Enhanced degradation of emerging contaminants by permanganate/quinone process: Case study with bisphenol A.

Permanganate (Mn(VII)) is widely used as a mild oxidant in water treatment. However, the reaction rates of some emerging contaminants with Mn(VII) are extremely low. In this study, benzoquinone (BQ), a redox mediator with the important component in dissolved organic matter (DOM), enhanced the oxidation of bisphenol A (BPA) by Mn(VII) in a wide pH range of 4.

MoS-assisted Fe/peroxymonosulfate oxidation for the abatement of phenacetin: efficiency, mechanisms and toxicity evaluation.

In this study, molybdenum disulfide (MoS) was chosen as a co-catalyst to enhance the removal efficiency of phenacetin (PNT) in water by a ferrous ion-activated peroxymonosulfate (Fe/PMS) process. Operating parameters, such as the initial solution pH and chemical dose on PNT degradation efficiency were investigated and optimized. Under an initial pH of 3, an Fe dose of 25 μM, a PMS dose of 125 μM and a MoS dose of 0.

Enhanced formation of iodinated trihalomethanes in a mixed chlorine/chloramine system and attenuation by UV-activated process.

Iodinated trihalomethanes (I-THMs) have drawn increasing concerns due to their higher toxicity than those of their chlorinated and brominated analogues. In this study, I-THM formation was firstly evaluated for three treatment scenarios - (i) chlorine alone, (ii) chloramine alone, and (iii) mixed chlorine/chloramine - in the presence and absence of UV irradiation for the iodide-containing humic acid solution or natural water. The results indicated that I-THM formation decreased in the order of mixed chlorination/chloramination > chloramination > > chlorination, which fitted the trend of toxicity evaluation results using Chinese hamster ovary cells.

Comparative study of degradation of ketoprofen and paracetamol by ultrasonic irradiation: Mechanism, toxicity and DBP formation.

The present study comparatively investigated the ultrasonic degradation of ketoprofen (KET) and paracetamol (PCT) in water. Ultrasonic irradiation at 555 kHz achieved rapid degradation of KET and PCT in water, the removal efficiencies of KET (2.5-80 μM) and PCT (2.

Electrochemically activated peroxymonosulfate for the abatement of chloramphenicol in water: performance and mechanism.

In this study, electrochemically activated peroxymonosulfate (EC/PMS) with a sacrificial iron electrode was used for the removal of chloramphenicol (CAP) from water. Compared to electrolysis alone, peroxymonosulfate (PMS) alone, and Fe/PMS, EC/PMS significantly enhanced the CAP degradation. Various parameters, such as the applied current, electrolyte concentration, and PMS dose, were investigated to optimize the process.

The formation, analysis, and control of chlor(am)ination-derived odor problems: A review.

Odors and tastes have become universal problems related to drinking water quality. In addition to the typical odor problems caused by algae or microorganisms, the occurrence of odors derived from drinking water disinfection have attracted attention. The chlor(am)ination-derived odor substances have certain toxicity and odor-causing characteristics, and would enter the tap water through water distribution systems, directly affecting drinking water safety and customer experience.

Formation and control of organic chloramines and disinfection by-products during the degradation of pyrimidines and purines by UV/chlorine process in water.

Pyrimidine and purine bases (adenine, cytosine, guanine and thymine) are important precursors of organic chloramines (OC) and disinfection by-products (DBPs) during chlor(am)ination. In this study, OC and DBP formation derived from pyrimidine and purine bases during chlor(am)ination, post-chlor(am)ination after pretreated by UV alone and UV/chlorination were systematically investigated with ultraviolet light-emitting diodes (UV-LEDs, 265 and 275 nm) and low pressure mercury lamp (LPUV, 254 nm). The results revealed that higher OC formation was observed during chlorination than that during chloramination of pyrimidine and purine bases.

Photodegradation pathway of iodate and formation of I-THMs during subsequent chloramination in iodate-iodide-containing water.

This study investigated the mechanisms of mixed IO/I system under UV irradiation in drinking water and compared the iodinated trihalomethanes (I-THMs) formation of a mixed IO/I system to that of single I and IO systems during subsequent chloramination. The effects of initial I/IO molar ratio, pH, and UV intensity on a mixed IO/I system were studied. The introduction of I enhanced the conversion rate of IO to reactive iodine species (RIS).

