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Pipe bursts in water distribution systems (WDSs) lead to large water losses, pollution risks, and public discontent, attracting widespread attention from researchers and water utilities around the world. This study provides insights into the knowledge structure and emerging trends of pipe burst research from a bibliometrics perspective. We used 845 original research and review articles on pipe bursts in the period of January 1991 − June 2022 that cited 16,813 references in the CiteSpace® software for reference co-citation analysis. The results indicate that the knowledge structure of pipe burst research is classified into four categories including pipe burst mechanism, pipe burst detection, pipe burst prediction, and use of sensors. The entire research on pipe bursts advances remarkably. First, pipe burst prediction is the core research category with continuous efforts to improve prediction performance. Second, pipe burst detection is likely to define new research focus to extend existing research focus on pipe burst prediction. Third, computer science and technology are widely and increasingly applied in burst process simulation and data pattern analysis to increase accuracy and effectiveness. This study grasps a full view of current achievements in pipe burst research and provides guidance for future research directions and technological development.

The degradation of atrazine (ATZ), sulfamethoxazole (SMX) and metoprolol (MET) in flow-through VUV/UV/H2O2 reactors was investigated with a focus on the effects of H2O2 dosage and reactor internal diameter (ID). Results showed that the micropollutants were degraded efficiently in the flow-through VUV/UV/H2O2 reactors following the pseudo first-order kinetics (R2 > 0.92). However, the steady-state assumption (SSA) kinetic model being vital in batch reactors was found invalid in flow-through reactors where fluid mixing was less sufficient. With the increase of H2O2 dosage, the ATZ removal efficiency remained almost constant while the SMX and MET removal was enhanced to different extents, which could be explained by the different reactivities of the pollutants towards HO•. A larger reactor ID resulted in lower degradation rate constants for all the three pollutants on account of the lower average fluence rate, but the change in energy efficiency was much more complicated. In reality, the electrical energy per order (EEO) of the investigated VUV/UV/H2O2 treatments ranged between 0.14–0.20, 0.07–0.14 and 0.09–0.26 kWh/m3/order for ATZ, SMX and MET, respectively, with the lowest EEO for each pollutant obtained under varied H2O2 dosages and reactor IDs. This study has demonstrated the efficiency of VUV/UV/H2O2 process for micropollutant removal and the inadequacy of the SSA model in flow-through reactors, and elaborated the influential mechanisms of H2O2 dosage and reactor ID on the reactor performances.

To ensure the safety of drinking water, ozone (O3) has been extensively applied in drinking water treatment plants to further remove natural organic matter (NOM). However, the surface water and groundwater near the coastal areas often contain high concentrations of bromide ion (Br−). Considering the risk of bromate (BrO3−) formation in ozonation of the sand-filtered water, the inhibitory efficiencies of hydrogen peroxide (H2O2) and ammonia (NH3) on BrO3− formation during ozonation process were compared. The addition of H2O2 effectively inhibited BrO3− formation at an initial Br− concentration amended to 350 µg/L. The inhibition efficiencies reached 59.6 and 100% when the mass ratio of H2O2/O3 was 0.25 and > 0.5, respectively. The UV254 and total organic carbon (TOC) also decreased after adding H2O2, while the formation potential of trihalomethanes (THMsFP) increased especially in subsequent chlorination process at a low dose of H2O2. To control the formation of both BrO3− and THMs, a relatively large dose of O3 and a high ratio of H2O2/O3were generally needed. NH3 addition inhibited BrO3− formation when the background ammonia nitrogen (NH3 N) concentration was low. There was no significant correlation between BrO3− inhibition efficiency and NH3 dose, and a small amount of NH3 N (0.2 mg/L) could obviously inhibit BrO3− formation. The oxidation of NOM seemed unaffected by NH3 addition, and the structure of NOM reflected by synchronous fluorescence (SF) scanning remained almost unchanged before and after adding NH3. Considering the formation of BrO3− and THMs, the optimal dose of NH3 was suggested to be 0.5 mg/L.

Heterogeneous peroxymonosulfate (PMS)–based advanced oxidation processes (AOPs) have shown a great potential for pollutant degradation, but their feasibility for large-scale water treatment application has not been demonstrated. Herein, we develop a facile coprecipitation method for the scalable production (∼10 kg) of the Cu-Fe-Mn spinel oxide (CuFeMnO). Such a catalyst has rich oxygen vacancies and symmetry-breaking sites, which endorse it with a superior PMS-catalytic capacity. We find that the working reactive species and their contributions are highly dependent on the properties of target organic pollutants. For the organics with electron-donating group (e.g., -OH), high-valent metal species are mainly responsible for the pollutant degradation, whereas for the organics with electron-withdrawing group (e.g., -COOH and -NO 2 ), hydroxyl radical (•OH) as the secondary oxidant also plays an important role. We demonstrate that the CuFeMnO–PMS system is able to achieve efficient and stable removal of the pollutants in the secondary effluent from a municipal wastewater plant at both bench and pilot scales. Moreover, we explore the application prospect of this PMS-based AOP process for large-scale wastewater treatment. This work describes an opportunity to scalably prepare robust spinel oxide catalysts for water purification and is beneficial to the practical applications of the heterogeneous PMS-AOPs.

