algae

backdrop

bacterium

basin

bubble

cleaning

close

closeup

concrete

danger

dirt

dirty

disaster

ecocatastrophe

ecology

environment

environmental

facility

flow

flowing

froth

grey

industry

lather

liquid

motion

natural

nature

plant

polluted

pollution

recycling

river

scum

sewage

silt

slime

slimy

sludge

spume

stage

stream

surface

swamp

toxic

treatment

unhygienic

unpleasant

waste

water

wet