Ultrasound Coupled With Fenton Oxidation Pre-treatment Of Sludge And The Mechanism Of Sludge Disruption

As an esential pre-treating technology in the field of sludge treatment and disposal, sludge disintegration can enhance dewatering and accomplish element recovery. Ultrasound coupled with Fenton oxidation was firstly proposed as a sludge disintegration technology. Results indicated that this technology can significantly disintegrate sludge zoogloea, improve dewatering performance and depress odor. The mechanism of sludge degradation under this technology was also interpreted in this work. Main conclusions are as follows:Ultrasound coupling Fenton oxidation remarkably reduced the dose of Fe2+ and H2O2 required for Fenton oxidation alone, and shortened processing time. With the same dewatering performance achieved, the dose of Fe2+ and H2O2 for coupling technology was, respectively, 66.7% and 75% lower than that for Fenton oxidation alone, and reaction time was 75.0% shortened.Coupling technology promoted the dissolution of SCOD, TOC, TN, TP, protein, PO43- and EPS from sludge. Under optimal disintegration conditions, SCOD and TOC released from sludge were respectively 2.1 and 2.4 times the amount under ultrasound treatment alone, and 1.4 and 1.5 times the amount under Fenton oxidation alone; TN and TP were 2.2 and 1.1 times the amount under ultrasound alone, and 2.1 and 1.8 times that under Fenton oxidation alone; protein was 2.0 times the amount under ultrasound alone, and 2.4 times Fenton oxidation alone; PO43- was 1.7 times ultrasound alone, and 2.6 times Fenton oxidation alone.Coupling technology and Fenton oxidation alone both depressed the release of H2 S, methylmercaptan, dimethyl sulfide and dimethyl disulfide from sludge, while ultrasound treatment alone promoted odor release. Coupling technology significantly reduced low valence sulfide in sludge supernatant. After 20 min treatment, the concentration of low valence sulfide in sludge supernatant was 8.1 mg/L, decreasing by 50% compared to ultrasound treatment and 34% compared to Fenton oxidation. Meanwhile coupling technology increased SO42- in sludge supernatant by 98% compared to ultrasound treatment and 5.2% than Fenton oxidation. It was confirmed that coupling technology transforms low valence sulfide into high valence, thus decreasing the potential of odor release.Electron spin-resonance spectroscopy(ESR) and three-dimensional fluorescence spectrum were conducted to examine the generation of OH? in sludge system. ESR analysis indicated that the signal of OH?under coupling technology was 1.9 times the value under Fenton oxidation alone. Three-dimensional fluorescence analysis detected 0.43 mmol/L of OH? under coupling technology, 1.8 times that under Fenton oxidation alone and 9 times ultrasound alone. The ability of coupling technology to increase OH?was therefore confirmed and the mechanism of efficient sludge disintegration by coupling technology was revealed.