Elsevier

Chemosphere

Volume 73, Issue 11, December 2008, Pages 1741-1748
Chemosphere

Reduction of pharmaceutically active compounds by a lagoon wetland wastewater treatment system in Southeast Louisiana

https://doi.org/10.1016/j.chemosphere.2008.09.020Get rights and content

Abstract

A number of pharmaceutically active compounds (PhACs) have been detected in the aquatic environment as a result of discharges of municipal wastewater. In the state of Louisiana, USA, many municipalities treat wastewater using natural systems, such as lagoons and wetlands, rather than conventional wastewater treatment technologies. Nearly all research to date has focused on the fate of PhACs in conventional treatment plants, not constructed and natural wetlands. In the wastewater treatment plant (WWTP) for Mandeville, Louisiana, USA, wastewater flows of 7600 m3 d−1 are treated in a series of aeration lagoons (basins), followed by a constructed wetland and UV disinfection, before being discharged into a natural forested wetland (i.e. Bayou Chinchuba) and eventually, Lake Pontchartrain. Thirteen out of the 15 PhACs investigated were detected in the wastewater inflow to the treatment plant. Only 9 of the 13 compounds were above the detection limits at the treatment plant effluent. The concentrations of most compounds were reduced by greater than 90% within the plant, while carbamazepine and sotalol were only reduced by 51% and 82%, respectively. The percent reductions observed in the Mandeville system were greater than reduction rates reported for conventional WWTPs; perhaps due to the longer treatment time (∼30 days). Most target PhACs were not completely removed before discharge into Lake Pontchartrain, although their collective annual loading was reduced to less than 1 kg and down to ppb with significant potential for dilution in the large lake.

Introduction

The fate of pharmaceutically active compounds (PhACs) in the aquatic environment is an emerging area of research (Ternes, 1998, Daughton and Ternes, 1999, Kolpin et al., 2002, Kolpin et al., 2004, Ternes et al., 2002, Webb et al., 2003, Jones et al., 2005a). A significant portion of this research has focused on the capacity of wastewater treatment plants (WWTPs) to remove PhACs from wastewater, and the contribution of WWTPs to PhAC loadings to receiving waters (Heberer et al., 2002, Boyd et al., 2003, Miao et al., 2004, Bendz et al., 2005, Joss et al., 2006, Lishman et al., 2006, Gobel et al., 2007). However, there are very few data on the ability of constructed wetlands and natural wetland systems to reduce the concentrations of pharmaceuticals before the release of wastewater into aquatic systems (White et al., 2006, Matamoros et al., 2008).

PhACs enter the environment through a variety of pathways, and the human body plays a major role. A portion (varies by drug and individual) of each pharmaceutical dose is retained in the human body, but residual parent compound and its metabolites are excreted in urine and feces (Daughton and Ternes, 1999, Khetan and Collins, 2007, Lienert et al., 2007). The PhACs are then released either through septic systems or in wastewater effluents (Jones et al., 2005b). Within wastewater treatment plants and in the natural environment, the rates of degradation of PhACs vary, depending on the chemical and physical properties of each compound, and environmental conditions (Jones et al., 2005b). Physical, chemical and biological parameters that influence degradation include; sorption/desorption, redox potential, temperature, pH, photolysis, microbial activity, and select minerals (Tolls, 2001, Zhang and Huang, 2003, Zhang and Huang, 2007, Vogna et al., 2004, Scheytt et al., 2005, Ter Laak et al., 2006).

It has been predicted that the discharge of pharmaceuticals into the environment will increase over time (Jones et al., 2005a). For example, in Germany in 1995, 100 tons of prescription drugs were purchased, which does not account for sales of non-prescription drugs and veterinary medicines (Ternes, 1998). As a result of greater reliance on pharmaceuticals and an aging population, the number of prescription and non-prescription drugs dispensed during doctor visits has risen from 190 per 100 people in the USA during 1995–1996 to 226 during 2003–2004 (NCHS, 2006). Monthly prescription drug usage as a percentage of the USA population has risen from 39.1% during 1988–1994 to 45.3% during 1999–2002 (NCHS, 2006).

