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Trihalomethanes (THM), a major class of disinfection by-products, are widespread and are associated with adverse health effects. We conducted a global evaluation of current THM regulations and concentrations in drinking water. We included 120 countries (∼7000 million inhabitants in 2016), representing 94% of the world population. We searched for country regulations and THM routine monitoring data using a questionnaire addressed to referent contacts. Scientific and gray literature was reviewed where contacts were not identified or declined participation. We obtained or estimated annual average THM concentrations, weighted to the population served when possible. Drinking water regulations were ascertained for 116/120 (97%) countries, with 89/116 (77%) including THM regulations. Routine monitoring was implemented in 47/89 (53%) of countries with THM regulations. THM data with a varying population coverage was obtained for 69/120 (58%) countries consisting of ∼5600 million inhabitants (76% of world's population in 2016). Population coverage was ≥90% in 14 countries, mostly in the Global North, 50–89% in 19 countries, 11–49% among 21 countries, and ≤10% in 14 countries including India, China, Russian Federation and Nigeria (40% of world's population). An enormous gap exists in THM regulatory status, routine monitoring practice, reporting and data availability among countries, especially between high- vs. low- and middle-income countries (LMICs). More efforts are warranted to regulate and systematically assess chemical quality of drinking water, centralize, harmonize, and openly report data, particularly in LMICs. We acknowledge support from the Spanish Ministry of Science and Innovation through the “Centro de Excelencia Severo Ochoa 2019–2023″ Program (CEX2018–000806-S) and support from the Generalitat de Catalunya through the CERCA Program, and from the University of South Carolina's Magellan scholarship and Honors College. This work was funded by the 7th Framework Programme EXPOSOMICS Project (Grant agreement 308610).

This research investigates the effects of landfill leachate effluent concentrations from moving bed biofilm reactor (MBBR) on stress-induced Chlorella vulgaris and Scenedesmus armatus lipid production and post-treatment micropollutant degradation. The effluent concentrations were varied between 25%, 50%, 75%, and 100% (v/v). The landfill leachate influent was treated using two-stage moving bed biofilm reactor under 24 h and 18 h hydraulic retention time (HRT). The results indicated that the effluent concentration was positively correlated with the stress-induced microalgae lipid production in the post-treatment of residual micropollutants. C. vulgaris and S. armatus completely remove residual micropollutants in the effluent. The superoxide dismutase and peroxidase activity were positively correlated with the cellular lipid content. The lipid content of C. vulgaris and S. armatus cultivated in the 18 h HRT effluent were 31-51% and 51-64%, while those in the 24 h HRT effluent were 15-16% and 5-19%. The optimal condition of microalgae cultivation for the post-treatment of residual micropollutants was 50-75% (v/v) effluent concentrations under 18 h HRT, achieving the highest lipid production of 113-116 mg/L for C. vulgaris and 74-75 mg/L for S. armatus. Essentially, the MBBR landfill leachate effluent holds promising potential as a substrate for microalgae lipid production.

The research aims for the simultaneous use of chlorine and UV irradiation (UV/Chlorine) to decolorize and detoxify Navy Blue 250 (NB250) and raw dye wastewater. The UV/Chlorine was the most effective in removing NB250 and color intensity (American Dye Manufacturers Institute, ADMI unit). The UV/Chlorine removed NB250 approximately 1.47–1.50 times faster than chlorination alone. The degradation constants in UV/Chlorine were 0.3317 mM-1min-1 and 0.3384 mM-1min-1 for NB250 and its ADMI color intensity, respectively. The optimum pH for decolorization was between 6 and 7. The UV/Chlorine with a chlorine dose of 1.0–2.0 mM was recommended for decolorization to meet the industrial discharge standard (300 ADMI). Reactive chlorine species (RCS) were more significant oxidants for NB250 removal than HO•. The presence of NB250 inhibited the germination of morning glory (Ipomoea aquatica) seeds, and exposure to raw dye wastewater (color = 6,658 ± 227 ADMI) completely inhibited seed germination. However, the samples treated by the UV/Chlorine were less toxic to seed germination and root growth. Therefore, the UV/Chlorine has a high potential in the decolorization and detoxification of dye wastewater. This is the first study to use the UV/Chlorine to treat industrial dye wastewater.

