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Reusing treated wastewater can effectively alleviate water shortages and water contamination problems but depends on ensuring the safety of the reclaimed water that is produced. The operating and management conditions for water reclamation plants in China have been changed since the outbreak of the COVID-19 epidemic in China at the end of 2019 to prevent emerging viruses being spread through wastewater treatment processes and the reclaimed water that is produced. Removal of pathogens and trace organic compounds (e.g., pharmaceuticals and personal care products and endocrine disrupting chemicals) in a real water reclamation plant after the start of COVID-19 epidemic was studied. Disinfection byproduct formation caused by chlorine being added to meet disinfection requirements was also assessed. The pathogenic microorganism concentrations in effluent were <2 (most probable number)/L, and the removal rates for most trace organic compounds were >80% when advanced treatments were performed using ozone, ultraviolet light, and chlorine doses of 2 mg/L, 20.5 mJ/cm 2 , and 2-3 mg/L, respectively. The main disinfection byproduct produced at a chlorine dose of 2 mg/L and a residence time of 1 h was chloroform (at concentrations <15 μg/L). The results indicated that the water reclamation processes with modified conditions gave high pathogen and trace organic compound removal rates and reasonably well-controlled disinfection byproduct concentrations., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Interactions of trace organic compounds (TOrCs) with polymeric nanofiltration (NF) membrane can affect their rejection. It is desirable to investigate whether solubility which depends on the free energy of interaction between these solutes and water correlates with rejection/adsorption and the potential to be incorporated in the partitioning terms of current NF model. A total of ten neutral disinfection by-products (DBPs) were selected as the model compounds for TOrCs to comprehensively investigate the role of solubility on rejection and adsorption. Pearson correlation analysis indicated that the correlation between MW and rejection ratio was highly significant (r = 0.778, p = 0.008) and that between solubility and rejection ratio was moderately significant (r = -0.636, p = 0.48) in a cross-flow system. By fitting Freundlich equation from adsorption isotherm experiment, the adsorption affinity (K f ) of DBPs was roughly correlated with their solubility with regard to the comparison of n value with 1. α was then introduced as a parameter of solute-membrane interaction from the perspective of partitioning term in the hydrodynamic model. Exponential relationship can be observed between the solubility and α, demonstrating the possibility of incorporating solubility into the partitioning terms in NF model to accurately predict the rejection of DBPs.

A detailed kinetic model comprised of mass transport (k tra ), pore diffusion (k dif ), adsorption and reduction reaction (k rea ), was developed to quantitatively evaluate the effect of corrosion films on the removal rate (k obs ) of halogenated compounds by metallic iron. Different corrosion conditions were controlled by adjusting the iron aging time (0 or 1 yr) and dissolved oxygen concentration (0-7.09 mg/L DO). The k obs values for bromate, mono-, di- and tri-chloroacetic acids (BrO 3 - , MCAA, DCAA and TCAA) were 0.41-7.06, 0-0.16, 0.01-0.53, 0.10-0.73 h -1 , with k tra values at 13.32, 12.12, 11.04 and 10.20 h -1 , k dif values at 0.42-5.82, 0.36-5.04, 0.30-4.50, 0.30-3.90 h -1 , and k rea values at 14.94-421.18, 0-0.19, 0.01-1.30, 0.10-3.98 h -1 , respectively. The variation of k obs value with reaction conditions depended on the reactant species, while those of k tra , k dif and k rea values were irrelevant to the species. The effects of corrosion films on k dif and k rea values were responsible for the variation of k obs value for halogenated compounds. For a mass-transfer-limited halogenated compound such as BrO 3 - , an often-neglected k dif value primarily determined its k obs value when pore diffusion was the rate-limiting step of its removal. In addition, the value of k dif might influence product composition during a consecutive dechlorination, such as for TCAA and DCAA. For a reaction-controlled compound such as MCAA, an increased k rea value was achieved under low oxic conditions, which was favorable to improve its k obs value. The proposed model has a potential in predicting the removal rate of halogenated compounds by metallic iron under various conditions., (Copyright © 2017. Published by Elsevier Ltd.)

