Temporary Storage or Permanent Removal? The Division of Nitrogen between Biotic Assimilation and Denitrification in Stormwater Biofiltration Systems
نویسندگان
چکیده
The long-term efficacy of stormwater treatment systems requires continuous pollutant removal without substantial re-release. Hence, the division of incoming pollutants between temporary and permanent removal pathways is fundamental. This is pertinent to nitrogen, a critical water body pollutant, which on a broad level may be assimilated by plants or microbes and temporarily stored, or transformed by bacteria to gaseous forms and permanently lost via denitrification. Biofiltration systems have demonstrated effective removal of nitrogen from urban stormwater runoff, but to date studies have been limited to a 'black-box' approach. The lack of understanding on internal nitrogen processes constrains future design and threatens the reliability of long-term system performance. While nitrogen processes have been thoroughly studied in other environments, including wastewater treatment wetlands, biofiltration systems differ fundamentally in design and the composition and hydrology of stormwater inflows, with intermittent inundation and prolonged dry periods. Two mesocosm experiments were conducted to investigate biofilter nitrogen processes using the stable isotope tracer 15NO3(-) (nitrate) over the course of one inflow event. The immediate partitioning of 15NO3(-) between biotic assimilation and denitrification were investigated for a range of different inflow concentrations and plant species. Assimilation was the primary fate for NO3(-) under typical stormwater concentrations (∼1-2 mg N/L), contributing an average 89-99% of 15NO3(-) processing in biofilter columns containing the most effective plant species, while only 0-3% was denitrified and 0-8% remained in the pore water. Denitrification played a greater role for columns containing less effective species, processing up to 8% of 15NO3(-), and increased further with nitrate loading. This study uniquely applied isotope tracing to biofiltration systems and revealed the dominance of assimilation in stormwater biofilters. The findings raise important questions about nitrogen release upon plant senescence, seasonally and in the long term, which have implications on the management and design of biofiltration systems.
منابع مشابه
Interaction and spatial distribution of wetland nitrogen processes
A spatially-explicit, two-dimensional model was developed to evaluate the processes which determine the fate and transport of nitrogen (N) in wetland systems. The wetland soil profile was partitioned into floodwater, and aerobic, and anaerobic soil layers, with diffusion and settling accounting for the transport of N between layers. Nitrogen transformations considered in the model were; enzyme ...
متن کاملAn assessment of nitrogen removal from headwater streams in an agricultural watershed, northeast Ohio, U.S.A
The objective of this project was to assess in-stream nitrogen removal capacity in a fragmented agricultural landscape and to compare removal capacities in streams with agricultural or residential (hereafter referred to as agricultural streams) and forested riparian land use. We also identified what stream characteristics control nitrogen removal in these systems. We examined paired reaches (on...
متن کاملNitroge Backwater of the Upper n Cycling and Fate in a Floodplain Mississippi River
PURPOSE: Backwaters connected to large rivers efficiently retain nitrate and can play an important role in reducing downstream loading to coastal marine environments. However, biotic assimilation and transient storage can account for a significant portion of the nitrate uptake versus denitrification. The fate of this nitrogen (N) pool is largely unknown. Is assimilated nitrate stored temporaril...
متن کاملEffect of Dissolved Oxygen and Chemical Oxygen Demand to Nitrogen Ratios on the Partial Nitrification/Denitrification Process in Moving bed Biofilm Reactors
Partial nitrification was reported to be technically feasible and economically favorable, especially for wastewaterwith high ammonium concentration or low C/N ratio. In this study, the effect of dissolved oxygen (DO)and influent ratio of chemical oxygen demand to nitrogen (COD/N) ratio on biological nitrogen removal fromsynthetic wastewater was investigated. Experiments were c...
متن کاملBiofilter treatment of stormwater: temperature influence on the removal of nutrients Traitement des eaux de ruissellement par biofiltration: influence de la température sur l’absorption des nutriments Godecke-Tobias Blecken*, Maria Viklander*, Tone Muthanna**,
Nutrients can cause eutrophication of natural water bodies. Thus, urban stormwater which is an important nutrient source has to be treated in order to reduce its nutrient loads. Biofilters which use media, biofilms and plants, are a good treatment option regarding nutrients. This paper presents the results of a biofilter column study in cold temperatures (+2°C, +8°C, control at +20°C) which may...
متن کامل