Mechanistic study on chlorine/nitrogen transformation and disinfection by-product generation in a UV-activated mixed chlorine/chloramines system.

The conversion mechanisms of chlorine species (including free chlorine, monochloramine (NHCl), dichloramine, and total chlorine), nitrogen species (including ammonium (NH), nitrate (NO), and nitrite (NO)) as well as the formation of disinfection by-products (DBPs) in a UV-activated mixed chlorine/chloramines system in water were investigated in this work. The consumption rates of free chlorine and NHCl were significantly promoted in a HOCl/NHCl coexisting system, especially in the presence of UV irradiation. Moreover, the transformation forms of nitrogen in both ultrapure and HA-containing waters were considerably affected by UV irradiation and the mass ratio of free chlorine to NHCl.

Effect of bromide and iodide on halogenated by-product formation from different organic precursors during UV/chlorine processes.

The effect of bromide and iodide on the transformation of humic acid (HA) and algal organic matter (AOM), and the formation of disinfection by-products (DBPs) during UV/chlorination were investigated. Experimental results indicated that the halides effectively inhibited mineralization, with multiple changes in organic molecule transformation due to differences in formation and speciation of reactive halogen species and free halogen. As a consequence, bromide and iodide also played important roles in DBP formation.

Persulfate activation by nano zero-valent iron for the degradation of metoprolol in water: influencing factors, degradation pathways and toxicity analysis.

In this study, nano zero-valent iron (nZVI) was utilized to activate persulfate (PS) for the degradation of metoprolol (MTP), a commonly used drug for curing cardiovascular diseases, in water. Quenching tests indicated that both the sulfate radical (SO˙) and hydroxyl radical (˙OH) contributed to the degradation of MTP, while SO˙ seemed to play a large role under natural pH conditions. Batch tests were conducted to investigate the effects of several influencing factors, such as PS concentration, initial MTP concentration, pH, temperature and common anions, on the degradation performance of MTP.

Comparison of different disinfection processes for controlling disinfection by-product formation in rainwater.

With increasing shortage of clean water, rainwater has been considered as a precious alternative drinking water source. The processes applied to rainwater treatment are responsible for the safety of drinking water. Therefore, we systematically compared different disinfection processes to evaluate the control of disinfection by-product (DBP) formation and integrated cyto- and genotoxicity of the treated rainwater for the first time.

Comparative evaluation of metoprolol degradation by UV/chlorine and UV/HO processes.

The degradation of metoprolol (MTP), a β-blocker commonly used for cardiovascular diseases, by UV/chlorine and UV/HO processes was comparatively evaluated. MTP direct photolysis at 254 nm could be neglected, but remarkable MTP degradation was observed in both the UV/chlorine and UV/HO systems. Compared with UV/HO, UV/chlorine has a more pronounced MTP degradation efficiency.

A comparison of dissolved organic matter transformation in low pressure ultraviolet (LPUV) and ultraviolet light-emitting diode (UV-LED)/chlorine processes.

This study compared the degradation of dissolved organic matter (DOM) by UV/chlorine advanced oxidation processes (AOPs) with emerging ultraviolet light-emitting diode (UV-LED, 275 nm) and traditional low pressure UV (LPUV, 254 nm) as UV sources. Excitation emission matrix-parallel factor (EEM-PARAFAC) analysis and two-dimensional (2D) correlation gel permeation chromatograph were applied to explore the evolutions of DOM during oxidation processes. The degradation behaviors of DOM indicated by UV absorbance at 254 nm (UV), dissolved organic carbon (DOC), and fluorophores fitted the pseudo-first-order kinetics well.

Degradation of diiodoacetamide in water by UV/chlorination: Kinetics, efficiency, influence factors and toxicity evaluation.

The formation and control of haloacetamides (HAcAms) in drinking water have raised high attention due to their high genotoxicity and cytotoxicity, especially the most cytotoxic one, diiodoacetamide (DIAcAm). In this study, the degradation of DIAcAm by UV/chlorination was investigated in terms of degradation kinetics, efficiency, influencing factors, oxidation products and toxicity evaluation. Results revealed that the degradation of DIAcAm by UV/chlorine process followed pseudo-first-order kinetics, and the rate constant between DIAcAm and OH radicals was determined as 2.

