An industrial byproduct as alternative labile carbon source enhances nitrogen removal in freshwaters receiving wastewater treatment plant inputs

MAYORA, G.; TRIADÓ-MARGARIT, X.; SOROLLA, A.; BERNAL, S.; SABATER, F.; CASAMAYOR, E.O.; RIBOT, M.; GACIA, E.; DEULOFEU, O.; MARTÍ, E.

Murcia

Congreso; XX Congress of the Iberian Association of Limnology (AIL-2020), III Iberoamerican Congress of Limnology (CIL-2020); 2020

Wastewater treatment plant (WWTP) effluents are relevant sources of nutrients and dissolved organic matter (DOM) that may cause eutrophication in freshwater ecosystems. As a consequence of WWTP operations, DOM bioavailability in the WWTP effluents is usually low, which can limit nitrate (NO3-) removal in the receiving streams. Here, we assessed the effect of a by-product rich in sugars (i.e., labile DOM) from the beer brewing process on the NO3- removal along flumes filled with gravels fed by a WWTP effluent. Experimental treatments included unvegetated and Iris pseudacorus flumes. We quantified the main biogeochemical pathways driving NO3 - removal (i.e., assimilation, denitrification and dissimilatory nitrate reduction to ammonium (DNRA)) using 15NO3- additions under unamended conditions and during labile DOM fertilizations. Under unamended experimental conditions, NO3- removal was mainly driven by assimilation (up to 98.0% of total uptake). Under labile DOM fertilizations, NO3- removal increased by one order of magnitude compared to unamended conditions, and denitrification contributed up to 45% of total NO3- uptake. Labile DOM also enhanced the contribution of DNRA to total NO3- uptake from