Present status and estimation method of pollutant load in wet
weather flow from urban areas

Yoshida, T.* and Tamoto, N.*** Senior Researcher, Wastewater System Division, Water Quality Control Department, National Institute for Landand Infrastructure Management, Ministry of Land, Infrastructure and Transport, Government of Japan, Address:
Asahi 1, Tsukuba, Ibaraki 305-0804, Japan, Email: yosida-t92e5@nilim.go.jp** Researcher, Wastewater System Division, Water Quality Control Department, National Institute for Land andInfrastructure Management, Ministry of Land, Infrastructure and Transport, Government of Japan, Address: Asahi
1, Tsukuba, Ibaraki 305-0804, Japan, Email: tamoto-n92ta@nilim.go.jp
Abstract This paper describes Japanese present status of controlling nonpoint source pollution from urban areas,
the field survey on urban pollution load and the related load estimation method. Promotion of point source control
has increased a relative importance of nonpoint source control, however urban nonpoint pollutant load throughseparate sanitary sewers are not yet fully addressed, while drastic measures on combined sewer overflows
alleviation were initiated in Japan. Then, the current framework and status of urban nonpoint pollution control werereviewed, and the field survey was conducted targeting on conventional water qualities, heavy metals, endocrine
disrupting chemicals, and so forth. The estimation method of urban nonpoint pollution load was also investigatedsuch as a use of prior dry weather days as an independent variable. This research began in fiscal 2004 and isongoing.
Keywords nonpoint source, nonpoint pollution, pollution load, field survey, estimation method

Introduciton
Promotion of point source control has increased a relative importance of nonpoint source control, however
nonpoint pollution are not yet fully addressed in Japan. Sewage works and other water pollution controls had
focussed on point sources, which contributed to conservation or restoration of ambient water quality, still theachievement ratio of water qualtiy standards are not satisfactory especially in closed water bodies in the nation.
In terms of watershed management, nonpoint pollution control should be considered for control efficiency.
Urban nonpoint pollution loads are to be mainly tackled through sewage works, but pollution loads fromseparate storm sewers has not been vigorously controlled while combined sewer overflows (CSOs), inclusive of
urban nonpoint pollution loads, have become a target of controls. New goals for CSOs control are to reduce thepollution loads under the level of separate serwer systems, to halve the overflow events from stormwater outlests
to satisfy secure in terms of public health, and to eliminate the debris. Subsequently, the Enforcement Order ofSewerage Law was amended to set technical standards of stormwater outlets structure such as weir height andscreen installation as well as wet weather water quality standard for CSOs (BOD 40mg/l) and monitoring
requirement of CSOs at least once a year for BOD. Also, the relevant manuals of planning and monitoring were
formulated, the national programs for CSOs control were initiated to subsidise the control projects, and thespecial research and development project were conducted (Sakakibara et al., 2005). On the other hand, runoff
from separate storm sewers is not distinctly a target of control, unlike the Stormwater National Pollutant
Discharge Ellimination System (NPDES) permit in the United States. Comprehensive Basin-wide Plans for
Sewage Works (CBPSW) in Japan perform as high-ranking schemes of sewage works, and set allocate allowable- 345 -

pollution load to each pollution source including urban nonpoint source (JSWA, 1999). In practice, however,allowable pollution loads could not be necessarily allocated to the urban nonpoint source pollution in an
effectively manner. Though "Tentative Guideline on Urban Nonpoint Pollution Control" (MLIT and JIWET,
2002) provides the relevant technical information on planning and related researches in accordance withhigher-ranking schemes such as CBPSW, there could be room for further knowledge and technical improvement
to better planning and the related researches.
Overall, urban nonpoint pollution load through separate sanitary sewers are not yet fully addressed in Japan, andfurther knowledge and technical improvement could serve for better planning and the related researches.
Especially, quantification of runoff pollution loads from urban areas and load reduction by control measures is a
key aspect. Then, the current framework and status of urban nonpoint pollution control were reviewed, and thefield survey was conducted targeting on conventional water qualities, heavy metals, endocrine disrupting
chemicals, and so forth. The estimation method of urban nonpoint pollution load was also investigated such as ause of prior dry weather days as an independent variable1.

Methods
Current framework and status
The current frameworks and status of urban nonpoint pollution control were reviewed mainly through theliterature. The relevant planning based on laws, the supporting documents, and the financial programmes areincluded in this review.
Field survey
Field surveys were conducted in three study sites; Drainage areas A, B and C. Their profiles are shown in Table
1. Each drainage area is located in an urban area served by a separate sewer system in the same prefecture. The
impervious area ratio of each drainage area was estimated to be around 60%. The surveys were carried out at thestorm sewer outlets of three drainage areas simultaneously during the same rainfall, concerning four rainfall
events as of the end of the fiscal 2005. To clarify the runoff characteristics and to calculate the pollution loads,
the rainfall close to the sampling point and the flow rate at the sampling point were also measured.
The sample was obtained by manually taking 14 to 20 bottles from each investigation point. The water quality
constituents that were analyzed were SS, VSS, BOD, CODMn, TN, and TP, but some surveys also analyzed thesamples for their content of heavy metals (copper, zinc, lead, cadmium) plus Benzo [a] pyrene (B(a)P) andBisphenol A (BPA). At the same time as the sampling, turbidity and electric conductivity (EC) were measured
with water quality sensor.2
Load estimation method
To enhance the reliability and to facilitate easier estimation methods, a regression method was researched. The
runoff load was produced by pollutants accumulated on the ground surface then washed off by rainwater. Suchpollutants consist of atmospheric depositions, tire scraps, fallen leaves, and other waste materials, and thefriction velocity when they are transported varies according to rainfall and rainfall intensity. Thus,
meteorological and precipitation conditions are assumed to be the major factors that determine the runoff load ineach drainage area. In emulation of the method of Nakamura (1993), multiple regression analyses were
performed with the rainfall and the prior dry weather days for each event as the explanatory variables (Eq. 1) inorder to predict the runoff load. The data of the said field survey was used for the analysis.
1

