This apparatus, employed in four units in the Anconella plant, is able to keep sludge in the form of an expansion mass which water, flowing upward, can cross in a uniform and regular way. For this reason, this apparatus is used in the presence of fragile precipitates which could be broken with a more violent troubling of water so it permits a greater upward speed. This is a very suitable apparatus thanks to its regularity in water circulation and complete absence of stormy movements.
Considering its construction, the Pulsator apparatus is formed by a flat bottomed basin at the basement of which there are several pipes (3) where we can introduce raw water to be treated in a uniform way on the whole surface of the apparatus. On the top, upon the pipes of introduction of water, there are other pipes (6) which permit a regular collection of the decanted water avoiding the creation of different types of upward speed in the various parts of the decanter.
The supply system of this apparatus is formed by a bell (2) into which the muddy water to be treated is pushed. After a compressor (7) sucks the air away. When the water into the bell reaches the level of 1 meter upon the level of the water in the decanter, a valve (8) opens which restores the air pressure so the liquid can fall and pass into the decanter. In the decanter the draining time of the bell is 5 s while the filling time is about 15/20 sec.
In this way a homogeneous sludge bed (5) which is crossed downward during the resting times and upward during the emptying of the bell is created on the bottom of the decanter.
As a consequence, the contact between the treated water with the reagents and the sludge is ensured and the best filtration of the colloidal particles present in it is realized. With the contribution of the mud present in the water the mass of the sludge bed will increase regularly until it is discharged. The discharge (4) takes place in certain ditches with an inclined bottom placed at the sides of the decanter where the sludge concentrates. From this basin the discharging is made by means of automatic valves connected by a timer. An advantage of this system is that discharging only the excess of sludge, the concentration of sludge in the decanter does not have to be lowered.
