aluminum
アルミニウム
analysis
arsenic
background
bleach
chemical
chlorine
close
closeup
cold
color
composition
concept
control
dirty
disinfection
exam
examination
faucet
flask
hand
hard
holding
home
iron
manganese
plumbing
pollutant
pollution
probe
quality
research
researching
sample
scientist
smell
soft
tap
test
trace elements
turbidity
up
vial
water
worker