Organic Degradation Potential of Real Greywater Using TiO2-Based Advanced Oxidation Processes

Abstract

In keeping with the circular economy approach, reclaiming greywater (GW) is considered a sustainable approach to local reuse of wastewater and a viable option to reduce household demand for freshwater. This study investigated the mineralization of total organic carbon (TOC) in GW using TiO2-based advanced oxidation processes (AOPs) in a custom-built stirred tank reactor. The combinations of H2O2, O3, and immobilized TiO2 under either dark or UVA irradiation conditions were systematically evaluated—namely TiO2/dark, O3/dark (ozonation), H2O2/dark (peroxidation), TiO2/UVA (photocatalysis), O3/UVA (Ozone photolysis), H2O2/UVA (photo-peroxidation), O3/TiO2/dark (catalytic ozonation), O3/TiO2/UVA (photocatalytic ozonation), H2O2/TiO2/dark, H2O2/TiO2/UVA, H2O2/O3/dark (peroxonation), H2O2/O3/UVA (photo-peroxonation), H2O2/O3/TiO2/dark (catalytic peroxonation), and H2O2/O3/TiO2/UVA (photocatalytic peroxonation). It was found that combining different treatment methods with UVA irradiation dramatically enhanced the organic mineralization efficiency. The optimum TiO2 loading in this study was observed to be 0.96 mg/cm2 with the highest TOC removal (54%) achieved using photocatalytic peroxonation under optimal conditions (0.96 mg TiO2/cm2, 25 mg O3/min, and 0.7 H2O2/O3 molar ratio). In peroxonation and photo-peroxonation, the optimal H2O2/O3 molar ratio was identified to be a critical efficiency parameter maximizing the production of reactive radical species. Increasing ozone flow rate or H2O2 dosage was observed to cause an efficiency inhibition effect. This lab-based study demonstrates the potential for combined TiO2-AOP treatments to significantly reduce the organic fraction of real GW, offering potential for the development of low-cost systems permitting safe GW reuse.

Photocatalytic degradation activity of goji berry extract synthesized silver-loaded mesoporous zinc oxide (Ag@ZnO) nanocomposites under simulated solar light irradiation

“…However, AOPs are widely used technology to remove any organic recalcitrant contaminants/pollutants in wastewater. Generally, AOPs such as Fenton-like processes, ozonation, sonolysis, and photocatalysis are used for the remediation treatments in the aqueous medium 3 , 4 . These AOPs utilize strong oxidants, such as hydroxyl and superoxide anion radicals for the remediation of pollutants and antimicrobial activity.…”

Advanced Ozonation Processes for Water and Wastewater Treatment

“…As an inexpensive, efficient and notable catalyst, titanium dioxide (TiO 2 ) is used in a variety of technological fields, especially those having to do with energy and environment. 49 Generally, TiO 2 comes in two types, anatase and rutile, and has been intensely applied in photocatalysis due to its semiconductor characteristics and other properties. According to previous studies, TiO 2 effectively accelerates ozone decomposition into OH for the improvement of catalytic efficiency in organic contaminants removal in the heterogeneous catalytic ozonation, especially the rutile phase.…”

A Review: Effects of air, water and land dumpsite on human health and analytical methods for determination of pollutants

“…For organic pollution, the treatment efficiencies that characterize a tertiary treatment are the accompanying: organic pollution reduction of essentially 95% for BOD, 85% for COD, the nitrogen reduction of essentially 70%, the phosphorus reduction of essentially 80% and the microbiological reduction accomplishing a waste coliform thickness of < 1000 of every 100 ml. Moreover, explicit industrial effluents might require extra treatment for explicit determinants that may not be normal in many wastewaters [18,19].…”