a case study in Bangkok, Thailand Nguyen Thai Hoa creator Satoh, Hiroyasu Chairperson Thammarat Koottatep Examination Committee Preeda Pakpian Examination Committee Government of Netherlands Scholarship donor text series technical report th Pathum Thani, Thailand Asian Institute of Technology 2004 continuing eng 74 leaves Fecal sterols such as Coprostanol (S{J-Cholestan-3{1-ol), cholesterol (cholest-S-en-3{1-ol) and cholestanol (Sa-Cholestan-3{1-ol), abundantly found in human feces. Coprostanol and its ratios have been used successfully as molecular sewage pollution indicators (Leeming et al., 1996 and Writer et al., 199S). Coprostanol is a non-ionic, non-polar, organic molecule that associates with sediments in surface waters, and concentrations of coprostanol in bed sediments provide an indication of long-term sewage loads. Because coprostanol concentration is dependent on particle size and percent of organic carbon, a ratio between coprostanol and coprostanol + cholestanol (S{Jl(S{J + Sa) has been used to remove the biases related to particle size and percent of organic carbon (Chan et al., 1998 and Writer et al., 199S). Concentrations of Coprostanol in sediment and the Coprostanol/(Coprostanol +S a cholestanol) ratio were obtained from 7 canals, Chao Phraya River and the influent in wastewater treatment plant in Bangkok and its surrounding areas. A simple and sensitive analytical method using gas chromatography-mass spectrometry. The concentration of Coprostanol from canals and river in Bangkok and Pathumthani varies from 0.007 ogig dry to 278.6S ogig dry. The fecal stanol ratio S{Jl(S{J + Sa) was found to range from O.OS to 0.67. Besides, the concentrations of all target sterols in the suspended solids in the influent into the primary sedimentation tank were also obtained from one waste water treatment plant in center Bangkok to demonstrate the sewage pollution level: 36 to 286.6S ogig dry of Coprostanol, and 0.4S to 0. 72 of fecal stanol ratio S{Jl(S{J +Sa). From the obtained results, it can be concluded there was high possibility of sewage impact on sampling sites, especially sampling sites in the central of the Bangkok city. A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Environment, Resources and Development Thesis (M.Eng.) - Asian Institute of Technology, 2004 Sterols Contamination (Technology) Asian Institute of Technology. http://203.159.5.9/ait-thesis/detail.php?q=B08943 http://203.159.5.9/ait-thesis/detail.php?q=B08943 041112 20260817162855.0