Annelies Aarts
Jeroen Langeveld
Marie-Claire ten Veldhuis
Luuk Rietveld


Is it necessary to collect local data to estimate
the Event Mean Concentrations from
Combined Sewer Overflow pollutants?
Which location specific properties cause
differences in EMC between CSO locations?
2

Event Mean Concentrations from literature
search
◦ Individual CSO events
◦ European locations
◦ Information about the CSO location available

The final database contained 278 CSO events
measured at 24 catchments in 8 countries
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Location specific
characteristics
Location
River
Population density
Catchment size
Land use
Impermeable area
Terrain
Runoff coefficient
Sewer length (collectors)
Sewer slope
Rainfall per year
CSO frequency per year
Rain event
characteristics
Rain depth
Mean intensity
Max intensity
Rain duration
Overflow duration
Overflow volume
Previous dry weather
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Pollutants
pH
Dissolved oxygen
Electrical conductivity
Total suspended solids, volatile suspended
solids
COD, BOD, TOC
Total nitrogen, ammonium, nitrate, nitrite
Total phosphate, ortho-phosphate
Chlorine, Sulphate
Cupper, Lead, Zinc, Iron, Chromium, Nickel,
Mercurium, Arsenicum
Calcium, Sodium
PAH
E.Coli
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

Kruskal Wallis (non-parametric equivalent of
ANOVA) to compare medians
Spearman rank correlations (no assumption
of linear relationships) to study the
correlations between the pollutant EMC and
the location specific properties
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TSS
COD
BOD
total-N
NH4+
total-P
Cd
Pb
Zn
Median
Mean
10%
90%
251
311
80
10
4
2
1
91
320
368
462
164
14
59
38
268
140
343
61
81
17
4
0.90
1.02
0.20
38
61
870
906
409
28
15
6.9
81
362
699
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Kruskal Wallis test



EMC of TSS, COD, BOD, total-N, total-P, Cd,
Pb and Zn is significantly different in at least
one location
EMC of NH4+ is NOT significant different
between the locations
(insufficient data from the other pollutants)
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Correlation matrix: location properties and EMC
Area Impermeable area Annual rainfall
TSS
COD
BOD
total-N
NH4+
total-P
Cd
Pb
Zn
0.18
0.32
0.37
-0.16
0.36
0.15
-0.17
0.33
0.34
-0.26
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Correlation matrix: rain event properties and EMC
TSS
Rain sum
Rain duration
COD BOD
tot-N NH4+ tot-P Cd
-0.35 -0.44 -0.43
-0.26
-0.54 -0.46 -0.60 -0.35 -0.58 -0.27
Mean
intensity
Max
0.32 0.16 0.60
Overflow
Volume
Duration
0.17 0.19 0.30 -0.18
0.23 0.21 0.33
0.22
PDWD
0.50 0.35 0.59 0.27
0.35
0.61 0.43 0.36 0.57
-0.33 -0.36 -0.41
Mean
Flow
Max
Zn
-0.33
0.46
0.24 0.39 0.47 0.51
Pb
-0.27
-0.44
0.48
10
0.53
0.37
Correlation matrix: location and rain properties!
A_i
A
A_i
AR
RS
RD
I_m
AR
RS
RD
I_m
0.93 0.12 -0.24
OV
OD
0.64
1
1 0.68
0.14 0.39 0.50 0.49-0.23
1 -0.49 -0.31
0.43
1 0.51 0.18
OV
1
Q_x
0.38
-0.24-0.29
1 0.55
Q_m
PWDP
0.55 0.64 -0.17 0.72
I_x
OD
Q_m Q_x
0.63 0.79 -0.33 0.82 0.50
0.35
1
I_x
-0.33
0.60 0.65
0.88 0.75
1 -0.41
1 0.87
1
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



There is a significant difference of the pollutant
EMC between locations but not for NH4+
Weak correlations between EMC and the location
specific properties was identified
Stronger correlations were observed between
EMC and PDWD, rain duration and max rain
intensity
Correlation with not included sewer and
land/area characteristics is possible but couldn’t
be verified
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
This CSO database could (should) be
◦ the start of CSO data sharing between city’s, countries
◦ a direct source of information for sewer, CSO
treatment designers
◦ a reference for future CSO monitoring campaigns
◦ a source of calibration data for wet sewage models
◦ other?

Would you like to add/share your own CSO data?
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