The presence and accumulation of microplastics (MPs) in water and wastewater is a growing concern. When released to the water bodies, microplastics can be subject to surface weathering due to ultraviolet (UV) exposure. In this study, the effects of UV aging of six MP polymers from three groups (e.g., polyamide, polyester, and polyolefin) on their chlorine reactivity, chemical transformation, and formation of disinfection byproducts (DBPs) were studied. Polyamide (e.g., polyamide 6) in both virgin and UV-aged forms showed significantly higher chlorine demands than other MP polymers (915.5-947.9 versus 7.0-21.1 μmol/g MP in 24 h), and polyolefins were relatively inert to chlorine. UV aging enhanced the destructions of functional groups of polyamide and polyester upon chlorination, promoting the chlorine demands and leaching of organics by up to 1.7- and 2.4-fold, respectively. Polymer monomer and oligomers of polyamide 6 and toxic or endocrine disrupting additives (e.g., dimethyl phthalate and butyl octyl phthalate) were identified in leachates from chlorinated MP polymers by mass spectrometry. Meanwhile, up to10-fold increases in the yields of trihalomethane, haloacetic acid, haloacetaldehyde, haloacetonitrile, and haloacetamide were observed from 30-day UV-aged MP polymers as compared to their virgin counterparts. Overall, this study reveals that UV aging can promote the reactivity and chemical transformation of MP polymers during chlorination, especially for polyamide and polyester, increase the release of polymer monomers, oligomers, and additives, and aggravate the role of MP polymers as DBP precursors.

The degradation kinetics of Sodium dodecylbenzene sulfonate (SDBS) surfactant in the UV/chlorine process was comprehensively investigated, and the formation of chlorinated disinfection by-products (Cl-DBPs) were determined. Results showed that the degradation of SDBS by UV, chlorine and UV/chlorine all followed pseudo-first-order kinetics. The rate constant by UV/chlorine in ultrapure water was approximately 3 times higher than the sum of those by UV and chlorine, and decreased from 0.297 to 0.063 min

The degradation of three micropollutants (i.e., atrazine (ATZ), sulfamethoxazole (SMX) and metoprolol (MET)) was comprehensively investigated in flow-through UV/chlorine reactors. Results showed that the micropollutants degradation fitted well with pseudo-first-order kinetics (R

Ultraviolet-based advanced oxidation processes (UV-AOPs) are highly effective for micropollutant degradation. However, it is considerably time and labor consuming to evaluate the practical performance of UV-AOPs. This study developed a novel method, through combination of model simulation with portable measurement (MS-PM), to facilitate prediction of the photon fluence-based rate constant of micropollutant degradation (k'

Permanganate (Mn(VII)) is a widely used oxidant in water treatment, which can oxidize trace organic contaminants (TrOCs) and Mn(II). Interestingly, this study found that presence of Mn(II) could accelerate the abatement of bisphenol A by Mn(VII) only under oxic condition. Herein, the effects of Mn(II) and dissolved oxygen (DO) on the abatement of TrOCs by Mn(VII) oxidation and the related mechanism were investigated. Results indicate that DO was involved in the Mn(VII)/Mn(II) reaction, with the reaction stoichiometry of Δ[Mn(VII)]:Δ[Mn(II)] determined to be 1:2 and 1:1.5 in the presence and absence of DO, respectively. Quenching and electron paramagnetic resonance tests verified that both superoxide radicals (O