The contents of the field survey and the load estimation method was derived from Fujiu et al. (2005), Fujiu et al. (2006),
Tamoto and Yoshida (2005), Tamoto et al. (2005), and Tamoto et al. (2007).
2
Not all measured water quality data are described in this paper for lack of space.

- 346 -

Table 1 Profile of Study Sites
Area (ha)Impervious area ratio

Drainage area A

95

69%

Drainage area B
Drainage area C

18
67

67%
61%

Land use
High/medium-rise residential
Commercial
Residential
Residential

Arterial roads
Included
Included
Not included

L = a･Σr + b･NDD ------------------------------------------------------------------------------------Eq. 1(where L: Specific load per rainfall event (kg/ha); Σr: total rainfall per event (mm); NDD: Number ofprior dry weather day (day); a, b: constants)

Results and Discussion
Current framework and status
Runoff from separate storm sewers is not distinctly a target of control. Comprehensive Basin-wide Plans for
Sewage Works (CBPSW) in Japan perform as high-ranking schemes of sewage works, and set allocate allowablepollution load to each pollution source including urban nonpoint source (JSWA, 1999). In practice, however,allowable pollution loads could not be necessarily allocated to the urban nonpoint source pollution in an
effectively manner. In formulation of CBPSW, at first, generating loads including non-point source on awatershed are estimated using unit pollution load data, and runoff loads are calculated through pollution analysis.
Secondary, the allowable load is calculated based on the water quality standard at a target point in the concernedwater body, and the pollution load that should be reduced, referred to as the reduction load, is determined as adifference of the total generating load and the allowable load. Lastly, the reduction load is distributed to eachpollution source category such as public sewerage, industrial, livestock, and non-point source (e.g. urban, farm).
On the estimation process of generating loads of urban non-point source, existing data in other watersheds are
frequently applied instead of collecting data for a target watershed for the reasons of costs and the difficulty of
performing field surveys. In CBPSW, unit loads are used for most sources, and the unit loads of urban nonpoint
pollution shown in JSWA (1999) are as in Table 2.
As a technical guidance, "Tentative Guideline for Urban Nonpoint Pollution Control" (MLIT and JIWET,
2002) was published for providing the knowledge of urban nonpoint pollution control as well as the relevant
planning and research methods. The Guideline includes detailed description in accordance with higher-ranking
schemes such as CBPSW, however it could have been scarcely referenced in practice. This situation, with urban
nonpoint pollution allocation practices in CBPSW, could indicate that there is room for further knowledge andtechnical improvement to better planning and the related researches.
For promotion of nonpoint pollution control, financial support programmes from the national government are
prepared by the name of "Program of Supporting Next Generation Sewerage Project." Still, the adopted projects
are limited as is shown in Fig 1.
Overall, urban nonpoint pollution load through separate sanitary sewers are not yet fully addressed in Japan, andfurther knowledge and technical improvement should be sought to better planning and the related researches.

Program of Supporting Next
Generation Sewerage Project

Water Environment
Creation Project
Recycle Promotion
Project
Function Upgrade
Promotion ProjectType of Water Circulation Restoration(178)
Type of Nonpoint Pollution Control(3)Type of Recycled Resources Utilisation(163)
Type of Potential Energy Utilisation(7)
Type of New Technology Utilisation(30)
Type of Advanced IT(15)(Number of projects adopted from fiscal 1996 to 2005)

Fig 1 Program of Supporting Next Generation Sewerage Project with Number of Adopted Projects- 347 -

Table 2 Unit Loads of Urban Nonpoint Source
Research
Organisation

Research area
Municipality

Drainagearea (ha)Unit load (kg/ha/year)
SS

BOD

CODMn

middle-size city
13.69
735
191
34
large-size city
17.17
562
166
102
Kitakyushu city
2,390
605
378
Kobe city
1,304
168
208
Environment Agency
Yamagata city
904
102
90
Chiba city
105
59
55
Public Works
17.17
1,134
167
159
Kobe city
Research Institute
26.75
755
41
101
Shiga town
46.71
151
39
53
Otsu city
66.18
210
24
34
Japan Institute of
Chino city
7.81
435
157
222
Wastewater
Okaya city
5.5
1,410
87
126
Engineering
Abiko city
15.88
183
36
45
Technology
Ushiku city
67
314
28
43
Tsukuba city
5.26
463
53
71
Ibaraki Prefecture
42.7
Shiga Prefecture
52.6
102.6
Max
2,390
605
378
Min
105
24
34
Mean
737
128
107
Note : Extracted from Guidline and Comentary on CBPSW. "-" means not described.
Saito and Okazawa