Metal Organic Frameworks (MOFs) represent a promising class of metallic catalysts for reduction of nitrogen-containing contaminants (NCCs), such as 4-nitrophenol (4-NP). Nevertheless, most researches involving MOFs for 4-NP reduction employ noble metals in the form of fine powders, making these powdered noble metal-based MOFs impractical and inconvenient for realistic applications. Thus, it would be critical to develop non-noble-metal MOFs which can be incorporated into macroscale and porous supports for convenient applications. Herein, the present study proposes to develop a composite material which combines advantageous features of macroscale/porous supports, and nanoscale functionality of MOFs. In particular, copper foam (CF) is selected as a macroscale porous medium, which is covered by nanoflower-structured CoO to increase surfaces for growing a cobaltic MOF, ZIF-67. The resultant composite comprises of CF covered by CoO nanoflowers decorated with ZIF-67 to form a hierarchical 3D-structured catalyst, enabling this ZIF-67@Cu foam (ZIF@CF) a promising catalyst for reducing 4-NP, and other NCCs. Thus, ZIF@CF can readily reduce 4-NP to 4-AP with a significantly lower Ea of 20 kJ/mol than reported values. ZIF@CF could be reused over 10 cycles and remain highly effective for 4-NP reduction. ZIF@CF also efficiently reduces other NCCs, such as 2-nitrophenol, 3-nitrophenol, methylene blue, and methyl orange. ZIF@CF can be adopted as catalytic filters to enable filtration-type reduction of NCCs by passing NCC solutions through ZIF@CF to promptly and conveniently reduce NCCs. The versatile and advantageous catalytic activity of ZIF@CF validates that ZIF@CF is a promising and practical heterogeneous catalyst for reductive treatments of NCCs.

This research investigates the use of propionate-cultured sludge to enhance methane (CH

The scarcity of water resources and climatic changes are among the factors facing many countries of the world. Also, conflicts between some countries over water resources are a new threat that threatens to lose large quantities that were received by these countries. Therefore, wastewater treatment and reuse provide a nonconventional water resource. The treatment and reuse reduce pollution of drinking water resources as a result of discharging untreated wastewater. Thereby reduces the spread of epidemic diseases. Decentralized low-cost technologies that do not consume a lot of energy are one of the important solutions that draw the attention of decision-makers in many countries. The integration of the upflow anaerobic sludge blanket reactor and different posttreatment systems such as constructed wetlands, downflow hanging sponge, and downflow hanging nonwoven fabric reactor.

This research comparatively investigates the biotoxicity of landfill leachate effluent from acclimatized and non-acclimatized sludge two-stage activated sludge (AS) systems. Both AS systems were operated with two leachate influent concentrations: moderate (condition 1) and elevated (condition 2). The biotoxicity of AS effluent of variable concentrations (10, 20, and 30% (v/v)) was assessed by the mortality rates of common carp (Cyprinus carpio) and glutathione-S-transferase (GST) enzyme activity. The treatment efficiency of the acclimatized sludge AS system for organic and inorganic compounds and nutrients (BOD, COD, TKN, NH4+, PO43−) were 75–96% under condition 1 and 79–93% under condition 2. The non-acclimatized sludge AS system achieved the treatment efficiency of 70–91% under condition 1 and 66–90% under condition 2. The acclimatized sludge AS system also achieved higher biodegradation of trace organic compounds, especially under condition 1. The effluent from acclimatized sludge AS system was less toxic to the common carp, as evidenced by lower mortality rates and higher GST activity. The findings revealed that the acclimatized sludge two-stage AS system could be deployed to effectively treat landfill leachate with moderate concentrations of compounds and trace organic contaminants. The acclimatized sludge AS is an efficient wastewater treatment solution for developing countries with limited technological and financial resources.

