Evaluation of Ecotoxicological Risks Related to the Discharge of Combined Sewer Overflows (CSOs) in a Periurban River

Abstract

Discharges of Combined Sewer Overflows (CSOs) into periurban rivers present risks for the concerned aquatic ecosystems. In this work, a specific ecotoxicological risk assessment methodology has been developed as management tool to municipalities equipped with CSOs. This methodology comprises a detailed description of the spatio-temporal system involved, the choice of ecological targets to be preserved, and carrying out bioassays adapted to each compartment of the river receiving CSOs. Once formulated, this methodology was applied to a river flowing through the outskirts of the city of Lyon in France. The results obtained for the scenario studied showed a moderate risk for organisms of the water column and a major risk for organisms of the benthic and hyporheic zones of the river. The methodology enabled identifying the critical points of the spatio-temporal systems studied, and then making proposals for improving the management of CSOs.

Assessment of long term ecotoxicity of urban stormwaters using a multigenerational bioassay on Ceriodaphnia dubia: A preliminary study

“…The absence of acute toxicity in D. magna. (mobility) observed in both samples tested is in accordance with previous results of Waara et al [20] , Angerville et al [1] , or Bi et al [21] , obtained after exposure to urban wet weather discharges, confirming the tendency that acute toxicity bioassays are not enough sensitive for stormwater toxicity evaluation.…”

“…McQueen et al [28] and Angerville et al [1] , showing with the standardized assay that for a majority of urban runoffs samples, no effect was detected after one single C. dubia generation exposure. As hypothesized, when second and third generations were exposed, acute and chronic toxicity appeared after both MIR and CHA sample exposure.…”

“…Therefore, a C. dubia multigenerational assay was performed. The choice of this organism and of reproduction as an end point was driven by previous results obtained in our laboratory by Angerville et al [1] They observed that C. dubia reproduction bioassay was the most sensitive one among a rather broad ecotoxicity test battery applied to urban combined sewer overflows (acute bioassays on : Vibrio This was done in an attempt to evaluate long term toxic events. Sufficient fulfilment of most of the validity criteria supported by the standardized method was achieved excepted for the number of brood that was slightly lower than three in average.…”

“…Several physico-chemical parameters (pH, Conductivity, Dissolved Organic Carbon (DOC), Total suspended Solids (TSS), etc.) were measured according to European standards as described by Angerville et al [1]…”

“…However, it has been shown that such standardized bioassays often fail to properly assess stormwater toxicity, mainly due to their low contamination level, and/or to the presence of nutrients interfering with the measured endpoint, in particular growth. [1,2] Angerville et al [1] showed that C. dubia reproduction bioassay was the most sensitive to assess the toxicity of this kind of matrixes. Moreover, previous studies using cladocerans (D. magna) highlighted that many environmental pollutants (pesticides, heavy metals, pharmaceuticals, phthalates, …) led to reproduction impairment with different modes of toxic action: estrogenic and antiestrogenic, androgenic and anti-androgenic activities through activation/blocking of specific receptors, modulation of steroid metabolism (others than estrogens and androgens), disturbance of ecdysis or juvenile hormone mimicry.…”