Abstract
We examined the effects of ultrasound and Fenton reagent on ultrasonic coupling Fenton oxidation (U+F) pre-treatment processes for the disintegration of wastewater treatment plant sludge. The results demonstrated that U+F treatment could significantly increase soluble chemical oxygen demand (SCOD), total organic carbon (TOC), and extracellular polymeric substances (EPS) concentrations in sludge supernatant. This method was more effective than ultrasonic (U) or Fenton oxidation (F) treatment alone. U+F treatment increased the release of SCOD by 2.1- and 1.4-fold compared with U and F alone, respectively. U+F treatment increased the release of EPS by 1.2-fold compared with U alone. After U+F treatment, sludge showed a considerably finer particle size and looser microstructure based on fluorescence microscopy, and the concentration of hydroxyl radicals (OH•) increased from 0.26 mM by F treatment to 0.43 mM by U+F treatment based on fluorescence spectrophotometer. This demonstrated that U+F treatment improves the release of organic matter from sludge.
Highlights
We examined the effects of ultrasound and Fenton reagent on ultrasonic coupling Fenton oxidation (U+F) pre-treatment processes for the disintegration of wastewater treatment plant sludge
Sludge is a potential resource because it contains large quantities of organic matter that can be converted into biogas through anaerobic digestion[3,4]
As reported in our previous study[21], the optimal dose of Fenton reagent for sludge disruption was prepared as follows: 2.0 g of FeSO4.7H2O were added to 1 L of sludge and stirred uniformly, after which 1.7 mL of 30% H2O2 was added to the system, in which the concentrations of Fe2+ and H2O2 were 0.4 and 0.50 g/L, respectively
Summary
We examined the effects of ultrasound and Fenton reagent on ultrasonic coupling Fenton oxidation (U+F) pre-treatment processes for the disintegration of wastewater treatment plant sludge. The results demonstrated that U+F treatment could significantly increase soluble chemical oxygen demand (SCOD), total organic carbon (TOC), and extracellular polymeric substances (EPS) concentrations in sludge supernatant. This method was more effective than ultrasonic (U) or Fenton oxidation (F) treatment alone. Sewage sludge contains considerable amounts of nutrients[5,6,7], especially phosphorus (0.5–0.7% total solid [TS]) and nitrogen (2.4–5.0% [TS])[8] These nutrients exist mainly in proteinaceous and zoogloea forms[6]. By examining COD, TOC and EPS release after U+ F treatment, the mechanism of sludge disruption was investigated and discussed
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