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

Research output: Contribution to journalArticlepeer-review


  • Susana Bernal
  • Jennifer Drummond
  • Sara Castelar
  • Esperança Gacia
  • Miquel Ribot
  • And 1 others
  • Eugènia Martí

External organisations

  • University of Birmingham


Wastewater treatment plant (WWTP) effluents alter stream water chemistry and metabolic activity. Yet, essential aspects influencing the biogeochemical response of receiving streams such as hydrology and diel oscillations of light and temperature remain largely unexplored. We measured day vs night water chemistry and in-stream net nutrient uptake velocity (Vf) in an intermittent forested stream, upstream and downstream of a WWTP effluent under contrasting hydrological conditions. The WWTP effluent negatively influenced stream water chemistry, especially during the dry period. Despite large diel oscillations in light inputs, day-night differences in nutrient and oxygen concentrations were small, suggesting that heterotrophic respiration drove stream metabolism with a minor contribution of gross primary production. The magnitude of Vf was similar between day and night at the two reaches. Yet, at the downstream reach, in-stream net DIN uptake occurred more often at night, and values of Vf for ammonia and nitrite indicated enhanced in-stream nitrification. The two reaches showed a small capacity to retain DIN and soluble reactive phosphorus from the water column. Positive values of in-stream net nutrient uptake (i.e. uptake > release) occurred mostly during the dry period, highlighting that in-stream biogeochemical processing can contribute to improve water quality in streams receiving point-sources effluents in regions with low water availability.


Original languageEnglish
Article number136733
Pages (from-to)1-10
Number of pages10
JournalScience of the Total Environment
Early online date15 Jan 2020
Publication statusPublished - 20 Apr 2020
Externally publishedYes


  • wastewater treatment plant, intermittent stream, in-stream nutrient uptake, nitrogen , phosphorus, day-night cycles