Potential Nitrification and Denitrification on Different Surfaces in a Constructed Treatment Wetland

Abstract

Improved understanding of the importance of different surfaces in supporting attached nitrifying and denitrifying bacteria is essential if we are to optimize the N removal capacity of treatment wetlands. The aim of this study was therefore to examine the nitrifying and denitrifying capacity of different surfaces in a constructed treatment wetland and to assess the relative importance of these surfaces for overall N removal in the wetland. Intact sediment cores, old pine and spruce twigs, shoots of Eurasian watermilfoil (Myriophyllum spicatum L.), and filamentous macro-algae were collected in July and November 1999 in two basins of the wetland system. One of the basins had been constructed on land that contained lots of wood debris, particularly twigs of coniferous trees. Potential nitrification was measured using the isotope-dilution technique, and potential denitrification was determined using the acetylene-inhibition technique in laboratory microcosm incubations. Nitrification rates were highest on the twigs. These rates were three and 100 times higher than in the sediment and on Eurasian watermilfoil, respectively. Potential denitrification rates were highest in the sediment. These rates were three times higher than on the twigs and 40 times higher than on Eurasian watermilfoil. The distribution of denitrifying bacteria was most likely due to the availability of organic material, with higher denitrification rates in the sediment than on surfaces in the water column. Our results indicate that denitrification, and particularly nitrification, in treatment wetlands could be significantly increased by addition of surfaces such as twigs.

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“…The use of artificial wetlands to reduce the impact of field or greenhouse effluent on the environment is promising. Artificial wetlands have a role to play in the elimination of pathogens and heavy metals (Vacca et al 2005) as well as nitrification and denitrification processes (Bastviken et al 2003). Their functioning is influenced by macrophytes (Brix 1997), evapotranspiration during the summer (Herbst and Kappen 1999;Pauliukonis and Schneider 2001;Chazarenc et al 2003), and microbial population diversity (Ibekwe et al 2003;McGarvey et al 2005).…”

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Towards recommendations for design of wetlands for post-tertiary treatment of waste water in the baltic sea region: Gdańsk case study

“…Another factor is the low density of macrophytes such as reed and bulrush compared to many other TWs and we regard the water level to be too high for their successful colonisation. The wetland plants have been shown in many studies to be of great importance as attachment sites for denitrifying bacteria and organic material will fuel the denitrification process [23]. Furthermore, when the hydraulic loading (HLR) of the wetland is compared to other FWS analysed by [9] it becomes clear that with an HLR of 15-18 cm/day it belongs to the upper quarter of the 205 FWS wetlands studied.…”