Simulated Drinking Water Research Articles

Sulfadiazine/ciprofloxacin promote opportunistic pathogens occurrence in bulk water of drinking water distribution systems.

Effects of sulfadiazine and ciprofloxacin on the occurrence of free-living and particle-associated opportunistic pathogens in bulk water of simulated drinking water distribution systems (DWDSs) were investigated. It was found that sulfadiazine and ciprofloxacin greatly promoted the occurrence of opportunistic pathogens including Pseudomonas aeruginosa, Legionella pneumophila, Mycobacterium avium and its broader genus Mycobacterium spp., as well as the amoebae Acanthamoeba spp. and Hartmanella vermiformis, in bulk water of DWDSs. Moreover, sulfadiazine and ciprofloxacin exhibited much stronger combined effects on the increase of these opportunistic pathogens. Based on the analysis of the antibiotic resistance genes (ARGs) and extracellular polymeric substances (EPS), it was verified that EPS production was increased by the antibiotic resistant bacteria arising from the effects of sulfadiazine/ciprofloxacin. The combined effects of sulfadiazine and ciprofloxacin induced the greatest increase of EPS production in DWDSs. Furthermore, the increased EPS with higher contents of proteins and secondary structure β-sheet led to greater bacterial aggregation and adsorption. Meanwhile, large numbers of suspended particles were formed, increasing the chlorine-resistance capability, which was responsible for the enhancement of the particle-associated opportunistic pathogens in bulk water of DWDSs with sulfadiazine/ciprofloxacin. Therefore, sulfadiazine and ciprofloxacin promoted the occurrence of particle-associated opportunistic pathogens in bulk water of DWDSs due to the role of EPS produced by the bacteria with ARGs.

Characterization of bacterial community and iron corrosion in drinking water distribution systems with O3-biological activated carbon treatment

Bacterial community structure and iron corrosion were investigated for simulated drinking water distribution systems (DWDSs) composed of annular reactors incorporating three different treatments: ozone, biologically activated carbon and chlorination (O3-BAC-Cl2); ozone and chlorination (O3-Cl2); or chlorination alone (Cl2). The lowest corrosion rate and iron release, along with more Fe3O4 formation, occurred in DWDSs with O3-BAC-Cl2 compared to those without a BAC filter. It was verified that O3-BAC influenced the bacterial community greatly to promote the relative advantage of nitrate-reducing bacteria (NRB) in DWDSs. Moreover, the advantaged NRB induced active Fe(III) reduction coupled to Fe(II) oxidation, enhancing Fe3O4 formation and inhibiting corrosion. In addition, O3-BAC pretreatment could reduce high-molecular-weight fractions of dissolved organic carbon effectively to promote iron particle aggregation and inhibit further iron release. Our findings indicated that the O3-BAC treatment, besides removing organic pollutants in water, was also a good approach for controlling cast iron corrosion and iron release in DWDSs.

Pyrosequencing analysis of source water switch and sulfate-induced bacterial community transformation in simulated drinking water distribution pipes.

Inter-basin water transfer and source water switching will be increasingly launched due to significant population increase and the shortage of the local water resources in cities around the world. Source water switch may cause physiochemical and microbiological de-stabilization of pipe material, biofilms, and loose deposits in drinking water distribution system (DWDS). Great sulfate alteration during source water switch had been deemed as the main cause of a red water case that occurred in a northern China city. To ascertain the relationship between water quality changing and bacterial communities of biofilms in DWDS and possible bacteria risk in a red water case, water quality changing experiments in simulated DWDSs were conducted for approximately 2years. Twenty-five corrosion scale samples and eight water samples collected from pipe harvest sites or during experimental periods were analyzed for their bacterial community composition by 454-pyrosequencing technology. Taxonomy results together with redundancy analysis (RDA) or canonical correspondence analysis (CCA) and hierarchical cluster analysis all indicated that bacterial community of samples with groundwater (GW) or surface water (SW) supply history and their variations under high sulfate water were rather different owing to different water source histories and the original pipe scale characteristics. Potential opportunistic pathogens: Burkholderia, Escherichia-Shigella, Mycobacterium, Serratia, Ralstonia, Novosphingobium, Flavobacterium, Sphingomonas, and Sphingopyxis were observed in scale or water samples.

