Water Research (v.44, #3)
Kenneth James Ives (1926–2009) by Mogens Henze (669).
Treatment of municipal solid waste leachate using a submerged anaerobic membrane bioreactor at mesophilic and psychrophilic temperatures: Analysis of recalcitrants in the permeate using GC-MS by Antoine P. Trzcinski; David C. Stuckey (671-680).
This study investigated the performance of two submerged anaerobic membrane bioreactors (SAMBRs) operating at a mean solids residence time (SRT) of 30 (SAMBR30) and 300 days (SAMBR300) at mesophilic and psychrophilic temperatures. At 35 °C results showed that SAMBR30 and 300 could achieve 95% soluble chemical oxygen demand (SCOD) removal at 1.5 and 1.1 days HRT, respectively, whereas at 20 °C only SAMBR300 could maintain the same performance. Low temperatures were associated with higher bulk SCOD concentrations, which contributed to reducing the flux, but this was partly reversible once the SCOD was degraded. The utilization rate of compounds was affected differently by the drop in temperature with the concentration of some recalcitrants increasing, while for others such as bisphenol A it decreased when the temperature was decreased. Among the recalcitrants detected in SAMBR30 at 20 °C there were not only long chain fatty acids such as undecanoic acid and dodecanoic acid, but also long chain alkanes such as tetracosane and heneicosane that could not be hydrolyzed at 20 °C. In SAMBR300 these alkanes and acids only appeared at 10 °C, whereas at 20 °C complex compounds such as phenol, 2-chloro-4-(1,1-dimethylethyl), 6-tert-butyl-2,4-dimethylphenol, benzophenone, and n-butyl benzenesulfonamide were found.
Keywords: Anaerobic digestion; Submerged anaerobic membrane bioreactor; Psychrophilic; Recalcitrants; Gas chromatography–mass spectrometry (GC–MS); Powdered activated carbon (PAC);
Removal of probable human carcinogenic polycyclic aromatic hydrocarbons from contaminated water using molecularly imprinted polymer by Reddithota J. Krupadam; Muntazir S. Khan; Satish R. Wate (681-688).
A molecularly imprinted polymer (MIP) adsorbent for carcinogenic polycyclic aromatic hydrocarbons (PAHs) was prepared using a non-covalent templating technique. MIP particles sized from 2 to 5 μm were synthesized in acetonitrile by using six PAHs mix as a template, methacrylic acid as the functional monomer, and ethylene glycol dimethacrylate as the cross-linker. When compared with the non-imprinted polymer (NIP), the MIP showed an excellent affinity towards PAHs in aqueous solution with binding capacity (B max) of 687 μg g−1MIP, imprinting effect of 6, and a dissociation constant of 24 μM. The MIP exhibited significant binding affinity towards PAHs even in the presence of environmental parameters such as dissolved organic matter (COD) and total dissolved inorganic solids (TDS), suggesting that this material may be appropriate for removal of carcinogenic PAHs. The feasibility of removing PAHs from water by the MIP demonstrated using groundwater spiked with PAHs. In addition, the MIP reusability without any deterioration in performance was demonstrated at least ten repeated cycles.
Keywords: Water treatment; Carcinogens; Molecularly imprinted polymers; Adsorption;
Impact of flow regime on pressure drop increase and biomass accumulation and morphology in membrane systems by J.S. Vrouwenvelder; J. Buiter; M. Riviere; W.G.J. van der Meer; M.C.M. van Loosdrecht; J.C. Kruithof (689-702).
Biomass accumulation and pressure drop development have been studied in membrane fouling simulators at different flow regimes. At linear flow velocities as applied in practice in spiral wound nanofiltration (NF) and reverse osmosis (RO) membranes, voluminous and filamentous biofilm structures developed in the feed spacer channel, causing a significant increase in feed channel pressure drop. Elevated shear by both single phase flow (water) and two phase flow (water with air sparging: bubble flow) caused biofilm filaments and a pressure drop increase. The amount of accumulated biomass was independent of the applied shear, depending on the substrate loading rate (product of substrate concentration and linear flow velocity) only. The biofilm streamers oscillated in the passing water. Bubble flow resulted in a more compact and less filamentous biofilm structure than single phase flow, causing a much lower pressure drop increase. The biofilm grown under low shear conditions was more easy to remove during water flushing compared to a biofilm grown under high shear. To control biofouling, biofilm structure may be adjusted using biofilm morphology engineering combined with biomass removal from membrane elements by periodic reverse flushing using modified feed spacers. Potential long and short term consequences of flow regimes on biofilm development are discussed. Flow regimes manipulate biofilm morphology affecting membrane performance, enabling new approaches to control biofouling.
Keywords: Flow regime; Shear force; Linear flow velocity; Biofilm streamers; Two phase bubble flow; Feed spacer channel pressure drop; Biomass cohesion strength; Flush; Biofouling; Nanofiltration; Reverse osmosis; Drinking water;
Evaluation of power ultrasound for disinfection of both Legionella pneumophila and its environmental host Acanthamoeba castellanii by Priscilla Declerck; Louise Vanysacker; Ann Hulsmans; Nico Lambert; Sven Liers; Frans Ollevier (703-710).
The objectives of this study were to (1) examine the effect of power ultrasound on the viability of both Legionella pneumophila and Acanthamoeba castellanii trophozoites and cysts, (2) investigate if intracellular Legionella replication in trophozoites positively affects bacterial resistance to ultrasound and (3) study if Legionella renders viable but non-culturable (VBNC) due to ultrasound treatments. Using laboratory scale experiments, microorganisms were exposed for various time periods to power ultrasound at a frequency of 36 kHz and an ultrasound power setting of 50 and 100%. Due to a fast destruction, trophozoite hosts were not able to protect intracellular Legionella from eradication by ultrasound, in contrast to cysts. No significant effects of ultrasound on cyst viability could be detected and power settings of 100% for 30 min only made intracellular Legionella concentrations decrease with 1.3 log units. Due to intracellular replication of Legionella in trophozoites, ultrasound no longer affected bacterial viability. Concerning the VBNC state, ultrasound treatments using a power setting of 50% partly induced Legionella (±7%) to transform into VBNC bacteria, in contrast to power settings of 100%. Promising results obtained in this study indicate the possible application of power ultrasound in the control of both Legionella and Acanthamoeba concentrations in anthropogenic water systems.
Keywords: Power ultrasound; Legionella pneumophila; Human pathogen; Acanthamoeba castellanii; Trophozoites; Cysts;
Production of Shiga-like toxins in viable but nonculturable Escherichia coli O157:H7 by Yanming Liu; Chuan Wang; Gregory Tyrrell; Xing-Fang Li (711-718).
