When the sewage plant handles small volumes of sludge, the most common dehydration system is through filter bags. It is a stainless steel structure that supports the aforementioned filter bags. The previously decanted sludges reach the bags by gravity. The function of the sacks is to contain the sludge and let the water they contain through, the pressure exerted by the weight of the mud facilitates this filtering. Once the bags are filled, they will be replaced by new ones.
This system is used when the amount of sludge generated is greater. It usually stands tall, on a structure. It consists of a robust frame containing high density polypropylene plates lined with filter cloth. One end is mobile and is connected to a piston driven by a hydraulic pressure group. Its operation is as follows: the hydraulic pressure group exerts the force through the piston against the plates, thanks to this pressure the sealing of the plates is achieved.
A pump introduces the sludge inside the plates, due to the pressure it is subjected to, the water seeps through the fabrics and out through the water outlet holes of the plates, leaving the mud inside compacted and practically dehydrated.
Once compacted, the piston opens the plates and the mud cakes that have been created are precipitating by gravity. This equipment is equipped with an electrical panel that allows automatic or manual operation (to perform maintenance work).
This system is used for spills with very little concentration of mud. This machine, with a stainless steel frame similar to a belt, passes the spill through a filter paper which is sliding at the proper speed to remove the solids contained in the water at the same time the clean water is filtered and precipitated by the exit. The paper is discarded.
It is a conventional auger that collects the spill in the initial zone and transports it towards the end of the screw, here a trapdoor with a weight prevents solids from leaving easily at the same time as the endless one compacts them until reaching a consistency able to lift the trapdoor and these fall into compact pieces.
Sludge Dehydration Systems
Once the solid particles are separated from the water and the sludge is concentrated by any of the systems mentioned, the sludge is dehydrated.
The most common and efficient systems are the following: filter bags, filter press, filter paper, compactor auger.
Depending on the phase of the purification process and the needs, a specific system will be advised.