Due to the wide-presence of organic amines in natural waters, organic chloramines are commonly formed during (pre-)chlorination. With the increasing application of UV disinfection in water treatment, both the activation mechanism of organic chloramine by UV photolysis and its subsequent impact on water quality are not clear. Using sarcosine (Sar) as an amine group-containing compound, it was found that organic chloramines (i.e., Cl-Sar) would be firstly formed during chlorination even in the presence of natural organic matter. Compared with self-decay of Cl-Sar, UV photolysis accelerated Cl-Sar decomposition and induced N Cl bond cleavage. Using metoprolol (MTP) as a model micro-pollutant, UV-activated Cl-Sar (UV/Cl-Sar) can accelerate micro-pollutant degradation, attributed to reactive radicals formation. HO• and Cl• were important contributors, with a total contribution of 45%‒64%. Moreover, the degradation rate of MTP by UV/Cl-Sar was pH-dependent, which monotonically increased from 0.044 to 0.065 min‒1 under pHs 5.5‒8.5. Although the activation of organic chloramine by UV could accelerate micro-pollutant degradation, UV/Cl-Sar treatment could also enhance disinfection by-products formation. Trichloromethane (TCM) formation was observed during MTP degradation by UV/Cl-Sar. After post-chlorination, TCM, 1,1-dichloropropanone, 1,1,1-trichloropropanone, and dichloroacetonitrile were detected. Their individual and total concentrations were all positively proportional to UV/Cl-Sar treatment time. The total concentration with 30 min treatment (66.93 μg L‒1) was about 2.3 times that with 1 min treatment (28.76 μg L‒1). Finally, the accelerated effect was verified with Cl-glycine and Cl-alanine. It is expected to unravel the non-negligible role of organic chloramine on water quality during UV disinfection.

Permanganate (PM) is a widely-used oxidant in water treatment. However, the oxidation rate of micro-pollutants by PM is highly variable, dependent on the electron density of certain moieties of micro-pollutants. Using a pesticide (carbendazim, CBZ) as a target micro-pollutant, this study compared the organic and inorganic activations of PM by benzoquinone (PM/BQ) and bisulfite (PM/BS), respectively. It was found that both the PM/BQ and PM/BS systems could accelerate the degradation of CBZ with different degradation rates. The PM/BS system completed the degradation of CBZ (96.6%) within 15 s, while the PM/BQ system took 2 h to achieve a 95.7% removal. The optimal molar ratios of [PM]ο:[BS]ο and [PM]ο:[BQ]ο were determined to be 1:5 and 1:0.1, respectively. Interestingly, both the degradation of CBZ in the PM/BQ and PM/BS systems were dependent on dissolved oxygen (DO) concentration. When DO was around 0.5 mg L−1, the removals of CBZ by the PM/BQ and PM/BS systems were just 3.6% and 36.8%, respectively after 2 h, significantly lower than those under 9.1-mg L−1 DO (95.7% and 96.6%, respectively). Based on the quenching experiments, the enhanced degradation in the PM/BQ system was mainly ascribed to the formations of Mn(III) and 1O2, while the formations of SO5 − and SO4 − mainly contributed to the accelerated degradation in the PM/BS system. The transformation products of CBZ in both the PM/BQ and PM/BS systems were identified and the degradation pathways including dehydrogenation, alkylation, carboxylation and hydroxylation were proposed. The inorganic activation of PM by BS exhibits a higher degradation rate and stability under different water matrices, indicating its potential engineering application in water treatment.

The decontamination of prometon (PMT) by ozone/hydroxylamine hydrochloride (O3/HAC) was systematically investigated in this study with focus on the degradation mechanism and kinetics. Experimental results revealed that there was an enhancement of PMT degradation efficiency by 42.1% and the pseudo-first-order rate constant by more than 5.7 times in O3/HAC process under low HAC dosage (5 mg L−1) after 3 min in comparison with O3 alone. The second-order rate constant of PMT with hydroxyl radical (•OH) was determined to be (1.84 ± 0.1) × 109 M−1 s−1 and 7.80 × 109 M−1 s−1 via competition kinetics and •OH steady-state hypothesis, respectively. The PMT removal in O3/HAC process was highly pH-dependent and the optimum degradation performance was achieved under pH 5.0. In addition, •OH and singlet oxygen were identified as the primary reactive oxygen radicals in O3/HAC process. Meanwhile, eleven transformation products of PMT were identified and possible degradation mechanisms were proposed. Moreover, a kinetic model based on chemical kinetics and steady-state hypothesis was developed and modified to predict the PMT abatement in O3/HAC process. The results demonstrated that the O3/HAC process provided a promising alternative for refractory organic pollutants decontamination in water treatment.

Permanganate is a versatile chemical oxidant, and has undergone a dramatic evolution toward deep insight into its reaction mechanism. However, the hydrogen abstraction of the N H bond by permanganate remains unclear. We studied the permanganate oxidation of the emerging micropollutant sulfamethoxazole in acidic aqueous solution. The reaction followed autocatalytic kinetics and demonstrated first-order with respect to each reactant. The presence of HMnO4 accelerated the reaction rate, which was four orders of magnitude higher than that of MnO4−. Based on the identified products, the rate-limiting step was determined to be simple N H bond oxidation by metal-oxo species permanganate. The mechanism was then studied computationally by density functional theory (DFT) using ammonia as the simplest model. Results showed that the N H bond oxidation by MnO4− (32.86 kcal/mol) was a concerted mechanism similar to that of C H bond oxidation, whereas HMnO4 oxidation of the N H bond (10.44 kcal/mol) was a stepwise electron-proton transfer. This reminds us that coordination of Bronsted acid could not only produce the stronger electrophile but also change the reaction mode by avoiding the bond cleavage in electron transfer process.