Escherichia coli O157:H7, a causative agent of hemolytic uremic syndrome, can enter into a viable but nonculturable (VBNC) state when under stress. To date, it is unknown whether VBNC cells produce Shiga-like toxins (Stx). To address this question, we confirmed the expression of the stx1 and stx2 genes and the production of Stx in VBNC E. coli O157:H7 cells. To quantitatively assess the production of Stx in VBNC cells, we developed a Vero-cell microplate cytotoxicity assay based on the correspondence of the cytotoxicity of VBNC cells on Vero cells to the number of inoculated VBNC cells. Using this method, we found that all VBNC cells induced by river water, PBS buffer, deionized water, or chloraminated water retained the ability to produce Stx, and that they had differing levels of Stx. Both aged (19-month-old) VBNC cells induced by river water and fresh VBNC cells induced by chloraminated water showed very low half maximal inhibitory concentration (IC50; 6.6 × 104 and 7.1 × 104 respectively), corresponding to higher levels of toxins produced than VBNC cells induced by deionized water and PBS buffer. VBNC cells originating from different isolates may vary in Stx production, and the VBNC cells from bovine isolates produced higher levels of Stx than those from clinical isolates. These results demonstrate a potential health risk of VBNC E. coli O157:H7 in environmental water and the importance of monitoring VBNC E. coli O157:H7.
Keywords: Escherichia coli O157:H7; VBNC; Shiga-like toxins; stx2; Vero cell; microplate cytotoxicity assay;
Extreme value theory applied to the definition of bathing water quality discounting limits by R.A. Haggarty; C.A. Ferguson; E.M. Scott; C. Iroegbu; R. Stidson (719-728).
The European Community Bathing Water Directive () set compliance standards for bathing waters across Europe, with minimum standards for microbiological indicators to be attained at all locations by 2015. The Directive allows up to 15% of samples affected by short-term pollution episodes to be disregarded from the figures used to classify bathing waters, provided certain management criteria have been met, including informing the public of short-term water pollution episodes. Therefore, a scientifically justifiable discounting limit is required which could be used as a management tool to determine the samples that should be removed. This paper investigates different methods of obtaining discounting limits, focusing in particular on extreme value methodology applied to data from Scottish bathing waters. Return level based limits derived from threshold models applied at a site-specific level improved the percentage of sites which met at least the minimum required standard. This approach provides a method of obtaining limits which identify the samples that should be removed from compliance calculations, although care has to be taken in terms of the quantity of data which is removed.
Keywords: Bathing water quality; EC Directive; Extreme value modelling; Discounting limits;
Comparison of the disinfection by-product formation potential of treated waters exposed to chlorine and monochloramine by Cynthia M.M. Bougeard; Emma H. Goslan; Bruce Jefferson; Simon A. Parsons (729-740).
The formation of disinfection by-products (DBPs) from chlorination and monochloramination of treated drinking waters was determined. Samples were collected after treatment at 11 water treatment works but before exposure to chlorine or monochloramine. Formation potential tests were carried out to determine the DBPs formed by chlorination and monochloramination. DBPs measured were trihalomethanes (THMs), haloacetic acids (HAAs), halonitromethanes (HNMs), haloacetonitriles (HANs), haloaldehydes (HAs), haloketones (HKs) and iodo-THMs (i-THMs). All waters had the potential to form significant levels of all the DBPs measured. Compared to chlorine, monochloramination generally resulted in lower concentrations of DBPs with the exception of 1,1-dichloropropanone. The concentrations of THMs correlated well with the HAAs formed. The impact of bromine on the speciation of the DBPs was determined. The literature findings that higher bromide levels lead to higher concentrations of brominated DBPS were confirmed.
Keywords: Disinfection by-products; Trihalomethanes; Haloacetic acids; Haloacetonitriles; Monochloramination; Semi-volatile DBPs;
Alumina nanofibers grafted with functional groups: A new design in efficient sorbents for removal of toxic contaminants from water by Dongjiang Yang; Blain Paul; Wujun Xu; Yong Yuan; Erming Liu; Xuebin Ke; Robert M. Wellard; Cheng Guo; Yao Xu; Yuhan Sun; Huaiyong Zhu (741-750).
A new design in efficient sorbents for the removal of trace pollutants from water was proposed: grafting the external surface of γ-alumina (γ-Al2O3) nanofibers with functional groups that have a strong affinity to the contaminants. This new grafting strategy greatly improves the accessibility of these sorption sites to adsorbates and thus efficiency of the fibrous sorbents. The product sorbents could capture the pollutants selectively even when the concentration of the contaminants is extremely low. Two types of γ-Al2O3 nanofibers with different size were prepared via facile hydrothermal methods. Thiol groups were then grafted on the γ-Al2O3 fibers by refluxing the toluene solution of 3-mercaptopropyltrimethoxysilane (MPTMS). The thiol group modified fibers not only can efficiently remove heavy metal ions (Pb2+ and Cd2+) from water at a high flux, but also display high sorption capacity under sorption equilibrium conditions. Similar result was obtained from the nanofibers grafted with octyl groups which are employed to selectively adsorb highly diluted hydrophobic 4-nonylphenol molecules from water. This study demonstrates that grafting nanofibers is a new and effective strategy for developing efficient sorbents.
Keywords: Sorbent; γ-Al2O3 Nanofibers; Grafting functional groups; Heavy metal ions; Organic pollutants;
Novel membrane bioreactor (MBR) coupled with a nonwoven fabric filter for household wastewater treatment by Xianghao Ren; H.K. Shon; Namjung Jang; Young Geun Lee; Minsu Bae; Jongho Lee; Kwangmyeung Cho; In S. Kim (751-760).
Conventional and modified membrane bioreactors (MBRs) are increasingly used in small-scale wastewater treatment. However, their widespread applications are hindered by their relatively high cost and operational complexity. In this study, we investigate a new concept of wastewater treatment using a nonwoven fabric filter bag (NFFB) as the membrane bioreactor. Activated sludge is charged in the nonwoven fabric filter bag and membrane filtration via the fabric is achieved under gravity flow without a suction pump. This study found that the biofilm layer formed inside the NFFB achieved 10 mg/L of suspended solids in the permeate within 20 min of initial operation. The dynamic biofilter layer showed good filterability and the specific membrane resistance consisted of 0.3–1.9 × 1012 m/kg. Due to the low F/M ratio (0.04–0.10 kg BOD5/m3/d) and the resultant low sludge yield, the reactor was operated without forming excess sludge. Although the reactor provided aerobic conditions, denitrification occurred in the biofilm layer to recover the alkalinity, thereby eliminating the need to supplement the alkalinity. This study indicates that the NFFB system provides a high potential of effective wastewater treatment with simple operation at reduced cost, and hence offer an attractive solution for widespread use in rural and sparsely populated areas.
Keywords: Nonwoven fabric filter bag; Gravity filtration; Self-alkali supplement; Membrane bioreactor; Wastewater treatment;
Chloramination of organophosphorus pesticides found in drinking water sources by Stephen E. Duirk; Lisa M. Desetto; Gary M. Davis; Cristal Lindell; Christopher T. Cornelison (761-768).
