Abstract

Although Floating treatment wetlands (FTWs) provide immense advantages over other natural treatment facilities, there is no information about biofilm functioning and microbial-based processes in FTW. Therefore, this study was aimed to evaluate the magnitude of microbial-based processes in the root, bottom and water column zones of the FTW by employing of macrophytes. For this experiment, primary domestic wastewater effluent was used in two pairs of FTWs (I. psuedacorus and P. stratiotes) and a pair of control. Total microbial activity was estimated using FDA hydrolytic activity and specific microbial activities were examined as denitrification and nitrification activities, whilst viable microbial number and distribution in the FTW compartments were determined using ATP assay. The average nitrification rates in the FTWs were 0.55, 0.81 and 2.75 μg/ml of water, gravel and root surface per hour respectively; and denitrification rates were 0.022, 0.053 and 0.132 μg/ml of water, gravel and roots surface respectively. The mean fluorescein concentration for the FTWs were 9.2, 1.1 and 0.06 μg/ml of root, gravel and freewater respectively, indicating that the highest total microbial activity in the FTW occurs in the biofilm associated with the root system. Mean viable microbial community 3.85 × 108, 3.7 × 107 and 1.3 × 107 cells/ml of root surface, water and gravel surface. Therefore, all the result suggested that active pollutant removal in all FTW stakes place in the root zone. 

Keywords: Floating treatment wetland; Macrophytes; Microbial activity; Biofilm