The study aims to simultaneously control micropollutants and bromate formations by using ozonation and peroxone process. The batch experiments were run with variations in specific ozone dose (SOD) and hydrogen peroxide-to-ozone (H2O2/O3) ratio. Based on the removal by ozonation and peroxone, micropollutants were categorized into three groups: non-reactive compounds (i.e. amidotrizoate), moderately reactive compounds (i.e. metoprolol, acesulfame potassium, bezafibrate, and benzotriazole), and highly reactive compounds (i.e. carbamazepine and diclofenac). For ozonation and peroxone process, the removals for highly reactive compounds and moderately reactive compounds were 82–99% and 29–99%, respectively. The removal of amidotrizoate was not observed in this study. The effect of ozonation on micropollutant removals was similar to the peroxone process. However, differences in bromate formation were observed. Bromate formation depended on the SOD, while addition of hydrogen peroxide suppressed the bromate formation. The peroxone process at the H2O2/O3 ratio of 0.3 was recommended to bromide-containing water below 100 µg·L−1 for simultaneous control of micropollutants and bromate. Enhancement in micropollutant removals, except for the non-reactive groups, was achieved with either higher SOD or the addition of hydrogen peroxide to ozonation. The micropollutant removal predicted from the second-order kinetic reaction with ozone and •OH exposures was higher than the observed data.

This research comparatively investigated the effects of effluents from three biological wastewater treatment systems on the phytotoxicity, seed germination, and accumulation of micropollutants and heavy metals in plants irrigated with the effluents under study. The three biological wastewater treatment systems were two-stage activated sludge (AS), two-stage moving bed bioreactor (MBBR), and two-stage moving bed bioreactor with microfiltration (MBBR/MF). The systems were operated in parallel with identical landfill leachate concentrations under different hydraulic retention time (HRT) (24, 18, and 12 h). The phytotoxicity experiments were carried out with golden pothos (Epipremnum aureum) planted in soil irrigated with AS, MBBR, and MBBR/MF effluent and those raised in the effluent (without soil). The malondialdehyde (MDA) concentrations in the plants were used to determine the plant stress. To evaluate the effect of water reuse to agricultural crops, this research measured the seed germination rates of lettuce (Lactuca sativa) irrigated with AS, MBBR, and MBBR/MF effluent and the accumulation of micropollutants and heavy metals. The results showed that under 24 h HRT, the AS, MBBR, and MBBR/MF systems could achieve high treatment efficiency of organics and nutrients and micropollutant degradation (73.4 – 100%). With shorter HRT (18 and 12 h), the treatment efficiency and micropollutant degradation of MBBR and MBBR/MF remained relatively unchanged (68.7 – 100%), unlike in the AS system. The MBBR/MF effluent exhibited the comparatively lowest MDA concentrations. Furthermore, the MBBR/MF effluent minimally affected the growth of lettuce, as evidenced by highest seed germination rates. No micropollutants and heavy metals were present in lettuce irrigated with MBBR/MF effluent. However, traces of bisphenol A and di-(ethylhexyl)-phthalate were detected in lettuce watered with AS and MBBR effluents. As a result, the MBBR/MF system is operationally and environmentally ideal for treating landfill leachate for high-quality effluent which can be reused to irrigate crop and replenish surface water.

Valorization of lignin derivative, vanillic alcohol (VL), to vanillic aldehyde (VE) represents a critical move towards sustainable utilization of lignocellulosic biomass. As conversion of VL into VE requires the specific oxidation of alcohol moiety of VL into an aldehyde moiety, it is crucial to develop effective processes to selectively oxidize the alcohol group of VL. Lately, 2,2,6,6-tetramethylpiperidin-oxyl (TPO) accompanied with Cu has been validated as a promising oxidative catalytic process for oxidizing alcohols. Since Cu-O cluster plays an important role in TPO-based oxidation of alcohols, and N-O moiety would facilitate the catalytic cycle of TPO regeneration, an interesting solid-phase material, copper hydroxide nitrate (CHN) is proposed here for the first time for co-catalyzing TPO to oxidize VL into VE. In particular, a convenient method is developed to fabricate CHN with a special morphology of 2D elliptical nanopetal, forming nanopetal CHN (NPCHN). As TPO or NPCHN could not convert VL into VE separately, the combination of NPCHN/TPO quickly oxidizes VL to VE with a selectivity of 100%. With higher concentrations of NPCHN and TPO, the conversion efficiency of VL into VE could be considerably enhanced and reached ~99% of CVL and YVE with SVE = 100%. The extended reaction duration and elevated reaction temperature would also lead to the significantly high VL conversion efficiency, which also outperforms many reported conversion efficiencies. NPCHN could be also recyclable for co-catalyzing with TPO for converting VL to VE. These findings confirm that NPCHN is certainly an advantageous heterogeneous catalyst for valorizing VL via selective oxidation.