The degradation of commonly detected organophosphorus (OP) pesticides, in drinking water sources, was investigated under simulated chloramination conditions. Due to monochloramine autodecomposition, it is difficult to observe the direct reaction of monochloramine with each OP pesticide. Therefore, a model was developed to examine the reaction of monochloramine (NH2Cl) and dichloramine (NHCl2) with chlorpyrifos (CP), diazinon (DZ), and malathion (MA). Monochloramine was found not to be very reactive with each OP pesticides, k NH 2 Cl,OP = 11 – 21 M − 1 h − 1 . While, dichloramine (NHCl2) was found to be 2 orders of magnitude more reactive with each of the OP pesticides than monochloramine, k NHCl 2 ,OP = 2000 – 2900 M − 1 h − 1 , which is still three orders of magnitude less than the hypochlorous acid reaction rate coefficient with each OP pesticide. For each pesticide, the reactivity of the three chlorinated oxidants was then found to correlate with half-wave potentials (E 1/2) of each oxidant. With reaction rate coefficients for the three chlorinated oxidations as well as neutral and alkaline hydrolysis rate coefficients for the pesticides, the model was used to determine the dominant reaction pathways as a function of pH. At pH 6.5, OP pesticide transformation was mostly due to the reaction of hypochlorous acid and dichloramine. Above pH 8, alkaline hydrolysis or the direct reaction with monochloramine was the primary degradation pathway responsible for the transformation of OP pesticides. This demonstrates the ability of models to be used as tools to elucidate degradation pathways and parameterize critical reaction parameters when used with select yet comprehensive data sets.
Keywords: Organophosphorus pesticides; Monochloramine; Dichloramine; Degradation pathway modeling;
Comparison of batch sorption tests, pilot studies, and modeling for estimating GAC bed life by Roger G. Scharf; Robert W. Johnston; Michael J. Semmens; Raymond M. Hozalski (769-780).
Saint Paul Regional Water Services (SPRWS) in Saint Paul, MN experiences annual taste and odor episodes during the warm summer months. These episodes are attributed primarily to geosmin that is produced by cyanobacteria growing in the chain of lakes used to convey and store the source water pumped from the Mississippi River. Batch experiments, pilot-scale experiments, and model simulations were performed to determine the geosmin removal performance and bed life of a granular activated carbon (GAC) filter–sorber. Using batch adsorption isotherm parameters, the estimated bed life for the GAC filter–sorber ranged from 920 to 1241 days when challenged with a constant concentration of 100 ng/L of geosmin. The estimated bed life obtained using the AdDesignS model and the actual pilot-plant loading history was 594 days. Based on the pilot-scale GAC column data, the actual bed life (>714 days) was much longer than the simulated values because bed life was extended by biological degradation of geosmin. The continuous feeding of high concentrations of geosmin (100–400 ng/L) in the pilot-scale experiments enriched for a robust geosmin-degrading culture that was sustained when the geosmin feed was turned off for 40 days. It is unclear, however, whether a geosmin-degrading culture can be established in a full-scale filter that experiences taste and odor episodes for only 1 or 2 months per year. The results of this research indicate that care must be exercised in the design and interpretation of pilot-scale experiments and model simulations for predicting taste and odor removal in full-scale GAC filter–sorbers. Adsorption and the potential for biological degradation must be considered to estimate GAC bed life for the conditions of intermittent geosmin loading typically experienced by full-scale systems.
Keywords: Geosmin; Taste and odor; Activated carbon; Sorption; Biodegradation;
Ozonation effect on natural organic matter adsorption and biodegradation – Application to a membrane bioreactor containing activated carbon for drinking water production by Ronan Treguer; Romuald Tatin; Annabelle Couvert; Dominique Wolbert; Annie Tazi-Pain (781-788).
More stringent legislation on dissolved organic matter (DOM) urges the drinking water industry to improve in DOM removal, especially when applied to water with high dissolved organic carbon (DOC) contents and low turbidity. To improve conventional processes currently used in drinking water treatment plants (DWTPs), the performances of a hybrid membrane bioreactor containing fluidised activated carbon were investigated at the DWTP of Rennes. Preliminary results showed that the residual DOC was the major part of the non-biodegradable fraction. In order to increase the global efficiency, an upstream oxidation step was added to the process. Ozone was chosen to break large molecules and increase their biodegradability. The first step consisted of carrying out lab-scale experiments in order to optimise the necessary ozone dose by measuring the process yield, in terms of biodegradable dissolved organic carbon (BDOC). Secondly, activated carbon adsorption of the DOC present in ozonated water was quantified. The whole process was tested in a pilot unit under field conditions at the DWTP of Rennes (France). Lab-scale experiments confirmed that ozonation increases the BDOC fraction, reduces the aromaticity of the DOC and produces small size organic compounds. Adsorption tests led to the conclusion that activated carbon unexpectedly removes BDOC first. Finally, the pilot unit results revealed an additional BDOC removal (from 0.10 to 0.15 mg L−1) of dissolved organic carbon from the raw water considered.
Keywords: Dissolved organic matter; Potable water treatment; Ozone; Biodegradation;
Analogies and differences between photocatalytic oxidation of chemicals and photocatalytic inactivation of microorganisms by Javier Marugán; Rafael van Grieken; Cristina Pablos; Carlos Sordo (789-796).
This study reports the analogies and differences found when comparing TiO2 photocatalytic treatment for chemical oxidation and microorganisms inactivation, using methylene blue and Escherichia coli as references, respectively. In both processes the activation is based on the same physicochemical phenomena and consequently a good correlation between them is observed when analyzing the effect of operational variables such as catalyst concentration or incident radiation flux, both factors influencing common stages such radiation absorption and generation of reactive oxygen species. However, different microbiological aspects (osmotic stress, repairing mechanism, regrowth, bacterial adhesion to the titania surface, etc) makes disinfection kinetics significantly more complex than the first-order profiles usually observed for the oxidation of chemical pollutants. Moreover, bacterial inactivation reactions are found to be extremely sensitive to the composition of water and modifications of the catalysts in comparison with the decolorization of the dye solutions, showing opposite behaviors to the presence of chlorides, incorporation of silver to the catalysts or the use of different types of immobilized TiO2 systems. Therefore, the activity observed for the photocatalytic oxidation of organics can not be always extrapolated to photocatalytic disinfection processes.
Keywords: Photocatalysis; Disinfection; E. coli; Methylene blue; Water composition; Immobilized TiO2;
Novel insights into sludge dewaterability by fluorescence excitation–emission matrix combined with parallel factor analysis by Guang-Hui Yu; Pin-Jing He; Li-Ming Shao (797-806).
Sludge dewatering is of major interest in sludge volume reduction and handling properties improvement. Here we report an approach of fluorescence excitation–emission matrix (EEM) combined with parallel factor (PARAFAC) analysis to elucidate the factors that influence sludge dewaterability. Sludge flocs from 11 full-scale wastewater treatment plants were collected to stratify into different extracellular polymeric substances (EPS) fractions and then to characterize their fluorescence EEMs. Both the normalized capillary suction time (CST) and specific resistance to filtration (SRF) were applied to determine sludge dewaterability. The results showed that fluorescence EEMs of tightly bound fractions were not affected by the wastewater sources. In contrast, fluorescence EEMs of loosely bound fractions were affected by the wastewater sources. All the fluorescence EEMs could be successfully decomposed into a six-component model by PARAFAC analysis. Both normalized CST and SRF were significantly correlated with component 1 [excitation/emission (Ex/Em) = (220, 275)/350] in the supernatant fraction, with components 5 [Ex/Em = (230, 280)/430] and 6 [Ex/Em = (250, 360)/460] in the slime and LB-EPS fraction. These results reveal that except for proteins-like substances (component 1), sludge dewaterability is also affected by humic acid-like and fulvic acid-like substances (components 5 and 6) in the slime and LB-EPS fractions. Furthermore, this paper presents a promising and facile approach (i.e., EEM-PARAFAC) for investigating sludge dewaterability.
