Sludge Dewatering

Three-chamber polymer system (click to enlarge)


When cleaning wastewater, large volumes of sludge accumulate. This so-called liquid sludge must be reduced to a smaller volume with a higher solid-matter concentration using suitable dewatering processes. For this purpose filter presses, wire presses, decanters and other dewatering machines are available. To obtain the highest possible flow rate and degree of dewatering, additives like organic flocculation agents are dosed into the liquid sludge before the dewatering machine. For this purpose liquid as well as powdery polyelectrolytes are available, to be prepared according to a process specified by the producer before use. The preparation method and the adherence of specified maturing times for the polymer solutions may substantially influence the effectiveness of the flocculation agent and with it the dewatering result.


A recurring problem when dosing flocculation agents is to continuously find out the correct, required quantity during permanently changing conditions. To obtain sufficient dewatering results over a long period, the comparatively expensive polyelectrolytes are overdosed in many systems over long periods. This can be a very costly process. For controlling the flocculation agent dosing, in many cases a technology has proven its effectiveness and is therefore employed for precisely dosing coagulation agents in the raw-water treatment.


Streaming current detectors (SCD) measure the entire surface potential of colloids and solid matters in their liquid phase. The charge neutralization effected by the flocculation agent is measurable and usable as a control factor for the dosing process.


However, liquid sludge may, depending on its origin, contain a hardly predictable amount of substances which may influence or disturb the measuring signal. To be on the safe side, pretests are recommended.

Talk to the experts of MPT when the preparation and the dosing of flocculation agents for the sludge dewatering are concerned.

From left to right (click to enlarge)

Polymer preparation system.

Manual preparation system.

Preparation tank.

Flocculation agent dosing sludge dewatering in the wastewater industry

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