black
canal
chemical
concrete
construction
contaminated
contamination
danger
dirty
disaster
drain
drainage
dump
ecology
environment
environmental
flow
flowing
garbage
green
industrial
industry
liquid
mud
natural
nature
pipe
plastic
polluted
pollution
pouring
problem
recycle
river
rubbish
sewage
sewer
sewerage
stream
substance
technology
toxic
trash
treatment
unclean
unhygienic
urban
waste
wastewater
water