Ozone application in different industries: A review of recent developments

Abstract

Ozone - a powerful antimicrobial agent, has been extensively applied for decontamination purposes in several industries (including food, water treatment, pharmaceuticals, textiles, healthcare, and the medical sectors). The advent of the COVID-19 pandemic has led to recent developments in the deployment of different ozone-based technologies for the decontamination of surfaces, materials and indoor environments. The pandemic has also highlighted the therapeutic potential of ozone for the treatment of COVID-19 patients, with astonishing results observed. The key objective of this review is to summarize recent advances in the utilisation of ozone for decontamination applications in the above-listed industries while emphasising the impact of key parameters affecting microbial reduction efficiency and ozone stability for prolonged action. We realise that aqueous ozonation has received higher research attention, compared to the gaseous application of ozone. This can be attributed to the fact that water treatment represents one of its earliest applications. Furthermore, the application of gaseous ozone for personal protective equipment (PPE) and medical device disinfection has not received a significant number of contributions compared to other applications. This presents a challenge for which the correct application of ozonation can mitigate. In this review, a critical discussion of these challenges is presented, as well as key knowledge gaps and open research problems/opportunities.

Keywords: Decontamination; Microbial inactivation; Ozone; Ozone dosage; Personal Protective Equipment (PPE).

Graphical abstract

Fig. 1

Factors affecting the efficiency of microbial inactivation during gaseous and aqueous ozonation of materials.

Fig. 2

Scanning electron microscopy (SEM) bacteria and fungi, showing the cell morphological defects imposed by ozone treatment and the resulting exploded debris – Db (a) E. coli, 6 ppmv aqueous O₃ for 30 s ; (b) E. coli, 20 ppmv gaseous O₃ for 8 min ; (c) C. albicans, 0.8 ppm aqueous ozone ; (d) B. subtilis, 0.167 ppm/min aqueous O₃ for 30 and 60 mins ; (e) S. aureus 0.8 ppm aqueous O₃; (f) Salmonella sp., 0.167 ppm/min aqueous O₃ for 30 and 60 min ; (g) E. coli on textile fibres, 20 ppmv gaseous O₃ for 8 min ; (h) B. atrophaeus, 4000 ppmv gaseous ozone for 3 h ; (i) F. fujikuroi, 1 L/min aqueous O₃ for 30 s ; (j) P. aeruginosa, 10 ppmv gaseous ozone for 10 mins ; (k) C. albicans, 10 ppmv gaseous ozone for 10 mins ; (l) S. aureus, 10 ppmv gaseous ozone for 10 mins .

Fig. 3

Oxidative action of ozone on the SARS-CoV-2 virus, showing a potential mechanism for its inactivation, via direct and indirect oxidation (adapted from Farooq and Tizaoui [48]).

Fig. 4

Mechanism of ozone decontamination relative to other disinfection methods (adapted from [55]).

Fig. 5

(a) Comparison of various oxidation processes for micropollutant abatement in municipal water treatment; (b) comparison of O₃-H₂O₂ and UV-H₂O₂ AOPs for disinfection and micropollutant abatement .

Fig. 6

A comparison of the inactivation of 3 fungal spores using chlorine (2 mg/L), chlorine dioxide (2 mg/L) and ozone (2 mg/L) in 40 mM PBS; (a) Aspergillus niger; (b) Penicillium polonicum; (c) Trichoderma harzianum; (d) inactivation rate constants of the 3 disinfectants .

Fig. 7

Recirculating aquacultural systems at different scales (a) large scale (adapted with permission from [119]); (b) pilot-scale (adapted from [120]); (c) laboratory scale (adapted with permission from [112]), showing the application of ozone nanobubbles for increased ozone dissolution.

Fig. 8

The impact of (a) temperature and (b) gaseous ozone centration on the survival population of Geobacillus stearothermophilus spores, showing a lag phase and first-order log-linear inactivation kinetics(adapted with permission from [23]); (c) an example of the relationship between a product bioburden and the biological indicator for the determination of the sterility assurance level (SAL) (adapted from [142]).

Fig. 9

(a-d) Typical PPEs used in clinical settings showing the fabric layers that prevent the transfer of droplets to/from the host (adapted with permission from [145]); (e) Negative impact of gaseous ozone treatment on the elastic band of facemasks (strain-induced ozone damage; the top band was not stretched during ozone treatment, and displayed no damage, whereas, the lower band was stretched (×2.4), and was degraded after treatment; (f, g) elastic band compatibility of different respirators with ozone treatment. The elastic bands that survived (f), were likely made of thermoplastic elastomers or polyisoprene with polypropylene overbraid (adapted from [146]).

Fig. 10

Small-scale gaseous ozone chambers in literature, that have been utilised for medical device sterilisation (adapted with permission from (a) ; (b – c) ; (d – f) ; g ; h [143]).

Fig. 11

Images of the dyed fabrics before and after aqueous ozone treatment, showing ozone’s bleaching properties under the different experimental conditions; OD represents the ozone dosage (adapted from [154]).

Fig. 12

(a) Application of gaseous ozone for the decontamination of garments (adapted with permission from [39]), showing (b) contamination levels in different regions of used garments (adapted from [36]).

Fig. 13

Impact of gaseous ozone treatment on the structural integrity of the cotton-polyester fibres (F); (a) shows Candida albicans cells (C) after applying an ozone doze of 100 ppmv.min; whereas (b) shows damaged fibre (DF) regions after 160 ppmv.min treatment in the presence of E.coli cells (C) (adapted with permission from [39]). Fabric swatches had undergone up to 10 previous ozone treatment cycles before this image was taken.

Fig. 14

(a) Combined effect of gaseous ozone dosage (CT) and RH on the inactivation of SARS-CoV-2 by ozone; these tests were carried out on a plastic (polystyrene) surface (adapted with permission from [54]). (b-c) Positive control repeats for SARS-CoV-2 virus inactivation assay; red stains indicate infected cells (VeroE6), which were stained with the virus’ nucleocapsid antibody on cotton face masks (adapted from [178]). (d-e) Effect of heat-drying (40 °C) and gaseous ozone inactivation (∼800 ppmv, 100 min) on the recovery of SARS-CoV-2 virus from cotton face masks; the samples are void of infection after treatment; d and e are repeats. .

Fig. 15

Summary of widely applied ozone concentrations for various applications at laboratory and industrial scale relative to naturally occurring ozone and Occupational Safety and Health Administration (OSHA) recommended exposure limits. It should be noted that drinking water disinfection would require rather small concentrations between 1 and 3 mg/L in a typical case; whereas wastewater disinfection (given its organic content) may require up to 10 mg/L. Higher doses than this are typically applied for industrial wastes when the oxidation of specific constituents is desired.