Keywords: Dewaterability; Excitation–emission matrix; Extracellular polymeric substances; PARAFAC; Sludge flocs; Wastewater treatment plant;
Enhanced biological phosphorus removal by granular sludge: From macro- to micro-scale by Chang-Yong Wu; Yong-Zhen Peng; Shu-Ying Wang; Yong Ma (807-814).
In this study, phosphorus accumulating microbial granules were successfully cultivated in a sequencing batch reactor (SBR) using synthetic wastewater. The average diameter of the granules was 0.74 mm and the diameter distribution fitted well with normal distribution with a correlation coefficient of 0.989. Good performance of biological phosphorus removal (BPR) was obtained in the granular system. The average phosphorus removal efficiency was over 94.3% and the level of phosphorus in the effluent was below 0.50 mg/L during 300 days of operation. Particle analysis showed that positive charged particles were formed with the release of phosphorus in the anaerobic stage. These particles served as the cores of granules and stimulate the granulation. The maturated granules had a well-formed micro-pore structure with an average pore width between 291.5 nm and 446.5 nm. The spatial distribution of phosphorus decreased gradually from the surface to the center of the granules. Smaller granules had a higher specific area, pore width and phosphorus removal activity than bigger granules.
Keywords: Granule; Enhanced biological phosphorus removal; Structure; Porosity;
Highly efficient removal of heavy metals by polymer-supported nanosized hydrated Fe(III) oxides: Behavior and XPS study by Bingjun Pan; Hui Qiu; Bingcai Pan; Guangze Nie; Lili Xiao; Lu Lv; Weiming Zhang; Quanxing Zhang; Shourong Zheng (815-824).
The present study developed a polymer-based hybrid sorbent (HFO-001) for highly efficient removal of heavy metals [e.g., Pb(II), Cd(II), and Cu(II)] by irreversibly impregnating hydrated Fe(III) oxide (HFO) nanoparticles within a cation-exchange resin D-001 (R-SO3Na), and revealed the underlying mechanism based on X-ray photoelectron spectroscopy (XPS) study. HFO-001 combines the excellent handling, flow characteristics, and attrition resistance of conventional cation-exchange resins with the specific affinity of HFOs toward heavy metal cations. As compared to D-001, sorption selectivity of HFO-001 toward Pb(II), Cu(II), and Cd(II) was greatly improved from the Ca(II) competition at greater concentration. Column sorption results indicated that the working capacity of HFO-001 was about 4–6 times more than D-001 with respect to removal of three heavy metals from simulated electroplating water (pH ∼4.0). Also, HFO-001 is particularly effective in removing trace Pb(II) and Cd(II) from simulated natural waters to meet the drinking water standard, with treatment volume orders of magnitude higher than D-001. The superior performance of HFO-001 was attributed to the Donnan membrane effect exerted by the host D-001 as well as to the impregnated HFO nanoparticles of specific interaction toward heavy metal cations, as further confirmed by XPS study on lead sorption. More attractively, the exhausted HFO-001 beads can be effectively regenerated by HCl–NaCl solution (pH 3) for repeated use without any significant capacity loss.
Keywords: Hydrated ferric oxide; Polymeric nanocomposites; Heavy metals; Enhanced removal; Mechanism;
Development of a novel fouling suppression system in membrane bioreactors using an intermittent electric field by Kazuki Akamatsu; Wei Lu; Takashi Sugawara; Shin-ichi Nakao (825-830).
A novel membrane bioreactor system that uses an intermittent electric field was successfully developed to suppress membrane fouling, caused mainly by activated sludge. We found that the surface of the activated sludge is negatively charged, and propose the utilization of an electric repulsive force to move the sludge away from the membrane by applying an electric field only when the permeate flux has drastically declined because of membrane fouling. The experimental results showed that a field of 6 V cm−1, switched on and off every 90 s, significantly improved the removal of the activated sludge from the membrane and accordingly improved the average permeate flux.
Keywords: Membrane bioreactor; Fouling; Electric field; Activated sludge; Intermittent;
Nitrous oxide generation in full-scale biological nutrient removal wastewater treatment plants by Jeffrey Foley; David de Haas; Zhiguo Yuan; Paul Lant (831-844).
International guidance for estimating emissions of the greenhouse gas, nitrous oxide (N2O), from biological nutrient removal (BNR) wastewater systems is presently inadequate. This study has adopted a rigorous mass balance approach to provide comprehensive N2O emission and formation results from seven full-scale BNR wastewater treatment plants (WWTP). N2O formation was shown to be always positive, yet highly variable across the seven plants. The calculated range of N2O generation was 0.006–0.253 kgN2O–N per kgN denitrified (average: 0.035 ± 0.027). This paper investigated the possible mechanisms of N2O formation, rather than the locality of emissions. Higher N2O generation was shown to generally correspond with higher nitrite concentrations, but with many competing and parallel nitrogen transformation reactions occurring, it was very difficult to clearly identify the predominant mechanism of N2O production. The WWTPs designed and operated for low effluent TN (i.e. <10 mgN L−1) had lower and less variable N2O generation factors than plants that only achieved partial denitrification.
Keywords: Nitrous oxide; Nitrite; Mass balance; Mass transfer; Greenhouse gas; Biological nutrient removal;
Disinfection effectiveness of organic chloramines, investigating the effect of pH by Fariba Amiri; Maria M.F. Mesquita; Susan A. Andrews (845-853).
The disinfection effectiveness of three organic N-chloramines (chlorinated amino acids and peptides) on the bacteria Escherichia coli (E. coli) was investigated, including a more detailed study into the pH dependency of the disinfection effectiveness of N-chloroglycine. The organic N-chloramines were prepared by combining sodium hypochlorite with each amino acid or peptide (glycine, Ala-Ala and Arg-Gly-Asp-Ser), at a N:Cl molar ratio of 1:0.4, and then used to treat E. coli suspensions for 180 min.No evidence of inactivation was observed at pH 8.1 for any of the tested organic N-chloramines. At pH 6.0 and 6.9, E. coli inactivation with N-chloroglycine was characterized by an initial lag phase, during which little or no measurable inactivation occurred, followed by a pseudo-first-order inactivation. This is in accordance with other results in the literature and supports the two step microbial inactivation mechanism proposed by some authors. Inactivation rate coefficients (Chick–Watson and lag coefficients) were calculated by fitting the experimental data with the Rennecker–Mariñas model. pH-dependent inactivation kinetics were observed, with faster inactivation rates occurring at lower pH values, when temperature and chlorine-to-nitrogen ratio where kept constant. N-chloroglycine was determined to be the only contributor to the inactivation process in these experiments. The free chlorine contribution was considered to be negligible in all experiments due to its very low concentration. As well, given that the anionic form of N-chloroglycine is expected to be the single predominant species over the tested pH range, changes in residual N-chloroglycine speciation could not be responsible for the observed pH-dependency of E. coli inactivation. However, while pH stress was considered as a possible synergistic factor, no significant effect of pH stress on E. coli viability was observed at the tested pH levels.
