Comparative study on hydrothermal treatment as pre- and post-treatment of anaerobic digestion of primary sludge: Focus on energy balance, resources transformation and sludge dewaterability

Tian Yuan, Yanfei Cheng, Zhenya Zhang, Zhongfang Lei and Kazuya Shimizu

Applied Energy, 2019, vol. 239, issue C, 180 pages

Abstract: Hydrothermal treatment (HTT) has been recognized as a highly efficient technology for organics decomposition and energy/nutrients recovery from waste biomass. Up to now, however, the efficiency of HTT as the pre- and post-treatment of anaerobic digestion (AD) has not been well compared and documented. In this study, the effects of HTT as the pre- (strategy I, HTT + AD) and post-treatment (strategy II, 1st AD + HTT + 2nd AD) of AD of primary sludge were evaluated based on comparative experiments in regards to energy balance, nutrients transformation, and sludge dewaterability. Results show that the optimal HTT temperature was 130 °C for strategy I and strategy II according to the maximum methane production rate (μ) estimated from Gompertz model and the net energy gain (ΔQ) calculated. Although HTT as the post-treatment of AD achieved higher total methane yield and solids reduction, the increment of methane yield was found to be similar through both strategies compared to their control counterparts (no HTT). The decomposition of insoluble organic carbon was also similar via both strategies. Insoluble nitrogen fraction was detected to be the lowest (6.8%) after HTT at 190 °C in strategy II, comparable to that after HTT at 210 °C (∼10.0%) using strategy I. The proportion of bioavailable phosphorus was found to slightly decrease with the increase of HTT temperature in strategy II, probably due to the alkaline pH in the treated digestate. The sludge dewaterability indicated by specific resistance to filtration (SRF) showed a similar trend after AD under the tested conditions of both strategies, which was remarkably improved when HTT was performed at temperatures higher than 170 °C. HTT as the pre-treatment (strategy I) was found to be more energy efficient in comparison to HTT as the post-treatment (strategy II) of AD of primary sludge. In addition, a positive energy efficiency could be achieved when the sludge solids content ≥2.2%.

Keywords: Hydrothermal treatment; Anaerobic digestion; Energy balance; Solids reduction; Sludge dewaterability (search for similar items in EconPapers)
Date: 2019
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (23)

Downloads: (external link)
http://www.sciencedirect.com/science/article/pii/S0306261919302259
Full text for ScienceDirect subscribers only

Related works:
This item may be available elsewhere in EconPapers: Search for items with the same title.

Export reference: BibTeX RIS (EndNote, ProCite, RefMan) HTML/Text

Persistent link: https://EconPapers.repec.org/RePEc:eee:appene:v:239:y:2019:i:c:p:171-180

Ordering information: This journal article can be ordered from
http://www.elsevier.com/wps/find/journaldescription.cws_home/405891/bibliographic
http://www.elsevier. ... 405891/bibliographic

DOI: 10.1016/j.apenergy.2019.01.206

Access Statistics for this article

Applied Energy is currently edited by J. Yan

More articles in Applied Energy from Elsevier
Bibliographic data for series maintained by Catherine Liu ().