The objective of the study is to evaluate the performance of conventional treatment process (i.e., coagulation, flocculation, sedimentation and sand filtration) on the removals of haloacetonitrile (HAN) precursors. In addition, the removals of HAN precursors by photo-based advanced oxidation processes (Photo-AOPs) (i.e., UV/H 2 O 2 , UV/O 3 , and UV/H 2 O 2 /O 3 ) are investigated. The conventional treatment process was ineffective to remove HAN precursors. Among Photo-AOPs, the UV/H 2 O 2 /O 3 was the most effective process for removing HAN precursors, followed by UV/H 2 O 2 , and UV/O 3 , respectively. For 20min contact time, the UV/H 2 O 2 /O 3 , UV/H 2 O 2 , and UV/O 3 suppressed the HAN formations by 54, 42, and 27% reduction. Increasing ozone doses from 1 to 5 mgL −1 in UV/O 3 systems slightly improved the removals of HAN precursors. Changes in pH (6–8) were unaffected most of processes (i.e., UV, UV/H 2 O 2 , and UV/H 2 O 2 /O 3 ), except for the UV/O 3 system that its efficiency was low in the weak acid condition. The pseudo first-order kinetic constant for removals of dichloroacetonitrile precursors ( k′ DCANFP ) by the UV/H 2 O 2 /O 3 , UV/H 2 O 2 and standalone UV systems were 1.4–2.8 orders magnitude higher than the UV/O 3 process. The kinetic degradation of dissolved organic nitrogen (DON) tended to be higher than the k′ DCANFP value. This study firstly differentiates the kinetic degradation between DON and HAN precursors.

Indirect potable reuse systems, which consist of wastewater treatment (WWT) and soil aquifer treatment (SAT), offer advantages such as their low cost and the underground storage of reuse water. In this study, the dissolved organic matter (DOM) profile of a sequential treatment system (i.e. WWT followed by SAT) was investigated using a pilot-scale SAT reactor. In addition, the biological DOM removal characteristics in the vadose zone of the SAT, which were found to play an important role in DOM removal for the entire SAT, were investigated using lab-scale reactors (LSRs). Composition of the removed DOM by WWT and SAT showed that the majority fraction of the removed DOM was different for the WWT (hydrophobic neutral 27.9%) and SAT (hydrophobic acids (HoA) 29.1%), suggesting that SAT exhibits unique DOM removal characteristics that contribute to water reclamation. Biological DOM removal was confirmed using the LSRs, and changes in the DOM removal characteristics 10–20 cm from the top of the vadose zone in the LSRs were revealed on the basis of the DOM fractionation and a BIOLOG assay, suggesting that microbial activity in the lower layer of the vadose zone contributed to the unique removal of the HoA fraction in the SAT.

This research aimed to investigate the degradation of natural organic matter responsible for the formation of trihalomethane (THM), haloacetic acid (HAA) and haloacetonitrile (HAN) during ultraviolet (UV) photolysis and a co-exposure of UV with chlorine (UV/chlorine) and chloramine (UV/chloramine). Low pressure UV (LPUV) and vacuum UV (VUV) lamps were used for photolysis. VUV and LPUV irradiation changed aromatic/unsaturated structures to aliphatic ones, resulting in decreased THM and HAN formation. Following irradiation for 60 min, LPUV decreased THM and HAN by 16% ± 2% and 20% ± 6%, respectively. VUV decreased THM and HAN formation by 23% ± 3% and 20% ± 8%, respectively. HAA formation increased following photolysis. UV/chlorine treatment decreased THM, HAA and HAN. Higher chlorine doses had an inversely proportional relationship with THM and HAN formation. A chlorine dose of 4 mg·L−1 led to the greatest reductions, corresponding to 42% ± 2%, 10% ± 10% and 18% ± 6% for THM, HAA and HAN, respectively. UV/chloramine decreased the formation of THM more than UV/chlorine. With a chloramine dose of 4 mg·L−1, THM, HAA and HAN formation decreased by 74% ± 10%, 10% ± 10% and 11% ± 10%, respectively. This study showed the potential use of UV/chlor(am)ine for controlling the formation of THM, HAA and HAN.