Keywords: Monochloroglycine; Disinfection; E. coli; Kinetics; pH; Water;
Engineering a lignocellulosic biosorbent – Coir pith for removal of cesium from aqueous solutions: Equilibrium and kinetic studies by Harshala Parab; M. Sudersanan (854-860).
A novel method of engineering lignocellulosic biosorbent- coir pith (CP) by incorporation of nickel hexacyanoferrate (NiHCF), also referred to as Prussian blue analogue (PBA) inside its porous matrix is reported. Structural characterization confirmed the successful synthesis of NiHCF in the coir pith matrix. Sorption capacity of coir pith (CP) before and after loading of NiHCF was investigated for cesium (Cs) in batch equilibrium studies. Kinetic studies showed that the sorption process was rapid and saturation was attained within 30 min. The applicability of non linear Langmuir, Freundlich and Redlich Peterson isotherms was examined for the experimental data. The present studies revealed that there was nearly 100% increase in the sorption capacity of CP after its surface modification with NiHCF. Owing to its low cost, fast sorption kinetics and high uptake capacity, coir pith loaded with NiHCF (CP-NiHCF) seems to be one of the most promising biosorbents for recovery of cesium from liquid nuclear wastes.
Keywords: Cesium; Coir pith; Lignocellulosic; Nickel hexacyanoferrate; Sorption;
Why low powdered activated carbon addition reduces membrane fouling in MBRs by Maxime Remy; Virginie Potier; Hardy Temmink; Wim Rulkens (861-867).
Previous research had demonstrated that powdered activated carbon (PAC), when applied at very low dosages and long SRTs, reduces membrane fouling in membrane bioreactor (MBRs). In this contribution several mechanisms to explain this beneficial effect of PAC were investigated, including enhanced scouring of the membrane surface by PAC particles, adsorption of membrane foulants by PAC and subsequent biodegradation and a positive effect of PAC on the strength of the sludge flocs. It was concluded that the latter mechanism best explains why low dosages of PAC significantly reduce membrane fouling. Cheaper alternatives for PAC may have a similar effect.
Keywords: Membrane fouling; Membrane bioreactor; Powdered activated carbon; Adsorption; Flocculation; Filterability;
Concentration and size distribution of particles in abstracted groundwater by C.G.E.M. van Beek; A.H. de Zwart; M. Balemans; J.W. Kooiman; C. van Rosmalen; H. Timmer; J. Vandersluys; P.J. Stuyfzand (868-878).
Particle number concentrations have been counted and particle size distributions calculated in groundwater derived by abstraction wells. Both concentration and size distribution are governed by the discharge rate: the higher this rate the higher the concentration and the higher the proportion of larger particles. However, the particle concentration in groundwater derived from abstraction wells, with high groundwater flow velocities, is much lower than in groundwater from monitor wells, with minimal flow velocities. This inconsistency points to exhaustion of the particle supply in the aquifer around wells due to groundwater abstraction for many years. The particle size distribution can be described with the help of a power law or Pareto distribution. Comparing the measured particle size distribution with the Pareto distribution shows that particles with a diameter >7 μm are under-represented. As the particle size distribution is dependent on the flow velocity, so is the value of the “Pareto” slope β.
Keywords: Particle concentration; Particle size distribution; Groundwater; Pareto;
Batch and column adsorption of herbicide fluroxypyr on different types of activated carbons from water with varied degrees of hardness and alkalinity by L.M. Pastrana-Martínez; M.V. López-Ramón; M.A. Fontecha-Cámara; C. Moreno-Castilla (879-885).
There has been little research into the effects of the water hardness and alkalinity of surface waters on the adsorption of herbicides on activated carbons. The aim of this study was to determine the influence of these water characteristics on fluroxypyr adsorption on different activated carbons. At low fluroxypyr surface concentrations, the amount adsorbed from distilled water was related to the surface hydrophobicity. Surface area of carbons covered by fluroxypyr molecules ranged from 60 to 65%. Variations in fluroxypyr solubility with water hardness and alkalinity showed a salting-in effect. Calcium, magnesium and bicarbonate ions were adsorbed to a varied extent on the activated carbons. The presence of fluroxypyr in solution decreased their adsorption due to a competition effect. K F from the Freundlich equation linearly increased with water hardness due to salt-screened electrostatic repulsions between charged fluroxypyr molecules. The amount adsorbed from distilled water was largest at high fluroxypyr solution concentrations, because there was no competition between inorganic ions and fluroxypyr molecules. The column breakthrough volume and the amount adsorbed at breakthrough were smaller in tap versus distilled water. Carbon consumption was lower with activated carbon cloth than with the use of granular activated carbon.
Keywords: Herbicide adsorption; Activated carbons; Fluroxypyr breakthrough curves; Water hardness; Water alkalinity;
Microwave-hydrothermal decomposition of perfluorooctanoic acid in water by iron-activated persulfate oxidation by Yu-Chi Lee; Shang-Lien Lo; Pei-Te Chiueh; Yau-Hsuan Liou; Man-Li Chen (886-892).
The microwave-hydrothermal decomposition of persistent and bioaccumulative perfluorooctanoic acid (PFOA) in aqueous solution using persulfate activated by zero-valent iron (ZVI) at 60 and 90 °C was examined. The results of laboratory study reveal that when PFOA is treated with 5 mM persulfate (PS) and ZVI at 90 °C for 2 h, 67.6% of PFOA is effectively decomposed to form shorter-chain perfluorinated carboxylic acids (PFCAs) and fluoride ions, with 22.5% defluorination efficiency. Introducing ZVI into the PFOA solution with PS addition will lead to synergetic effect that accelerates the PFOA decomposition rate, and reduces the reaction time. ZVI not only decomposes PFOA, but also releases ferrous ions to lower the activation energy of PS while forming sulfate free radicals at a lower reaction temperature. The combined use of ZVI and persulfate will lead to significant savings in energy consumption and reduction of process time.
Keywords: Microwave; Perfluorooctanoic acid; PFOA; Persulfate; Zero-valent iron; Hydrothermal decomposition;
Detection of Toxoplasma gondii oocysts and surrogate microspheres in water using ultrafiltration and capsule filtration by Karen Shapiro; Jonna A.K. Mazet; Alexander Schriewer; Stefan Wuertz; Heather Fritz; Woutrina A. Miller; John Largier; Patricia A. Conrad (893-903).
While reports on waterborne infections with Toxoplasma gondii are emerging worldwide, detection of this zoonotic parasite in water remains challenging. Lack of standardized and quantitative methods for detection of T. gondii oocysts in water also limits research on the transport and fate of this pathogen through aquatic habitats. Here, we compare the ability of hollow-fiber ultrafiltration and capsule filtration to concentrate oocysts in spiked tap water, fresh surface water, and seawater samples. Detection of T. gondii oocysts in concentrated samples was achieved using molecular methods, as well as visually via epifluorescent microscopy. In addition to oocysts, water samples were spiked with T. gondii surrogate microspheres, and detection of microspheres was performed using flow cytometry and epifluorescent microscopy. Results demonstrate that both water concentration methods followed by microscopy allowed for quantitative detection of T. gondii oocysts and surrogate microspheres. For T. gondii oocysts, microscopy was more sensitive than TaqMan and conventional PCR, and allowed for detection of oocysts in all water samples tested. Compared with flow cytometry, microscopy was also a more cost-efficient and precise method for detection of fluorescent surrogate microspheres in tap, fresh and seawater samples. This study describes a novel approach for quantitative detection of T. gondii oocysts in drinking and environmental water samples. The techniques described for concentrating and detecting surrogate microspheres have broad application for evaluating the transport and fate of oocysts, as well as the efficiency of water treatment methods for removal of T. gondii from water supplies.
