Wastewater treatment plant effluent inputs induce large biogeochemical changes during low flows in an intermittent stream but small changes in day-night patterns

Bernal, Susana; Drummond, Jennifer; Castelar, Sara; Gacia, Esperança; Ribot, Miquel; Martı́, Eugènia

doi:10.1016/j.scitotenv.2020.136733

Cited by 22 publications

(48 citation statements)

References 43 publications

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“…Our study encompassed rivers receiving WWTP inputs and spanning a gradient of land use in the riparian area. We observed that WWTP inputs had a considerable effect on river nutrient processing with potential implications for downstream nutrient exports, which has already been observed in other studies (Martí et al, 2004;Figueroa-Nieves et al, 2016;Bernal et al, 2020). In our study, the retention mechanisms that potentially emerged from the surface water connection with riparian areas determined the role of these areas as sources or sinks of nutrients (Tockner et al, 1999).…”

Section: Implications For River and Land Use Managementsupporting

confidence: 81%

“…Nonetheless, depending on treatment technology and efficiency, treated effluents can still be a major source of several contaminants to the receiving aquatic systems (Meng et al, 2013;Mußmann et al, 2013;Carr et al, 2016;Aubertheau et al, 2017). Such inputs, for example, can induce a suite of changes in the water chemistry and ecosystem functioning in different ways, from shifts in nutrient availability shaping the biological community's structure to alterations in biogeochemical cycles and nutrient export to downstream waters , Gücker et al, 2011Atashgahi et al, 2015;Rodriguez-Castillo et al, 2017;Bernal et al, 2020). The impacts of WWTP effluents can be especially relevant in developing countries with economic limitations, where the removal of several particulate/dissolved compounds may not or only partially occur (Oliveira and von Sperling, 2011).…”

Section: Introductionmentioning

confidence: 99%

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Riparian Land Use and Hydrological Connectivity Influence Nutrient Retention in Tropical Rivers Receiving Wastewater Treatment Plant Discharge

Finkler

Gücker

Boëchat

et al. 2021

Front. Environ. Sci.

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Riparian areas are recognized for their buffering capacity regarding phosphorus and nitrogen from agricultural and urban runoff. However, their role in attenuating nutrient loads of rivers receiving point source nutrient inputs (e.g., from wastewater treatment plants, WWTPs) is still little understood. Here, we investigated whether ammonium (NH4-N), nitrate (NO3-N), and soluble reactive phosphorus (SRP) retention were influenced by the riparian land use in three Brazilian rivers receiving WWTP effluents. We hypothesized that nutrient attenuation would be potentially influenced by the hydrological connectivity between the main channel and riparian areas with native vegetation. We estimated retention from longitudinal patterns of dilution-corrected nutrient concentrations below the WWTPs. We assessed nutrient retention during periods with high (i.e., the wet) and low connectivity (i.e., the dry season). Relationships between non-conservative (nutrients) and conservative (chloride) solutes in both seasons were used to identify potential changes in the river chemistry due to the hydrological connectivity with the riparian areas. We also evaluated the relationship between net uptake velocities (Vf-net) and the accumulated percent native vegetation cover in the 100-m buffer using linear regressions, comparing the response for each nutrient between seasons with Analysis of Covariance. Slopes of regressions between nutrients and chloride significantly differed between seasons for NO3-N and SRP but not for NH4-N. The relationships between Vf-net and accumulated native vegetation in the riparian buffer presented steeper slopes for SRP in the wet than in the dry season. No significant relationships between NO3-N Vf-net and native vegetation cover were observed in either season. In contrast, increases in Vf-net with increasing vegetation cover were observed for NH4-N in the dry season. In periods with expected higher connectivity, NO3-N and SRP concentrations tended to be lower relative to chloride concentrations, with a potential effect of native vegetation in the riparian area on SRP retention. Our results suggest that seasonal connectivity between nutrient-rich river water and riparian areas is likely to induce changes in the predominant nutrient transformation processes, thereby favoring either nutrient retention or export in such rivers.

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Section: Implications For River and Land Use Managementsupporting

confidence: 81%

Section: Introductionmentioning

confidence: 99%

Riparian Land Use and Hydrological Connectivity Influence Nutrient Retention in Tropical Rivers Receiving Wastewater Treatment Plant Discharge

Finkler

Gücker

Boëchat

et al. 2021

Front. Environ. Sci.

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“…The organic fraction of the FPM (i.e., fine particulate organic matter, FPOM) can consist of fecal particles from shredder invertebrates as well as fragments of organic particles generated both in streams and adjacent soils (Bundschuh and McKie, 2015). Stream FPOM can also derive from anthrogenic point sources such as wastewater treatment plant (WWTP) effluents which usually act as important sources of particles, dissolved organic carbon and nutrients (Marti et al, 2004;Merbt et al, 2014;Bernal et al, 2020;Kelso and Baker, 2020). Although FPOM can be highly processed organic matter; and therefore, expected to be a more recalcitrant OM source than the dissolved organic fraction, FPOM can act both as a colonizing surface for microorganisms and as a carbon source for microbial activity within streams (Hope et al, 1994;Brugger et al, 2001;Gottselig et al, 2014) and eventually can be more labile than dissolved organic matter (Stutter et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

