Distribution and Fate of the Human Drug Carbamazepine in Treatment Wetlands

The anti-seizure medication carbamazepine has been shown to be recalcitrant in sewer treatment facilities and in the environment. It has been proposed that artificially constructed wetlands offer a low cost treatment alternative to remove carbamazepine from treated sewage effluent prior to disposal in the environment. Carbamazepine concentrations were measured on two different dates within a 1.2 ha treatment wetland that receives treated municipal effluent. Carbamazepine concentration ranged from 12.9 ng L^-1 to 45.1 ng L^-1. In addition, 4 hour composite average samples were collected over 8 days at the inlet and analyzed for carbamazepine. The average inflow concentration was 35.4 ng L^-1 with a maximum of 53.7 ng L^-1 and a minimum of 27.7 ng L^-1. Within the wetland sorption to sediment is the most probable means for carbamazepine removal. It was found that naturally occurring wetland sediments were capable of removing carbamazepine from solution. Average removal of carbamazepine was 4 µg per g of sediment. It was also found that on a mass basis the ability to remove carbamazepine from solution was 100 times greater for organic matter than the mineral fraction. Using mass balance it was also found that organic matter accounted for 86% of the total adsorptive capacity of the sediment. Results indicate that wetland sediments are capable of removing carbamazepine from solution and that designs that promote organic matter accumulation and sediment water contact are needed to remove carbamazepine from solution.