Radical Chemistry and Structural Relationships of PPCP Degradation by UV/Chlorine Treatment in Simulated Drinking Water.

The UV/chlorine process is an emerging advanced oxidation process (AOP) used for the degradation of micropollutants. However, the radical chemistry of this AOP is largely unknown for the degradation of numerous structurally diverse micropollutants in water matrices of varying quality. These issues were addressed by grouping 34 pharmaceuticals and personal care products (PPCPs) according to the radical chemistry of their degradation in the UV/chlorine process at practical PPCP concentrations (1 μg L-1) and in different water matrices. The contributions of HO• and reactive chlorine species (RCS), including Cl•, Cl2•-, and ClO•, to the degradation of different PPCPs were compound specific. RCS showed considerable reactivity with olefins and benzene derivatives, such as phenols, anilines, and alkyl-/alkoxybenzenes. A good linear relationship was found between the RCS reactivity and negative values of the Hammett ∑σp+ constant for aromatic PPCPs, indicating that electron-donating groups promote the attack of benzene derivatives by RCS. The contribution of HO•, but not necessarily RCS, to PPCP removal decreased with increasing pH. ClO• showed high reactivity with some PPCPs, such as carbamazepine, caffeine, and gemfibrozil, with second-order rate constants of 9.2 × 107, 1.03 × 108, and 4.16 × 108 M-1 s-1, respectively, which contributed to their degradation. Natural organic matter (NOM) induced significant scavenging of ClO• and greatly decreased the degradation of PPCPs that was attributable to ClO•, with a second-order rate constant of 4.5 × 104 (mg L-1)-1 s-1. Alkalinity inhibited the degradation of PPCPs that was primarily attacked by HO• and Cl• but had negligible effects on the degradation of PPCPs by ClO•. This is the first study on the reactivity of RCS, particularly ClO•, with structurally diverse PPCPs under simulated drinking water condition.

Removal of Diclofenac, Ketoprofen, and Carbamazepine from Simulated Drinking Water by Advanced Oxidation in a Model Reactor

The objective of this study was to examine the degradation of pharmaceutical compounds diclofenac, ketoprofen, and carbamazepine in a bench-scale batch type advanced oxidation treatment system combining non-thermal plasma and UV photocatalysis. The key factors affecting pollutant decomposition were studied in a dielectric barrier discharge (DBD) plasma reactor. This was followed by the comparative assessment of various advanced oxidation processes (O3; UV+O3; TiO2+O3; TiO2+UV+O3) in a UV-photocatalysis reactor. The overall effectiveness of the treatment process was established according to the decomposition efficiency of the individual compound determined by high-performance liquid chromatography with ultraviolet detection (HPLC/UV), removal of total organic carbon (TOC), energy consumption, and acute toxicity test with Chironomus sp. larvae. Depending on the pharmaceutical compound and oxidation system, complete decomposition of the target compound was reached within 3–6 min. The TOC removal ranged between 25 and 100% with energy consumption varying 3.1–10.6 MJ/g. TiO2+UV+O3 revealed slightly higher toxicity of treated water as compared to TiO2+O3 (22–50% vs 17–33% mortality rate of Chironomus sp. larvae). TiO2+O3 and TiO2+UV+O3 systems proved as an efficient combination of AO processes for the decomposition of pharmaceuticals in water, as long as the treatment duration is sufficient to fully mineralize organic substances.

