Degradation and sorption of commonly detected PPCPs in wetland sediments under aerobic and anaerobic conditions

Purpose

Wetlands are a popular tool to treat/polish wastewater by reducing nutrient loading into the environment. In addition to nutrients, organic contaminants, such as pharmaceuticals and personal care products (PPCPs), are commonly detected in treated wastewater. Treatment wetlands may reduce concentrations of PPCPs before the treated effluent enters rivers and streams. Oxygen status may greatly affect the attenuation of PPCPs in wetland sediments by influencing microbial makeup and activity. An understanding of the effect of redox conditions on the degradation of PPCPs and the factors influencing PPCP sorption to wetland sediments is needed to maximize PPCP removal in treatment wetlands.

Materials and methods

Three wetland sediments from the San Diego Creek and Newport Bay watershed in Southern California, USA, were incubated under aerobic and anaerobic conditions to assess the degradation of several regularly occurring PPCPs and their phase distribution as a function of time.

Results and discussion

Under aerobic conditions, ibuprofen, N,N-diethyl-meta-toluamide (DEET), and gemfibrozil generally had half-life values around 20?days, while the half-life of carbamazepine was substantially longer (between 165 and 264?days). The anaerobic half-lives of gemfibrozil and ibuprofen increased by factors of 11?C34 and carbamazepine increased by factors of 1.5?C2.5. There was no detectable anaerobic degradation of DEET. The apparent phase distribution coefficient increased over time for DEET, carbamazepine and gemfibrozil, indicating that sorption of PPCPs to wetland sediments may be more limited than that predicted using equilibrium sorption coefficient values.

Conclusions

Knowledge of the capacity of wetland sediments for degrading and sorbing PPCPs is vital to the design of treatment wetlands. Degradation of the selected PPCPs was enhanced under aerobic conditions as compared to anaerobic conditions. Sorption to sediments increased with contact time, indicating that longer hydraulic retention will increase wetland capabilities for removing PPCPs.