abominate
bacterium
bad
biology
biomass
care
circle
clean
dirt
dirty
disdain
earth
ecology
engineering
environmental
excremental
excretion
factory
foul
garbage
global
industry
life
midden
nasty
natural
not
plant
plastic
pollute
pollution
processing
protection
purity
recycle
reduce
reflection
refuse
repulsive
responsible
rot
rubbish
save
sedimentation
settling
sewage
smell
trash
treatment
unhygienic
warming
waste
wastewater
wastrel
water