Nutrient Retention Efficiency in Streams Receiving Inputs from Wastewater Treatment Plants
- Eugènia Marti *ad,
- Jordi Aumatella,
- Lluís Godéb,
- Manel Pocha and
- Francesc Sabaterc
- a Laboratori d'Enginyeria Química i Ambiental, Facultat de Ciències, Universitat de Girona, Campus Montilivi, s/n, 17071 Girona, Spain
d Centre d'Estudis Avançats de Blanes (CSIC), Accés a la Cala St. Francesc 14, 17300 Blanes, Girona, Spain
b Agència Catalana de l'Aigua, Departament de Medi Ambient, Generalitat de Catalunya, Provença 204-208, 08036 Barcelona, Spain
c Departament d'Ecologia, Universitat de Barcelona, Diagonal 645, 08028 Barcelona, Spain
We tested the effect of nutrient inputs from wastewater treatment plants (WWTPs) on stream nutrient retention efficiency by examining the longitudinal patterns of ammonium, nitrate, and phosphate concentrations downstream of WWTP effluents in 15 streams throughout Catalonia (Spain). We hypothesized that large nutrient loadings would saturate stream communities, lowering nutrient retention efficiency (i.e., nutrient retention relative to nutrient flux) relative to less polluted streams. Longitudinal variation in ambient nutrient concentration reflected the net result of physical, chemical, or biological uptake and release processes. Therefore, gradual increases in nutrient concentration indicate that the stream acts as a net source of nutrients to downstream environments, whereas gradual declines indicate that the stream acts as a net sink. In those streams where gradual declines in nutrient concentration were observed, we calculated the nutrient uptake length as an indicator of the stream nutrient retention efficiency. No significant decline was found in dilution-corrected concentrations of dissolved inorganic nitrogen (DIN) and phosphate in 40 and 45% of streams, respectively. In the remaining streams, uptake length (estimated based on the decline of nutrient concentrations at ambient levels) ranged from 0.14 to 29 km (DIN), and from 0.14 to 14 km (phosphate). Overall, these values are longer (lower retention efficiency) than those from nonpolluted streams of similar size, supporting our hypothesis, and suggest that high nutrient loads affect fluvial ecosystem function. This study demonstrates that the efficiency of stream ecosystems to remove nutrients has limitations because it can be significantly altered by the quantity and quality of the receiving water.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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