Hydromorphologic Control of Streambed Fine Particle Standing Stocks Influences In-stream Aerobic Respiration

et al. 2021

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Fine particulate organic matter (FPOM) accumulated in streambeds is a major component of organic matter budgets in headwater streams and greatly affects productivity and metabolism of stream communities. The spatiotemporal distribution of benthic FPOM in the stream, as well as its quantity and quality, depend on inputs from different source types. These can be natural such as soils, streambanks and riparian vegetation, or anthropogenic such as effluents from wastewater treatment plants (WWTP). In addition, stream flow is a key driver of FPOM dynamics, which influences the balance between its transport and accumulation in the streambed. Yet, the link between FPOM dynamics and its effects on stream metabolism is still largely unknown. The aim of this study was to investigate the influence of stream channel hydromorphology on water transport and streambed accumulation of fine particulate matter (FPM) (mineral and organic fractions), FPOM (organic fraction) and its quality (characterized by %OM, %C, %N and the C:N molar ratio). In addition, we quantified the metabolic activity associated with FPM at the habitat scale, and its potential contribution to whole-reach ecosystem respiration using the resazurin-resorufin bioreactive tracer as a proxy for aerobic respiration. We also characterized water transport and metabolic activity with combined additions of hydrological and bioreactive tracers at the reach scale. The study was conducted in the Cànoves stream (Catalonia, NE Spain) downstream of a WWTP that contains three reaches that were hydromorphologically modified using bioengineering techniques. Slower local velocities at the habitat scale increased accumulation of FPM, but did not influence the spatial variability of its quality. Instead, FPM quality declined further downstream from the WWTP. Accumulation of FPM did not increase metabolic activity, but higher %OM of FPM and lower C:N ratios favored the microbial metabolic activity efficiency (normalized by the gram of FPM). Reach-scale metabolic activity was higher in reaches with higher water exchange rate and longer relative travel times, highlighting hydromorphology as an important driver of microbial metabolic activity at the reach-scale. This demonstrates that the interplay of hydrologic exchange and residence time in streambed sediments associated with the microbial metabolic activity of FPOM can ultimately influence reach-scale metabolic activity.

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“…Previous studies have shown that WWTP e uent inputs diminish the e ciency of receiving streams to take up N and P because excess nutrient loads can cause the saturation of nutrient demand by in-stream biota (Martí et al 2004;Grimm et al 2005; Gücker et al 2006;Merseburger et al 2011). Yet, longitudinal decreases in N and P ambient concentration have been observed in WWTP receiving streams, suggesting that even when the nutrient retention e ciency is low, the stream biota can reduce to some extent the pervasive concentrations of nutrients in those systems (Haggard et al 2005;Ribot et al 2012;Bernal et al 2020). In this regard, previous studies show that stream reaches located downstream from WWTP can become hot spots of nitri cation because of the colonization of the streambed bio lm by ammonium oxidizing bacteria from the WWTP active sludge together with the high NH 4 + concentration (Mußmann et al 2013; Merbt et al 2015).…”

Section: Introductionmentioning

confidence: 99%

“…During high ows, the e ciency for stream biota to take up nutrients is low because the interaction between the active streambed and the water column height and the water residence time are also low and therefore, downstream transport might overwhelm in-stream biogeochemical processing (Martí et al 1997;Algerich et al 2008). Conversely, during low ows, receiving streams can act as net sinks of nutrients because higher water residence time favors the interaction between in-stream biota and bioreactive solutes (Ribot et al 2012;Rahm et al 2016;Bernal et al 2020). Besides in uencing water residence time, stream hydrology also affects water chemistry, especially in reaches located downstream of WWTP inputs.…”

Section: Introductionmentioning

confidence: 99%

Inputs from wastewater treatment plant effluent influence the temporal variability of nutrient uptake in an intermittent stream

Castelar

Bernal

Ribot

et al. 2021

Preprint

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Effluents from wastewater treatment plants (WWTP) affect water chemistry and in-stream nutrient uptake capacity from receiving freshwaters, thus altering the amount and fate of nutrients exported. In Mediterranean regions, the dilution capacity of receiving streams to buffer the WWTP biogeochemical fingerprint can vary seasonally due to changes in hydrologic conditions. We assessed the temporal patterns and controls on nutrient uptake in an intermittent Mediterranean stream receiving WWTP effluent inputs. We compiled data on longitudinal profiles of ambient concentrations of dissolved inorganic nitrogen and phosphorus along a 800 m reach on 47 sampling dates between 2001 and 2017 that cover a wide range of hydrological conditions. Data were used to estimate net nutrient uptake in the receiving stream. Ammonium concentration decreased along the reach in 72% of dates, and these decreases were coupled with increases of either nitrite or nitrate. This phenomenon suggests that the stream acted as a hot spot of nitrification. Conversely, concentration of phosphorus did not show any longitudinal pattern in 75% of dates, suggesting that uptake and release processes for this element were commonly counterbalanced. Finally, ammonium net uptake decreased when the stream had a low dilution capacity, suggesting that excess of available nutrients associated with WWTP inputs control de temporal variation of the bioreactive capacity of the receiving streams. Overall, this study suggests that water management should consider the biogeochemical interplay between WWTP operation and the functioning of receiving streams as a strategy to improve stream water quality in urban landscapes.

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Wastewater treatment plant effluent inputs induce large biogeochemical changes during low flows in an intermittent stream but small changes in day-night patterns

Cited by 22 publications

References 43 publications

Riparian Land Use and Hydrological Connectivity Influence Nutrient Retention in Tropical Rivers Receiving Wastewater Treatment Plant Discharge

Riparian Land Use and Hydrological Connectivity Influence Nutrient Retention in Tropical Rivers Receiving Wastewater Treatment Plant Discharge

Hydromorphologic Control of Streambed Fine Particle Standing Stocks Influences In-stream Aerobic Respiration

Inputs from wastewater treatment plant effluent influence the temporal variability of nutrient uptake in an intermittent stream

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