chemical
concrete
conservation
construction
crude oil
dirty
discharge
discharging
drain
drainage
ecology
effluent
engineering
environment
environmental
flow
flowing
garbage
green
greenpeace
industrial
industry
liquid
mud
nature
oil
pipe
pipeline
plant
pollution
production
recycling
removal
river
rusty
sedimentation
sewage
sewer
sewerage
sludge
smell
stream
system
treatment
tube
turbidity
waste
wastewater
water