Haloacetaldehydes (HAs) are the third prevalent group of disinfection by-products (DBPs) of great health concern. In this study, their formation and speciation during chlorination were investigated for raw and process waters collected at three O3-biological activated carbon (BAC) advanced drinking water treatment plants. The results showed that all HA formation potentials (HAFPs) were highly enhanced whenever ozone was applied before or after conventional treatment. Sand filtration and BAC filtration could substantially reduce HAFPs. Trihalomethanes (THMs) were also measured to better understand the role of HAs in DBPs. Very different from HAFPs, THMFPs kept decreasing with the progress of treatment steps, which was mainly attributed to the different precursors for HAs and THMs. Brominated HAs were detected in bromide-containing waters. Chloral hydrate (CH) contributed from 25% to 48% to the total HAs formed in waters containing 100-150 μg L(-1) bromide, indicating the wide existence of other HAs after chlorination besides CH production. In addition, bromide incorporation factor (BIF) in HAs and THMs increased with the progress of treatment steps and the BIF values of THMs were generally higher than those of HAs. The BAC filtration following ozonation could significantly reduce HA precursors produced from ozonation but without complete removal. The brominated HAFPs in the outflow of BAC were still higher than their levels in the raw water. As a result, O3-BAC combined treatment was effective at controlling the total HAs, whereas it should be cautious for waters with high bromide levels., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

The effects of calcium, cupric, ferrous and ferric ions on the formation of trihalomethanes (THMs) and haloacetic acids (HAAs) were investigated using natural organic matter (NOM), small molecular weight NOM surrogates and natural water samples. The results showed that the effects were greatly dependent on the disinfection byproduct (DBP) precursor structure and molecular weight, and metal ions species. While using NOM as precursors, addition of 4.00 mM calcium ions increased the formation of THMs, dihaloacetic acids (DHAAs) and trihaloacetic acids (THAAs) by 24-47%, 51-61% and 15-25%, respectively. Addition of cupric ions at 0.02 mM increased the formation of THMs and DHAAs by 74-83% and 90-100%, respectively, but decreased the formation of THAAs by 26-27%. Similar effect was not observed when 0.04 mM ferrous or ferric ions were added. The effects of calcium and cupric ions on DBP formation were generally more evident for the NOM surrogates than that for NOM. The primary catalytic effect of calcium ions was due to complexation and less sensitive to molecular structure or weight, while that of cupric ions was attributed to redox reactions and greatly dependent on molecular structure. Both ferric and ferrous iron had substantial effects on the DBP formation of surrogates (citric acid and catechol in particular), which implied that the catalytic effects of ferric and ferrous iron mainly depended on molecular weight. The catalytic effect of cupric ions was also observed on natural water samples, while the effects of calcium, ferrous and ferric ions on natural water samples were not evident., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Hydrolysis could contribute to the loss of trihalomethanes (THMs) in the drinking water at elevated temperatures. This study was aimed at investigating THM hydrolysis pertaining to the storage of hot boiled water in enclosed containers. The water pH value was in the range of 6.1-8.2 and the water temperature was varied from 65 to 95 °C. The effects of halide ions, natural organic matter, and drinking water matrix were investigated. Results showed that the hydrolysis rates declined in the order following CHBrCl2 > CHBr2Cl > CHBr3 > CHCl3. THM hydrolysis was primarily through the alkaline pathway, except for CHCl3 in water at relatively low pH value. The activation energies for the alkaline hydrolysis of CHCl3, CHBrCl2, CHBr2Cl and CHBr3 were 109, 113, 115 and 116 kJ/mol, respectively. No hydrolysis intermediates could accumulate in the water. The natural organic matter, and probably other constituents, in drinking water could substantially decrease THM hydrolysis rates by more than 50%. When a drinking water was at 90 °C or above, the first order rate constants for THM hydrolysis were in the magnitude of 10(-2)‒10(-1) 1/h. When the boiled real tap water was stored in an enclosed container, THMs continued increasing during the first few hours and then kept decreasing later on due to the competition between hydrolysis and further formation. The removal of THMs, especially brominated THMs, by hydrolysis would greatly reduce one's exposure to disinfection by-products by consuming the boiled water stored in enclosed containers., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

