Enhancing Digestibility of Waste Activated Sludge by Microwave-Alkali Thermochemical Pretreatment
Date Issued
2010
Date
2010
Author(s)
Chang, Chia-Jung
Abstract
Proper management of wastewater sludge has become increasingly important in recent decades due to environmental and economical concerns. Aerobic digestion is commonly used for sludge treatment; however, it takes a long time to achieve a desirable level of volatile solids destruction. Degradation of large molecular-weight organic compounds is rate-limiting in the sludge. This study promoted hydrolysis of organic compounds to improve subsequent digestion by pretreatments of microwave, acid and alkaline, and combined microwave with alkali.
In this study, batch-scale experiments were conducted to compare the effectiveness of various pretreatment methods on subsequent aerobic digestion. In pretreatment processes, effects of waste activated sludge concentration, temperature, pH and pretreatment methods (alkaline and microwave heating) on solubilization of COD were first investigated. Compared to conventional heating, microwave pretreatment required a shorter time in heating; and it achieved COD solubilization of 8% within 2 min at 600 W. In the alkaline pretreatment, the dose of 1.5 g NaOH/L was found optimal and the COD solubilization could reach approximately 18%. Two sequences of combined alkaline and microwave pretreatments were also evaluated, and the COD solubilization reached 39.3% (Alkali-Microwave) and 45.5% (Microwave-Alkali), respectively. As demonstrated in the batch aerobic digestion tests, the combined microwave-alkali pretreatment was proven to enhance the digestibility of volatile solids in the waste activated sludge samples.
Subjects
Microwave-alkali process
thermochemical pretreatment
sludge digestion
waste activated sludge
Type
thesis
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