Environmental Engineering Reference
In-Depth Information
two land use states, shown in Fig. 4 , was much smaller and was only several folds.
The large pollution loads in commercial districts compared to those in residential
and industrial districts suggest that pedestrians have large effects on runoff loads.
Commercial activities and wastes produced by pedestrians are possibly a major
source of pollutants.
Percentage of Runoff Load in Potential Load (Pollutant Runoff
Coefficient)
The percentage of runoff load in potential load was defined as the “pollutant runoff
coefficient” and is expressed as:
L
R LL
r
=
×
100
(1)
+
s
r
where R , L r and L s are the pollutant runoff coefficient, runoff load, and scrubbed
load, respectively. The mean pollutant runoff coefficient is shown in Fig. 6 for each
city. In commercial districts, the coefficients were about 40% for BOD, COD Mn and
TN but were smaller than 20% for SS and TP. The results suggest that pollutants
that exist in particle forms are scarcely discharged just by natural rain. The coeffi-
cient was smaller in residential districts than in the other districts.
The data was compared with the pollutant runoff coefficients determined by the
Public Works Research Institute in 1975 [5] . The values calculated in this study
were smaller than those of the Public Works Research Institute in general, but a
similar trend was shown between the two when the ratio was calculated for each
water quality constituent.
100%
100%
Residential
Commercial
Industrial
Residential
Commercial
Industrial
80%
80%
60%
60%
40%
40%
20%
20%
0%
0%
BOD
COD
SS
TN
TP
BOD
CODSS N P
Fig. 6 Pollutant runoff coefficients. Left : this study, right : by the Public Works Research Institute
(1975)
 
Search WWH ::




Custom Search