Enhanced ronidazole degradation by UV-LED/chlorine compared with conventional low-pressure UV/chlorine at neutral and alkaline pH values.

Ultraviolet light-emitting diodes (UV-LEDs) are promising alternatives to conventional low-pressure UV (LPUV) lamps, mainly because they contain no toxic mercury and have a potential for less energy consumption and longer lifetime. In this study, UV sources including UV-LEDs (265, 275 and 285 nm) and LPUV (254 nm) were compared in UV/chlorine degradation of an organic contaminant, ronidazole (RNZ). UV-LED/chlorine performed better than LPUV/chlorine at neutral and alkaline pH values for RNZ degradation considering the fluence-based rate constant.

Effect of UV wavelength on humic acid degradation and disinfection by-product formation during the UV/chlorine process.

The efficiency of the ultraviolet (UV)/chlorine process strongly depends on UV wavelength because chlorine photolysis and its subsequent radical formation are highly wavelength-dependent. This study compared the degradation of humic acid (HA) during the UV/chlorine process by low pressure mercury lamp (LPUV, 254 nm) and ultraviolet light-emitting diode (UV-LED, 275 and 310 nm). The results indicated that HA degradation followed the pseudo-first-order kinetics, and the fluence-based degradation rate constants (k) were significantly affected by UV wavelength and solution pH.

Kinetic and mechanistic investigations of the degradation of propranolol in heat activated persulfate process.

This study investigated the heat activated persulfate (heat/PS) process in the degradation of propranolol from water. Various factors (, temperature, persulfate dose, initial pH and natural water constituent) on PRO degradation kinetics have been investigated. The results showed that the PRO degradation followed a pseudo-first-order kinetics pattern.

Effect of UV irradiation on iodinated trihalomethane formation during post-chloramination.

Ultraviolet (UV) irradiation has been widely used in drinking water treatment processes, but its influence on the formation of disinfection by-products (DBPs), especially the emerging iodinated trihalomethanes (I-THMs) during post-chloramination remains unclear. This study evaluated the impact of low pressure (LP) UV treatment on the formation of I-THMs during post-chloramination through two pathways. The first pathway is through the transition of DOM structure and composition during UV-chloramination, resulting significant increase of I-THM formation with increasing UV dosage in different dissolved organic matter (DOM)-containing water (49.

Ultrasound-assisted heterogeneous activation of persulfate by nano zero-valent iron (nZVI) for the propranolol degradation in water.

This study investigated the degradation of propranolol (PRO), a beta (β)-blockers, by nano zero-valent iron (nZVI) activated persulfate (PS) under ultrasonic irradiation. Effects of several critical factors were evaluated, inclusive of PS concentration, nZVI dosage, ultrasound power, initial pH, common anions, and chelating agent on PRO degradation kinetics. Higher PS concentration, nZVI dosage and ultrasound power as well as acidic pH favored the PRO degradation.

Enhanced inactivation of E. coli by pulsed UV-LED irradiation during water disinfection.

Pulsed ultraviolet (UV) irradiation has presented enhanced inactivation efficiency in water disinfection and food decontamination. As an emerging UV source, UV light-emitting diodes (UV-LEDs) are an attractive alternative for pulsed irradiation because they can be turned on and off with a high and adjustable frequency. In this study, disinfection efficiencies of pulsed and continuous UV-LED irradiation were compared for Escherichia coli (E.

Factors affecting the water odor caused by chloramines during drinking water disinfection.

Chloramine disinfection is one of the most common disinfection methods in drinking water treatment. In this study, the temporal variability of water odors during monochloramine auto-decomposition was investigated to elucidate the characteristics of odor problems caused by adopting chloramine disinfection in tap water. Odor intensities and dominant odorant contributions were determined using the flavor profile analysis (FPA) and odor active value (OAV), respectively.

Formation of iodinated trihalomethanes during breakpoint chlorination of iodide-containing water.

This study investigated the formation of toxic iodinated trihalomethanes (I-THMs) during breakpoint chlorination of iodide-containing water. Impact factors including I concentration, natural organic matter (NOM) concentration and type, pH as well as Br/I molar ratio were systematically investigated. Moreover, the incorporation of I into I-THM formation was also calculated.