Abstract
It is urgent to determine suitable municipal sludge treatment solutions to simultaneously minimize the environmental negative impacts and achieve sustainable energy benefits. In this study, different sludge pretreatment techniques were applied and investigated to enhance the sludge solubility and, subsequently, facilitate the anaerobic biodegradation performance of the mixed sludge under different sludge concentrations and pretreatment techniques. The sludge characteristics before and after pretreatment and batch experiments of anaerobic digestion of sludge samples under different conditions were analyzed and discussed. The results showed that the mechanical pretreatment method, alone and in combination with low-temperature heat treatment, significantly improved the sludge solubility, with the highest solubility at 39.23%. The maximum biomethane yield achieved was 0.43 m3/kg after 10 d of anaerobic digestion of a 3% sludge sample subjected to mechanical and thermal pretreatment prior to anaerobic biodegradation. In comparison, it took more than 28 d to achieve the same biomethane production with the unpretreated sludge sample. Mechanical pretreatment and subsequent heat treatment showed a high ability to dissolve sludge and, subsequently, accelerate anaerobic digestion, thereby providing promising prospects for increasing the treatment capacity of existing and new sludge treatment plants.
Highlights
IntroductionA large amount of biological sludge is generated daily from municipal wastewater treatment systems worldwide
Published: 21 November 2021A large amount of biological sludge is generated daily from municipal wastewater treatment systems worldwide
This study evaluated the applicability of a new method of crushing solubilization using shearing force by analyzing the shearing force in the physical crushing solubilization process, the changes in the physicochemical properties of the mixed sludge, and the biodegradability effect at the time of anaerobic digestion, which may depend on the solubilization duration of mixed sludge according to the total solids (TS) concentration
Summary
A large amount of biological sludge is generated daily from municipal wastewater treatment systems worldwide. In the Republic of Korea, 11,726 thousand t/d of sewage sludge was produced in 2019, an increase of 39.4% from 2009. As the percentage of the population with sewer system connection increases, sewage sludge production is forecasted to continue to increase [1]. Plants that produce biogas from biomass waste in the Republic of Korea increased dramatically, from 90 plants (2016) to 98 plants (2017). Plants that convert sewage sludge into biogas increased from 34 plants to 36 plants and are forecasted to continue to increase in the coming decades due to the environmental and economic benefits these systems provide [1].
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