Iron powder activated peroxymonosulfate combined with waste straw to improve sludge dewaterability

ABSTRACT

In an activated sludge system, the high hydrophilicity of extracellular polymeric substances (EPS) and the high compressibility of sludge greatly hinder sludge dewatering. A new method for improving the dehydration of waste activated sludge was explored by using iron powder activated peroxomonosulfate combined with waste straw (Fe⁰+PMS + WS). Specific resistance to filtration (SRF) and water content (Wc) were used to characterize the dewatering performance of sludge. Under the optimal measurement, Wc and SRF were significantly reduced. To reveal the synergistic effect of this joint treatment, zeta potential, particle size distribution, three-dimension excitation emission matrix (3D-EEM) fluorescence spectroscopy, bound water content analysis, and scanning electron microscopy (SEM) were used to investigate the mechanism of sludge dewatering. Results showed that the tightly bound EPS (TB-EPS) was oxidized by sulfate radicals (${\mathrm{SO}}_4^{-}\bullet$) to loose bound EPS (LB-EPS) and soluble EPS(S-EPS). SEM analysis displayed that the Fe⁰+PMS + WS combination regulated the formation of a more porous sludge filter cake structure. In addition, the low calorific value of the dewatered sludge after 12 h in open air was significantly increased, and the Wc of the dewatered sludge cake was reduced to 25%. These parameters were beneficial to the subsequent disposal of sludge.

GRAPHICAL ABSTRACT

KEYWORDS:

• Sludge dewatering
• sulfate radicals
• waste straw
• skeleton
• calorific value

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This study was financially supported by Science Research Program of Higher Education Institutions of Inner Mongolia Autonomous Region (NO. NJZY17095); the National Natural Science Foundation of China (NO. 21107041); the Natural Science Foundation of Inner Mongolia (NO. 2017MS0216); the Young and Middle-Aged Academic Backbone Program of the Inner Mongolia University of Technology.