Disinfection byproduct formation resulting from settled, filtered, and finished water treated by titanium dioxide photocatalysis

Abstract

This study evaluated strategies targeting disinfection byproduct (DBP) mitigation using TiO2 photocatalysis with varying influent water quality. A Purifics Photo-CAT Lab reactor was used to assess total trihalomethane (TTHM) and haloacetic acid (HAA) formation as a function of photocatalytic treatment using water from a conventional coagulation/flocculation/sedimentation process, granular activated carbon filtration, and a DBP hot spot in the water distribution system. Regardless of influent water quality, photocatalysis reduced DBP precursors; however, low-energy limited photocatalysis (<5 kW h m(-3)), exacerbated the production of TTHMs and HAA5s beyond initial levels. Accordingly, limited photocatalysis is not a suitable option when TTHMs and HAA5s are a concern, regardless of the level of pretreatment. Limited photocatalysis yields incomplete oxidation, wherein larger, more aromatic, humic organic compounds are broken into smaller molecular weight, less aromatic, and less humic moieties, which have considerable potential to produce DBPs. More complete mineralization of DBP precursors is obtained using extended photocatalysis (80-160 kW h m(-3)), which substantially decreases DBP precursors as well as TTHM and HAA5 concentrations. In order to balance DBP mitigation, energy, and chemical usage, targeted use of TiO2 photocatalysis is necessary in a water treatment train (e.g., extended photocatalysis at a distribution system hot spot, where the volumetrically high energy requirements may be justifiable).

Comparison of Infectious Agents Susceptibility to Photocatalytic Effects of Nanosized Titanium and Zinc Oxides: A Practical Approach

“…Due to their virucidal [ 19 , 20 ], bactericidal [ 21 , 22 ] and fungicidal [ 23 , 24 ] properties, photocatalytic layers are increasingly applied to coat surfaces in miscellaneous premises, such as farms, abattoirs, production halls, hospitals, and laboratories. The usefulness of photocatalysis has also been proven in water treatment [ 25 ], purification of drinking water [ 26 ], and air disinfection [ 27 ]. The researchers presume that the introduction of photocatalytic surfaces in the food industry, animal production, and health-care facilities will also be beneficial, as it will help prevent food poisonings and food contaminations, contribute towards the animal welfare, and improve the efficiency of pathogen eradication [ 28 – 30 ].…”

Trihalomethane (THM) formation from synergic disinfection of biologically treated municipal wastewater: Effect of ultraviolet (UV) irradiation and titanium dioxide photocatalysis on dissolve organic matter fractions

“…In the UV/TiO 2 photocatalysis, hydroxyl radicals ( Å OH) can enhance DOM degradation, accelerating DOM transformation to smaller molecules [36]. Complete mineralization of DOM (signified by loss of DOC), however, may only be achieved after extended treatment due to the presence and/or production of refractory compounds [25]. Therefore, these treatments usually result in changes of DOM structure and molecular characteristics.…”

“…Mayer et al investigated disinfection byproduct (DBP) formation in TiO 2 photocatalysis with varying influent water quality. They found that photocatalysis exacerbated the production of total trihalomethane (TTHM) and haloacetic acid (HAA) beyond initial levels until economically prohibitive high energy UV lamp was used [25]. On the other hand, Wang et al found that UV irradiation could eliminate trichloromethane formation but enhanced the formation of dichloroacetic acid [24].…”

Application of liquid chromatography/electrospray ionization tandem mass spectrometry for the elucidation of hydroxyl radical oxidation of metsulfuron methyl and related sulfonylurea pesticide products: evidence for the triazine skeleton scission

“…However, this process may lead to the formation of various stable products that accumulate well in the solution since the total mineralization of polluted aqueous solutions is not possible with such photochemical reaction . In order to reach a high degree of mineralization of contaminated media, several Advanced Oxidation Processes (AOPs) using solar light excitation have been developed and studied in depth . They have emerged as interesting ways for an efficient decontamination of polluted media because of their large‐scale use.…”