The monochloroacetic, dichloroacetic and trichloroacetic acid (MCAA, DCAA and TCAA) removed by metallic iron under controlled dissolved oxygen conditions (0, 0.75, 1.52, 2.59, 3.47 or 7.09 mg/L DO) was investigated in well-mixed batch systems. The removal of CAAs increased first and then decreased with increasing DO concentration. Compared with anoxic condition, the reduction of MCAA and DCAA was substantially enhanced in the presence of O2, while TCAA reduction was significantly inhibited above 2.59 mg/L. The 1.52 mg/L DO was optimum for the formation of final product, acetic acid. Chlorine mass balances were 69-102%, and carbon mass balances were 92-105%. With sufficient mass transfer from bulk to the particle surface, the degradation of CAAs was limited by their reduction or migration rate within iron particles, which were dependent on the change of reducing agents and corrosion coatings. Under anoxic conditions, the reduction of CAAs was mainly inhibited by the available reducing agents in the conductive layer. Under low oxic conditions, the increasing reducing agents and thin lepidocrocite layer were favorable for CAA dechlorination. Under high oxic conditions, the redundant oxygen competing for reducing agents and significant lepidocrocite growth became the major restricting factors. Various CAA removal mechanisms could be potentially applied to explaining the effect of DO concentration on iron efficiency for contaminant reduction in water and wastewater treatment., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

The temperature of drinking water fluctuates naturally in water distribution systems as well as often deliberately heated for household or public uses. In this study, the temperature effect on the formation of disinfection by-products (DBPs) was investigated by monitoring the temporal variations of twenty-one DBPs during the chlorination of a humic precursors-containing water at different temperatures. It was found that chloroform, DCAA, TCAA, DCAN and CH were detected at the considerable level of tens of μg L(-1). The three regulated DBPs (chloroform, DCAA and TCAA) were found increasing with both contact time and water temperature, while the five typical emerging DBPs (DCAN, CH, TCNM 1,1-DCPN and 1,1,1-TCPN) revealed the significant auto-decomposition in addition to the initial growth in the first few hours. Increasing water temperature could enhance the formation rates of all the eight detected DBPs and the decomposition rates of the five emerging DBPs. Further, a kinetic model was developed for the simulation of DBP formation. The validity and universality of the model were verified by its excellent correlation with the detected values of each DBP species at various temperatures. The formation rates of 1,1-DCPN and 1,1,1-TCPN, and the decomposition rate of 1,1,1-TCPN were faster as compared to the other DBPs. And the formation reaction activation energies of CH, DCAN and 1,1-DCPN were relatively large, indicating that their occurrence levels in the finished water were more susceptible to temperature variations., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

An innovative haloacetic acid (HAA) removal process was developed. The process consisted of a zero-valent iron (Fe(0)) column followed by a biologically active carbon (BAC) column that were efficient in degrading tri- and di-HAAs, and mono- and di-HAAs, respectively. The merit of the process was demonstrated by its performance in removing trichloroacetic acid (TCAA). An empty bed contact time of 10 min achieved nearly complete removal of 1.2 μM TCAA and its subsequent products, dichloroacetic acid (DCAA) and monochloroacetic acid (MCAA). HAA removal was a result of chemical dehalogenation and biodegradation rather than physical adsorption. Preliminary kinetic analyses were conducted and the pseudo-first-order rate constants were estimated at ambient conditions for Fe(0) reduction of TCAA and biodegradation of DCAA and MCAA by BAC. This innovative process is highly promising in removing HAAs from drinking water, swimming pool water, and domestic or industrial wastewater., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Water temperature has significant effects on the disinfection by-product (DBP) formation and concentration in many water utilities and distribution systems. To study the temperature effect on the DBP concentration, the uniform formation condition (UFC) test was referred in testing the formation concentration of DBPs [including (trihalomethanes) THMs and (haloacetic acids) HAAs] at different temperatures during chlorination of the humic acid (HA) solution. A kinetic model was consequently proposed to predict DBP concentration during chlorination. Results show that for the three detected DBPs, including chloroform (CHCl3), dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA), increasing temperature could considerably enhance both the DBP formation rates and the maximum DBP concentrations, where the maximum concentrations increase exponentially with the water temperature (R2 > 0.90). By using the data-processing software Origin, the detected DBP values were fitted using the proposed first order kinetic model, and the result showed a strong correlation for each DBP at various temperatures (R > 0.94). The apparent reaction rate constant k was also derived for each DBP. In order to quantify the temperature effect on DBP formation, the Arrhenius Equation was employed to calculate the apparent reaction activation energy for each DBP-22.3, 25.5 and 40.8 kJ x mol(-1) for CHCl3, DCAA and TCAA, respectively. By comparing the model predicted and the detected DBP values at 20 and 30 degrees C, the model showed a strong performance in predicting DBP formation concentrations, which indicated the reliability and validity of this proposed kinetic model.

