Comparison of colorimetric and membrane introduction mass spectrometry techniques for chloramine analysis (original) (raw)
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Chemosphere, 2016
Chlorination is commonly used to control levels of bacteria in drinking water; however, viable bacteria may remain due to chlorine resistance. What is concerning is that surviving bacteria, due to co-selection factors, may also have increased resistance to common antibiotics. This would pose a public health risk as it could link resistant bacteria in the natural environment to human population. Here, we investigated the relationship between chlorine- and antibiotic-resistances by harvesting 148 surviving bacteria from chlorinated drinking-water systems and compared their susceptibilities against chlorine disinfectants and antibiotics. Twenty-two genera were isolated, including members of Paenibacillus, Burkholderia, Escherichia, Sphingomonas and Dermacoccus species. Weak (but significant) correlations were found between chlorine-tolerance and minimum inhibitory concentrations against the antibiotics tetracycline, sulfamethoxazole and amoxicillin, but not against ciprofloxacin; this ...
Water Research, 2009
The interactions of co-present Cr(VI) and As(V), and the influences of humic acid and bicarbonate in the process of Cr(VI) and As(V) removal by Fe0 were investigated in a batch setting using simulated groundwater with 5 mM NaCl, 1 mM Na2SO4, and 0.8 mM CaCl2 as background electrolytes at an initial pH value of 7. Cr(VI) and As(V) were observed to be subject to different impacts induced by co-existing As(V) or Cr(VI), humic acid and bicarbonate, originating from their distinct removal mechanisms by Fe0. Cr(VI) removal is a reduction-dominated process, whereas As(V) removal principally involves adsorption onto iron corrosion products. Experimental results showed that Cr(VI) removal was not affected by the presence of As(V) and humic acid. However, As(V) removal appeared to be inhibited by co-present Cr(VI). When the Cr(VI) concentration was 2, 5, and 10 mg/L, in the absence of humic acid and bicarbonate, As(V) removal rate constants were decreased by 27.9%, 49.0%, and 61.2%, respectively, which probably resulted from competition between Cr(VI) and As(V) for adsorption sites of the iron corrosion products. Furthermore, the presence of humic acid significantly varied As(V) removal kinetics by delaying the formation and aggregation of iron hydroxides due to the formation of soluble Fe–humate complexes and stably dispersed fine iron hydroxides colloids. In the presence of bicarbonate, both Cr(VI) and As(V) removal was increased and the inhibitory effect of Cr(VI) on As(V) removal was suppressed, resulting from the buffering effects and the promoted iron corrosion induced by bicarbonate, and the formation of CaCO3 in solution, which enhanced As(V) adsorption.
Formation and removal of disinfection by-products in a full scale drinking water treatment plant
Science of The Total Environment, 2020
In this case study, high sensitivity simple methods for the analysis of trihalomethanes (THM4), iodinated-trihalomethanes (I-THMs), haloacetic acids (HAAs), bromide, iodide and iodate have been developed. A one-step procedure for the analysis of haloacetic acids by head-space GC-MS provides good reproducibility and low limits of quantification (≤ 50 ng L-1). These methods were applied to characterize the formation of DBPs in a full scale drinking water treatment plant. In this treatment plant, the incorporation of bromine into THMs increases throughout the water treatment line, due to the formation of bromine reactive species favored by the decrease of competition between DOC and bromide towards chlorine. A linear correlation has been observed between the bromine incorporation factor and the Br-/DOC mass ratio. The conversion of iodine to iodate by chlorination occurs in this water due to the relatively high bromide concentration. Moreover, a higher formation of iodate compared to iodide levels in the raw water is observed indicating a degradation of organic iodinated compounds. The formation of I-THMs was constant in terms of quantity and speciation between campaigns despite fluctuating concentrations of DOC and total iodine in the raw water. A preferential 2 removal of DBPs formed by the intermediate chlorination in the order I-DBPs>Br-DBPs>Cl-DBPs occurs during the subsequent activated carbon filtration. The removal rates range from 25 to 36% for the regulated THM4, from 82 to 93% for the ∑I-THMs and 95% for haloacetic acids. The assessment of the relative toxicity shows that despite a much lower concentration of HAAs (less than 10% of the total mass of measured DBPs) compared to THMs, these compounds are responsible for 75% of the relative cytotoxicity of the treated water. Bromoacetic acid on its own accounts for more than 60% of the overall toxicity of the 17 compounds included in this study.