Keywords: Toxoplasma gondii; Surrogate; Microsphere; Water; Detection; Ultrafiltration;
Development of solar-driven electrochemical and photocatalytic water treatment system using a boron-doped diamond electrode and TiO2 photocatalyst by Tsuyoshi Ochiai; Kazuya Nakata; Taketoshi Murakami; Akira Fujishima; Yanyan Yao; Donald A. Tryk; Yoshinobu Kubota (904-910).
A high-performance, environmentally friendly water treatment system was developed. The system consists mainly of an electrochemical and a photocatalytic oxidation unit, with a boron-doped diamond (BDD) electrode and TiO2 photocatalyst, respectively. All electric power for the mechanical systems and the electrolysis was able to be provided by photovoltaic cells. Thus, this system is totally driven by solar energy. The treatment ability of the electrolysis and photocatalysis units was investigated by phenol degradation kinetics. An observed rate constant of 5.1 × 10−3 dm3 cm−2 h−1 was calculated by pseudo-first-order kinetic analysis for the electrolysis, and a Langmuir–Hinshelwood rate constant of 5.6 μM−1 min−1 was calculated by kinetic analysis of the photocatalysis. According to previous reports, these values are sufficient for the mineralization of phenol. In a treatment test of river water samples, large amounts of chemical and biological contaminants were totally wet-incinerated by the system. This system could provide 12 L/day of drinking water from the Tama River using only solar energy. Therefore, this system may be useful for supplying drinking water during a disaster.
Keywords: Boron-doped diamond electrode; TiO2 photocatalyst; Wastewater treatment; Photovoltaic cells; Sterilization;
Measurement of phenols dearomatization via electrolysis: The UV-Vis solid phase extraction method by Ronald Vargas; Carlos Borrás; Jorge Mostany; Benjamin R. Scharifker (911-917).
Dearomatization levels during electrochemical oxidation of p-methoxyphenol (PMP) and p-nitrophenol (PNP) have been determined through UV-Vis spectroscopy using solid phase extraction (UV-Vis/SPE). The results show that the method is satisfactory to determine the ratio between aromatic compounds and aliphatic acids and reaction kinetics parameters during treatment of wastewater, in agreement with results obtained from numerical deconvolution of UV-Vis spectra. Analysis of solutions obtained from electrolysis of substituted phenols on antimony-doped tin oxide (SnO2 ―Sb) showed that an electron acceptor substituting group favored the aromatic ring opening reaction, preventing formation of intermediate quinone during oxidation.
Keywords: Dearomatization level; Electrochemical oxidation of phenols; Solid phase extraction; UV-Vis spectroscopy; Metal oxide anode;
Effect of Ni2+ ion doping on the physical characteristics and chromate adsorption behavior of goethite by Syed Mustafa; Sadullah Khan; Muhammad Iqbal Zaman (918-926).
Pure and 0.25% Ni2+ ion doped goethite samples, prepared by the coprecipitation method, were characterized for pH of Point of Zero Charge (pHpzc), Surface area, XRD, TG-DTA, FTIR and TEM. Effect of Ni2+ ions doping on the adsorption of chromate on goethite was investigated at pH-3, -5 and -7 in the temperature range 303–323 K. It was found that adsorption of chromate increases with decreasing pH and increasing temperature on both pure and Ni2+-doped goethite. Adsorption of chromate was found to increase from 61.4% to 82.92% with Ni2+ ion doping in goethite matrix at the lowest pH (pH-3) and highest temperature (323 K), using 1.02 mmol L−1 chromate solution. Langmuir isotherm was found applicable to the experimental data. The values of Δ H ¯ (isosteric heat of adsorption) calculated for both the samples of goethite were positive, showing endothermic nature of the adsorption process.
Keywords: Ni-doped goethite; Chromate; % adsorption; Isosteric heat;
Ferrate(VI) oxidation of glycine and glycylglycine: Kinetics and products by Nadine Noorhasan; Bhavesh Patel; Virender K. Sharma (927-935).
Amino acids and peptides may form potentially harmful disinfection byproducts during the conventional treatment of water and wastewater. Removal of these parent compounds by the use of the environmental-friendly oxidant, ferrate(VI) (FeVIO4 2−, Fe(VI)) was assessed by studying the kinetics of the oxidation of glycine (NH3 +CH2COOH, Gly) and glycylglycine (NH3 +CH2CONHCH2COOH, Gly–Gly) as a function of pH (4.0–12.4) at 25 °C. This study with Gly–Gly represents an initial investigation of oxidation of peptides by Fe(VI). Generally, the second-order rate constant (k) increased with decreased pH in the basic pH region, but this trend was reversed in the acidic pH range. Consideration of the reactivity of three oxidants (H2FeO4, HFeO4 −, and FeO4 2−) with three species of Gly and Gly–Gly (positive, neutral, and negative) reasonably explained the pH dependence of the rates. At pH 9.0, the molar consumption of Fe(VI) was nearly equal to that of Gly. The reaction of Fe(VI) with Gly at molar ratios of 1.0 and 2.0 ([Fe(VI)]:[Gly]) produced ammonia, carbon dioxide, and acetate. A reaction scheme is proposed which explains the formation of these products. The values of k for oxidation of iminodiacetate and nitriloacetate at pH 7.0 were also determined in order to compare oxidation of amines by Fe(VI). The calculated half-lives at neutral pH for the oxidation of primary and secondary amines were in seconds while decomposition of tertiary amines would occur in minutes. Overall, the reactivity of Fe(VI) with Gly and Gly–Gly indicates the significant potential of Fe(VI) to remove amine- and peptide-containing pollutants in water and wastewater.
Keywords: Amines; Amino acids; Ferrate; Oxidation; Peptides; Removal;
Fate of β-blocker human pharmaceuticals in surface water: Comparison of measured and simulated concentrations in the Glatt Valley Watershed, Switzerland by Alfredo C. Alder; Christian Schaffner; Marius Majewsky; Jörg Klasmeier; Kathrin Fenner (936-948).
