environmental
bustard
clean
construction
dirty
drain
drainage
environment
factory
filter
flow
flowing
icon
illustration
industrial
industry
line
liquid
management
nature
pipe
pipeline
plant
pollution
purification
purity
recycle
recycling
river
sewage
sewer
sludge
smart
symbol
system
tank
tap
technology
the city
trap
treatment
tube
use
vector
waste
wastewater
water