Water Research, 2016
Membrane surface hydrophilic modification has always been considered to mitigating biofouling in membrane bioreactors (MBRs). Four hollow-fiber ultrafiltration membranes (pore sizes ~0.1 µm) differing only in hydrophobic or hydrophilic surface characteristics were operated at a permeate flux of 10 L/m 2 .h in the same lab-scale MBR fed with synthetic wastewater. In addition, identical membrane modules without permeate production (0 L/m 2 .h) were operated in the same lab-scale MBR. Membrane modules were autopsied after 1, 10, 20 and 30 days of MBR operation, and total extracellular polymeric substances (EPS) accumulated on the membranes were extracted and characterized in detail using several analytical tools, including conventional colorimetric tests (Lowry and Dubois), liquid chromatography with organic carbon detection (LC-OCD), fluorescence excitation-emission matrices (FEEM), fourier transform infrared (FTIR) and confocal laser scanning microscope (CLSM). The transmembrane pressure (TMP) quickly stabilized with higher values for the hydrophobic membranes than hydrophilic ones. The sulfonated polysulfone (SPSU) membrane had the highest negatively charged membrane surface, accumulated the least amount of foulants and displayed the lowest TMP. The same type of organic foulants developed with time on the four membranes and the composition of biopolymers shifted from protein dominance at early stages of filtration (day 1) towards polysaccharides dominance during later stages of MBR filtration. Nonmetric multidimensional scaling of LC-OCD data showed that biofilm samples clustered according to the sampling event (time) regardless of the membrane surface chemistry (hydrophobic or hydrophilic) or operating mode (with or without permeate flux). These results suggest that EPS composition may not be the
Chemical Engineering Journal
A serially connected lab-scale Greater duckweed constructed wetland (CW)stabilization tank (ST)-GAC sandwich slow sand filtration system was tested to remove four widely detected pharmaceuticals and personal care products (PPCPs) compounds from natural water with a spiked concentration of 25 μg/L. High removals were achieved rapidly (93.5~100%), being on average 95.9%, 99.1%, 98.1% and 97.4% for DEET, paracetamol, caffeine and triclosan (n=3), respectively. Except for DEET, no significant difference was observed between overall removals with and without artificial aeration in CW tank (p>0.05), showing good stability of the system. COD was considerably removed under aeration and final TOC removal was 64.7%. No nitrite, nitrate, ammonia and phosphate were detected at the test end (day 26). The microbial community structure in three connected units of the tested system showed differences and good stability after the aerators were removed. Proteobacteria was the most dominant phylum among the 47 phyla found. Microbes attaching to the Greater duckweed contributed more to the microbial community structure in CW and ST than *Revised Manuscript (clean for typesetting) Click here to view linked References original natural water. However, at the end of the run, the structural differences among three units decreased. After aeration stopped, phylum composition became more stable in ST tank while CW tank showed small structural variation throughout the test. Various correlations were found between detected phyla, among which Proteobacteria and Bacteroidetes showed a significant negative correlation (R=-0.73, p<0.001, FDR corrected). Good removal of target PPCPs and stability of the system show the potential applicability of this combined treatment process.
Water Research, 2010
Formation of nitrogenous disinfection by-products (N-DBPs) of cyanogen chloride (CNCl), dichloroacetonitrile (DCAN) and chloropicrin was evaluated during chloramination of several selected groups of nitrogenous organic (organic-N) compounds, including a-amino acids, amines, dipeptides, purines, and pyrimidines, The intermediates generated, reaction pathways, and nitrogen origin in N-DBPs were explored as well. CNCl was observed in chloramination of all tested organic-N compounds, with glycine giving the highest yields. DCAN was formed during chloramination of glutamic acid, cytosine, cysteine, and tryptophan. Chloramination of most organic-N compounds except for cysteine and glutamic acid generated chloropicrin. Aldehydes and nitriles were identified as the intermediates by negative mode electrospray ionization mass spectrometry during reactions of NH 2 Cl and organic-N compounds. Labeled 15 N-monochloramine (15 NH 2 Cl) techniques showed that nitrogen in N-DBPs may originate from both NH 2 Cl and organic-N compounds and the nitrogen partition percentages vary as functions of reactants and pH.
Turkish Journal of Biochemistry
Objectives Acute kidney injury (AKI) is a critical clinical event characterized by a reduction in the excretory function of the kidneys. N-acetylcysteine (NAC), N-acetylmethionine (NAM) and N-acetylglucosamine (NAG) are antioxidants with scanty known genetic mechanisms. We aimed to assess both kidney injury molecule-1 (KIM-1) and growth-arrested DNA damage-inducible gene-153 (GADD-153) genes expression in paracetamol (PA) induced AKI. Also, to recognize whether NAC, NAM and/or NAG have roles in altering the expression of these genes for ameliorating the AKI induced by PA. Methods The present preliminary study achieved the AKI model by oral administration of PA therapeutic dose for 15 days in experimental male rats. Serum urea, creatinine, and renal oxidative stress parameters were analyzed. Genetic expression of KIM-1 and GADD-153 were determined using real time-PCR. Results Significant elevations of serum urea, creatinine and nitric oxide in renal tissue after PA administration; ho...
Water Research, 2020
Iron electrocoagulation (Fe-EC) is an effective technology to remove arsenic (As) from groundwater used for drinking. A commonly noted limitation of Fe-EC is fouling or passivation of electrode surfaces via rust accumulation over long-term use. In this study, we examined the effect of removing electrode surface layers on the performance of a large-scale (10000 L/d capacity) Fe-EC plant in West Bengal, India. We also characterized the layers formed on the electrodes in active use for over two years at this plant. The electrode surfaces developed three distinct horizontal sections of layers that consisted of different minerals: calcite, Fe(III) precipitates and magnetite near the top, magnetite in the middle, and Fe(III) precipitates and magnetite near the bottom. The interior of all surface layers adjacent to the Fe(0) metal was dominated by magnetite. We determined the impact of surface layer removal by mechanical abrasion on Fe-EC performance by measuring solution composition (As, Fe, P, Si, Mn, Ca, pH, DO) and electrochemical parameters (total cell voltage and electrode interface potentials) during electrolysis. After electrode cleaning, the Fe concentration in the bulk solution increased substantially from 15.2 to 41.5 mg/L. This higher Fe concentration led to increased removal of a number of solutes. For As, the concentration reached below the 10 µg/L WHO MCL more rapidly and with less total Fe consumed (i.e. less electrical energy) after cleaning (128.4 µg/L As removed per kWh) compared to before cleaning (72.9 µg/L As removed per kWh). Similarly, the removal of P and Si improved after cleaning by 0.3 mg/L/kWh and 1.1 mg/L/kWh, respectively. Our results show that mechanically removing the surface layers that accumulate on electrodes over extended periods of Fe-EC operation can restore Fe-EC system efficiency (concentration of solute removed/kWh delivered). Since Fe release into the bulk solution substantially increased upon electrode cleaning, our results also suggest that routine electrode maintenance can ensure robust and reliable Fe-EC performance over year-long timescales.