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WATER &EFFLUENT TREATMENT NEVER AGAIN BATTLE


AGAINST SLUDGE Individual solutions fordrying sludge


Sludge from the industrial sewage


treatment has avery high water content and, therefore, is


voluminous and heavy.


In order to dry this sludge effectively


and efficiently,there are appropriate drying plants.


However,the matter is difficult when special architectural conditions must be observed by the construction of such plants, or the


operator must exercise certain specifications for the procedure.


Then, user-specific solutions are demanded.


Amultitude of substances are constantly separated from industrial effluents, using a physical or chemical process. Thereby,the result is usually afine sludge with awater ratio of approximately 95 %–too much in order to use it as aresource, or be cost-effective to dispose of.The wet sludge must be predrained, for example by using achamber filter press. This generates afilter cake that is mainly firm and compact, but still has ahigh ratio of water, approximately 65 %. Therefore, because of the high disposal or recycling costs, the predraining is often not sufficient. The filter cake must be further dried. With aremaining water content of 20 to 5%,the volume and weight of the sludge is reduced, so that the costs for further treat- ment or disposal are substantially reduced.


Prevent laborious transportation of sludge


Daily,alarge quantity of calcium phosphate sludge accumulates in the effluent pretreatment plant of the company BK Giulini at the site in Ladenburg.The company,with headquarters in Ludwigshafen/Germany,offers, amongst other things, special products for the pharmaceutical and food industries. The products also include various


phosphate- base


compounds.


The phosphate products range from phosphoric acid to special phosphates. The liquid waste from cleaning processes is pre-treated in an effluent plant.


The resulting phosphate sludge contains ahigh amount of water and is heavy,sothat further treatment is expensive and, because of the large volume, very laborious. Therefore, the fine sludge is dried. However,the procedure up to now was laborious and much too expensive: The sludge was taken from afilter press, conveyed by a conveyor belt into an intermediate silo and from there, using an eccentric screw pump, into afine film evaporator.Thereupon, it once again is conveyed by aconveyor screw and was collected in Big-bags. When 24 of these bags were filled, they were loaded onto alorry and transported away.“Furthermore, the old fine film evaporator and the preselected eccentric screw pump were very susceptible to failure, therefore, cost intensive and not available for alonger period”, Armin Etzel, responsible for the project at BK Giulini, stating further disadvantages of the old procedure.


“Primarily,wewanted to simplify and accelerate our whole process.”


Drying sludge and transportation in acontainer


Forthis, Harter offered aspecial sludge drying plant. This can dry the predrained sludge so that the approximate remaining water content is 20 to 5%.The containers, in which the filter cake should be dried, were already specified by BK Giulini, so that the plant must be exactly matched. Despite these high requirements, operation with the new plant could already be started after three months: As before, the sludge is predrained using achamber filter press. However,the filter cake now falls from the filter press directly into a7m3


container.Aforklift


takes this on aheavy goods trailer to the drying plant. There, the sludge is dried for 24 huntil the solid content is 80 %, as required by the operator.


The predrained filter cake is filled in acontainer and also conveyed for drying in there and transported for further treatment


48 SURFACEWORLD april 2013 (continued on page 50) read online @www.surfaceworld.com


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