英文關鍵字
cement
chemical
circular
concrete
conduit
culvert
danger
day
dirt
dirty
ditch
drain
dump
ecology
energy
environment
environmental
factory
flow
flowing
fluid
garbage
green
gushing
industrial
industry
irrigation
liquid
natural
nature
old
outlet
pipe
pipeline
polluting
pollution
pouring
refinery
sewage
sewer
sky
stream
toxic
treatment
tube
waste
water
waterfall
waterpipe