SLUDGE THICKENER - Operation Manual - Stone Food Machinery

Mariestad 20061109 

Operation Manual 

MEVA SLUDGE THICKENER MST15 

Function 

• The special LOW-PITCHED screen in the Sludge Thickener will lift the sludge flocs 

from the water and this is achieved using a LOW water level in the incoming sludge 

water. 

• Next there is a gentle dewatering, by gravity, as the sludge flocs are lifted upwards by 

the screen. 

• By varying the Screen`s speed it is possible to adjust the solids contents of the 

thickened sludge. 

• We keep a constant and LOW water level to guarantee that no sludge particles go into 

the reject/waste water. 

• A HIGH water level in the SLUDGE THICKENER simply means that sludge particles 

can be pressed through the bars by the Hydraulic Pressure and results in excessive 

suspended solids in the reject/waste water. 

• This is the significant difference in function from the Monoscreen that needs a high 

water level to work as a FineScreen in a Normal Waste Water Treatment Plant or 

Industrial Effluent Plant. 

Operation 

The sludge thickener starts as soon as the sludge water pump starts. On the photo you can 

easily see the effect. The thickened Sludge simply Rolls off the end of the Screen somewhat 

like a big, round, “Sausage” and is now ready to proceed to the next stage in the process at 5 

to 9% Solids. 

Annika Kjellkvist 

Vatten och Miljöteknik 80 p 

KY-utb. Hallsberg 

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D:\EQUIPMENT-SUPPLIERS\Swedish\MEVA\BROCHURES\SLUDGE THICKENER\MANUAL\1-9-07- 

Operation Manual MST15.doc


Level Controls for Sludge Water 

A level meter is placed in a pipe in the incoming sludge water and set at a level about 25 cm. 

The Exact level has to be adjusted, from experience, later. The level meter is used to interlock 

the sludge water pump to ensure the reject/waste water quality remains optimal in terms of 

Suspended Solids. 

As the pump is interlocked, the screen will continue to lift up the sludge and the pump will 

start when the right water level has been reached. 

Frequency Inverter 

The SLUDGE THICKENER is controlled by a Frequency Inverter with the ability to adjust 

the screen speed and therefore the Sludge Solids. 

Regulation of Dry Solids content 

• The variation of the Screen`s speed is used to adjust the content of dry solids in the 

thickened sludge. 

• High volumes of incoming sludge water and high speed gives a LOWER content of 

dry solids. 

• LOWER volumes of sludge water and LOW Screen speed gives a HIGHER content of 

solids. 

• The same polymer dosing can be used. 

• The regulation can also be done by advance knowledge of the solid contents and the 

quality of the incoming sludge water. Less solids gives a higher frequency and a 

higher speed and vice versa. 

Operation time 

Operation time depends on the load on the screen, the amount of suspended solids in the 

incoming sludge water and desired content of solids in the final thickened sludge. Effective 

use is reached with an even covering of flocculated sludge over the entire screen surface. 

Polymer 

The polymer dose is best set by eye. Clear water should be seen between the sludge flocs. If 

the polymer is added before the sludge pump there is enough flocculation in the pump and the 




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following pipe. To increase the flocculation effect, two rubber cloths with a cross-cut, can be 

mounted in flanges along the pipe run to the SLUDGE THICKENER TANK. 

Reject water quality 

• A suspended solids meter in the reject water is set to alarm at a pre-set solids content. 

• This alarm is used to indicate that a manual inspection of the SLUDGE THICKENER 

and an adjustment of the polymer dose may well be required. 

• The suspended solids meter will not regulate the polymer dose as it can give the 

opposite effect than that required ! 

• Both under and over dose of polymer can give suspended solids in the reject/waste 

water so care and attention is required. 

• A maintenance technician needs to check if and when the alarm is triggered. 

• The Suspended Solids meter will ensure that there is not too much suspended solids in 

the reject/waste water. 

• We expect a solids content in reject/waste water to be < 100 mg/l. 

Loading of the SLUDGE THICKENER 

• The loading of the sludge thickener will be calculated by the amount of sludge as kg 

solids/h. 

• Recommended load is 125 kg solids/h for model MST 15-50-1.Maximum load is 150 

kg solids/h for model MST 15-50-1. 

• Loading will vary with the size of each particular Sludge Thickener Model 

Example: 

• 10 m 3 sludge water with 1% solids contains about 120 kg solids. 

• 20 m 3 sludge water with 2% solids contains about 480 kg solids 

• One client loads the waste water with 90 gram solids/day !! 

• Industrial waste water can give different loads and has to be calculated. 

Maintenance 

Regular inspection – On a monthly basis. 

Check that: 

• The screen goes freely and quietly 

• The screen’s electric controls are working properly. 




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• Rinse the pipe to the level meter and the edges at the incoming sludge water area. 

• The bar screen is clear so that no screenings can build up and cause blockage between 

the bars. This is especially important for the section closest to the bottom of the 

thickener. 

• There is no sand or gravel in front of the bars. 

• Power Hose the face of the Screen at least once every two weeks 

Lubrication: 

• The machine is equipped with a bearing lubrication system and should be greased 

manually every month. Be careful as over greasing is not good for the bearings. The 

opposite is also true !! 

• The worn gear transmission oil should be changed once every one/two years 

depending on use. 

• Use SHELL OMALA 680 or equivalent. 

Thorough inspection – Once a year: 

• Wear components should be inspected and replaced if necessary. Wear 

components have a lifetime between one and seven years. 

• The following parts are considered as wear components: 

• Connecting rod bearings and axel bearing. 

• Slide pad and lower cross member slide plate. 

• Intermediate bar spacers. 

• The inlet and blade spacer and the discharge end blade spacer. 

Also check: 

• The bar units, their position and if they are straight. 

• The worm gear transmission. 

• That the screen can work freely and without noise. 

After inspection and service, re-fit, close and lock all covers! 




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SLUDGE THICKENER - Operation Manual - Stone Food Machinery

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