Characterization of titanium dioxide nanoparticle removal in simulated drinking water treatment processes

This study characterized the fate of nano-TiO2 in both powder (TiO2(P)) and suspension (TiO2(S)) forms in simulated drinking water treatments. Nano-TiO2 solutions of 0.1, 1.0, and 10mg/L were prepared with deionized water and raw waters from the Changxing and Fengshan Water Treatment Plants in Taiwan to assess the effects of water matrices on nano-TiO2 behavior during water treatment. After the laboratory simulated water treatment, including pre-chlorination, coagulation, sedimentation, filtration and post-chlorination, the residual Ti concentration ranged from 2.7 to 47.4% in different treatment units and overall removal efficiency was between 52.6% and 97.3% in all cases except for nano-TiO2 at concentration of 0.1mg/L. Overall removal efficiency for the TiO2 at 10mg/L concentration ranged from 9.3 to 53.5%. Sedimentation (after coagulation) and filtration were the most important processes for removing nano-TiO2 due in part to particle agglomeration, which was confirmed by size distribution and zeta potential measurements. The size of nano-TiO2 increased from 21–36nm to 4490nm in the supernatant after sedimentation, and subsequent filtration treatment further removed all agglomerates at size >1μm. Zeta potential revealed interactions between nano-TiO2 particles and anionic functional groups or negatively-charged natural organic matters, leading to a decrease in surface charge. After sedimentation and filtration, the zeta potential of supernatants and filtrates were close to zero, meaning the absence of nanoparticles. The highest Ti removal after sedimentation occurred in Fengshan raw water due to higher ionic strength and coagulant dosage applied. On the other hand, the surfactant additives in TiO2(S) promoted dispersion of nano-TiO2 particles, which in turn led to lower particle removal. SEM images of nanoparticles after chlorination or coagulation revealed the coverage of nano-TiO2 particles by viscous substances and formation of colloidal structures.

Effect of Disinfectant Exposure on Legionella pneumophila Associated with Simulated Drinking Water Biofilms: Release, Inactivation, and Infectivity.

Legionella pneumophila, the most commonly identified causative agent in drinking water associated with disease outbreaks, can be harbored by and released from drinking water biofilms. In this study, the release of biofilm-associated L. pneumophila under simulated drinking water flow containing a disinfectant residual was examined. Meanwhile, the inactivation and infectivity (to amoebae) of the released L. pneumophila were studied. To simulate drinking water system conditions, biofilms were prepared under either disinfectant exposure (predisinfected biofilms) or disinfectant-free (untreated biofilms) conditions, respectively. For experiments with water flow containing a disinfectant to release the biofilm-associated L. pneumophila from these two types of biofilms, the L. pneumophila release kinetics values from predisinfected and untreated biofilms under flow condition were not statistically different (one-way ANOVA, p > 0.05). However, inactivation of the L. pneumophila released from predisinfected biofilms was 1-2 times higher and amoeba infectivity was 2-29 times lower than that from untreated biofilms. The higher disinfectant resistance of L. pneumophila released from untreated biofilms was presumably influenced by the detachment of a larger amount of biofilm material (determined by 16S rRNA qPCR) surrounding the released L. pneumophila. This study highlights the interaction among disinfectant residual, biofilms, and L. pneumophila, which provides guidelines to assess and control pathogen risk.

Emerging pollutant mixture mineralization by TiO2 photocatalysts. The role of the water medium

Pharmaceutics and personal care products (PPCPs) are raising growing concern due to their widespread usage and resistance to conventional remediation techniques. Several of them raise significant health and environmental concerns, especially when present in complex mixtures. Due to their chemical resistance, Advanced Oxidation Processes (AOPs) are needed for their complete removal from surface and wastewaters. In the present work, photocatalysis by titanium dioxide (TiO2) under UV and simulated solar irradiation was adopted to degrade tetracycline hydrochloride, paracetamol, caffeine and atenolol, both as single pollutants and in mixtures. All molecules showed high removal and mineralization degrees. Moreover, no interference effects decreased the efficiency of the processes in the case of pollutant mixtures, achieving 60% of mineralization after 6 h. An immobilized TiO2 system was also developed by depositing titania on titanium meshes. A 50% mineralization degree of the pollutant mixture was obtained after 6 h, revealing a suitable efficiency for field applications. Eventually, the impact of the matrix composition on the photocatalytic efficiency was investigated by studying the reaction both in simulated drinking water and in commercial bottled mineral water. The scavenger role played by HCO3− species appears to be dominant in inhibiting the mineralization.

