Full-Scale Assessment of Ultrasonic Sewage Sludge Pretreatment Using a Novel Double-Tube Reactor

Abstract

The performance of a novel double-tube ultrasound (US) reactor for waste activated sludge (WAS) pretreatment was assessed at a full-scale wastewater treatment plant (WWTP). For high transferability of the results, a well-performing WWTP with rather typical operating conditions was selected. The effects of the treatment (conducted at a specific energy input of 200 kJ per kg of total solids) were monitored regarding improvements in sludge viscosity, methane production, biosolids removal, and digestate dewaterability. The pretreatment caused a significant reduction of WAS viscosity (−5.8% on average, at p < 0.01) and a maximum yet insignificant increase in methane yield (+6.2%, at p < 0.1). No effect was observed for solids content, viscosity, or dewaterability of the digestate. The economic benefit of the reduced WAS viscosity was negligible, as the reduced pumping costs were less than 1‰ of the US reactor’s electricity costs. Additional methane yields enabled for partial cost recovery (roughly equivalent to the energy costs), while investment costs of the US equipment could not be regained. Yet, the incorporation of improved methane production in the economic assessment remains somewhat speculative, given the only insignificant increase. Results suggest that an economical application of ultrasonic WAS pretreatment is challenging for typical, well-performing WWTPs.

Enhancement of biogas production from individually or co-digested green algae Cheatomorpha linum using ultrasound and ozonation treated biochar

“…The pretreatment of biochar in the United States was carried out using a sonicator (QSonica 700). We employed a maximum power of 700 W (99 percent amplitude) and a fixed working frequency of 20 kHz for this experiment [22] , [23] . The Pyrex glass beakers (100 mL) were filled with the US tip.…”

Superparamagnetic Iron Oxide Nanoparticles as Additives for Microwave-Based Sludge Prehydrolysis: A Perspective

“…In recent years, several sludge prehydrolysis methods have been developed and integrated into full-scale WWTPs in the U.S. and around the world, including thermal, ultrasonic, and electrocatalytic approaches. ,− Some of these full-scale applications are in regions that have a large capacity of anaerobic digestion, but some regions may benefit from enhanced prehydrolysis of anaerobically digested sludge (Figure ). In principle, sludge prehydrolysis aims at enhancing organic matter (bio)­availability by breaking cell walls and disrupting sludge floc assemblies; however, chemical complexity of the sludge matrix and abundance of water limit the selectivity and energy efficiency of pretreatment processes.…”

Recent Developments in the Application of Ultrasonication in Pre-Treatment of Municipal Sewage Sludge

“…Only evaluation of mass and energy balances of the full system might allow for a successful implementation (Pilli et al, 2011). It should be pointed out that as a result of US application, not only increased methane production might be achieved, but also decreased pump energy demand might be obtained by lower SS viscosity (Lippert et al, 2021). Moreover, the reduced cost related with dosing of reagents might be found.…”