Reduction of ozone dosage by using ozone in ultrafine bubbles to reduce sludge volume

Techno-Economic Evaluation of Ozone Application to Reduce Sludge Production in Small Urban WWTPs

“…In this sense, in applications carried out at an industrial level, specific doses of ozone less than 0.05 g O 3 /g TSS are applied [17,36,50] since they optimize the ratio of g TSS hydrolyzed /g O 3applied . However, factors such as ozone concentration used during the sludge-hydrolysis process [46] or the efficiency of O 3 transfer to the liquid phase [10,18] are still poorly studied, and their optimization could improve the economics of the process. On the other hand, the ozone required to hydrolyze a given amount of secondary sludge depends on its composition, which could be determined based on its COD fractions (X H , X P and X I ) [43].…”

“…Until now, only ozonation and ultrasonic methods have been applied in full-scale urban WWTPs [16]. Ozonation promotes the disintegration and solubilization of biodegradable and non-biodegradable compounds in the sludge [17,18]. This process can be applied to a fraction of the sludge recycled from the secondary decanter to the biological reactor.…”

Role of bulk nanobubbles in removing organic pollutants in wastewater treatment

“…Thus, ozone consumption outside the flocs is avoided, while ozone plays key role in killing bacteria. Hashimoto et al ( 2021 ) employed the death ratio of bacteria in sludge as an indicator of the effectiveness of sludge reduction and compared the ability to supply ozone for sludge reduction of nanobubbles and microbubbles; the results demonstrated that the ozone dose required to reach a death ratio of 80% was 15 mg-O 3 /g-MLSS in a system where ozone was carried by nanobubbles versus 25 mg-O 3 /g-MLSS when ozone was supplied by spiral, liquid-type microbubbles. In addition, the depth of the dead cell layer from the surface to the interior of the sludge floc was larger in a system with nanobubbles than in one lacking nanobubbles at the same rate of ozone consumption, indicating that nanobubble ozone carriers improved the efficiency of sludge reduction (Hashimoto et al 2021 ).…”

Characteristics and Stability of Ozone Nanobubbles in Freshwater Conditions

“…While oxygen, nitrogen, and air are the most common types of gases studied as nanobubbles (NBs), research with ozone NBs is still emerging: (i) remediation of sludge, sediments, and groundwater, − (ii) removal of micropollutants, − (iii) reduction of bacterial pathogens, − and (iv) antimicrobial effectiveness for fresh vegetables . Ozone readily reacts with organic and inorganic compounds in water, and it has been widely used as an oxidant and/or disinfectant in water and wastewater treatment.…”