To understand the present status of the heavy metal (Cr, Cu, Zn, Cd, Pb and Hg) pollution of the sediments in water supply reservoirs in Huizhou, sediment cores were sampled from three representative reservoirs. The heavy metal concentrations were analyzed by ICP-MS, and the pollution status was assessed by geo-accumulation index (Igeo) and potential ecological risk index (RI). In the meantime, the possible sources of the heavy metals were analyzed by the principal component analysis (PCA). In the sediments of the three reservoirs, the test heavy metals had different vertical distribution, some had less change, the others decreased or increased with depth, and the distribution patterns differed with the reservoirs. According to the Igeo, the sediments in the reservoirs were seriously polluted by Zn and Pb (Zn: 49.98-640.29 mg x kg(-1); Pb: 21.94-300.66 mg x kg(-1)), reaching slight to high pollution, and the middle or bottom part of the sediments was slightly polluted by Cu (16.85-45.46 mg x kg(-1)). On the whole, the sediments were not polluted by Cr, Cd and Hg. According to the RI and the potential ecological risk coefficient [Er(i)], the sediments in the three reservoirs were under low potential ecological risk. Based on the PCA and relevant information, the human activities such as mining and smelting, urbanization, and agriculture and forestry had great contribution to the heavy metal pollution. The Zn and Pb pollution mainly originated from mining and smelting, Pb pollution also came from motor vehicle exhaust emission and domestic wastes, and Cu pollution mainly derived from agriculture and forestry.

Core sediments were collected from the riverine, transition and lacustrine zones of Hedi Reservoir in southern China to investigate the spatial distributions of nutrients and heavy metals and assess the potential ecological risk of heavy metals. The total nitrogen (TN) contents of the sediments at three sampling sites are between 2.314-2.427 mg x g(-1), while total phosphorus (TP) contents range from 0.591 mg x g(-1) to 0.760 mg x g(-1), TN contents of the surface sediments increase from the riverine zone to the lacustrine zone, but the TP content in the transition zone is higher than that in the other two sites (riverine zone and lacustrine zone). The mean contents of heavy metals are: 31.094, 46.85, 75.615, 385.739, 0.624 and 0.171 mg x kg(-1) respectively, except Cr, the contents of heavy metals in sediment of lacustrine zone are higher than the sediment of transition zone. In all core sediments, the contents of nutrients and heavy metals decrease from the surface to the bottom of core sediments. Inorganic phosphorus (IP) is the dominant fraction of phosphorus in the sediment and the NaOH-P is the main forms of inorganic phosphorus. The potential ecological risk assessed by using of the highest environmental background values before industrialization as the reference indicates that each single heavy metal only causes slightly pollution, but two heavy metals (Cd and Hg) cause heavy pollution based on the soil environmental background values of Guangdong province. In spite of the slight difference between two kinds of risk assessment, all demonstrated that Cd and Hg resulted in more serious pollution than the other metals and these two metals contributed most to the RI values.

Dissolved organic matter (DOM) in raw water is a precursor for the formation of disinfection by-products (DBPs) during chlorination at a water treatment plant in southern Taiwan. The presence of DOM also has a large impact on the behavior of nanoparticles. The adsorption kinetics of single-walled carbon nanotubes (SWCNTs) was investigated in the presence of DOM as a possible technique for the pretreatment of DBP precursors. pH, ionic strength and temperature are major factors in adsorption tests. Experimental results indicated that adsorption reached equilibrium after 120 min. Additionally, the adsorption capacity of SWCNTs increased with an increasing DOM concentration and decreased with an increasing ionic strength. The optimum adsorption model out of a selection including the Modified Freundlich equation, the Pseudo-first-order equation and Pesudo-second order equation, was the Modified Freundlich equation model. The intraparticle diffusion equation model was also examined. The adsorption process was controlled by pore diffusion that was confirmed by the fits of intra-particle diffusion model. The maximum adsorption capacity was 26.1-20.8 mg/g at 4°C and 45°C. Isotherm adsorption results demonstrated that the adsorption of DOM onto SWCNTs was favorable at a high initial DOM concentration and at low ionic strength, pH and temperature. These findings highlighted the importance of pretreatments and the presence of DOM on the adsorption behavior of nanomaterials.

