Provided are an apparatus and a method for purification of water in which
impurities in contaminated water can be removed with a reduced amount of
flocculant and with high efficiency. The apparatus comprises, in the order
from the side where contaminated water is introduced, an electrolysis tank
(1) for electrolyzing the contaminated water, a gas mixing tank (2) for
mixing carbon dioxide into the contaminated water electrolyzed, a
coagulation tank (3) for mixing Fe.sup.3+ supplied from a flocculant
producing device (7) to coagulate impurities in the contaminated water,
and a floatation tank (4) for floating and separating the impurities
coagulated. The electrolysis tank (1) electrolyzes the contaminated water
to lower zeta potential of colloid particles in the contaminated water,
and then the contaminated water is mixed with Fe.sup.3+ in the coagulation
tank (3), thereby reducing the amount of positively charged Fe.sup.3+ to
be added for neutralizing the colloid particles.