This study focused on the occurrence and fate of four β-blockers (atenolol, sotalol, metoprolol, propranolol) in wastewater and surface water. Measured concentrations were compared with predicted concentrations using an implementation of the geo-referenced model GREAT-ER for the Glatt Valley Watershed (Switzerland). Particularly, the question was addressed how measured and simulated data could complement each other for the exposure assessment of human pharmaceuticals and other micropollutants entering surface water through wastewater treatment plants (WWTP).Concentrations in the Glatt River ranged from <LOQ to 83 ng L−1 with the highest concentrations found for atenolol. Higher loads were measured on days with combined sewer overflow events during high flow conditions.GREAT-ER was able to predict spatially resolved river concentrations based on average consumption and excretion data, removal in wastewater treatment plants (WWTPs) and dissipation and degradation processes in surface water within a factor of 2. These results indicate that modelling might be sufficient to estimate daily average exposure concentrations for compounds that are either recalcitrant or whose degradation and sorption behaviour can be predicted with confidence based on laboratory experiments. Chemical measurements, in contrast, should be reserved for assessing point sources, investigating mechanisms which lead to short-term temporal fluctuations in compound loads, and determining in-situ degradation rates in conjunction with modelling.
Keywords: Beta blockers; Wastewater; Surface water; Exposure assessment; Model evaluation; GREAT-ER;
Differentiation and identification of Shigella spp. and enteroinvasive Escherichia coli in environmental waters by a molecular method and biochemical test by Bing-Mu Hsu; Shu-Fen Wu; Shih-Wei Huang; Yu-Jung Tseng; Dar-Der Ji; Jung-Sheng Chen; Feng-Cheng Shih (949-955).
Both Shigella spp. and enteroinvasive Escherichia coli (EIEC) are important human pathogens that are responsible for the majority of cases of endemic bacillary dysentery. However, they are difficult to identify and differentiate by biochemical tests or molecular methods alone. In this study, we developed a procedure to detect Shigella spp. and EIEC from environmental water samples using membrane filtration followed by nutrient broth enrichment, isolation using selective culture plates, and identification of the invasion plasmid antigen H (ipaH) gene by PCR amplification and DNA sequencing. Finally, we used a biochemical test and a serological assay to differentiate between Shigella and EIEC. Among the 93 water samples from nine reservoirs and one watershed, 76 (81.7%) water samples of culture plates had candidate colonies of Shigella and EIEC and 5 water samples were positive (5.4%) for a Shigella- and EIEC-specific polymerase chain reaction targeting the ipaH gene. Guided by the molecular method, the biochemical test, and the serological assay, 11 ipaH gene-positive isolates from 5 water samples were all identified as EIEC.
Keywords: Shigella; Enteroinvasive Escherichia coli; Invasion plasmid antigen H gene;
Tap water consumers differ from non-consumers in chlorine flavor acceptability but not sensitivity by Sabine Puget; Noëlle Beno; Claire Chabanet; Elisabeth Guichard; Thierry Thomas-Danguin (956-964).
Unpleasant taste and especially chlorine flavor is one of the most common reasons advocated for choosing tap water alternatives as drinking water. As a consequence, the putative link between sensitivity to chlorine flavor and tap water consumption is an issue in drinking water habits studies. In the present study, we set out to examine such a link following a strategy in which we measured chlorine flavor perception at threshold and supra-threshold level for two groups of participants selected on their drinking water consumption habits. The first group included exclusive tap water consumers and the second group included exclusive bottled water consumers. In a first experiment, we used the constant stimuli procedure to evaluate the chlorine flavor detection threshold of a group of 20 tap water consumers and a group of 20 non-consumers. In a second experiment, a group of 18 tap water consumers and a group of 17 non-consumers evaluated supra-threshold flavor intensity, liking and acceptability for eight chlorinated solutions (0–10 mg/L Cl2). The results revealed no significant difference in chlorine flavor detection threshold and supra-threshold sensitivity between tap water consumers and non-consumers. Nevertheless, tap water consumers showed a higher liking score for chlorinated solutions and were found to be more inclined to accept these solutions as drinking water. Taken together these findings suggested that consumers may disparage chlorine flavor in drinking water on the basis of their tap water cognitive representation.
Keywords: Chlorine flavor; Tap water consumption; Thresholds; Flavor intensity; Liking; Acceptability;
Arsenic sorption on TiO2 nanoparticles: Size and crystallinity effects by Gautham Jegadeesan; Souhail R. Al-Abed; Vijayakumar Sundaram; Hyeok Choi; Kirk G. Scheckel; Dionysios D. Dionysiou (965-973).
Single solute As (III) and As (V) sorption on nano-sized amorphous and crystalline TiO2 was investigated to determine: size and crystallinity effects on arsenic sorption capacities, possible As (III) oxidation, and the nature of surface complexes. Amorphous and crystalline nanoparticles were prepared using sol-gel synthesis techniques. For amorphous TiO2, solute pH in the range of 4–9 had a profound impact on only As (V) sorption. As (III) and As (V) sorption isotherms indicated that sorption capacities of the different TiO2 polymorphs were dependent on the sorption site density, surface area (particle size) and crystalline structure. When normalized to surface area, As (III) surface coverage on the TiO2 surface remained almost constant for particles between 5 and 20 nm. However, As (V) surface coverage increased with the degree of crystallinity. X-ray absorption spectroscopic analysis provided evidence of partial As (III) oxidation on amorphous TiO2 rather than crystalline TiO2. The data also indicated that As (III) and As (V) form binuclear bidentate inner-sphere complexes with amorphous TiO2 at neutral pH.
Keywords: Arsenic; TiO2; Speciation;
Detection method and toxicity study of a new disinfection by-product, 2,2,4-trichloro-5-methoxycyclopenta-4-ene-1,3-dione (TCMCD), in chlorinated drinking water by Xing Shen; Zhijuan Shao; Qiming Xian; Huixian Zou; Shixiang Gao; Jinqi Zhang (974-980).
The detection method of 2,2,4-trichloro-5-methoxycyclopenta-4-ene-1,3-dione (TCMCD), a new disinfection by-product, was established and optimized. Drinking water samples from eight cities in Jiangsu Province, China, were analyzed and TCMCD was detected ranging from 42 to 171 ng/L among the water samples from the three cities. Toxicity of TCMCD was studied using the exposure of zebrafish and the human peripheral blood lymphocyte micronucleus assay. The results showed that TCMCD is fatal to zebrafish embryos and is a potential mutagen to human beings.
Keywords: Drinking water; New disinfection by-products; TCMCD; Detection method; Toxicity;
Sorption of the pharmaceuticals carbamazepine and naproxen to dissolved organic matter: Role of structural fractions by Adi Maoz; Benny Chefetz (981-989).
Pharmaceutical compounds and dissolved organic matter (DOM) are co-introduced into the environment by irrigation with reclaimed wastewater and/or application of biosolids. In this study, we evaluate the role and mechanism of interaction of the pharmaceuticals naproxen and carbamazepine with structural fractions of biosolids-derived DOM. Sorption interactions were estimated from dialysis-bag experiments at different pHs.Sorption of naproxen and carbamazepine by the hydrophobic acid fraction exhibited strong pH-dependence. With both pharmaceuticals, the highest sorption coefficients (K DOC) were at pH 4. With the hydrophobic neutral fraction, pH affected only naproxen sorption (decreasing with increasing pH). Among the hydrophilic DOM fractions, the hydrophilic acid fraction exhibited the highest K DOC value for carbamazepine, probably due to their bipolar character. In the hydrophilic acid fraction-naproxen system, significant anionic repulsion was observed with increasing pH. The hydrophilic base fraction contains positively charged functional groups. Therefore with increasing ionization of naproxen (with increasing pH), K DOC to this fraction increased. The hydrophilic neutral fraction exhibited the lowest K DOC with both studied pharmaceuticals.The K DOC value of carbamazepine with the bulk DOM sample was higher than the calculated K DOC value based on sorption by the individual isolated fractions. The opposite trend was observed with naproxen at pH 8: the calculated K DOC value was higher than the value obtained for the bulk DOM. These results demonstrate that DOM fractions interact with each other and do not act as separate sorption domains.