Marine recirculating aquaculture system (MRAS) is an effective technology that provides sustainable farming of food fish globally. However, dissolved organics material (chemical oxygen demand, COD) and especially ammonia are produced from uneaten feed and metabolic wastes of fish. To purify the MRAS water, this study adopted a sequencing biofilm batch reactor (SBBR) and comparatively investigated the performances of four different carriers on ammonia and COD removal. Results indicated that the NH4+-N removal rates were 0.045 +/- 0.05, 0.065 +/- 0.008, 0.089 +/- 0.005, and 0.093 +/- 0.003 kg/(m(3)center dot d), and the COD removal rates were 0.019 +/- 0.010, 0.213 +/- 0.010, 0.255 +/- 0.015, and 0.322 +/- 0.010 kg/(m(3)center dot d) in the SBBRs packed with porous plastic, bamboo ring, maifan stone, and ceramsite carriers, respectively. Among the four carriers, ceramsite exhibited the best performance for both NH4+-N (80%) and COD (33%) removal after the SBBR reached the steady-state operation conditions. For all carriers studied, the NH4+-N removal kinetics could be well simulated by the first-order model, and the NH4+-N and COD removal rates were logarithmically correlated with the carrier's specific surface area. Due to its high ammonia removal, stable performance and easy operation, the ceramsite-packed SBBR is feasible for MRAS water treatment.

To date, little is known about the removal of fluoroquinolones (FQs) in the in-situ sludge ozone-reduction (SOR) process. Hence, this study investigated the behavior of five commonly used FQs, including ciprofloxacin, enrofloxacin, lomefloxacin, norfloxacin and ofloxacin in the SOR process. Batch experiments indicated that ozonation could effectively eliminate the target FQs present in the sludge, which was accelerated by increasing the initial pH (5.0–9.5). Continuous operation of an anaerobic/anoxic/oxic process coupled with sludge ozonation and phosphorus recovery showed that the SOR process could achieve zero yield of excess sludge. In addition, chemical oxygen demand and nitrogen species were stably removed, with efficiencies comparable to those obtained in the conventional activated sludge (CAS) process. However, an increase in the effluent total phosphorus concentration was observed in the SOR process. The effluent FQ concentrations in the SOR process remained quite stable and were close to those in the CAS process, whereas the FQ concentrations in the sludge decreased remarkably after ozonation. Mass balance analysis revealed that the FQs were released to the environment mainly through excess sludge disposal (69.9 ± 2.3%) in the CAS process, whereas were degraded mainly by ozone in the SOR process (75.8 ± 2.0%). Therefore, the SOR process was able to minimize the excess sludge and the release of FQs to the environment simultaneously.

Kinetic comparisons of micropollutant degradation by ultraviolet (UV) based advanced oxidation processes among various radiation sources are an important issue, yet this is still a challenge at present. This study investigated comparatively the kinetics of sulfamethazine (SMN) degradation by the UV/H2O2 process among three representative radiation sources, including low-pressure mercury UV (LPUV, monochromatic), medium-pressure mercury UV (MPUV, polychromatic), and vacuum UV(VUV)/UV (dual wavelengths causing different reaction mechanisms) lamps. Experiments were conducted with a newly developed mini-fluidic MPUV photoreaction system and a previously developed mini-fluidic VUV/UV photoreaction system. Measured and modeled results both indicate that the photon fluence-based SMN degradation rate constant ( kp') followed a descending order of VUV/UV/H2O2 > MPUV/H2O2 (200-300 nm) > LPUV/H2O2, and the kp' of the MPUV lamp was dependent on the wavelength range selected for photon fluence calculation. Analysis of potential errors revealed that a shorter effective path-length could have a lower error, and the maximum errors for the MPUV/H2O2 and LPUV/H2O2 processes in this study were 7.7% and 18.2%, respectively. This study has developed a new method for kinetic comparisons of micropollutant degradation by UV-AOPs among various radiation sources at bench-scale, which provides useful reference to practical applications.

