Streams receiving effluents of urban wastewater treatment plants (WWTP) have a high ability to transform ammonium (NH4 +) from the effluent to nitrate (NO3–). This process, so-called nitrification, is a key pathway of the nitrogen cycle in streams, and may be particularly relevant in those streams receiving an effluent from a WWTP because not only may reduce the high loads of NH4+, potentially toxic for in-stream biota, but also because produced NO3– can be removed from the ecosystem via denitrification.
WWTP effluents may also inoculate nitrifying bacteria and archaea (AOA and AOB respectively) in the receiving streams which may colonize benthic substrata. Therefore, AOB and AOA are part of the microbial communities (i.e., biofilms) developing in cobbles (epilithic biofilm) and sediments (episamic biofilm) from the riverbed. However, the relative abundance of AOA and AOB in the two biofilms types may differ due to the fact that those microorganisms have different ecofisiologies. Therefore, we would expect differences in the nitrification capacity of the two biofilm types as well as in their relative contribution to total nitrification at reach-scale.
The NITRISED project aims to explore the factors and mechanisms that regulate nitrification rates in streams receiving an effluent from a wastewater treatment plant. The aim of the NITRISED project is to examine nitrification capacity of AOA and AOB present in the epilithic and episamic biofilms and how these activities are affected by the presence of helophytes. These vascular plants may affect the hydrological interaction between surface and hyporheic water and therefore the concentration of oxygen and nutrients in the hyporheic zones.
The NITRISED project is funded by the Ministry of Economy and Competitiveness of the Spanish Government.