Enhanced dewaterability of food waste digestate by biochar/potassium ferrate treatments: Performance and mechanisms

Xinwen Li; Qingliang Zhao; Lili Li; Wangyang Mei; Zhaoxia Wang; Qingwei Gao; Kun Wang; Huimin Zhou; Liangliang Wei; Junqiu Jiang

doi:10.1016/j.jenvman.2024.120268

Enhanced dewaterability of food waste digestate by biochar/potassium ferrate treatments: Performance and mechanisms

J Environ Manage. 2024 Mar:354:120268. doi: 10.1016/j.jenvman.2024.120268. Epub 2024 Feb 15.

Authors

Affiliations

¹ Department of Environment Science and Engineering, School of Environment, Harbin Institute of Technology, Harbin, 150090, China.
² Department of Environment Science and Engineering, School of Environment, Harbin Institute of Technology, Harbin, 150090, China; State Key Laboratory of Urban Water Resources and Environment (SKLUWRE), School of Environment, Harbin Institute of Technology, Harbin, 150090, China.
³ Department of Environment Science and Engineering, School of Environment, Harbin Institute of Technology, Harbin, 150090, China. Electronic address: lill199504@163.com.
⁴ Department of Environment Science and Engineering, School of Environment, Harbin Institute of Technology, Harbin, 150090, China; State Key Laboratory of Urban Water Resources and Environment (SKLUWRE), School of Environment, Harbin Institute of Technology, Harbin, 150090, China. Electronic address: jiangjq_hit@126.com.

PMID: 38364546
DOI: 10.1016/j.jenvman.2024.120268

Abstract

The combined process of biochar (BC) and potassium ferrate (PF) offers a fascinating technique for efficient dewatering of digestate. However, the effects of BC/PF treatment on the dewaterability and mechanisms of FWD are still unknown. This study aimed to reveal the impact mechanisms of BC/PF treatment on digestate dewatering performance. Experimental results indicated that BC/PF treatment significantly enhanced the dewaterability of digestate, with the minimum specific resistance to filtration of (1.05 ± 0.02) × 10¹⁵ m·kg^-1 and water content of 57.52 ± 0.51% being obtained at the concentrations of 0.018 g·g^-1 total solid (TS) BC300 and 0.20 g·g^-1 TS PF, which were 8.60% and 13.59% lower than PF treatment, respectively. BC/PF treatment proficiently reduced the fractal dimension, bound water content, apparent viscosity, and gel-like network structure strength of digestate, as well as increased the floc size and zeta potential of digestate. BC/PF treatment promoted the conversion of extracellular polymeric substances (EPS) fractions from inner EPS to soluble EPS, increased the fluorescence intensity of the dissolved compounds, and enhanced the hydrophobicity of proteins. Mechanisms investigations showed that BC/PF enhanced dewatering through non-reactive oxygen species pathways, i.e., via strong oxidative intermediate irons species Fe(V)/Fe(IV). BC/PF treatment enhanced the solubilization of nutrients, the inactivation of fecal coliforms, and the mitigation of heavy metal toxicity. The results suggested that BC/PF treatment is an effective digestate dewatering technology which can provide technological supports to the closed-loop treatment of FWD.

Keywords: Biochar; Digestate dewatering; EPS; Intermediate irons; Potassium ferrate.

MeSH terms

Charcoal*
Food
Food Loss and Waste*
Iron Compounds*
Iron*
Potassium Compounds*
Refuse Disposal*
Sewage / chemistry
Waste Disposal, Fluid / methods
Water / chemistry

Substances

potassium ferrate
biochar
Food Loss and Waste
Sewage
ferryl iron
Water
Charcoal
Iron
Potassium Compounds
Iron Compounds