led to a flux overestimation because part of the pollution within the combined sewer
is due to the remobilisation of runoff contaminants deposited during wet weather.
Consequently, the quality rate was downgraded to 2. The flux was estimated by
summing the daily volume of domestic wastewater over the year multiplied by a
concentration value randomly drawn within the database; this led to an averaged
value of F22a ¼ 450 Æ 50 kg year
À1 (Σ15). However, the measurement of the PAH
concentrations in domestic wastewater alone collected in house disposals would be
necessary to better assess this flux.
According to the SIAAP, industries discharged a volume of 25 Mm
3 year
À1
. Given
that no data on PAH concentration in industrial wastewater in the Seine River basin
was available, the flux was estimated using data from the literature [32] because it was
reported to be similar to that measured in the Paris area [33]. The PAH flux released
by industries into the sewer system was E22h ¼ 510 Æ 220 kg year
À1 (Σ15). However,
this result could not be backed up by actual measurements in the Paris conurbation,
and the quality rate was downgraded to 0. In addition, 30% of industrial wastewater
was released directly into the Seine River without any preliminary treatment [2],
leading to a direct discharge of PAHs into the Seine River of E22g ¼ 220 Æ 90 kg year
À1
(Σ15).
3.1.5 Discharges from the Sewer System
During the past few years, the chemical quality of storm water in the Paris area has
been extensively investigated, especially within the OPUR research programme
[10, 26]. The resulting database was described in “Runoff” above, leading to the
same quality grade (3). The volume of runoff water collected in the separate sewer
system was 95 Mm
3 for 2014. Based on these data, the flux of PAHs directly
discharged into the Seine River by storm water was F22c ¼ 120 Æ 12 kg year
À1
(Σ15).
PAH input into the river system also occurred from combined sewers during
storms or during sewer system dysfunction. In 2014, 20.5 Mm
3 of combined sewer
overflows (wet weather), and 18.2 Mm
3 of untreated wastewater (dry weather)
were discharged. To quantify the flux of PAHs related to these overflow events,
concentrations of PAHs in samples collected in combined sewers were matched
to the corresponding water volumes depending on the weather conditions. The
databases were constituted of 22 samples from three different studies [24, 34, 35]
for dry weather conditions and 99 samples from five studies [16, 24, 30, 36, 37]
for wet weather conditions. A total flux of F22d ¼ 50 Æ 4 kg year
À1 (Σ15) was
estimated, nearly 80% being released during wet weather conditions. The database
used to quantify this flux summarised data from various sites and was therefore
spatially representative. However, the lack of information on intra-event variability
in PAH concentrations resulted in a quality grade of 2.
172
D. Gateuille et al.
is due to the remobilisation of runoff contaminants deposited during wet weather.
Consequently, the quality rate was downgraded to 2. The flux was estimated by
summing the daily volume of domestic wastewater over the year multiplied by a
concentration value randomly drawn within the database; this led to an averaged
value of F22a ¼ 450 Æ 50 kg year
À1 (Σ15). However, the measurement of the PAH
concentrations in domestic wastewater alone collected in house disposals would be
necessary to better assess this flux.
According to the SIAAP, industries discharged a volume of 25 Mm
3 year
À1
. Given
that no data on PAH concentration in industrial wastewater in the Seine River basin
was available, the flux was estimated using data from the literature [32] because it was
reported to be similar to that measured in the Paris area [33]. The PAH flux released
by industries into the sewer system was E22h ¼ 510 Æ 220 kg year
À1 (Σ15). However,
this result could not be backed up by actual measurements in the Paris conurbation,
and the quality rate was downgraded to 0. In addition, 30% of industrial wastewater
was released directly into the Seine River without any preliminary treatment [2],
leading to a direct discharge of PAHs into the Seine River of E22g ¼ 220 Æ 90 kg year
À1
(Σ15).
3.1.5 Discharges from the Sewer System
During the past few years, the chemical quality of storm water in the Paris area has
been extensively investigated, especially within the OPUR research programme
[10, 26]. The resulting database was described in “Runoff” above, leading to the
same quality grade (3). The volume of runoff water collected in the separate sewer
system was 95 Mm
3 for 2014. Based on these data, the flux of PAHs directly
discharged into the Seine River by storm water was F22c ¼ 120 Æ 12 kg year
À1
(Σ15).
PAH input into the river system also occurred from combined sewers during
storms or during sewer system dysfunction. In 2014, 20.5 Mm
3 of combined sewer
overflows (wet weather), and 18.2 Mm
3 of untreated wastewater (dry weather)
were discharged. To quantify the flux of PAHs related to these overflow events,
concentrations of PAHs in samples collected in combined sewers were matched
to the corresponding water volumes depending on the weather conditions. The
databases were constituted of 22 samples from three different studies [24, 34, 35]
for dry weather conditions and 99 samples from five studies [16, 24, 30, 36, 37]
for wet weather conditions. A total flux of F22d ¼ 50 Æ 4 kg year
À1 (Σ15) was
estimated, nearly 80% being released during wet weather conditions. The database
used to quantify this flux summarised data from various sites and was therefore
spatially representative. However, the lack of information on intra-event variability
in PAH concentrations resulted in a quality grade of 2.
172
D. Gateuille et al.