Potential of Road Surface for a Non-point Source of Pollutants – Result of Nationwide Survey in Japan - Highway and Urban Environment - page 243

15

Scrubbed load
Runoff load

10

11.6

5

3.2

3.3

2.0

0.8

0.5

0.42

1.35 0.39

0.58 1.96 1.41

0

BOD COD BOD COD BOD COD

Residential Commercial Industrial

150

1

Scrubbed load
Runoff load

Scrubbed load
Runoff load

0.8

100

0.6

0.66

139

0.4

0.23

50

0.25

0.2

74

0.11

0.19

0.06

0.22

0.03

0.14

35

0.03

0.01 0. 01

0

TN TP TN TP TN TP 4.1 4.4 4.1

0

Residential Commercial Industrial Residential Commercial ndustrial

Fig. 4 Average unit loads (runoff and scrubbed loads)

loads larger than runoff loads. BOD, COD Mn , and SS showed a trend of values in
commercial district being larger than those in residential district, which were
almost equal to those in industrial district. The mean runoff loads and scrubbed load
shown in Fig. 2 were decided to be the load units obtained in this study.

Factors of Variation

A two-way layout analysis of variance was conducted on the collected 72 data sets
of runoff loads using the nearby land use state and the city as the two factors of
variation for each water quality constituent. The analysis showed that the factors
affected the runoff loads of COD Mn and TN at a level of significance of 5%. The
factors were statistically suggested to little affect the runoff loads of the other con-
stituents: BOD, SS and TP.