The study attempted to determine the hydraulic retention time (HRT) required for soil aquifer treatment (SAT) to reclaim water as potable water in an aspect of controlling disinfection byproduct (DBP) precursors. In order to evaluate the removal of DBP precursors, the uniform formation condition was used to estimate the formations of trihalomethanes (THMs) and haloacetic acids (HAAs). Effluent water from anaerobic-anoxic-oxic processes (A2O water) was fed through soil columns at different HRTs. Sand with low organic content and less specific surface area was selected to represent the ‘worst available case’ of subsurface environment in Japan. Overall, annual data (n ≥ 14) indicated that the average concentrations of THMs and HAAs for water passed through SAT with HRT less than 7 days were below the standard of drinking water. However, risks of exposure to THMs and HAAs were observed. Increasing HRT to 30 days resulted in the concentrations of regulated THM and HAA species lower than the 10% of the drinking water standard values, except for dichlorobromoform. Therefore, a treatment unit for bromide ion removal (e.g., anion exchanger) prior to chlorination is recommended to lower the risk levels of exposure to dichlorobromoform.

This work aimed to enhance the photocatalytic degradation of methyl orange (MO) by crystallinity transformation of titanium dioxide (TiO2 ). In addition, the kinetic degradation of MO was determined. To transform its crystallinity, TiO2 was synthesized using a sol-gel method and calcined at between 200°C to 600°C. Calcination at a temperature of 250°C resulted in TiO2 that showed the best performance, corresponding to MO removal of 87% ± 7%. MO removal by TiO2 calcined between 250°C to 400°C was higher than for commercial TiO2 powder (Sigma-aldrich) (62% ± 4%). TiO2 with a small crystallite size and high anatase fraction enhanced the photocatalytic degradation of MO, while the specific surface area and surface roughness seemed to play a minor role. The photocatalytic degradation of MO was NaCl-independent, while the photocatalytic activity increased with decreased pH. Reused TiO2 showed similar photocatalytic degradation of MO compared with pristine TiO2 , at 84 ± 2%. The oxidation kinetics of TiO2 calcined at 250°C were fitted to the Langmuir-Hinshelwood model (R2 = 0.9134). The kr and Ks values were 0.027 mg L-1 min-1 and 0.621 L/mg, respectively. Crystallinity transformation was a major factor in the enhancement of photocatalytic degradation of MO. PRACTITIONER POINTS: Photocatalytic activity of TiO2 depends on calcination temperature, pH, and a number of UVC lamps. TiO2 with a small crystallite size and high anatase fraction enhanced the photocatalytic degradation of MO.

Occurrence of estrone (E1) and 17β-estradiol (E2) in the environment has attracted the public attention since E1 and E2 cause estrogenicity in aquatic microorganisms. Microalgae cultivation in wastewater is considered as an economical practice since microalgae can be used for not only pollutant removals, but also as energy resources. This research aims to investigate the removals of E1 and E2 in synthetic wastewater by microalgae (i.e. Chlorella vulgaris and Scenedesmus obliquus). At the steady state, S. obliquus removed E1 and E2 by 91% and 99%, respectively. C. vulgaris removed E1 and E2 by 52% and 99%, respectively. Interestingly, the occurrence of E1 was observed when E2 was degraded by microalgae. The predominant mechanism for E1 and E2 removals was biodegradation, followed by adsorption. The adsorption kinetic and isotherm for both E1 and E2 can be described by the pseudo-second-order and Freundlich model. The addition of E1 and E2 resulted in a higher lipid content of microalgae by 1–9%.

The objective of this study was to remove regulated DBP precursors by using ozonation and peroxone process (H 2 O 2 /O 3 ). Regarding formation potentials of trihalomethanes (THMs) and haloacetic acids (HAAs), the role of chloride in chlorination and ozonation/peroxone processes was revealed. The organic compounds in water samples from rapid sand filtration preferably yielded the THM formation potentials, rather than HAAs. Ozonation with the typical applied doses (1–5 mg L −1 ) was ineffective for removals of THM and HAA precursors. The peroxone process only decreased the formation potentials of THMs. The reduction of THMs by the peroxone process resulted from decreases in either chloroform or dibromochloromethane. However, the limitation was found in the H 2 O 2 /O 3 ratios of 2.0–3.0. The removals of HAA precursors were much more difficult than that of THM precursors by ozonation and peroxone processes. The oxidation of organic compounds was able to promote the HAA formations. Ozonation with the typical ozone doses increased the chloroform formations, while decreases in bromide-containing THMs occurred. Effect of ozonation on changes in HAAs speciation was unclear. The peroxone process likely promoted the dichloroacetic acids and trichloroacetic acids. The presence of chloride (1–5 g L −1 ) highly enhanced the THM and HAA formation potentials. NaCl addition greatly increased the bromide-containing THMs, while the chloroform decreased. For HAAs, the presence of chloride promoted the bromide-containing HAAs and monochloroacetic acids. The presence of chloride played a role as a promotor for strong chlorinating agents in chlorination, rather than as a scavenger in ozonation and peroxone processes.