With increasing water reuse as a sustainable water management strategy, antibiotic resistance genes (ARGs) which have been identified as emerging contaminants in wastewater are attracting global attentions. Given that wastewater treatment plants are now well-established as a sink and source of ARGs in both cell-associated and non-cell-associated forms, a need is acknowledged to reduce their proliferation and protect public health. Due to their different characteristics, cell-associated and non-cell-associated ARGs may have distinct responses to membrane filtration processes which are widely used as advanced treatment to the secondary effluent. This review improves the understanding of the abundance of cell-associated and non-cell-associated ARGs in wastewaters and the secondary effluents and compares the elimination of ARGs in cell-associated and non-cell-associated forms by low-pressure and high-pressure membrane filtration processes. The former process reduces the concentration of cell-associated ARGs by more than 2-logs on average. An increase of the retention efficiency of non-cell-associated ARGs is observed with decreasing molecular weight cut-offs in ultrafiltration. The high-pressure membrane filtration (i.e., nanofiltration and reverse osmosis) can effectively eliminate both cell-associated and non-cell-associated ARGs, with averagely more than 4.6-log reduction. In general, the two forms of ARGs can be removed from water by the membrane filtration processes via the effects of size exclusion, adsorption, and electrostatic repulsion. The size and conformation of cell-associated and non-cell-associated ARGs, characteristics of membranes, coexisting substances, and biofilm formation influence ARG retention. Accumulation and potential proliferation of cell-associated and non-cell-associated ARGs in foulants and concentrate and corresponding control strategies warrant future research.

Morphology, the important feature of bloom-forming cyanobacteria, was studied for its impacts on the harmful cyanobacterial bloom (HCB) treatment by coagulative colloidal ozone microbubbles (CCOMBs). The globally-appeared HCB species - Microcystis aeruginosa (spherical cells, block mass colonies), Microcystis panniformis (spherical cells, flat penniform-like colonies) and Anabaena flos-aquae (filamentous morphology) were chosen as representative species. CCOMBs were generated by modifying the bubble surface and the gas core with coagulant and ozone, respectively. The removal of spherical cells and filaments was 99.5% and ≤ 34.6%, individually, and the latter was ascribed to chain breakage. CCOMBs collected Microcystis panniformis via complexing with the fluorescent and non-fluorescent functional groups of cell colonies but captured Anabaena flos-aquae through the fluorescent ones. More Microcystis aeruginosa got membrane-damaged than Microcystis panniformis; nevertheless, the microcystin-LR (MC-LR) removal was guaranteed through efficiently oxidizing the released MC-LR. Although the outer peptidoglycan sheet of Anabaena flos-aquae was destroyed, the inner cyte membrane remained intact, preventing intracellular MC-LR from releasing. The HCBs dominated by single species with spherical cells were more readily treated than those with co-occurred species. The toxicological tests imply that, as a robust tool for HCB treatment, the CCOMB technology could be eco-environmentally friendly to the aquatic environment.

The lack of stability in catalytic ozonation treatment of reverse osmosis (RO) concentrate from coal chemical industry calls for new advanced oxidation processes. Herein, UV/H

Ultraviolet (UV) is a green and effective technique that has been widely applied in water disinfection. The reliability of UV disinfection is an important issue, in which the aim is to ensure the delivery of adequate real-time fluence in a UV reactor. Unlike chemical disinfection systems whose disinfection dose can be directly measured with disinfectant residuals, UV is a physical process and the determination of fluence is complicated in practical reactors. To date, several fluence determination methods have been developed, including conventional methods such as biodosimetry and model simulation, as well as emerging methods such as dyed microsphere method and the model-detector method. However, a systematic and comprehensive review of these methods is still needed to discuss the attributes and application scenarios of each method. In this review, we summarized the principal theories, procedures, applications, and pros/cons of these fluence determination methods. Further, the selection and application of appropriate fluence determination methods were discussed based on different purposes (e.g., feedbacks for reactor design, evidence for third-party validation, as well as on-site determination and long-term monitoring of fluence). Overall, this review could provide useful information and new insights regarding the application of current fluence determination methods to ensure the reliability of UV disinfection.

This work investigated the removal efficiency of disinfection by-product (DBP) precursors by different drinking water treatment processes and evaluated the feasibility of using fluorescence components removal as an indicator. A four-component (including tryptophan-like, protein-bound, tyrosine-like, and humic-like components) parallel factor analysis model was developed basing on 288 fluorescence excitation-emission matrices. Among all treatment processes, coagulation-sedimentation process showed the best performance, with mean removal ratios of 30% in total fluorescence intensity and 31% in total formation potential (FP) of DBPs, respectively. It preferentially removed humic-like component C4 (43%). Advanced treatment processes were less effective in comparison. Ozone and biological activated carbon (BAC) combined process reduced 20% of total fluorescence intensity, while ultrafiltration process reduced 3%. Ozonation and BAC filtration preferentially removed free amino acids (i.e., C1 and C3) and protein-bound (i.e., C2) components, with mean removal ratios of 12% and 17%, respectively. Significant correlations (p 0.01, double-tailed) were observed between four fluorescence components removal and FPs reduction of three trihalomethanes, dichloroacetonitrile (DCAN), and 1,1-dichloropropanone (1,1-DCP). Specifically, the correlation coefficients for three trihalomethanes and 1,1-DCP followed the order of C4 C1 C2 C3, while the order for DCAN was C2 C4 C1 C3.

