Sludge continued

Sludge Removal. Metal fines can catalyze reactions that lead to decomposition of the solution, and sludge buildup. Paint chips can absorb solution and swell, forming a viscous sludge. Routine maintenance should be performed to remove sludge. Continuous filtering is often helpful. 

Open sand bed (natural convection) batch feed of waste water sludge. Continuous ... 

Another technique is to remove sludge continuously at a reasonable rate by pumping it to an elevated tank. This provides some clarification, with the brine overflowing to the clarifier. A conical bottom on the tank enhances thickening of the sludge, which can go to a receptacle or to further processing. 

Originally designed for the continuous filtration of conditioned sewage sludges, as were most of the filter belt presses available, the Manor Tower press is increa singly used for the treatment of paper mill sludge, coal, or flocculated clay slurries. 

Design and operation of recirculation systems can be compHcated. Problems are avoided by using a sludge-blanket clarifier, in which feed enters below a blanket of accumulated and flocculated soflds which become fluidized in the zone-settling regime by the upflowing feed. Feed soflds are trapped in the blanket. The soflds content of the blanket continuously increases and part must be bled off in order to maintain the mass balance. 

Clarifiers typically are used in chemical precipitation and biological treatment processes to remove precipitated metal soHds and suspended biological soHds. To prevent the sludge blanket from becoming too thick or heavy, part of the sludge blanket is removed continuously or intermittently from the system and thickened prior to disposal. 

A vacuum filter is a cloth-covered dmm which operates under an appHed vacuum. As the dmm passes through the sludge vat, soHds are deposited on the filter. As the dmm passes through the air, drying of the cake occurs. The cake is continuously discharged to a conveyor belt. 

Screw presses (Fig. 2) do not produce a clear liquid product. Frequendy, the product is further filtered in a filter press to give a clear Hquid product. Press aids are added to feed materials containing fine particles or particles that can deform and plug the slots in the edge of a screw press. Typical press aids include sawdust, rice hulls, perlite, and diatomaceous earth (see Diatomite). A vertical screw press is a continuous press that has been used for dewatering sewage sludge (2). 

Comparisons are available on the relative performance and costs for dewatering municipal sludges (2). The relative performance of different filters and conditioners on waste sludges is shown in Table 3. The same sludge was treated on two belt-filter presses, two different centrifuges, and rotary vacuum filter (75). In another study, a variable chamber filter press, fixed-volume filter press, continuous belt-filter press, and rotary vacuum filter were compared for performance, capacity, and capital and operating costs (69). 

Liquids Slurries Pastes and sludges Free-flowing powders Granular, crystalbne, or fibrous solids Large sobds, special forms and shapes Continuous sheets Discontinuous sheets... 

Tunnel. Continuous Ti ay. Direct type, continuous operation Not apphcahle Not apphcahle Suitable for small and large-scale production. See comments under Pastes and Sludges. Vertical-turbo apphcahle... 

In contrast to vacuum flotation, dissolved-air flotation units can be operated on a continuous basis by the application of pressure. This consists of pressurizing and aerating the process stream and introducing it into the flotation vessel that is maintained at the atmospheric pressure. The reduction of pressure results in the formation of fine air bubbles and the collection of fine particulates to be floated and removed as sludge. 

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