Biosolids Engineering
Authored by a diplomate of the American Academy of Environmental Engineers, this expert guide offers professional help for designing and managing a biosolids program and decreasing the burden on landfills.
TABLE OF CONTENTS Biosolids Engineering
3.4: Dewatering
3.4 Dewatering
Dewatering is the removal of water from sludge to achieve an overall volume reduction. Sufficient water is removed during the dewatering process to produce a sludge that is no longer fluid and must be handled and transported as a solid. The principal variables in any dewatering process include
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Solids concentration and volumetric flow rate of the feed sludge stream
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Chemical demand and costs
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Solids concentration and volumetric flow rate of the dewatered sludge
3.4.1 Strategy for dewatering process selection
The most common methods of dewatering sludge include (1) belt press filtration, (2) centrifugation, (3) pressure filtration, (4) vacuum filtration, (5) drying beds, (6) drying lagoons, and (7) heat drying. Although heat drying is included in the list of dewatering methods, it is normally preceded by a mechanical dewatering process.
A dewatering process cannot be evaluated without consideration of the overall sludge-handling system, including prior sludge treatment processes and subsequent disposal practices. Determining the most cost-effective dewatering system is normally an iterative process that should account for the various combinations of unit operations available [39,48]. The strategy involved in selection of a dewatering process consists of the following five stages of analysis:
Stage 1. Initial screening of dewatering concepts
Stage 2. Initial cost evaluation
Stage 3. Laboratory testing
Stage 4. Field-level testing
Stage 5. Final evaluation based on detail design parameters
Collectively, these stages represent a screening procedure in which dewatering processes under consideration are given increasing scrutiny as more detailed cost, operational, and design...
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