Fluence rate (FR) distribution (optical field) is of great significance in the optimal design of ultraviolet (UV) reactors for disinfection or oxidation processes in water treatment. Since the 1970s, various simulation models have been developed, which can be combined with computational fluidic dynamic software to calculate the fluence delivered in a UV reactor. These models strive for experimental validation and further improvement, which is a major challenge for UV technology in water treatment. Herein, a review of the simulation models of the FR distribution in a UV reactor and the applications of the current main experimental measurement approaches including conventional flat-type UV detector, spherical actinometer, and micro-fluorescent silica detector (MFSD), is presented. Moreover, FR distributions in a UV reactor are compared between various simulation models and MFSD measurements. In addition, the main influential factors on the FR distribution, including inner-wall reflection, refraction and shadowing effects of adjacent lamps, and turbidity effect are discussed, which is helpful for improving the accuracy of the simulation models and avoiding dark regions in the reactor design. This paper provides an overview on the simulation models and measurement approaches for the FR distribution, which is helpful for the model selection in fluence calculations and gives high confidence on the optimal design of UV reactors in regard to present methods.

Disinfection by-products (DBPs) formed during water disinfection has drawn significant public concern due to its toxicity. Since the first discovery of the trihalomethanes in 1974, continued effort has been devoted on DBPs worldwide to investigate the formation mechanism, levels, toxicity and control measures in drinking water. This review summarizes the main achievements on DBP research in China, which included: (1) the investigation of known DBP occurrence in drinking water of China; (2) the enhanced removal of DBP precursor by water treatment process; (3) the disinfection optimization to minimize DBP formation; and (4) the identification of unknown DBPs in drinking water. Although the research of DBPs in China cover the whole formation process of DBPs, there is still a challenge in effectively controlling the drinking water quality risk induced by DBPs, an integrated research framework including chemistry, toxicology, engineering, and epidemiology is especially crucial.

The degradation of atrazine (ATZ), sulfamethoxazole (SMX) and metoprolol (MET) in flow-through VUV/UV/H

Significant iron release from cast iron pipes in water distribution systems (WDSs), which usually occurs during the source water switch period, is a great concern of water utilities because of the potential occurrence of “red water” and customer complaints. This study developed a new method which combined in-situ water stagnation experiments with mathematical models and numerical simulations to predict the iron release caused by source water switch. In-situ water stagnation experiments were conducted to determine the total iron accumulation in nine cast iron pipes in-service in Beijing when switching the local water to treated Danjiangkou Reservior water. Results showed that the difference in the concentration increment of total iron in 24 hr (ΔCITI,24), i.e. short-term iron release, caused by source water switch was mainly dependent on the difference in the key quality parameters (pH, hardness, nitrate, Larson Ratio and dissolved oxygen (DO)) between the two source waters. The iron release rate (RFe) after switch, i.e. long-term iron release, was closely related to the pipe properties as well as the DO and total residual chlorine (TRC) concentrations. Mathematical models of ΔCITI,24 and RFe were developed to quantitatively reveal the relationship between iron release and the key quality parameters. The RFe model could successfully combine with EPANET-MSX, a numerical simulator of water quality for WDSs to extend the iron release modeling from pipe level to network level. The new method is applicable to predicting iron release during source water switch, thus facilitating water utilities to take preventive actions to avoid “red water”.

Cupric oxide (CuO) is able to catalyze the reactions among disinfectant, extracellular polymeric substances (EPS) and bromide (Br

Recently, sulfate radical-based advanced oxidation processes (SR-AOPs) have been known as an alternative to hydroxyl radical-based advanced oxidation processes (•OH-AOPs) in the treatment of different industrial wastewaters. During the SR-AOPs, various precursors such as peroxymonosulfate (PMS), peroxydisulfate, and bisulfite (BS) are usually employed to generate sulfate radical (SO4•−) through a series of activations (e.g., O3, UV, and transition metal). Although these strategies contribute to the improvement of the removal efficiency of recalcitrant and/or toxic contaminants and wastewater biodegradability, the high energy consumption and low efficiency in real water treatment limit the practical applications. In this chapter, the degradation kinetics and activation mechanisms of the SR-AOPs, especially in homogeneous catalytic processes [O3/PMS, UV/persulfate (PS), Fe(II)/PS, and Mn(VII)/BS], are systematically assessed and analyzed. Generally, there are several types of oxidative intermediates (e.g., SO4•−, HO•, and high-valent transition metal) with high redox potential and different selectivity during these processes; it is necessary to integrate quenching experiments, electron spin resonance experiments, and competitive kinetics experiments for the examination of the activation mechanisms. The influencing factors, practical applications, and integrated treatment processes of the SR-AOPs are discussed in detail in the industrial wastewaters treatment. The advantages and shortcomings of SR-AOPs for practical applications are also discussed, emphasizing the integrated treatment processes of SR-AOPs, which are desired for future exploration.

