adult
analysis
bacillus
background
bacteria
biochemistry
biology
chemical
cholera
closeup
day
environment
experiment
female
glass
glove
hand
holding
industry
laboratory
lake
liquid
medicine
microbiology
mineral
natural
nature
outdoors
pharmacy
pink
pollution
pond
research
river
salination
salinization
salt
sample
saturate
science
scientific
taking
test
tube
waste
water
woman
work
worker