The objective of the study is to evaluate the performance of conventional treatment process (i.e., coagulation, flocculation, sedimentation and sand filtration) on the removals of haloacetonitrile (HAN) precursors. In addition, the removals of HAN precursors by photo-based advanced oxidation processes (Photo-AOPs) (i.e., UV/H

To demulsify oil-in-water (O/W) emulsions, a zinc-based zeolitic imidazolate framework (ZIF-8) was employed for the first time to remove oil droplets from water. ZIF-8 exhibits a high surface area and positive surface charges, making it a suitable adsorbent to adsorb negatively-charged oil droplets. Adsorption behaviors of oil droplets to ZIF-8 were studied by analyzing the adsorption kinetics and isotherm with theoretical models. The activation energy of adsorption of oil droplets to ZIF-8 was determined as 24.1kJmol(-1). The Langmuir-Freundlich (L-F) model was found to be most applicable to interpret the isotherm data and the predicated maximum adsorption capacity of ZIF-8 can reach 6633mgg(-1), revealing a promising capability of ZIF-8 for demulsification. Factors influencing the adsorption of oil droplets to ZIF-8 were investigated including temperature, pH, salt and surfactants. The adsorption capacity of ZIF-8 for oil was improved at elevated temperatures, whereas alkaline condition was unfavorable for the adsorption of oil droplets due to the electrostatic repulsion at high pH. The adsorption capacity of ZIF-8 remained similar in the presence of NaCl but it was reduced in the presence of surfactants. ZIF-8 was regenerated by a simple ethanol-washing method; the regenerated ZIF-8 exhibited more than 85% of regeneration efficiency over six cycles. Its crystalline structure also remained intact after the regeneration. These characteristics indicate that ZIF-8 can be a promising and effective adsorbent to remove oil droplets for demulsification of O/W emulsions.

Simultaneous control of chlorinous odor and bromate ion formation was attempted by using an advanced oxidation process (AOP, O3/H2O2). Also, the relationship between trichloramine (NCl3, a suspected odor compound in drinking water) and chlorinous odor in drinking water was studied through a headspace GC-MS analysis and the triangle sensory test. Odor strength after chlorination decreased by more than 50% for the samples pretreated with conventional ozonation and AOP. The change of hydroxyl radical exposure (•OH-ct) when AOP was applied did not show the clear difference in terms of the removal of chlorinous odor compared with conventional ozonation, but AOP was better for the control of bromate ion. Trichloramine seemed not to be a major odor compound in the chlorinated water of this experiment. The change of ammonium ion, bromide ion, and ozone dose did not clearly affect the efficiency of odor removal.

To identify the primary fraction of dissolved organic matter (DOM) responsible for chlorinous odor, waters treated by the conventional treatment (i.e., coagulation, flocculation, sedimentation and rapid sand filtration (RSF)) and ozonation were characterized by a fractionation technique prior to chlorination. Furthermore, chlorinous odor strengths originated from organic fractions were compared with that resulted from trichloramine (NCl3). Odor strengths and trichloramine concentrations were determined by the triangle sensory test and head space-GC/MS, respectively. The major DOM fraction for outlet water of RSF was hydrophobic acid (HoA), whereas the hydrophilic acid (HiA) fraction was dominant in the ozonated water. For a fixed DOC level (1 mgC/L), the base (Bas) or hydrophilic base (HiB) fraction was found to be the major organic precursor of chlorinous odor for the effluent of RSF. Even the mass percentages of DOM fractions in RSF water were considered, Bas was the major DOM fractions responsible for chlorinous odor. For ozonated water, two major precursors of chlorinous odor were HiA and hydrophilic neutral (HiN) fractions. Furthermore, the influence of trichloramine on chlorinous odor intensity for ozonated water should not be negligible. Under variation of seasonal organic contents, changes in precursors of chlorinous odor were observed.