T-N
4.5
14.1
33.5
34.2
17.6
19.1
23.1
11.1
8.5
6.4
39.6
11.1
11.6
5.0
7.8
5.5
14.1
25.0
39.6
4.5
16.2

T-P

Estimation method

1.6
1.3 Product of annual average
6.5 concentration, annual
5.8 precipitation, and runoff
3.0 percentage
0.9
1.9
0.9
Summation of pollution
1.9
loads per rainfall event,
0.7
which are estimated with
3.0
correlation equation between
2.7
event precipitation and runoff
0.9
load
0.6
0.8
0.55 0.73 0.89 6.5
0.6
1.9

Field survey
Characteristics of the observed rainfalls are described in Table 3. Selected constituents concentration of eachstudy site in Rainfall 3 is shown in time series in Fig 2 to Fig. 4. Concentration varies by order of magnitude,
corresponding to the rainfall runoff flow. First flushes are observed with their variation of degree among
constituents and drainage areas.
In order to characterise concentrations of rainfall runoff, which can vary widely during a storm event, Event
Mean Concentrations (EMCs) were calculated (Table 4). Comparison with Environmental Quality Standards(EQSs) (EA, 1971) or Predicted No Effect Concentrations (PNECs) (MOE, 2003) shows EMCs of almost all
constituents exceed EQSs or PNECs, and they could have not an ignorable effect on receiving waters. Especially,
EMC of zinc, recently incorporated into EQSs, is larger than the standard almost by order of ten. EMC of BPA ismuch lower than PNEC while EMC of B(a)P exceeds PNEC. Overall, though not so heavily polluted, rainfall
runoff through storm sewers could be a source of ambient water quality degradation.
Specific load per rainfall event are shown in Table 5. The variation of specific loads is also observed among
different rainfalls similarly to EMCs. The analysis of relationship between specific loads, and total precipitationor number of prior dry weather days shows a tendency of good linear relationship, which leads to the load
estimation method of using multiple regression.
Table 3 Characteristics of Observed Rainfalls
Rainfall 1
Rainfall 2
Rainfall 3
Rainfall 4
NDD
Total
Max
NDD
Total
Max
NDD
Total
Max
NDD
Total
Max
(d)
(mm) (mm/hr)(d)(mm) (mm/hr)(d)(mm) (mm/hr)(d)(mm) (mm/hr)
Drainage area A
7
14.0
2.5
10
6.0
2.5
63
37.5
11.0
3
16.5
6.0
Drainage area B
7
15.0
3.5
10
9.5
2.5
63
42.5
10.5
Drainage area C
7
14.5
3.0
10
8.0
2.5
63
34.0
9.5
12
13.5
5.5
Note ; NDD: Number of prior dry weather days (d), Total: Total precipitation (mm), Max: Maximum precipitation intensity(mm/hr), "-" measn field survey was not conducted.

- 348 -

800

600

600

400

400

200

200

0

0

13:00

15:00

17:00

19:00
Time

21:00

5

0

4

2

3

4

2

6

1

8

0

10

Precipitation(mm/30min)

SS(mg/l)800

Flow(m3/s)

1000
SS
CODM nZn

CODMn(mg/l), Zn(mg/l x100)

1000

13:0015:0017:0019:0021:0023:00 1:00
Time
Precipitation
Flow

23:00

Fig 2 Runoff Concentration and Flow of Rainfall 3 from Drainage Area A

80

300

60

200

40

100

20

0

0

13:00

15:00

17:00

19:00
Time

21:00

5

0

4

2

3

4

2

6

1

8

0

10

Precipitation(mm/30min)

SS(mg/l)400

Flow(m3/s)

100
SS
CODM nZn

CODMn(mg/l), Zn(mg/l x100)

500

13:0015:0017:0019:0021:0023:00
Time
Precipitation
Flow

23:00

Fig 3 Runoff Concentration and Flow of Rainfall 3 from Drainage Area B

80

600

60

400

40

200

20

0

0

13:00

15:00

17:00

19:00
Time

21:00

23:00

5

0

4

2

3

4

2

6

1

8

0

10

13:0015:0017:0019:0021:0023:00
Time
Precipitation

Fig 4 Runoff Concentration and Flow of Rainfall 3 from Drainage Area C- 349 -

Flow

Precipitation(mm/30min)

SS(mg/l)800

100

Flow(m3/s)

SS
CODM nCODMn(mg/l), Zn(mg/l x100)

