Sublethal and chronic effects of reclaimed water on aquatic organisms. Looking for relationships between physico-chemical characterisation and toxic effects.

The use of reclaimed water for irrigation and aquaculture purposes is generally considered a reliable alternative for sustainable water management in regions with water scarcity. Many organic compounds, generally called compounds of emerging concern (CECs), have been detected in reclaimed water, which implies continuous exposure for aquatic organisms. To date no quality criteria have been proposed for this group of compounds. This work aims to assess the acute, sublethal and chronic effects of reclaimed water using two representative organisms of the aquatic compartment; the green alga Chlorella vulgaris and the microcrustacean Daphnia magna. The study comprises the 72 h-algal growth inhibition test, the D. magna feeding bioassay and the D. magna reproduction test. The results highlighted, for the selected characterised compounds, no differences in the concentrations between the different tertiary WWTP treatments, except for the particular case of carbamazepine. Considering seasonality, no differences were observed between the two different sample collection campaigns. The sublethal and chronic effects observed for these samples could not be explained by the lower concentrations found in the chemical characterisation. However, in the majority of cases, dilution of raw reclaimed water reduced the toxic effects of these samples. Several interactions among compounds can affect the mixture's toxicity. Canonical correlation analyses (CCA) were included to explore the potential relationships between the physico-chemical characterisation of reclaimed water and effects on aquatic organisms. The results corroborated the toxic effect of some pharmaceuticals, in particular beta-blockers and antibiotics, on the growth and yield of green algae, as well as inhibition of daphnia reproduction. Thus the CCA methods could help to elucidate the potential relationships between the physico-chemical characterisation and toxic effects by considering all the potential interactions.