Enzymatic Activities in the Rhizosphere Soil as Influenced by Filterbeds and Hydrophytes in the Vertically Constructed Wetland

Abstract

An experiment with different filter beds and macrophytes was carried out to study their phytoremediation capacity on the efficiency of domestic wastewater treatment through constructed wetland (CW) at the University of Agricultural Sciences, Dharwad campus, Karnataka, between November 2017 and March 2018. Twenty treatment combinations involving five types of filter beds (FB-1: gravel, FB-2: gravel-sand-gravel, FB-3: gavel-sand-brick-gravel, FB-4: gravel-sand-charcoal-gravel and FB-5: gravel-sand-(charcoal+brick)-gravel) and four macrophytes (MP-1: Typha latifolia, MP-2: Brachiaria mutica, MP-3: Canna indica and MP-4: Phragmites sp.) were evaluated for treating domestic waste water. After 120 days from the start, across treatment combinations, the plant in each column was uprooted, and the soil adhered to the root was collected in a polyethylene cover. The samples were brought to the laboratory, refrigerated, and then analysed for dehydrogenase, phosphatase, and urease activities, as well as for biofilm formation. Results revealed that the highest biofilm growth was observed on brick (1.18 and 0.05 mg g-1) had the maximum biofilm formation, followed by sand (0.68 and 0.04 mg g-1), charcoal (0.67 and 0.02 mg g-1), and gravel (0.31 and 0.01 mg g-1) at depths ranging from 0 to 5 and 5 to 15 cm, respectively. Since the CW can be implemented with flexibility, it can be used as the primary, secondary or tertiary treatment stage depending on the site and its configuration.