1000

Table 4 Event Mean Concentrations of Urban Runoff

Drainagearea C

Drainagearea B

Drainagearea ASS
BOD CODMn
TN
TP
Cu
Zn
Pb
Cd
BPA
B(a)P
(mg/L) (mg/L) (mg/L) (mg/L)(mg/L)(mg/L) (mg/L) (mg/L) (mg/L) (μg/L) (μg/L)
Rainfall 1
66
12.8
15.5
2.9
0.30
0.07
0.008
0.001
0.21
0.007
Rainfall 2
86
19.8
29.3
4.0
0.51
0.06
0.35
N.D.
N.D.
0.23
0.025
Rainfall 3
72
11.2
23.5
2.4
0.27
0.27
1.10
0.006
N.D.
0.08
0.011
Rainfall 4
62
5.4
12.0
2.0
0.22
0.03
0.25
0.021
0.004
Mean
71
12.3
20.1
2.8
0.32
0.12
0.44
0.009
0.001
0.17
0.015
Rainfall 1
27
4.0
5.7
2.1
0.12
0.00
0.04
2.300
3.354
0.11
0.018
Rainfall 2
83
21.3
28.9
3.3
0.25
0.04
0.38
0.015
N.D.
0.67
0.041
Rainfall 3
84
6.5
11.0
2.1
0.24
0.20
0.38
0.000
N.D.
Mean
65
10.6
15.2
2.5
0.20
0.08
0.26
0.772
1.118
0.39
0.030
Rainfall 1
31
4.6
9.0
2.1
0.12
0.03
0.09
N.D.
N.D.
0.08
0.014
Rainfall 2
54
12.4
20.2
2.4
0.16
0.05
0.14
0.001
N.D.
0.16
0.033
Rainfall 3
68
7.0
11.4
1.6
0.19
Rainfall 4
29
3.2
6.5
1.7
0.07
0.12
0.07
0.014
0.003
Mean
46
6.8
11.8
1.9
0.14
0.07
0.10
0.005
0.001
0.12
0.023
EQS
25
(2, 3)(3, 5) (0.4, -) (0.03, 0.05)
0.03
0.01
0.01
PNEC
11
0.005
Note : "N.D." means not detected. "-" means deficiency, not measured, or not applicable. In EQS of BOD, CODMn, TN, and TP, (, ) means (EQS of receiving water of Drainage areas A and B, EQS of receiving water of Drainage area C).

Table 5 Specific Loads of Urban Runoff

Drainagearea C

Drainagearea B

Drainagearea A

CODMn
SS
BOD
TN
TP
Cu
(kg/ha) (kg/ha) (kg/ha) (kg/ha) (kg/ha) (g/ha)
Rainfall 1
3.83
0.751
0.908
0.172 0.0174
Rainfall 2
2.25
0.519
0.767
0.104 0.0135
1.6
Rainfall 3
22.95
3.566
7.478
0.763 0.0845
84.6
Rainfall 4
4.44
0.382
0.852
0.145 0.0156
1.8
Mean
8.37
1.304
2.501
0.296 0.0327
29.3
Rainfall 1
0.17
0.026
0.037
0.013 0.0008
0.0
Rainfall 2
0.47
0.122
0.165
0.019 0.0014
0.2
Rainfall 3
1.34
0.103
0.175
0.033 0.0039
3.2
Mean
0.66
0.083
0.126
0.022 0.0020
1.1
Rainfall 1
0.14
0.020
0.040
0.009 0.0005
0.1
Rainfall 2
0.27
0.063
0.103
0.012 0.0008
0.3
Rainfall 3
2.21
0.226
0.372
0.051 0.0061
Rainfall 4
0.32
0.035
0.071
0.019 0.0008
1.3
Mean
0.73
0.086
0.146
0.023 0.0021
0.6Note : "N.D." means not detected. "-" means deficiency, or not measured.

Zn(g/ha)
4.4
9.1
349.2
17.8
95.1
0.2
2.2
6.0
2.8
0.4
0.7
0.7
0.6

Pb
(g/ha)
0.49
N.D.
1.87
1.53
0.97
0.02
0.09
0.00
0.03
N.D.
6.18
0.16
2.11

Cd
BPA
B(a)P
(g/ha) (mg/ha) (mg/ha)
0.035
12.04
0.42
N.D.
6.05
0.65
N.D.
24.79
3.65
0.250
0.071
14.29
1.58
0.022
0.73
0.12
N.D.
3.84
0.23
N.D.
0.007
2.28
0.18
N.D.
0.35
0.06
N.D.
0.84
0.17
0.029
0.010
0.59
0.11

Load estimation method
Using the data of the field survey in Drainage areas A and C, multiple regression analyses were conducted for SS,
BOD, CODMn, TN, TP, and zinc according to Eq. 1. The regression result is summarised in Table 6, and thecomparison between the measured and estimated values are shown in Fig 5 and Fig 6. The comparison revealed
that regardless of the drainage areas, the estimated values conformed with the measured values in most cases.
Generally, there are several principal estimation methods for urban nonpoint pollution loads as shown in Table 7.
In Method (1), average annual concentration of runoff is calculated from several EMCs, and that multiplied byrunoff percentage and annual precipitation is an estimation of annual unit load. In Method 2, field survey isconducted in each land use such as roof and road, and a runoff load is summed up. Method (3) reflects eachrainfall event, so does Method (4) with prior dry weather days considered. Regardless of methods, more data
produce more reliable estimation results, and it is desirable that more appropriate data are obtained. In terms of
the fact that Methods (1) and (2) do not explicitly consider meteorological or hydrological information in eachrainfall event, Methods (3) or (4) could have more reliable estimation results with not a large data required. The
above analysis adopted Method (4), which suggested that the method is a viable option, and more dataacquisition and analysis are ongoing.

