0.1 ppm

0.01 ppm

0.001 ppm

0.0001 ppm

0.1 mg/litre

1.5 mg/litre

5 mg/litre

10 mg/litre

hardness in water

residual chlorine in water

turbidity in water

dissolved oxygen in water

only (i)

both (i) and (ii)

both (i) and (iii)

all (i), (ii) and (iii)

calcium carbonate

magnesium carbonate

sodium carbonate

calcium hydroxide