Detection and dissolution of needle-like hydroxyapatite nanomaterials in infant formula

The unknowns surrounding presence, composition and transformations during the use phase of engineered nanoparticles (ENPs) in consumer products raises potential human and environmental health concerns and public discourse. This research developed evidence and confirmatory analytical methods to determine the presence and composition of ENPs in a consumer product with a complex organic matrix (six different infant formula samples). Nano-scale crystalline needle-shaped hydroxyapatite (HA; appx. 25nm×150nm) primary particles, present as aggregates (0.3–2μm), were detected in half the samples. This is the first report of these ENPs in infant formula. Dissolution experiments with needle-shaped HA were conducted to assess potential transformations of nano-HA particles. Rapid dissolution of needle-shaped HA occurred only under lower pH conditions present in simulated biological fluids (acidic gastric fluids), but not in simulated drinking water (near-neutral pH). Other non-nanosized HA minerals exhibited less dissolution under the same low pH conditions. This work demonstrates the occurrence of engineered nanomaterials in the food supply of a sensitive population (infants) and the need to consider transformations in nanomaterials that occur during use, which result in different exposures between pristine/as-produced ENPs and nanomaterials after passing through the human gut.

Impacts of bacteria and corrosion on removal of natural organic matter and disinfection byproducts in different drinking water distribution systems

Impacts of bacteria and corrosion on removal of natural organic matter (NOM) and disinfection byproducts (DBPs) were studied in simulated drinking water distribution systems (DWDSs) using two annular reactors (ARs) with different disinfection. The results verified that the removal of NOM and DBPs was related very well to the corrosion and bacterial regrowth in both ARs. The initial stages (before 50 days) at which the rate of corrosion is higher in both ARs is considered as stage I. At stage I, UV controlled bacterial regrowth and more chlorine reacted with iron to promote corrosion rate, inducing the higher removal of NOM and DBPs in AR treated with UV/Cl2 than that treated with Cl2 alone. At stage II (from 50 days to 250 days), comparing with Cl2 disinfection alone, UV/Cl2 decreased the number of the total bacteria in effluents and the dehalogenation related bacteria in biofilms effectively. Moreover, UV/Cl2 induced the bacterial genus Dechloromonas dominant in the biofilms, resulting in the lower corrosion rate. The lower bacterial regrowth and corrosion rate caused the less removal of NOM and DBPs. These results are very helpful for the control of NOM and DBPs in DWDSs with different disinfection.

Removal of uranium ions from synthetic wastewater using ZnO/Na-clinoptilolite nanocomposites

Abstract Uranium is one of the heavy metals that is found in industrial wastewater and is very toxic for human and environment. In this work, natural clinoptilolite is used as a low-cost adsorbent for uranium removal from aqueous solutions. The sodium form of clinoptilolite and ZnO/Na-clinoptilolite nanocomposite were prepared. The sample sorption capacities for uranium removal from simulated drinking water in the presence of other anions and cations were investigated. Natural zeolite and its modified forms were characterized by XRD, XRF, FTIR, TEM and BET. Batch experiments were used to determine the best adsorption conditions. The effects of various parameters such as contact time, pH, initial uranium concentration, temperature and mass sorbent on the removal efficiency of uranium ions were studied. The equilibration was attained after 2 and 6 h for the Na-clinoptilolite and ZnO/Na-clinoptilolite nanocomposite, respectively. Both adsorbents showed relatively fast adsorption. Effective removal of uranium was demonstrated at pH values of 4–8 for both forms of zeolite. Temperature had no significant effect on adsorption. The maximum removal efficiency of uranium by the ZnO/Na-clinoptilolite nanocomposite in pH=7.2 and room temperature was 98.55%. Langmuir, Freundlich and Sips models were used for describing the equilibrium isotherms for uranium uptake. The Sips model corresponded well with the experimental data. The thermodynamic parameters, such as ΔG°, ΔH° and ΔS°, have been calculated and interpreted. The pseudo-first order and pseudo-second order models were applied to describe the kinetic data. The pseudo-second order kinetic model had excellent kinetic data fitting (R2=1).

