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Open Access item Nitrogen processing and the role of epilithic biofilms downstream of a wastewater treatment plant

Authors:Ribot, Miquel
Martí, Eugènia
von Schiller, D.
Sabater, Francesc
Daims, H.
Battin, T. J.
Keywords:Nitrification, Denitrification, Nitrogen, Wastewater treatment plant, Stream, Biofilm, Stable isotopes
Issue Date:2012
Publisher:Society for Freshwater Science
Citation:Freshwater Science 31(4 ): 1057–1069 (2012)
Abstract:We investigated how dissolved inorganic N (DIN) inputs from a wastewater treatment plant (WWTP) effluent are processed biogeochemically by the receiving stream. We examined longitudinal patterns of NH4 + and NO3 2 concentrations and their 15N signatures along a stream reach downstream of a WWTP. We compared the d15N signatures of epilithic biofilms with those of DIN to assess the role of stream biofilms in N processing. We analyzed the d15N signatures of biofilms coating light- and dark-side surfaces of cobbles separately to test whether light constrains functioning of biofilm communities. We sampled during 2 contrasting periods of the year (winter and summer) to explore whether changes in environmental conditions affected N biogeochemical processes. The study reach had a remarkable capacity for transformation and removal of DIN, but the magnitude and relevance of different biogeochemical pathways of N processing differed between seasons. In winter, assimilation and nitrification influenced downstream N fluxes. These processes were spatially segregated at the microhabitat scale, as indicated by a significant difference in the d15N signature of light- and dark-side biofilms, a result suggesting that nitrification was mostly associated with dark-side biofilms. In summer, N processing was intensified, and denitrification became an important N removal pathway. The d15N signatures of the light- and dark-side biofilms were similar, a result suggesting less spatial segregation of N cycling processes at this microhabitat scale. Collectively, our results highlight the capacity of WWTP-influenced streams to transform and remove WWTP-derived N inputs and indicate the active role of biofilms in these in-stream processes.
Description:13 páginas, 4 figuras, 1 tabla.
Publisher version (URL):http://dx.doi.org/10.1899/11-161.1
E-ISSNmetadata.dc.identifier.doi = DOI:2161-9565
Appears in Collections:(CEAB) Artículos

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