background
brown
canal
chemical
china
clean
concrete
construction
corrosion
dirty
drain
drainage
ecology
environment
equipment
factory
fatal
flow
flowing
fluid
garbage
global
grass
industrial
industry
liquid
natural
nature
old
outdoor
pipe
pipeline
pollution
problems
pump
refinery
river
rusty
season
sewage
sewer
stream
substance
technology
toxic
tube
warming
waste
water
waterfall