title: Associations of chemical tracers and faecal indicator bacteria in a tropical urban catchment.
abstract: Surface water contamination by human faecal wastes is a widespread hazard for human health. Faecal indicator bacteria (FIB) are the most widely used indicators to assess surface water quality but are less-human-specific and have the potential to survive longer and/or occur naturally in tropical areas. In this study, 13 wastewater chemicals (chloride, boron, orthosphophate, detergents as methylene blue active substances, cholesterol, cholestanol, coprostanol, diethylhexyl phthalate, caffeine, acetaminophen, ibuprofen, sucralose and saccharin) were investigated in order to evaluate tracers for human faecal and sewage contamination in tropical urban catchments. Surface water samples were collected at an hourly interval from sampling locations with distinct major land uses: high-density residential, low-density residential, commercial and industrial. Measured concentrations were analysed to investigate the association among indicators and tracers for each land-use category. Better correlations were found between different indicators and tracers in each land-use dataset than in the dataset for all land uses, which shows that land use is an important determinant of drain water quality. Data were further segregated based on the hourly FIB concentrations. There were better correlations between FIB and chemical tracers when FIB concentrations were higher. Therefore, sampling programs must be designed carefully to take the time of sampling and land use into account in order to effectively assess human faecal and sewage contamination in urban catchments. FIB is recommended as the first tier in assessment of surface water quality impairment and chemical tracers as the second tier. Acetaminophen and coprostanol are recommended as chemical tracers for high-density residential areas, while chloride, coprostanol and caffeine are recommended for low-density residential areas.
authors.affiliation: School of Civil and Environmental Engineering, Nanyang Technological University (NTU), 50 Nanyang Avenue, Singapore 639798, Singapore. Electronic address: ev0001ia@e.ntu.edu.sg.
authors.forename: E
authors.initials: E
authors.lastname: Ekklesia
authors.affiliation: Department of Civil and Environmental Engineering, Massachusetts Institute of Technology (MIT), 77 Massachusetts Avenue, Cambridge, MA 02139, USA; Centre for Environmental Sensing and Modeling (CENSAM), Singapore-MIT Alliance for Research and Technology (SMART), 1 Create Way, Singapore 138602, Singapore.
authors.forename: P
authors.initials: P
authors.lastname: Shanahan
authors.affiliation: School of Civil and Environmental Engineering, Nanyang Technological University (NTU), 50 Nanyang Avenue, Singapore 639798, Singapore.
authors.forename: L H C
authors.initials: LH
authors.lastname: Chua
authors.affiliation: Environmental Technology & Chemistry, DHI Water & Environment (S) Pte Ltd, 1 CleanTech Loop, Singapore 637141, Singapore.
authors.forename: H S
authors.initials: HS
authors.lastname: Eikaas
mesh_terms: D001419:Bacteria / Q000302:isolation & purification*; D015415:Biomarkers / Q000032:analysis*; D004784:Environmental Monitoring; D005243:Feces / Q000382:microbiology; D005618:Fresh Water / Q000032:analysis*; D006801:Humans; D012621:Seasons; D012846:Singapore; D014329:Tropical Climate; D062065:Wastewater / Q000032:analysis*; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D015415:Biomarkers; D062065:Wastewater; D014874:Water Pollutants, Chemical
keywords: Association; Chemical tracers; Correlation; Faecal indicator bacteria; Urban catchment