Adsorption behaviors of phosphate on the desert particulates of inflow Yellow River were investigated in natural water (river water and sea water) and the experimental data was fitted by both the improved Langmuir and Freundlich isotherm adsorption models. The results show that (1) With more clear physical meaning and more reasonable fitting parameters, the improved Langmuir isotherm adsorption model is much better for describing phosphate adsorption on the desert particulates than the improved Freundlich isotherm adsorption model; (2) The maximum phosphorus (P) adsorption capacity Qmac is in the range of 41.322-357.143 mg x kg(-1), which is the biggest in Y2 (Juyanhai Lake particulates). There is remarkable positive correlation between Qmax and organic matter of the particulates (Y1-Y5); (3) Except for Y1 (Badain Jaran Desert particulates), the EPC0 (zero equilibrium P concentration) of the particulates are higher than the concentration of P in corresponding water. The EPC0 of P adsorption on Y1 in Yellow River is lower than P concentration in corresponding water (0.010 mg x L(-1) < 0.053 mg x L(-1)), while the EPC0 of P adsorption on Y1 in Bohai Sea water is higher than the P concentration in their corresponding water (0.109 mg x L(-1) > 0.074 mg x L(-1)), which shows that Y1 adsorbs P from the water of the Yellow River, then it releases its NAP (native adsorbed exchangeable phosphorus) into Bohai Seawater. However, in the process of the P exchange between other desert particulates and their corresponding water, only desorption phenomenon were observed, which means all other desert particulates release P to their corresponding water; (4) The adsorption isotherms of phosphate on the desert particulates of inflow Yellow River are cross-axis-type with over 0.00, a new cross-axis-type adsorption-desorption model, which provide a better explanation for adsorption characteristics of P and for the dual role of natural particulates.

The effects of excess aluminum on water distribution system and human health were mainly attributable to the presences of some aluminum species in drinking water. A prediction model for the concentrations of aluminum species was developed using three-layer front feedback artificial neural network method. Results showed that the reaction rates of both inorganic monomeric aluminum and soluble aluminum varied with reaction time and water quality parameters, such as water temperature, pH, total aluminum, fluoride, phosphate and silicate. Their reaction orders were both three. The reaction kinetic parameters of inorganic monomeric aluminum and soluble aluminum could be predicted effectively applying artificial neural network; the correlation coefficients of k and 1/C0(2) between calculated value and predicted value were both greater than 0.999. Aluminum species prediction results in the drinking water of City M showed that when the concentration of total aluminum was less than 0.05 mg x L(-1), the relative prediction error was large for inorganic monomeric aluminum. When the concentration of total aluminum was above 0.05 mg x L(-1), the model could predict inorganic monomeric aluminum and soluble aluminum concentrations effectively, with relative prediction errors of +/- 15% and +/- 10% respectively.

The effects of aluminum on water distribution system and human health are mainly attributable to their presence in drinking water. Laboratory experiments were performed to investigate the influence of temperature and pH on the distribution of aluminum species applying alum synthetic water. Aluminum species studied in the experiments included monomeric aluminum, soluble aluminum, suspended aluminum, and polymeric aluminum, which were determined by fluorescence spectrophotometry method. Results indicated that suspended aluminum was the major species at pH 6.5, occupied about 62.2% in the total aluminum mass concentration. While at pH above 7.0, monomeric aluminum was the major species; and varied little as reaction time increased. Polymeric aluminum mass concentration was low at studied water quality condition and also varied little as reaction time increased. The influence of temperature on aluminum species distribution was similar to solution pH; and both could be explained by pOH. Aluminum species in drinking water could be controlled by adjusting the pOH value, which provided theoretical guidance for the operation of the water distribution system and aluminum toxicity control.

The residual Al concentration and species distribution of a north Chinese city was surveyed using fluorimetry. Results showed that the highest total Al concentration was 0.078 mg x L(-1) and the mean concentration was 0.038 mg x L(-1), lower than the latest portable water standard of 0.2 mg x L(-1). Inorganic mono-aluminum and inorganic poly-aluminum, the main toxicity-leading species, were also the major existence species with the mean concentration 0.011 mg x L(-1) and 0.013 mg x L(-1) respectively. While organic combined aluminum concentration was quite low. Correlation analysis results showed that the Al concentration and species distribution in a certain pipe line was connected with the water quality. When the distribution system contained more salts and less soluble organic matter, the Al concentration would be controlled in a low level, which was important to guide the local operation.