Nutrient Dynamics at the Sediment-Water Interface: Influence of Wastewater Effluents

Abstract

Uptake and regeneration fluxes and concentrations of nutrients, i.e., nitrate (NO3−), ammonium (NH4+), phosphate (PO43−) and dissolved organic carbon (DOC), were evaluated upstream and downstream of a wastewater treatment plant (WWTP) in the River Wandle, UK, from July to October 2019. Using chamber techniques, water-specific nutrient concentrations were measured at two exposures (3 and 10 min) to calculate fluxes. The WWTP effluent contributed to elevated concentrations and modified flux rates, resulting in significant differences at the study sites. Compared with summer, the concentrations of NO3− and DOC increased while NH4+ and PO43− decreased in autumn. Nutrient fluxes varied both temporally and spatially in uptake (i.e., storage in sediments) or regeneration (i.e., release into river water). Under the actions of physical and biological processes, the fluxes of NO3− and NH4+ showed opposite flux directions. Dissolved oxygen (DO) and bioabsorption mainly affected PO43− and DOC fluxes, respectively. Specifically, across all sites, NO3− was −0.01 to +0.02 mg/(m2 s), NH4+ was −29 to +2 μg/(m2 s), PO43− was −2.0 to +0.5 μg/(m2 s), and DOC was −0.01 to +0.05 mg/(m2 s). Further, we did find that these variations were related to nutrient concentrations in the overlying water. Our results provide further evidence to show that reductions in river nutrients are paramount for improving river ecological conditions. Additionally, we suggest that more research is needed to evaluate chamber-based experimental approaches to make them more comparable to in-situ flux methods. Highlights • Sewage effluent resulted in elevated nutrient concentrations and modified fluxes. • Flux was affected by initial nutrient concentrations, DO and microbial activity. • Inexpensive approaches to study nutrient dynamics are needed for river restoration.

Solute flow and particle transport in aquatic ecosystems: A review on the effect of emergent and rigid vegetation

“…Suspended load refers to the fine particles in suspension, and bedload refers to coarse particles that move along the bed through rolling, sliding, and hopping [ 70 ]. Sediment is the most extensively studied particle, given its crucial role in habitat stability, biogeochemical cycles, and pollutant transport [ [9] , [10] , [11] , [12] , [13] , [14] , [15] , [16] , [17] , [18] , [19] , [20] ]. For low-density particles such as plastics, surface transport or transport in the water-air interface also occurs due to the buoyancy effect [ 107 ].…”

“…Fine sediment particles can also suspend in the water column, reducing visibility, smothering fishes, and irritating the digestive systems of fishes and other aquatic animals [ [11] , [12] , [13] ]. Fine sediment, characterized by electrochemically active surfaces [ 14 ], adsorbs abundant nutrients [ 15 , 16 ], heavy metals [ 17 , 18 ], organic contaminants such as pesticides [ 19 , 20 ], and pathogens [ 21 , 22 ]. Consequently, fine sediment transport, a carrier of nutrients and contaminants, significantly impacts the biogeochemical cycle [ 23 ] and contaminant dispersion [ [24] , [25] , [26] ] in aquatic ecosystems.…”

Influences of Elevated Nutrients and Water Temperature from Wastewater Effluent on River Ecosystem Metabolism

“…3) to investigate the influence of the WWTP effluent (i.e., 4 nutrient concentrations in the effluent and elevated water temperatures) on downstream water quality and REM. The arrow points at the affected factor; among them, the nutrient concentrations in the WWTP effluent were derived from Zhang et al (2021), the PAR data was from http://environment.data.gov.uk, other data, except bioactivity, were derived from our measurements and estimates. Bioactivity (e.g., phytoplankton and aquatic animals) is a variable we did not measure and cannot obtain data directly from the literature or websites (referred to as central latent variable, in the oval) but aquatic organisms are the main body of river metabolic processes.…”

“…Table 1 Framework for assessing river ecosystem health using metabolism measurements; Impacts refer to the degree of impaired ecosystem functioning (Young et al 2008). GPP = gross primary production; ER = ecosystem respiration Assessment parameter Criterion Impacts to impaired functioning Urban rivers often receive WWTP effluents (Preisner 2020;Zhang et al 2021), but there are few studies on the mechanism of REM responding to effluents. Furthermore, considering that elevated nutrients and water temperature in effluents can be used as indicators for REM prediction under environmental changes, we measured REM of the River Wandle, an urban tributary to the River Thames, which is affected by WWTP effluent.…”

Uncertainty Evaluation of Best Management Practice Effectiveness Based on the AnnAGNPS Model

“…Non-point source pollutants, such as nitrogen (N) and phosphorus (P), sediments, and agricultural chemicals, have become a major cause of water quality degradation in rivers and streams worldwide. Large amounts of phosphorus and nitrogen loading loss may result in the eutrophication of freshwater, severely restricting water use (Schürz et al 2019;Zhang et al, 2021). Thus, reduction or alleviation of nutrient load is a key issue for water quality improvement and aquatic ecosystem restoration (Schuwirth et al 2019).…”