英文關鍵字
abandoned
background
canal
chanel
channel
concrete
conduit
current
dark
dead
dirty
drain
end
environment
fall
fast
filth
filthy
flow
flowing
gray
green
hole
industrial
industry
manhole
metro
pipe
pipeline
pollution
pour
round
sanitary
sewage
sewer
sewerage
splash
system
treatment
tube
tunnel
underground
waste
water