- 350 -

25

4

20
15
10
5
0

10
Estimated CODMn (kg/ha)

5
Estimated BOD (kg/ha)

Estimated SS (kg/ha)

30

3
2
1

6
4
2
0

0

0

5

10

15

20

25

30

0

1

M easured SS (kg/ha)

2

3

4

0

5

1

0.5

0.8

0.8

0.4

0.4
0.2

Estimated Zn (kg/ha)

1

0.6

0.6

0

0.2

0.4

0.6

0.8

0.4
0.2

6

8

10

0.2
0.1
0

0

1

4

0.3

0

0

2

M easured CODM n (kg/ha)

M easured BOD (kg/ha)

Estimated TP (kg/ha)

Estimated TN (kg/ha)

8

0.2

0.4

0.6

0.8

1

0

0.1

M easured TP (kg/ha)

M easured TN (kg/ha)

0.2

0.3

0.4

0.5

M easured Zn (kg/ha)

0.3

2.5

0.25

2
1.5
1
0.5

0.5
Estimated CODMn (kg/ha)

3
Estimated BOD (kg/ha)

Estimated SS (kg/ha)

Fig 5 Comparison of Measured and Estimated Values (Drainage area A)

0.2
0.15
0.1
0.05

0

0.5

1

1.5

2

2.5

0

3

0.05 0.1 0.15 0.2 0.25 0.3
M easured BOD (kg/ha)

0.1

0.01

0.08

0.008

Estimated TP (kg/ha)

Estimated TN (kg/ha)

M easured SS (kg/ha)

0.06
0.04
0.02

0.3
0.2
0.1
0

0

0

0.4

0

0.1

0

0.02 0.04 0.06 0.08
M easured TN (kg/ha)

0.1

0.006
0.004
0.002

0

0.002 0.004 0.006 0.008 0.01
M easured TP (kg/ha)

Fig 6 Comparison of Measured and Estimated Values (Drainage area C)- 351 -

0.3

0.4

M easured CODM n (kg/ha)

0

0

0.2

0.5

Table 6 Result of Regression
Drainagre a (kg/ha/mm)
area A b (kg/ha/day)Drainage a (kg/ha/mm)
areaC b (kg/ha/day)

SS
0.211
0.243
-0.01200.0414

BOD
0.021
0.046
-0.0003
0.0038

CODMn
0.025
0.106
0.00050.0057

TN
0.00770.00770.000650.00048TP
Zn
0.0174-0.0010-0.0050
0.0062-0.00003 0.00011 -Table 7 Principal Estimation Methods for Pollution Loads
No.

MethodProductofannualaverage(1) concentration, annual precipitation,and runoff percentage(2)

Summation of pollution loads fromeach land use area

Equation∑L=k･C･∑R∑L=(1/A)･∑(Di･Li･Ai)

Summation of pollution loads per
rainfall event, which are calculated(3)with correlation equation between
event precipitation and runoff load-

Summation of pollution loads per(4) rainfall event, which are calculatedwith multiple regression equation

L=a･∑r＋b･NDD

Notation∑L: Unit load (kg/ha/year)
k: Runoff percentage
C: Annual average concentration (kg/ha/mm)∑R: Annual precipitation (mm/year)
A: Catchment area (ha)Di: Runoff coefficient for land use "i" for pollution
at the concerning point
Li: Pollution load from land use "i"Ai: Area of land use "i" in catchment area (ha)
L: Pollution load per a rainfall event (kg/ha)∑r: Event precipitation (mm)a, b: Coefficients in multiple regression equation
NDD: Number of prior dry weather days (day)Conclusion
The Japanese current framework and status of urban nonpoint pollution control was reviewed, and it was pointed
out that the control has not yet been vigorously addressed though there are a planning framework, a technicalguidance, and a financial programme to support the control. Further knowledge and technical improvement
should be sought to better planning and the related researches.
Field survey was conducted, focusing on the clarification of the state of runoff of conventional constituents,
heavy metals and endocrine disrupting chemicals. It revealed that concentration in time series varied by order ofmagnitude, corresponding to the rainfall runoff flow, and runoff quality characteristics varied among drainage
areas. EMCs of almost all analysed constituents exceeded EQSs or PNECs, and they could have not an ignorable
effect on receiving waters.
A load estimation method was researched based on the field survey data. A multiple regression equation,
incorporating meteorological or hydrological information in each rainfall event, could produce more reliable
estimation results with not a large data required, and more data acquisition and analysis are ongoing.

Acknowledgement
The authors express their gratitude to the cooperating staffers of municipalities in the field survey for miscellanious supports.

References
Environmental Agency (EA) (1971) Notification of Environmental Quality Standards on Water Pollution. (amended in 1974,
1975, 1982, 1985, 1986, 1991, 1993, 1995, 1998, 1999, 2000, and 2003) (in Japanese)
Water Quality Management Division, Water Quality Conservation Bureau, Environmental Agency (EA) (1990) Manual for
Research of Nonpoint Pollution Load. March, 1990 (in Japanese)
Fujiu, K., Yoshida, T. and Tamoto, N. (2005) Research on urban nonpoint pollution control. FY2004 Annual Report of
Wastewater Management and Water Quality Control. July 2005 (in Japanese)
Fujiu, K., Yoshida, T. and Tamoto, N. (2006) Research on urban nonpoint pollution control. FY2005 Annual Report of
Wastewater Management and Water Quality Control. June 2006 (in Japanese)- 352 -

