Optimization of freeze-thaw conditioning

Mechanical freeze-thaw conditioning of water treatment residuals (sludge) produces a product with extremely high solids content. Intuitively, the process appears too expensive to be feasible. This article presents a model that can be used to investigate the economics of mechanical freeze-thaw condit...

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Bibliographic Details
Published in:Journal - American Water Works Association 2000-05, Vol.92 (5), p.77-85
Main Authors: Parker, Philip J., Collins, Anthony G.
Format: Article
Language:English
Subjects:
Capital costs
Cost control
Cost efficiency
Costs
Design
Dewatering
Economic costs
Electricity
Experiments
Freezing
Gels
Ice
Modeling
Operating costs
Optimization
Residual volume
Sludge
Total costs
Variables
Water treatment
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Summary:Mechanical freeze-thaw conditioning of water treatment residuals (sludge) produces a product with extremely high solids content. Intuitively, the process appears too expensive to be feasible. This article presents a model that can be used to investigate the economics of mechanical freeze-thaw conditioning. Model results reveal two cost-optimum freezing conditions: typically an initial solids content of 10 percent w/w or higher, and curing times > 6 h. Also, the model is used to compare the cost of the optimum freeze-thaw designs with the costs of traditional residuals management trains. Results show that freeze-thaw conditioning may be cost-effective for moderate to high disposal costs (> $25/t [$28/metric t]) and low electricity rates (< $0.075 • kW⁻¹ • h⁻¹).
ISSN:0003-150X
1551-8833
DOI:10.1002/j.1551-8833.2000.tb08946.x