Formation and occurrence of new polar iodinated disinfection byproducts in drinking water.

During drinking water disinfection, iodinated disinfection byproducts (I-DBPs) can be generated through reactions between iodide, disinfectants, and natural organic matter. Drinking water I-DBPs have been increasingly attracting attention as emerging organic pollutants as a result of their significantly higher toxicity and growth inhibition than their chloro- and bromo-analogues. In this study, by adopting ultra performance liquid chromatography/electrospray ionization-triple quadrupole mass spectrometry precursor ion scan, multiple reaction monitoring, and product ion scan analyses, 11 new polar I-DBPs with confirmed structures and eight new polar I-DBPs with proposed structures were detected in simulated drinking water samples. Chloramination of simulated raw waters containing natural organic matter with higher aromaticity produced higher levels of new phenolic I-DBPs. Formation of new polar I-DBPs and total organic iodine (TOI) was most favored in chloramination, followed by chlorine dioxide treatment, and relatively minor in chlorination. Lower pH in chloramination substantially enhanced the formation of new polar I-DBPs and TOI. NH2Cl and dissolved organic nitrogen could be important nitrogen sources and precursors for formation of the two new nitrogenous phenolic I-DBPs. Notably, in tap water samples collected from nine major cities located in the Yangtze River Delta region of China, seven of the 11 new polar I-DBPs with confirmed structures were detected at levels from 0.11 to 28 ng/L, and the two new nitrogenous phenolic I-DBPs were ubiquitous with concentrations from 0.12 to 24 ng/L, likely due to the relatively high dissolved organic nitrogen levels in regional source waters.

Effects of microbial cycling of Fe(II)/Fe(III) and Fe/N on cast iron corrosion in simulated drinking water distribution systems

Effects of microbial cycling of Fe(II)/Fe(III) and Fe/N, as driven by the bacterium Dechloromonas hortensis, on iron corrosion were studied in simulated drinking water distribution systems (DWDSs) with different nitrate concentrations. Fe/N redox cycling accelerated Fe(II) oxidation and α-FeOOH formation in DWDSs with 22.0mg/L initial NO3−-N. The greatest amount of Fe3O4 was formed through Fe(II)/Fe(III) redox cycling in DWDSs with 2.2mg/L initial NO3−-N. This resulted in the lowest corrosion rate and iron release. Therefore, the redox cycling of Fe(II)/Fe(III) driven by D. hortensis was favourable to the formation of more stable corrosion scales in DWDSs.

Role of biofilm roughness and hydrodynamic conditions in Legionella pneumophila adhesion to and detachment from simulated drinking water biofilms.

Biofilms in drinking water distribution systems (DWDS) could exacerbate the persistence and associated risks of pathogenic Legionella pneumophila (L. pneumophila), thus raising human health concerns. However, mechanisms controlling adhesion and subsequent detachment of L. pneumophila associated with biofilms remain unclear. We determined the connection between L. pneumophila adhesion and subsequent detachment with biofilm physical structure characterization using optical coherence tomography (OCT) imaging technique. Analysis of the OCT images of multispecies biofilms grown under low nutrient condition up to 34 weeks revealed the lack of biofilm deformation even when these biofilms were exposed to flow velocity of 0.7 m/s, typical flow for DWDS. L. pneumophila adhesion on these biofilm under low flow velocity (0.007 m/s) positively correlated with biofilm roughness due to enlarged biofilm surface area and local flow conditions created by roughness asperities. The preadhered L. pneumophila on selected rough and smooth biofilms were found to detach when these biofilms were subjected to higher flow velocity. At the flow velocity of 0.1 and 0.3 m/s, the ratio of detached cell from the smooth biofilm surface was from 1.3 to 1.4 times higher than that from the rough biofilm surface, presumably because of the low shear stress zones near roughness asperities. This study determined that physical structure and local hydrodynamics control L. pneumophila adhesion to and detachment from simulated drinking water biofilm, thus it is the first step toward reducing the risk of L. pneumophila exposure and subsequent infections.

