英文關鍵字
pipe
water
flowing
river
ecology
contamination
sewer
tube
drainage
environment
background
pollution
nature
natural
liquid
industry
sewage
flow
environmental
industrial
chemical
waste
dirty
drain
dump
splash
wastewater
sluice
sludge
system
stream
sewerage
canal
contaminated
eco
outdoor
pipes
pouring
production
sanitation
negligence