If the water plant sludge is not treated, but directly discharged into the water body or into the municipal sewage pipeline, which not only causes environmental pollution, increases the load of the sewage treatment plant, but also causes a great waste of water resources.
Therefore, sludge should be properly treated. Sludge dewatering is an important link in the whole process of sludge treatment. Its purpose is to enrich solids, reduce the volume of sludge, and create conditions for the final disposal of sludge.
The binding force between solid and liquid sludge must be overcome in order to separate them. Different dewatering effects can be obtained by using different external measures according to different forms of solid-liquid binding force of sludge. Different sewage treatment technology, different sludge stabilization process, and different sludge conditioning process and different dewatering way, the resulting sludge water removal is often very different.
At present, the main methods of sludge dewatering include natural drying, mechanical dehydrating and granulation.
Natural drying mainly spreads the sludge to the sludge drying field padded with sand and stone, and realizes dehydration by means of evaporation, infiltration and clear liquid overflow.
Mechanical dehydration involves filtration and centrifugation.
Among the mechanical sludge dewatering equipment, the decanter centrifuge (hereinafter referred to as decanter) is one of the most important equipment.
The decanter has the following advantages
- 1. Simple maintenance. Decanter uses centrifugal sedimentation principle for solid-liquid separation, does not use filter screen, reduces washing filter screen work, and does not need to replace the filter screen regularly.
- 2. Simple operation and high degree of automation. In the process of sludge dewatering, the decanter differential speed and torque value can be adjusted automatically to adapt to the change of feed amount with the change of feed concentration and feed amount, without the need for the operator to control.
- 3. Save the amount of flocculant. Decanter uses centrifugal force to dehydrate, fine sludge can also be separated from the liquid, so the amount of flocculant is less.
- 4. Small occupation area and little pollution to the workshop. Decanter working area requirements is relatively small, and the supporting mechanical equipment is less, in the process of operation, no sewage, sludge and odor overflow, the operation of the space pollution is less, can better ensure the health of the operator.
The dehydration of decanter can be roughly divided into three stages. The first stage is the coagulation of flocculant, which makes the colloidal particles in the sludge unstable and condensed. The second stage is the sludge in the dehydration of the same settlement zone by centrifugal action for settling, then forms solid/liquid separation layers; The third stage is extrusion dehydration and drying, and the residual water in the sediment is extruded by the extrusion action of the decanter spiral.
The sludge in the sewage pool is agitated by the agitator and then flows into the pump house.
After the sludge is broken by the sludge cutting machine, it is fed into the decanter by the sludge feed pump.
Sludge is mixed with flocculate prepared by the dispensing system in the decanter.
The clear liquid processed by the decanter enters the water system through the drainage pipe for subsequent treatment.
The dehydrated sludge processed by the decanter is sent to the mud storage silo through the shaftless screw conveyor, and then transported abroad.
Inside the drum is a set of disc-shaped parts, called discs, which are stacked on top of each other. There are small gaps between discs. Suspension (or emulsion) is added to the drum through a feed tube located in the center of the drum.
As the suspension (or emulsion) flows through the gaps between the discs, the solid particles (or droplets) sink under the action of the centrifuge and fall onto the discs to form a sediment (or liquid layer). The sediment slides off the disc surface and accumulates in the largest diameter part of the drum.
The separated liquid is discharged from the drum through the outlet. The function of the disc is to shorten the settling distance of solid particles (or liquid drops) and expand the settling area of the drum. The production capacity of the separator is greatly improved due to the installation of the disc in the drum.
The solids that have accumulated in the drum are removed manually or discharged from the drum without stopping the machine by means of a slag discharge mechanism.