Keywords: Binding; Municipal wastewater; Sludge; Pharmaceutical; DOM; Hydrophobic; Hydrophilic; Fractionation;
Improvement of desalination efficiency in capacitive deionization using a carbon electrode coated with an ion-exchange polymer by Yu-Jin Kim; Jae-Hwan Choi (990-996).
A composite carbon electrode coated with a cation-exchange polymer, crosslinked poly(vinyl alcohol) with sulfosuccinic acid, was fabricated to enhance the desalination performance of a capacitive deionization (CDI) system. The electrochemical properties of the prepared electrode were characterized by impedance spectroscopy, and desalination experiments were carried out at various operating conditions using a CDI cell with carbon electrodes only, and a membrane-capacitive-deionization (MCDI) cell including a coated-carbon electrode, to evaluate the effect of the coated-carbon electrode on desalination performance. The electrical resistance of the coated electrode was increased by a small amount over the uncoated electrode, but the capacitance was improved by the coating. In the CDI cell, the salt-removal efficiencies were in the range of 50–67%, while the efficiencies increased to 75–85% for the MCDI cell. Depending on the operating conditions, the salt-removal and current efficiencies of the MCDI cell were enhanced by 27–56% and 69–95%, respectively, compared to the CDI cell. The enhanced efficiency for the MCDI cell was attributed to the selective transport of cations between the electrode surface and bulk solution due to the cation-exchange coating layer.
Keywords: Capacitive deionization; Ion-exchange polymer; Carbon electrode; Electric double layer; Salt-removal efficiency; Current efficiency;
Study of a membrane bioreactor with glass fiber flat grille modules and the modules' optimization based on the local critical flux theory by Dongdong Yuan; Yaobo Fan; Yan Yu; Guoliang Xu; Wenjing Yang; Guangxia Wu (997-1005).
A novel flat grille membrane module using inorganic glass fibers as filter media is proposed for use in a membrane bioreactor for wastewater treatment. A model which integrates the concepts of back transport velocity, spatial local critical flux and temporal variation of the local flux has been developed. The membrane module was optimized based on experimental results and calculations using the model. The optimized parameters include the volume ratio of membrane solution for the surface modification of glass fibers, the fiber inner diameter and fiber length. The optimal values were 1:2 and 5 mm respectively but the length had little effect on the performance of the module. The critical time was then calculated with the model and an equation developed. The result was in very good agreement with the observed one. Finally, the performance of the glass fiber MBR was monitored. The effluent quality and stability of the system were comparable to that of conventional MBRs. This MBR will be a promising technique for wastewater treatment given its low cost, high strength and good effluent quality.
Keywords: Inorganic glass fiber; MBR; Module configuration; Surface modification; Local critical flux; Critical time;
Bayesian model for flow-class dependent distributions of fecal-indicator bacterial concentration in surface waters by Mary E. Schoen; Mitchell J. Small; Jeanne M. VanBriesen (1006-1016).
A Bayesian statistical water quality model is demonstrated to predict fecal-indicator bacterial concentrations for waterbodies without sufficient monitoring data for data-intensive modeling techniques. Using a truncated bivariate normal likelihood function and the readily available observations of flow and bacterial concentration, the Bayesian approach propagates the uncertainty in the model parameterization to the final predictions of in-stream bacterial concentration. The proposed model captures the variation in the magnitude of bacterial loading between dry and wet conditions by estimating separate sets of model parameters for different flow conditions, but also has the capability to pool the data among flow conditions. The model can be used in two ways: first, the model specifies the percent of time that the recreational season in-stream concentration is not in compliance with the relevant water quality standard, and second, the model estimates the necessary bacterial load reduction for multiple flow conditions to meet the relevant water quality standard. Using an eleven year monitoring record for a site sampled at a monthly frequency on the Youghiogheny River in southwestern Pennsylvania, USA, the model parameters are updated and posterior predictions are generated for each 2-year increment. After six years of sampling, the predicted percent of time that the recreational season in-stream bacterial concentration is not in compliance with the relevant water quality is 82% with 95% CI(80,85), and the bacterial load reductions required to meet the standard are 14.7 CI(14.6,14.8), 14.5 CI(14.3, 14.6), and 14.0 CI(13.9, 14.2) log10(cfu/day) for the high, normal, and dry flow conditions, respectively. The change in estimated load reduction and percent exceedance resulting from additional monitoring for this site becomes small after six years of sampling, indicating that a decision does not need to be postponed for additional monitoring.
Keywords: Fecal indicator; Bayesian model; Surface water;
Design parameters for sludge reduction in an aquatic worm reactor by T.L.G. Hendrickx; H. Temmink; H.J.H. Elissen; C.J.N. Buisman (1017-1023).
Reduction and compaction of biological waste sludge from waste water treatment plants (WWTPs) can be achieved with the aquatic worm Lumbriculus variegatus. In our reactor concept for a worm reactor, the worms are immobilised in a carrier material. The size of a worm reactor will therefore mainly be determined by the sludge consumption rate per unit of surface area. This design parameter was determined in sequencing batch experiments using sludge from a municipal WWTP. Long-term experiments using carrier materials with 300 and 350 μm mesh sizes showed surface specific consumption rates of 45 and 58 g TSS/(m2 d), respectively. Using a 350 μm mesh will therefore result in a 29% smaller reactor compared to using a 300 μm mesh. Large differences in consumption rates were found between different sludge types, although it was not clear what caused these differences. Worm biomass growth and decay rate were determined in sequencing batch experiments. The decay rate of 0.023 d−1 for worms in a carrier material was considerably higher than the decay rate of 0.018 d−1 for free worms. As a result, the net worm biomass growth rate for free worms of 0.026 d−1 was much higher than the 0.009–0.011 d−1 for immobilised worms. Finally, the specific oxygen uptake rate of the worms was determined at 4.9 mg O2/(g ww d), which needs to be supplied to the worms by aeration of the water compartment in the worm reactor.
Keywords: Lumbriculus variegatus; Oxygen uptake rate; Sludge load; Sludge reduction; Sludge type; Worm density;
Erratum to “Effect of bromide on the formation of disinfection by-products during wastewater chlorination” [Water Research 43 (2009) 9] by Ying-Xue Sun; Qian-Yuan Wu; Hong-Ying Hu; Jie Tian (1024).
Erratum to “Startup of reactors for anoxic ammonium oxidation: Experiences from the first full-scale anammox reactor in Rotterdam” [Water Research 41 (2007) 18] by Wouter R.L. van der Star; Wiebe R. Abma; Dennis Blommers; Jan-Willem Mulder; Takaaki Tokutomi; Marc Strous; Cristian Picioreanu; Mark C.M. van Loosdrecht (1025).