Abstract
A membrane ozonation contactor was built to investigate ozonation using tubular membranes and inform computational fluid dynamics (CFD) studies. Non-porous tubular polydimethylsiloxane (PDMS) membranes of 1.0–3.2 mm inner diameter were tested at ozone gas concentrations of 110–200 g/m3 and liquid side velocities of 0.002–0.226 m/s. The dissolved ozone concentration could be adjusted to up to 14 mg O3/L and increased with decreasing membrane diameter and liquid side velocity. Experimental mass transfer coefficients and molar fluxes of ozone were 2.4 × 10−6 m/s and 1.1 × 10−5 mol/(m2 s), respectively, for the smallest membrane. CFD modelling could predict the final ozone concentrations but slightly overestimated mass transfer coefficients and molar fluxes of ozone. Model contaminant degradation experiments and UV light absorption measurements of ozonated water samples in both ozone (O3) and peroxone (H2O2/O3) reaction systems in pure water, river water, wastewater effluent, and solutions containing humic acid show that the contactor system can be used to generate information on the reactivity of ozone with different water matrices. Combining simple membrane contactors with CFD allows for prediction of ozonation performance under a variety of conditions, leading to improved bubble-less ozone systems for water treatment.
Highlights
Ozone is a chemical oxidant used for water treatment for more than a century [1]
In a previous study we developed a modelling approach based on computational fluid dynamics (CFD) and convection-diffusion theory to calculate ozone and oxygen gradients and their mass transfer through non-porous PDMS membranes into the aqueous phase [35]
The experimental and computational results showed that the membrane size is an important parameter, while the concentration of ozone in the gas phase has minor importance for the ozone mass transfer
Summary
Ozone is a chemical oxidant used for water treatment for more than a century [1]. Ozone has a wide range of applications [2], including disinfection [3], control of disinfection byproducts [4,5], addressing taste and odour issues [6], and the removal of trace contaminants from both drinking water and during advanced wastewater treatment schemes [7,8,9,10]. Ozone is an unstable gas that needs on-site production. The main costs of ozone operation relate to a combination of energy and oxygen consumption [12]. Ozone is dissolved into the water phase via bubbling using various types of gas diffusers or side stream injection [13]. Knowledge and quantification of ozone mass transfer is crucial for the design of treatment operations [14].
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