Spatial and temporal influence of onsite wastewater treatment systems, centralized effluent discharge, and tides on aquatic hazards of nutrients, indicator bacteria, and pharmaceuticals in a coastal bayou

• Published in: The Science of the total environment 2019-02, Vol.650 (Pt 1), p.354-364
• Main Authors: Scott, W. Casan, Breed, Christopher S., Haddad, Samuel P., Burket, S. Rebekah, Saari, Gavin N., Pearce, Paul J., Chambliss, C. Kevin, Brooks, Bryan W.
• Format: Article
• Language: English
• Subjects: Bacteria - isolation & purification; Bioavailability; Coastal; Environmental Monitoring; Estuaries; Estuarine; Gulf of Mexico; Pharmaceutical Preparations - analysis; Seasons; Septic; Surface water monitoring; Texas; Urbanization; Waste Disposal, Fluid; Waste Water - chemistry; Waste Water - microbiology; Water Pollutants, Chemical - analysis; Water Quality
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2018.09.029

In the rapidly urbanizing watersheds and estuaries flowing to the Gulf of Mexico in Texas, USA, instream flows are increasingly influenced by point source and nonpoint source discharges. Spatial and temporal tidal influences on water quality, especially for contaminants of emerging concern (CECs), is poorly understood in estuaries and coastal systems. We selected Dickinson Bayou, an urban estuary in Galveston County, Texas, for study because it has historically impaired water quality, receives point source discharge from one major wastewater treatment plant (WWTP), while also being influenced by high densities of onsite sewage facilities upstream in the watershed. We explored the occurrence and potential hazards of aquatic contaminants, including nutrients, indicator bacteria for pathogens, and CECs, in relation to this point source discharge, across seasons and at high and low tides. Aquatic contaminants and associated hazards varied significantly in relation to the WWTP discharge, and were influenced by onsite systems. In fact, spatiotemporal water quality varied by class of contaminants (e.g., nutrients, indicator bacteria, CECs), which indicates that traditional surface water monitoring activities should account for such environmental complexity. This study provides a diagnostic approach for future studies of emerging water quality challenges across gradients of rapidly urbanizing coastal bays and estuaries. [Display omitted] •Emerging contaminants from onsite wastewater are poorly studied in urban estuaries.•Tidal influences on aquatic contaminants were examined in an urban coastal bayou.•Onsite wastewater affected surface water quality across seasons, regardless of tide.•Site-specific pH altered therapeutic hazards of a model ionizable pharmaceutical.•Environmental assessments should spatially and temporally examine water quality.