EFFECTS OF NATURAL AND ANTHROPOGENIC DRIVERS ON EMERGING ORGANIC CONTAMINANTS IN WASTEWATER AND DRINKING WATER SYSTEMS: OCCURRENCE AND REMOVAL
Open Access
- Author:
- Kibuye, Faith Awino
- Graduate Program:
- Biorenewable Systems
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- June 22, 2019
- Committee Members:
- Heather E. Gall, Dissertation Advisor/Co-Advisor
Heather E. Gall, Committee Chair/Co-Chair
Herschel A. Elliott, Committee Member
John E. Watson, Committee Member
Rachel A. Brennan, Outside Member - Keywords:
- emerging contaminants groundwater quality
wastewater irrigation
wastewater treatment
water reuse
emerging contaminants
groundwater quality
wastewater treatment
water reuse
wastewater irrigation
private wells
septic tanks
pharmaceuticals
pharmaceuticals and personal care products (PPCPs)
surface water quality
seasonal variations
concentration-discharge
drinking water treatment
drinking water
ecological risk
human health risk
risk assessment - Abstract:
- Indirect potable water reuse is considered an effective management practice for augmenting declining water resources. However, the occurrence of emerging organic contaminants (EOCs) such as prescription and non-prescription drugs, health and beauty products, among others in wastewater effluent challenges reuse practices due to the underlying risk to aquatic ecosystem health and potential human health impacts. It is important therefore to understand the fate, transport and risks of EOCs in surface and groundwater drinking water sources that are impacted by various indirect potable reuse practices. The objectives of this study were to evaluate the occurrence and removal of selected EOCs during wastewater treatment, assess their fate, transport and risks in impacted surface and groundwater sources, and evaluate their removal during conventional drinking water treatment. While land application of wastewater effluent is beneficial for recharging groundwater aquifers and avoiding direct pollutant discharges to surface waters, it provides a pathway of EOCs that persist in wastewater effluent to underlying aquifers. The extent to which effluent irrigation activities at the Penn State Living Filter has impacted groundwater was investigated. Commonly used pharmaceuticals (acetaminophen, ampicillin, caffeine, naproxen, ofloxacin, sulfamethoxazole, and trimethoprim) were targeted for analysis in wastewater influent, effluent and monitoring wells at the spray irrigation site. In wastewater influent, acetaminophen and trimethoprim were the most frequently detected (93%) above the limit of quantification (LOQ), while in the effluent, caffeine and trimethoprim were detected most frequently (70%). Acetaminophen and caffeine were generally well removed (>88%) during wastewater treatment while other compounds including antibiotics and the anti-inflammatory drug naproxen were removed to a lesser extent and in some cases, were present at higher concentrations in effluent samples. The removal efficiencies of the pharmaceuticals varied seasonally with the least removals recorded in colder months. The impact of long-term wastewater irrigation on groundwater was observed through the presence of studied compounds at levels above the LOQ. Detection frequencies were however lower in groundwater samples compared to the effluent, with sulfamethoxazole (40%) and caffeine (32%) as the most frequently detected compounds. Similarly, average concentrations of pharmaceuticals in groundwater were nearly two orders of magnitude lower than concentrations in the effluent. Effluent irrigation performs an ecosystem service by mitigating an ecosystem risk to aquatic organisms as wastewater effluent posing medium to high risk to aquatic systems is not discharged directly in streams but allowed to infiltrate through the soil and decrease in concentration before recharging groundwater. Furthermore, human health risk assessments indicate that concentrations of studied EOCs in groundwater, which is used as a drinking water source, appear to pose minimal risk. Domestic drinking water wells are common in the U.S. and serve about 1 million homes and farms in the commonwealth of Pennsylvania. These private wells are often located in areas served by onsite wastewater treatment systems such as septic systems where treated domestic wastewater effluent is discharged in subsurface leach fields for further treatment before recharging groundwater. The occurrence, range of concentrations, and potential human health risks of seven pharmaceutical compounds (acetaminophen, ampicillin, caffeine, naproxen, ofloxacin, sulfamethoxazole, and trimethoprim) in 26 private wells located in central PA were evaluated. Ofloxacin (100%) and sulfamethoxazole (58%) were the most frequently detected compounds while naproxen was not detected in any sample and other pharmaceuticals were present in <50% of samples. Fate and transport modelling in the vadose zone suggest that detection frequencies and concentrations in groundwater are influenced by physicochemical properties of pharmaceutical compounds including sorption potential and biodegradation rates in soil. Average concentrations were typically < 20 µg/L in private wells however, groundwater concentrations were higher when compared to nearby surface water samples. Additionally, human health risk calculations were conducted and revealed that none of the concentrations observed in the groundwater samples posed significant human health risk. Factors influencing the fate and transport of 20 EOCs in surface water sources impacted by both point source inputs from wastewater discharges and non-point inputs were investigated during a 2-yr. monitoring study. Six drinking water sources consisting of 3 riverine and reservoir types located in the Susquehanna River Basin were used as study sites. Higher detection frequencies and concentrations of targeted EOCs were observed in riverine sources in comparison to reservoir sources where longer residence times can promote natural attenuation processes. Detection frequencies of EOCs were linked to dominant land use types in associated watersheds with lower frequencies of detections observed in highly forested watersheds potentially due to reduced pollutant sources. Seasonal influences in concentrations of EOCs were observed as higher concentrations were recorded in the fall, winter and spring seasons since these colder seasons are associated with lower biodegradation rates in surface water. Statistically significant (p<0.05) seasonal variations were observed for acetaminophen, caffeine, naproxen, and sulfamethoxazole. EOCs depicted diverse hydrologic contaminant transport responses. EOCs of wastewater origin such as metformin and sulfamethoxazole exhibited dilution responses whereby aqueous concentrations reduced during high streamflow conditions. Thiamethoxam, a neonicotinoid insecticide depicted concentration accretion patterns with lower in stream concentrations during low streamflow conditions and higher levels following high precipitation events which results in surface runoff that transports agricultural EOCs from diffuse sources. Risk calculations indicate that measured EOCs posed medium to high risk to aquatic organisms, however human health risks through consumption of fish was low. The occurrence of pharmaceuticals in various surface water sources raises concern over their removal through conventional drinking water treatment processes. A 1-yr. monitoring study was conducted in two conventional drinking water treatment plants (DWTPs) to evaluate seasonality in the occurrence of seven pharmaceutical compounds (acetaminophen, ampicillin, caffeine, naproxen, ofloxacin, sulfamethoxazole, and trimethoprim) in source waters, intermediate treatment steps and finished treated water distributed to consumers. At least one pharmaceutical compound was quantified in 88% of samples collected from untreated source waters, 80% of intermediate treatment step samples, and 64% of finished drinking water samples. Average concentrations in source water samples ranged between 0.12-14.66 µg/L to 0.05 µg/L-7.87 µg/L in finished drinking water. In general, concentrations of pharmaceuticals in finished water samples were lower than source water samples indicating that most of the pharmaceutical compounds are degraded during water treatment, though occurrence in finished water imply incomplete removal during treatment. Concentrations in source and treated drinking water varied seasonally with the highest concentrations recorded during fall, winter and spring seasons while lower concentrations occurred in the summer months. Environmental risk assessment reveal that the studied pharmaceuticals pose medium to high risk to the aquatic organisms. Although occurrence of pharmaceuticals in finished drinking water indicate their ability to persist during water treatment, concentrations measured in finished water pose minimal human health risks.