Japan Sewerage Works Association (JSWA) (1999) Guideline and Commentary on Comprehensive Basin-wide Planning of
Sewage Works (Version of 1999). October 1999 (in Japanese)
Water Quality Management Department, Ministry of Land, Infrastructure and Transport (MLIT) and Japan Institute of
Wastewater Engineering Technology (JIWET) (2002) Tentative Guideline on Urban Nonpoint Pollution Control.
March 2002 (in Japanese)
Environmental Risk Assessment Office, Ministry of the Environment (MOE) (2003) Environmental Risk Assessment on
Chemical Substances. March 2003 (in Japanese)
Nakamura, E. (1993) Loadings Characteristics of Stormwater Runoff. Journal of Japan Sewerage Works Association, Vol.30,
No.364, 1-13, 1993 (in Japanese)
Sakakibara, T., Masuta, T., Matsubara, M. and Kato, S. (2005) New Goals and Strategies for CSOs Control from Legal
Aspect. Proc. 10th International Conference on Urban Drainage, Copenhage/Denmark.
Tamoto, N. and Yoshida T. (2005) Research on Runoff characteristics of bis-phenol A and Benzo(a)piren. Proc. 33rd
Environmental System Conference, Sapporo. (in Japanese)
Tamoto, N., Yoshida, T. and Fujiu, K. (2005) Runoff characteristics of pollutants inclusive of heavy metals from urban areas.
Proc. 5th Environmental Technology Conference, Osaka. (in Japanese)
Tamoto, N., Yoshida, T. and Fujiu, K. (2007) Field Survey and Alternative Estimation on Runoff Pollution Load from Urban
Areas. Proc. Novatech 2007 (under contribution)- 353 -

- 354 -[Investigation on load reduction measures]“Load reduction in domestic and commercial wastewater is madeby sewerage construction, while other load reduction is made byeach source, and the control measures should be clarified”.
“--- in case urban areas are targets of load reduction, thereduction loads and the measures should be clarified. As control
measures of urban nonpoint pollution, there are “Plans of CSOs
National InstituteLand and Infrastructure
abatement,” and “Programofforsupporting
next generation
3
Management, Japansewerage projects (Type of nonpoint pollution control).”Comprehensive Basin-wide Plans for Sewage Works(CBPSW) in Japan perform as high-ranking schemes ofsewage works.
 Allowable pollution loads are allocated to each pollution
source in order to achieve environmental water quality
standards.
 “--- in case closed water areas are targeted, ---- allowablepollution loads are allocated also to nonpoint sources suchas urban areas and agricultural.”[CBPSW as hihg-ranking scheme][1] Current framework/status

National Institute for Land and Infrastructure Management (NILIM),
Ministry of Land, Infrastructure and Transport, Government of Japan

Yoshida, T. and Tamoto, N.

Present status and estimation methodof pollutant load in wet weather flowfrom urban areas

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

National Institute for Land and InfrastructureManagement, Japan(1) Generating loads including non-point
source on a watershed are estimatedusing unit pollution load data, andrunoff loads are calculated throughpollution analysis.
(2) The allowable load is calculated
based on the water quality standard
at a target point in the concernedwater body, and the pollution load thatshould be reduced (=reduction load)
is determined as a difference of thetotal generating load and theallowable load.
(3) The reduction load is distributed toeach pollution source category suchas public sewerage, industrial,
livestock, and non-point source (e.g.
urban, farm).

[Formulation of CBPSW]National Institute for Land and InfrastructureManagement, Japan

2

許容負荷量

4

点源 生活・営業
点源 工場
点源 家畜
面源 市街地系
面源 農地系面源 山林系

T流総-T沼(COD)

流達負荷量[3] Research on load estimation methods ofurban runoff[2] Field survey of urban runoff, focusing onconventional, heavy metals, and endocrine
disrupting chemicals[1] Review of the current framework/status ofurban nonpoint pollution control

Outline

負荷量(kg/日)

- 355 -57Type of Water Circulation Restoration(178)
Type of Nonpoint Pollution Control(3)Type of Recycled Resources Utilisation(163)
Type of Potential Energy Utilisation(7)
Type of New Technology Utilisation(30)
Type of Advanced IT(15)(Number of projects adopted from fiscal 1996 to 2005)

National Institute for Land and InfrastructureManagement, Japan

Water Environment
Creation Project
Recycle Promotion
Project
Function Upgrade
Promotion Project

National subsidy program to promote newly required
roles of sewage works, such as water environment
creation, recycle promotion, and coping with IT.
Type of nonpoint pollution control = Pollution load
reduction in initial rainfall runoff or gray water

Program of Supporting Next
Generation Sewerage Project[Financial assistance]

National Institute for Land and InfrastructureManagement, Japanbe necessarily allocated to the urban nonpoint
source pollution in an effectively manner.
 On the estimation process of generating loads ofurban non-point source, existing data in otherwatersheds are frequently applied instead ofcollecting data for a target watershed for thereasons of costs and the difficulty of performing
field surveys.

 In practice, allowable pollution loads could not[Issues of load allocation to urban areas]

National Institute for Land and InfrastructureManagement, Japan

Observe four rainfall events

Runoffcharacteristics
Different land uses
(Three drainage areas)

Runoff load

To clarify

Sampling atoutlets of the drainage areas

served by separate storm sewers

 Analyze runoff quality from urban areas[2] Field survey

National Institute for Land and InfrastructureManagement, Japan[Planning steps]
Investigate prioritisation of block areas.
Select areas to be controlled, and viable control measures.
Determine control measures and the scale(for cost-minimisation)[Issue]The Guideline could have been scarcely referenced inpractice.

"Tentative Guideline for Urban Nonpoint Pollution Control"
provides the knowledge of urban nonpoint pollution control
as well as the relevant planning and research methods.
The Guideline includes detailed description in accordance withhigher-ranking schemes such as CBPSW.

