow rate, and dissolved oxygen (DO) were conducted along the sewer. It was found that 16% of the DOC was removed in the section with an estimated 18-minute retention time. Throughout the entire sewer section, a slow flow rate favors a higher DOC removal efficiency because it offers a longer retention time, which implies that oxygen would n...[
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This research studies the utilization of dissolved organic matter and oxygen for sewage purification and to evaluate the feasibility of the application of the sewer as a pretreatment system for municipal sewage. The experiment was carried out in a 1.5-km section of a sanitary gravity sewer in a slope of 0.0075. This sewer is a cement pipe with an inner diameter of 450 mm. Continuous monitoring of dissolved organic carbon (DOC), suspended solids (SS), flow rate, and dissolved oxygen (DO) were conducted along the sewer. It was found that 16% of the DOC was removed in the section with an estimated 18-minute retention time. Throughout the entire sewer section, a slow flow rate favors a higher DOC removal efficiency because it offers a longer retention time, which implies that oxygen would not be a limiting factor. The DO decreased progressively along the sewer line and the mean concentration difference between the influent and effluent was found almost constant at 3.1 mg/L throughout the entire sewer section. Batch tests using both sewage and sediment were carried out to determine their specific DOC removal rates and the specific oxygen uptake rate (SOUR), and the mean values were found to be 1.3 mg DOC/mg SS/day (0.054 mg DOC/mg SS/day) for DOC removal and 17.7 mg O
2/g SS/hr for oxygen uptake in the sewage phase and 2.6 mg DOC/mg SS/day (0.108 mg DOC/mg SS/day) for DOC removal and 32 mg O
2/g SS/hr for oxygen uptake in the sediment phase, respectiveIy. Adenosine triphosphate (ATP) content analysis of the SS and sediment samples also confirmed that both the SS and the sediments contained substantial amount of active biomass. The oxygen budget analysis of this sewer found that the oxygen demand for the sediment and the sewage is 22.8 kg O
2/day and 4.3 kg O
2/day, respectively. If this entire 1.5-km sewer system is taken as a tubular bioreactor, it can be estimated that 39.13 Kg of DOC can be stabilized per day, to which the sewage phase contributes 40% while the sediment phase contributes 60%. The sediment is more effective in both removing DOC and utilizing oxygen in this sewer system.
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