Ultrasonic irradiation as pretreatment for the reduction of excess sludge by Fenton-acclimation treatment

Abstract

Ultrasonic irradiation as a pretreatment of Fenton-acclimation treatment was investigated to enhance the efficiency of sludge reduction and effectiveness of operating cost. A series of batch experiments were conducted to optimize the reaction conditions for ultrasonic-Fenton treatment. Separate ultrasonic treatment suggested that input power of 0.4 W/mL and ultrasonic time of 10 min were the optimal conditions for sludge disintegration, and the efficiency was reduced with the increase of sludge mixed liquor suspended solids. Separate Fenton treatment revealed that 9 g/L and 40 mg/L were the optimal dosages of H2O2 and Fe(2+) respectively for sludge lysis under pH of 3. Particle distribution (75.49% of the particles distributed between 7.18 and 31.11 μm after Fenton treatment while 93.35% of the particles distributed between 4.62 and 18.50 μm after ultrasonic-Fenton treatment) and chemical oxygen demand (51.89% higher in ultrasonic-Fenton treatment than that in Fenton treatment) demonstrated that combined ultrasonic-Fenton treatment was effective in sludge disintegration compared to separate Fenton treatment. With ultrasound as pretreatment, sludge reduction rate increased from 26.53 to 63.59% with operating cost reduction of 51.46%, indicating ultrasonic irradiation was effective in improving both sludge reduction efficiency and operating cost-effectiveness.

Ultrasonic application to boost hydroxyl radical formation during Fenton oxidation and release organic matter from sludge

“…Some studies have been reported on the degradation of bisphenol A in waste water sludge by ultrasonication, Fenton’s oxidation or combination of both (ferro-sonication) pre-treatment processes1819. Ultrasound coupled with Fenton oxidation pre-treatment of sludge was also investigated to enhance the efficiency of sludge reduction and effectiveness of operating cost20. Herein, we use ultrasound coupled with Fenton oxidation pre-treatment of sludge to promote sludge disintegration.…”

Mechanism of Ozone Oxidation of Polycyclic Aromatic Hydrocarbons During the Reduction of Coking Wastewater Sludge

“…Ozone decomposition proceeds with the following five-step chain reaction, as is shown in Eqs. (9)(10)(11)(12)(13) [40]. These equations show that alkaline conditions can increase ozone decomposition to form free radicals such as hydroxyl radicals ( • OH), superoxide O •À 2 À Á , and ozonide ions O •À 3 À Á .…”

“…The conventional methods for sludge treatment and disposal (e.g., landfill and incineration) [11] are confronting severe challenges due to more stringent environmental regulations. Various novel reduction technologies to treat excess sludge have been developed, such as thermal, ultrasonic, mechanical, alkaline, or oxidative treatments [12][13][14][15], along with biological treatment processes.…”

Effect of deflocculation on the efficiency of sludge reduction by Fenton process

“…Equations 7 and 8 detail the scavenging effect of H2O2 on OH radicals (Feng et al 2003;Qiu et al 2013 . HO2 + .…”