Southeast Louisiana has been shaped by deltaic processes over several hundreds of years by the meandering of the Mississippi River. The majority of this region is near, at or below sea level. Due to the low elevation, much of the area is covered by freshwater wetlands. The Mississippi River, which receives treated wastewater from urban centers within the watershed, has the potential to carry significant amounts of contaminants, including PhACs into the coastal waters of Louisiana and the Gulf of Mexico. There is an opportunity in this region to utilize the natural wetlands to provide a final level of treatment (i.e. “polishing”) to wastewater, prior to release into surface waters. These wetlands can be used to naturally remove nutrients, organic loads and contaminants, while other regions must use advanced treatment technologies to achieve the same concentration reductions. Natural systems, however, require significantly longer retention times versus conventional wastewater treatment systems due to slower treatment.

Constructed wetlands are effective at removing or reducing the concentrations of nutrients (Braskerud, 2002), pathogens (Karim et al., 2004) and microcontaminants, such as endocrine disruptors, PhACs and personal care products (Belmont et al., 2006, Matamoros et al., 2005a, Matamoros et al., 2005b, Matamoros and Bayona, 2006, Waltman et al., 2006, White et al., 2006). Natural wetlands are known to mitigate the effects of both point and non-point source pollution (Johnston et al., 1990), but their capacity for removing PhACs has not been previously assessed. Evaluating the benefits and services provided by natural wetlands, and employing these systems, requires an understanding of the system processes, as well as the responses of the systems to point and non-point source pollution. For example, wetlands that are subject to pollution can become impaired as a result of inputs of wastewater, resulting in contamination of local wildlife (Barber et al., 2006, Pelley, 2006).

Two recent publications have identified PhACs and other “down the drain” chemicals in surface waters in southeastern Louisiana. As reported by Boyd et al., 2003, Zhang et al., 2007, these compounds have been detected in the Mississippi River at New Orleans, in Lake Pontchartrain bordering New Orleans to the north, within the discharge from the Jefferson Parrish East WWTP and at the influent of the drinking water treatment plant. Of the 9 target analytes in the Boyd et al. (2003) study, two were detected (naproxen, triclosan) in WWTP effluent at ng L−1. The Zhang et al. (2007) study found 10 of the 12 compounds of interest including; naproxen, ibuprofen, carbamazepine, clofibric acid, caffeine, triclosan, acetaminophen, bisphenol A, estrone, 17α-ethinylestradiol and the natural estrogen, 17β-estradiol. It is possible that a range of other PhACs were also present in these samples.

The goal of this study was to evaluate the reduction of a select group of PhACs from untreated municipal wastewater in a lagoon-constructed wetland treatment system discharged into a receiving forested wetland in southeastern Louisiana. The study objectives included: (1) determining concentrations of PhACs loaded to and within the wastewater treatment system, (2) estimating the loading of PhACs to the forested wetland, and to the final receiving waters of Lake Pontchartrain, and (3) comparing reduction rates for PhACs in this natural treatment system to removal rates for more conventional wastewater treatment plants.

Section snippets

Study area

Mandeville, LA, USA is located on the north shore of Lake Pontchartrain. The Mandeville WWTP is a nontraditional plant that treats the water in a constructed wetland, followed by a natural wetland. Untreated wastewater flows into three 61 × 183 × 3 m aerated lagoons in series, (Fig. 1). Each basin has a retention time of nine days, for a total of 27 days of treatment. After retention in the aeration lagoons (basins), the water flows through a surface flow constructed wetland. Water is evenly

Results and discussion

Nearly all of the target compounds were detected in the untreated wastewater entering the treatment plant, with the exception of fluoxetine and propranolol (Table 2). Nadolol, sotalol, and sulfapyridine were the only compounds that were detected in the untreated wastewater but not at the outfall into Lake Pontchartrain, indicating near complete aqueous concentration reduction. The data indicate that the WWTP constructed wetland significantly decreased the concentrations of most target

Conclusions

Results demonstrate that a wastewater treatment system consisting of earthen lagoons and a constructed wetland such as those used in the Mandeville WWTP show a greater reduction in compound concentration than previous investigations of conventional plants. Further polishing in a natural forested wetland produced removal rates for PhACs that averaged 96% for the entire system. There is variation with inflow concentration in the WWTP, but these concentrations are normalized on a daily to weekly

Acknowledgements

The authors would like to acknowledge Maria Figueroa for providing expertise and assistance in preparation of the samples and Dr. Hongxia Li for conducting the analytical determinations. Funding was provided by the Louisiana Board of Regents, the Faculty Research Grant Program LSU and the NSF – (PFund) Pilot Fund Program.

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