Defluoridation of Drinking Water Using PURAL® MG-20 Mixed Hydroxide Adsorbent

The potential of mixed alumina-magnesia hydroxide adsorbent (PURAL® MG-20) for defluoridation of drinking water using batch and continuous mode of operations has been reported in the present article. Systematic adsorption experiments were carried out to elucidate the effects of different process parameters such as adsorbent dose, initial fluoride concentration, pH of the solution and effect of other ions (usually present in groundwater). These studies were aimed to understand the adsorption behaviour of the PURAL® MG-20 adsorbents. Fluoride adsorption by PURAL® MG-20 sorbent was found pH dependent. Maximum fluoride removal efficiency was observed in the range of pH 5–7. Langmuir isotherm described the data better than Freundlich and Temkin isotherm models and the adsorption capacity was found to be 5.62 mg g−1 at initial fluoride concentration of 5.13 mg L−1, pH 7 and contact time 24 h. The kinetic result shows that the fluoride sorption follows pseudo-second-order kinetics. Column breakthrough studies were performed to test the performance of the adsorbent media at continuous mode of operation. Thus, it can be concluded that PURAL® MG-20 adsorbent can be used directly for field applications since it shows high fluoride uptake capacity under simulated drinking water conditions and it is also commercially available.

Fate of Salmonella Typhimurium in laboratory-scale drinking water biofilms

Investigations were carried out to evaluate and quantify colonization of laboratory-scale drinking water biofilms by a chromosomally green fluorescent protein (gfp)-tagged strain of Salmonella Typhimurium. Gfp encodes the green fluorescent protein and thus allows in situ detection of undisturbed cells and is ideally suited for monitoring Salmonella in biofilms. The fate and persistence of non-typhoidal Salmonella in simulated drinking water biofilms was investigated. The ability of Salmonella to form biofilms in monoculture and the fate and persistence of Salmonella in a mixed aquatic biofilm was examined. In monoculture S. Typhimurium formed loosely structured biofilms. Salmonella colonized established multi-species drinking water biofilms within 24 hours, forming micro-colonies within the biofilm. S. Typhimurium was also released at high levels from the drinking water-associated biofilm into the water passing through the system. This indicated that Salmonella could enter into, survive and grow within, and be released from a drinking water biofilm. The ability of Salmonella to survive and persist in a drinking water biofilm, and be released at high levels into the flow for recolonization elsewhere, indicates the potential for a persistent health risk to consumers once a network becomes contaminated with this bacterium.

Novel insights in Al-MCM-41 precursor as adsorbent for regulated haloacetic acids and nitrate from water

High concentration of NO (3) (-) in groundwater has raised concern over possible contamination of drinking water supplies. In addition, the formation of haloacetic acids (HAAs) as by-products during disinfection with chlorine-based agents is still a relevant issue, since HAAs pose serious health hazard. In this work, we investigated the affinity of a precursor of Al-MCM-41 (a mesostructured hexagonal aluminosilicate containing the template surfactant) towards nitrate and HAAs, for its possible application in the removal of these pollutants from natural and drinking waters. Additionally, adsorption kinetics and isotherms were studied. The adsorbent was synthesized using cetyltrimethylammonium bromide as surfactant and characterized by physico-chemical techniques. Simulated drinking water was spiked with the EPA-regulated HAAs (monochloroacetic (MCAA), monobromoacetic (MBAA), dichloroacetic (DCAA), dibromoacetic (DBAA), and trichloroacetic (TCAA) acids) and placed in contact with the adsorbent. The effect of matrix composition was studied. Adsorption kinetic studies were performed testing three kinetics models. For the adsorption studies, three adsorption isotherm approaches have been tested to experimental data. The pollutant recoveries were evaluated by suppressed ion chromatography. The affinity of the adsorbent was TCAA = DBAA = DCAA > MBAA > MCAA with DCAA, DBAA, and TCAA completely removed. A removal as high as 77% was achieved for 13mg/L nitrate. The adsorption isotherms of NO (3) (-) and monochloroacetic acid can be modeled by the Freundlich equation, while their adsorption kinetics follow a pseudo-second-order rate mechanism. The adsorbent exhibited high affinity towards HAAs in simulated drinking water even at relevant matrix concentrations, suggesting its potential application for water remediation technologies.

