Lamella clarifiers - Increase settling performance

(marker squeaking)

(uplifting music)

- [Narrator] Already in 1904,

Allen Hazen defined the
laws of sedimentation.

He noticed that a particle
in water can only settle down

when its sedimentation velocity Vs,

is higher than the result flow Q,

divided by tank area A.

Q divided by A is called
surface loading qa.

Except with flocculation,

the sedimentation velocity Vs of particles

and flow Q cannot be changed.

By increasing the only
variable, tank area,

we decrease the surface loading qa

and therefore increase
the settling performance.

To increase tank area,

more horizontal surfaces
have to be installed.

Obviously, this is not practical,

so the horizontal plates are
replaced by incline plates.

The additional surface area of
the incline plates is created

by their projection in
horizontal direction.

Nowadays, settling plates are
replaced by plastic modules

as provided by AET, because
they have a lower cost,

are easier to maintain and install.

Lamella clarifiers
increase the settling area

by 5 to 10 times.

Also, advantages is that incoming
water will be slowed down

and redirected to flow
between lamella plates,

which improves the flow pattern.

Another advantage is that
incline plates result

in a countercurrent flow,

one upward flow of water

and one downward stream of sludge.

As in a water pipe,
frictional forces get higher

as closer water gets to the pipe surface.

Therefore, particle settling

and sludge accumulation is improved,

because drag forces are
reduced by frictional forces.

In total, lamella clarifiers
are a great solution

to upgrade existing sedimentation tanks.

Compared to conventional
sedimentation tanks,

the installation is significantly faster,

and the total cost is about one third.

If you wish more information

or need support with a particular project,

please use the link below to contact us.