The effect of phosphate on marine anammox bacteria (MAB)-dominated anammox process in nitrogen-laden saline wastewater was first investigated. The activity of MAB was enhanced by dosing low concentrations of phosphate (5–30 mg/L PO43−-P), and the time of complete ammonium removal was shortened by 0.5 h. When PO43−-P exceeded 160 mg/L, the calcium magnesium phosphate precipitation was formed in the reactor. The contact between substrates and biomass was hindered by the sediments, and the nitrogen removal performance of MAB was also worsened. At 400 mg/L PO43−-P, the ammonium removal rate and nitrite removal rate decreased to 0.45 and 0.43 kg/(m3⋅d), respectively. During the 158-day operation, MAB was still the dominant strain, but its relative abundance decreased by 15.4% at 400 mg/L PO43−-P. Besides, the presence of sediments stimulated the production of extracellular polymeric substances and the maximum yield reached 11.25 mg/g⋅wet weight at 200 mg/L PO43−-P.

Bromate (BrO3−) is a predominant undesired toxic disinfection by-product (DBP) during ozonation of bromide-containing waters. The reduction of BrO3− by zero valent iron (ZVI) and its effect on formation of organic halogenated DBPs during chlorination were investigated in this study. The presence of ZVI could reduce BrO3− to bromide (Br−), and Br− formed could be transformed to free bromine (HOBr/OBr−) during chlorination, further leading to organic brominated (Br-) DBPs formation. Formation of DBPs during chlorination, including trihalomethanes (THMs) and haloacetonitriles (HANs) was detected under different conditions. The results showed that when ZVI dosage increased from 0 to 1 g L−1, the formation of Br-DBPs (e.g., TBM and DBCM) was significantly improved, while the formation of Cl-DBPs (e.g., TCM, TCAN and DCAN) reduced. Higher ZVI dosage exhibited inhibitory effect on Br-DBPs formation due to the competition between ZVI and free chlorine (HOCl/OCl−). The bromine substitution factor (BSF) of THMs significantly decreased from 0.61 ± 0.06 to 0.22 ± 0.02, as the pH was raised from 5.0 to 9.0. Besides, the increase of initial BrO3− concentration significantly improved the formation of Br-DBPs and decreased the formation of Cl-DBPs, leading to an obvious rise on the BSF of THMs. As the initial concentration of HOCl increased, all THMs and HANs gradually increased. Moreover, the analysis based on the cytotoxicity index (CTI) of the determined DBPs showed that reduction of BrO3− by ZVI during chlorination had certain risks in real water sources, which should be paid attention to in the application.

Vacuum ultraviolet/ultraviolet (VUV/UV) process has been applied to water treatment recently, but little is known about its efficacy and mechanism for pesticide degradation. This study investigated the degradation kinetics and mechanism of a typical organophosphorus pesticide, dimethoate (DMT) by VUV/UV, and then the economic feasibility was assessed. DMT degradation followed well the pseudo-first-order reaction kinetics at an initial concentration of ≤5.0 mg L−1. DMT was degraded by 97.8% after 10 min of VUV/UV exposure (VUV fluence = 12 mJ cm−2), whereas by only 5.2% after 10 min of UV exposure (UV fluence = 156 mJ cm−2). The apparent quantum yield of DMT degradation by VUV/UV was determined to be 0.19, and at most 50.7% of hydroxyl radicals (HO•) generated from VUV photolysis of water could be utilized for DMT degradation. As the pH increased from 5.0 to 9.0, the DMT degradation rate decreased from 0.43 to 0.23 min−1. DMT degradation pathways in the VUV/UV process were proposed based on identified organic intermediates and inorganic ions. SO42− was first released due to HO• attack on the S P bond of DMT, which governed the DMT degradation efficiency; while the release of PO43− was pertinent to the DMT mineralization efficiency. DMT solution toxicity was significantly reduced after VUV/UV treatment. An electrical energy-per-order (EEO) value of 0.57 kWh m−3 Order−1 demonstrated the economic feasibility of the VUV/UV process for DMT removal in small-scale drinking water treatment.