United States Environmental Protection Agency Perchlorate Method 332.0. Statistically Sound Recovery Studies in Simulated Drinking Water

This research is a continuation of an earlier work, which evaluated the United States Environmental Protection Agency's Perchlorate Method 332.0, in which standards were prepared in deionized water over an extended concentration range (i.e., to a maximum of 200 μg/L). This current paper investigates the performance of the same method in which standards were made in simulated drinking water. A microbore format with a 15-μL injection volume was employed to conduct a recovery study and generate recovery curves (which hold the key to a statistically sound assessment of method performance in more complex matrices). The maximum analyte concentration range was 1 to 200 μg/L. For various subset concentration ranges, recovery evaluations were made using both raw peak-area data and analyte responses scaled by the internal standard (ISTD). The results indicate that in complicated matrices such as drinking water, ISTDs may not provide simultaneously high precision and recovery.

Formation and Decomposition of New and Unknown Polar Brominated Disinfection Byproducts during Chlorination

Brominated disinfection byproducts (Br-DBPs) are generally more cytotoxic and genotoxic than their chlorinated analogues. A great portion of total organic bromine in chlorinated drinking water is still unknown and may be ascribed to polar Br-DBPs. In this work, a novel approach, precursor ion scan using ultra-performance liquid chromatography/electrospray ionization-triple quadrupole mass spectrometry, was adopted and further developed for selective detection and identification of polar Br-DBPs, which made it possible to reveal the whole picture of the formation and decomposition of polar Br-DBPs during chlorination. Simulated drinking water samples with chlorine contact times from 1 min to 7 d were analyzed. Many new polar aromatic and unsaturated aliphatic Br-DBPs were detected and tentatively proposed with chemical structures, of which 2,4,6-tribromophenol, 3,5-dibromo-4-hydroxybenzoic acid, 2,6-dibromo-1,4-hydroquinone, and 3,3-dibromopropenoic acid were confirmed or identified with authentic standards. It was found that various polar Br-DBPs formed and reached the maximum levels at different chlorine contact times; high molecular weight Br-DBPs might undergo decomposition to relatively low molecular weight Br-DBPs or even finally to haloacetic acids and trihalomethanes. The decomposition of newly detected intermediate Br-DBPs (including molecular ion cluster m/z 345/347/349/351, 2,4,6-tribromophenol, and 3,5-dibromo-4-hydroxybenzoic acid) during chlorination was investigated in detail. The "black box" from the input of "humic substances + bromide + chlorine" through the output of "haloacetic acids + trihalomethanes" was opened to a significant extent.

Preparation and Characterization of Modified Bamboo-Charcoal by Ferric Sulfate Dipping and Microware Radiation

Modified bamboo-charcoal (MBC) was prepared by Ferric sulfate dipping and microwave radiation with 20～30 mesh bamboo-charcoal (BC) pretreated by water boiling as the support. The original and modified BC were characterized by SEM, FTIR, XRD, BET and BJH. Fluoride removal from simulated drinking water containing fluoride was probed into with MBC. The results indicated that MBC took on minor average pore diameter (1.172nm), major microspores and greater specific surface area (99.891 m2/g). Loaded iron combined with BC by bonds from BC such as H-O-H bond, C-O bond and O-H bond. The increase of fluoride removal after BC being modified suggests that MBC is a more potential defluorinate agent.