[Planning of urban nonpoint pollution control]

86

- 356 -Prior dry weather days (d)

0

30

60

90

Rainfall 2

Rainfall 3

Rainfall 4

40

30

20

9

TP

Bisphenol A

Zn

TN

11

14 to 20 samples / rainfall event

Total precipitation (mm)National Institute for Land and InfrastructureManagement, Japan

Drainage area A

Rainfall 1

Prior dry weatherdays (d)Total precipitation
(mm)

10

0

National Institute for Land and InfrastructureManagement, Japan

Observed rainfalls

120

Cd

CODMn

Benzo [a] pyrene

Pb

Cu

Heavy metals

Endocrine disrupting
chemicals

BOD

SS[Drainage are A]

13:00

0

200

17:00

19:00
Time

21:00

23:00

12

10

8

6

13:0015:0017:0019:0021:0023:00 1:00
Time
Precip itation
Flow

0

1

2

4

2

4
3

0

5

National Institute for Land and InfrastructureManagement, Japan

0

200

400

400

800

1000

600

15:00

SS
CODM n
Zn
600

800

1000

[Drainage area A]

10

Arterial road： Not
included

Arterial road：Included
National Institute for Land and InfrastructureManagement, Japan

Area： 67ha
Impervious area： 61%
Land use：Residential[Drainage C]

Area： 18ha
Impervious area： 67%
Land use：Residential[Drainage area B]

Result in Rainfall 3

Area： 95ha
Impervious area：69%
Land use：
High/medium rise
residential,
Commercial
Arterial road: IncludedSS(mg/l)Conventional

CODMn(mg/l), Zn(mg/l x100)

Study sites

Flow(m3/s)

Constituents analysed

Precipitation(mm/30min)

- 357 -SS(mg/l)

17:00

19:00
Time

21:00

10

0

tr

0

13

8

1

13:0015:0017:0019:0021:0023:00
Time
Precipitation
Flow

6

2

4

2

4
3

0

5
Precipitation(mm/30min)

CODMn(mg/l), Zn(mg/l x100)

SS

CODM n (mg/L)

Drainagearea A

CODMn

Drainagearea B

15

Drainagearea CR1 R2 R3 R4 R1 R2 R3 R1 R2 R3 R4National Institute for Land and InfrastructureManagement, Japan

Drainagearea C

00

Drainagearea B

10

20

Drainagearea A

2040

R1 R2 R3 R4 R1 R2 R3 R1 R2 R3 R4

30

60

50
40

SS (mg/L)

80

100

∫

Event mean concentration EMC = M = ∫0 ctr(t )q(t )dtVq (t )dt[SS, CODMn]

Flow(m3/s)

National Institute for Land and InfrastructureManagement, Japan

23:00

0

0

15:00

20

100

13:00

40

200

80

100

60

SS
CODM n
Zn

300

400

500

[Drainage area B]

15:00

23:00

0

20

40

60

80

100

0.4

TN

Flow

14

10

8

6

Drainagearea ATP

Drainagearea B

16

Drainagearea CR1 R2 R3 R4 R1 R2 R3 R1 R2 R3 R4

TP (mg/L)

Precipitation

13:0015:0017:0019:0021:0023:00
Time

0

1

2

4

2

4
3

0

5

National Institute for Land and InfrastructureManagement, Japan

Drainagearea C

0.0

0

Drainagearea B

0.1

1

Drainagearea A

0.2

2

0.3

0.5

0.6

4
3

Flow(m3/s)

National Institute for Land and InfrastructureManagement, Japan

21:00

TN (mg/L)

19:00
Time

R1 R2 R3 R4 R1 R2 R3 R1 R2 R3 R4

17:00

SS
CODM nCODMn(mg/l), Zn(mg/l x100)56[TN, TP]

13:00

0

200

400

600

800

1000

[Drainage area C]

Precipitation(mm/30min)

SS(mg/l)

0.04
0.03
0.02
0.01
0.00

0.4

0.3

0.2

0.1

0.0

Zn

Drainagearea B
Drainagearea A

National Institute for Land and InfrastructureManagement, Japan

Drainagearea C

L:
Σr :
NDD :
a, b :Pb (mg/L)

Pb

Drainagearea B

17

Drainagearea C

National Institute for Land and InfrastructureManagement, Japan

Specific load per rainfall event (kg/ha)
Total rainfall per event (mm)Number of prior dry weather day (day)Parameters
19

Pollutants to be conveyed
Æ Meteorological condition

L = a･Σr + b･NDD

Pollutants to be conveyed
Æ Meteorological condition

2.3

R1 R2 R3 R4 R1 R2 R3 R1 R2 R3 R4[3] Load estimation method

Drainagearea AR1 R2 R3 R4 R1 R2 R3 R1 R2 R3 R40.05

Zn (mg/L)

0.5

1.10

[Zn, Pb]
BPA (μg/L)

0.01
0.00

0.0

0.32

Rainfall 4

0.14

Rainfall 1

0.27

4.44

Rainfall 4

2.21

22.95

Rainfall 3

Rainfall 3

2.25

Rainfall 2

Rainfall 2

3.83

Rainfall 1

0.071

0.372

0.103

0.040

0.852

7.478

0.767

0.908

(kg/ha)

CODMn

TN

0.019

0.051

0.012

0.009

0.145

0.763

0.104

0.172

(kg/ha)TP

0.00080.00610.00080.00050.01560.08450.01350.0174(kg/ha)National Institute for Land and InfrastructureManagement, Japan

0.035

0.226

0.063

0.020

0.382

3.566

0.519

0.751

BOD
(kg/ha)SS

Drainagearea B

Zn

0.7

0.7

0.4

17.8

349.2

9.1

4.4

(g/ha)