Salt stress can be naturally overcome by marine anammox bacteria (MAB), while their low growth rate and sensitivity to operational conditions are still challenges for the application of anammox. To enhance the enrichment of MAB and decipher the effects of ultraviolet (UV) irradiation on MAB, UV was introduced in the nitrogen removal of MAB treating nitrogen-laden saline wastewater for the first time. The results indicated that MAB were resistant to a fairly high UV-C dose, 12000 mJ/cm2. Their relative abundance was enhanced by 1.2 folds under 12000 mJ/cm2 UV-C. However, the relative abundance of Actinobacteria, Acidobacteria, Chloroflexi and Marinicella were greatly dropped with enhanced UV-C dose. The tolerance mechanism was diversified, e.g. excessive extracellular polymeric substances, special structure of MAB and interspecific competition/cooperation. Although further study was still needed, the findings shed a light on MAB enrichment and exploited great potentials of MAB in nitrogen-laden saline wastewater treatment.

Microplastic (MP) contamination in water has garnered significantly global concerns. The MP removal particularly challenges when the particle size decreases to several microns and other contaminants co-exist. This study used the coagulative colloidal gas aphrons (CCGAs) to simultaneously remove the micron-scale MP particles (~5 µm in diameter) and dissolved organic matter (DOM). Carboxyl-modified poly-(methyl methacrylate) (PMMA) and unsurface-coated polystyrene (PS) were chosen as target MPs. Over 94% of PS particles and almost 100% of color were simultaneously removed with lower CCGA consumption than the scenarios with either contaminant in water. The PMMA removal was not as high as the PS removal since the HA polyanions could compete with the negatively-charged PMMA for CCGAs. High salinity reduced the removal of HA by changing its interfacial behaviors without impacting the MP separation. In river water or influent of wastewater treatment plant, the MP particles were almost completely eliminated whereas the DOM (tyrosine-like or tryptophan-like) was partially removed. The fluorescence quenching titration revealed that CCGAs preferably captured the free DOM and the DOM-coated MP particles through complexation interaction. The study denoted that the CCGA system could be a robust tool for efficiently and synergistically removing micron-scale MPs and DOM from different water matrixes.

Upgrades of wastewater treatment plant (WWTP) and full-scale application of additional advanced oxidation processes have been proven to be effective in reducing the nutrient emissions to the environment; however, the impacts of WWTP upgrades on the receiving waters with regard to the occurrence and ecological risks of pharmaceuticals are still unclear. In this study, 27 pharmaceuticals with diverse physicochemical properties were monitored in four rivers in Beijing, each of which was heavily impacted by a large-scale WWTP. Three-year sampling campaigns were conducted, covering the periods before and after the WWTP upgrades. The results show that the newly added combined treatment processes (e.g., biological filter, ultrafiltration, ozonation, and NaClO disinfection) reduced the total pharmaceutical concentrations in the effluents by 45–74%. The composition profiles reveal that the upgrades of two studied WWTPs resulted in a significant reduction of pharmaceutical concentrations in the receiving rivers, while little impacts were observed for the other rivers. The risk assessment shows that the acute toxic pressures in the studied rivers were generally low and the WWTP upgrades were conducive to reduce the risks for most of pharmaceuticals. However, erythromycin and ofloxacin still posed high risk, indicating the potential adverse effect of pharmaceuticals on aquatic environment.

Sodium hydroxide treated rice hulls were investigated to preconcentrate, remove, and recover metal ions including Be2+, Al3+, Cr3+, Co2+, Ni2+, Cu2+, Zn2+, Sr2+, Ag+, Cd2+, Ba2+, and Pb2+ in both batch mode and column mode. Sodium hydroxide treatment significantly improved the removal efficiency for all metal ions of interest compared to the untreated rice hull. The removal kinetics were extremely fast for Co, Ni, Cu, Zn, Sr, Cd, and Ba, which made the treated rice hull a promising economic green adsorbent to preconcentrate, remove, and recover low-level metal ions in column mode at relatively high throughput. The principal removal mechanism is believed to be the electrostatic attraction between the negatively charged rice hulls and the positively charged metal ions. pH had a drastic impact on the removal for different metal ions and a pH of 5 worked best for most of the metal ions of interest. Processed rice hulls provide an economic alternative to costly resins that are currently commercially available products designed for metal ion preconcentration for trace metal analysis, and more importantly, for toxic heavy metal removal and recovery from the environment.

Cast iron pipes are commonly applied in drinking water distribution systems (DWDSs); peroxymonosulfate (PMS) is a promising alternative for drinking water disinfection; organic micropollutants is still present in drinking water after waterworks' treatment. However, iron corrosion products may affect the reactions between a disinfectant and organic micropollutants. The study investigated the transformation of iopamidol (IPM) and atrazine (ATZ) by PMS under the catalysis of a composite iron corrosion product (Fe/Fe

This study investigated the occurrence and removal of 29 pesticides in 4 drinking water treatment plants (DWTPs) with conventional and advanced treatment processes (i.e., ozonation + biological activated carbon, and ultrafiltration) in Shanghai, China from 2018 to 2019. The concentration levels of target pesticides in raw waters ranged from below the limit of quantification (LOQ) to 2391.3 ng L