| Summary: | 碩士 === 國立臺灣大學 === 農業工程學系研究所 === 86 === The test site of this study was selected in the An-Keng farm of National Taiw
an University, in Hsin-tien, Taipei county. One of the best management practic
es (BMPs) which was selected and tested in the site was vegetative filter stri
p. To evaluate the effects of vegetative filter strips on non-point source pol
lution control, the following items were measured or tested. They were: runoff
rate, total suspended solids (TSS), biochemical oxygen demand (BOD5), chemica
l oxygen demand (COD), phosphate (PO4-3-P), n
rate (NO3--N), ammonia nitrogen (NH4+-N), and electric conductivity
(EC). Experiments of this stu
dy were divided into three stages. In the first stage, 16 tests were respectiv
ely conducted on different vegetative filter strips. The slope steepnesses of
the test plots were 5%, 10%, 15% and 20%; their lengths were 4m, 8m, 12m and 1
6m, and their widths were 2.5m for all test plots. In the second and the third
stages, flow rate and pollution concentration of the inflow water were increa
sed. Aside from these, bared plots with a slope length of 16m and with three d
ifferent slope steepn
ses of 5%, 10
% and 15% were also tested. In addition, a test with clean water rather than w
ith artificially made polluted water and a test with a running time of two hou
rs (rather than one hour) were also conducted.
The results showed that in regard to the reduct
ion effects of vegetative filter strips, it was the best for total suspended s
olids. Then; in the decreasing order, they were chemical oxygen demand, phosph
ate, ammonia nitrogen and nitrate. Average reduction rates for the above five
pollutants were 0.808, 0.723, 0.66, 0.58 and 0.34, respectively. In
general, pollution reduction effects of vegetative filter strips decreased wit
h increase of hydraulic loading. The relationships were better for that slope
steepnesses ranged from 5% to 15%, and pollutants were total suspended solid,
phosphate and ammonia nitrogen.
The relationships between two factors
, namely, slope steepnesses and hydraulic loading, and pollution reduction rat
e due to vegetative filter strips were then obtained. By using the equations o
f the relationships, effects of the vegetative filter strips can be evaluated.
Regression analyses were done by using the data obtained from the test plots
with slope steepnesses of 5%, 10% and 15%. It was found that squares of the sa
mple correlation coefficient (R2) for total suspended solid, phosphate and amm
onia niogen were 0.667, 0.713 and
0.718, respectively.
Using the obtained equations, the relationships between the t
wo factors (namely, slope steepness and hydraulic loading) and pollution reduc
tion rate can be plotted as curves. And by using the curves, vegetative filter
strips can be designed for specific given conditions.
Besides, in this
study, cost of vegetative filter strips were analyzed. Concept of factor of sa
fety was introduced to the application of the curves of inflow pollution reduc
tion rates. In addition, two examples were given for further description.
Keywords: best management practice, vegetative filt
er strip, non-point resource pollution, hydraulic loading
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