Σr

12

63

10

7

3

63

10

7

(mm)

20

13.5

34.0

8.0

14.5

16.5

37.5

6.0

14.0

(day)

NDD

18

Drainagearea C

Benzo [a] pyrene

Drainagearea A

Data of regression analysis(kg/ha)B(a)P (μg/L)

R1 R2 R3 R4 R1 R2 R3 R1 R2 R3 R4National Institute for Land and InfrastructureManagement, Japan

Bisphenol A

Drainagearea C

0.02

0.2

Drainagearea B

0.03

0.4

Drainagearea A

0.04

0.05

0.6

R1 R2 R3 R4 R1 R2 R3 R1 R2 R3 R4

11.0

0.8

1.0

[B(a)P, BPA]

Drainagearea A
Drainagearea C- 358 -

-0.01200.0414a (kg/ha/mm)

b (kg/ha/day)

0

0.02

0.04

0.06

0.08

0.1

0

0.5

1

1.5

2

2.5

3

0

0

1

1.5

2

2.5

0.02 0.04 0.06 0.08
M easured TN (kg/ha)

M easured SS (kg/ha)

0.5

0.1

3

(Drainage area C)

Drainage
areaC

0.046

0.243

0.00570.0005

0.106

0.025

CODMn

0

0

0.2

0.3

0.4

0.5

0.002 0.004 0.006 0.008 0.01
M easured TP (kg/ha)

M easured CODM n (kg/ha)

0.1

National Institute for Land and InfrastructureManagement, Japan

0

0.002

0.004

0.006

0.008

0.01

0

0.1

0.2

0.3

0.4

0.5

National Institute for Land and InfrastructureManagement, Japan

0.0038-0.0003

0.021

BOD

0.211

SS

0

0.05

0.1

0.15

0.2

0.25

0.3

0

0.000480.00065

0.00770.0077

TN

21

-

-

0.0062-0.0010Zn

M easured BOD (kg/ha)

23

0.05 0.1 0.15 0.2 0.25 0.3

0.00011-0.00003-0.00500.0174

TP

1

0

0

1

1.5

2

2.5

0.4

0.6

0.8

M easured TN (kg/ha)

0.2

M easured SS (kg/ha)

0.5

1

3

0

0

1

2

3

4

0.4

0.6

0.8

M easured TP (kg/ha)

0.2

M easured BOD (kg/ha)

15

National Institute for Land and InfrastructureManagement, Japan

0

0.2

0.4

0.6

0.8

1

0

1

2

3

4

5

0

0.1

0.2

0.3

0.4

0.5

0

2

4

6

8

10

0

0

Method

4

6

8

0.2

0.3

0.4

0.5

L =a ･∑r ＋b ･NDD-

∑L =(1/A )･∑(D i･L i･A i)∑L =k ･C ･∑R

Equation

M easured Zn (kg/ha)

0.1

10

22

∑L: Unit load (kg/ha/year)
k: Runoff percentage
C: Annual average concentration (kg/ha/mm)∑R: Annual precipitation (mm/year)
A: Catchment area (ha)Di: Runoff coefficient for land use "i" for pollution at the concerning point
Li: Pollution load from land use "i“
Ai: Area of land use "i" in catchment area (ha)
L: Pollution load per a rainfall event(kg/ha)∑r:
precipitation (mm)National
Institute for Landand EventInfrastructure
24Management,
Japan Number of prior dry weather days (day)a, b: Coefficients in multiple regression equation
NDD:

Summation of pollution loads per rainfall event,(4) which are calculated with multiple regression
equation

Summation of pollution loads per rainfall event,(3) which are calculated with correlation equation
between event precipitation and runoff load

Product of annual average concentration,
annual precipitation, and runoff percentage
Summation of pollution loads from each land(2)
use area
(1)

No.

2

M easured CODM n (kg/ha)

Principal estimation methods

0

0.2

0.4

0.6

0

0.5

1

1.5

2

2.5

0.8

Estimated SS (kg/ha)

Estimated TN (kg/ha)

3

Estimated TP (kg/ha)(Drainage area A)
Estimated BOD (kg/ha)

Comparison estimated/measured
Estimated CODMn (kg/ha)

Estimated Zn (kg/ha)

Result of regression

Estimated BOD (kg/ha)

Drainagre a (kg/ha/mm)
area Ab (kg/ha/day)

Estimated SS (kg/ha)

Estimated TN (kg/ha)

Estimated CODMn (kg/ha)

Estimated TP (kg/ha)- 359 -

- 360 -25

Field survey revealed concentration in time series varied byorder of magnitude, corresponding to the rainfall runoff flow,
and runoff quality characteristics varied among drainage areas.
EMCs of almost all analysed constituents exceeded EQSs or
PNECs, and they could have not an ignorable effect onreceiving waters.



National Institute for Land and InfrastructureManagement, JapanThe Japanese current framework/status of urban nonpoint
pollution control was reviewed.
The control has not yet been vigorously addressed though
there are a planning framework, a technical guidance, and afinancial programme.
Further knowledge and technical improvement should besought to better planning and the related researches.

ConclusionNational Institute for Land and InfrastructureManagement, Japan26

A load estimation method was researched based on the fieldsurvey data.
A multiple regression equation, incorporating meteorologicalor hydrological information in each rainfall event, could
produce more reliable estimation results with not a large datarequired.
More data acquisition and analysis are ongoing.

Cont.