Removal of 17α-ethynylestradiol from aqueous solutions by a hybrid PAC/UF process

This study investigated the removal of 17α-ethynylestradiol (EE2) from water using activated carbon adsorption and powdered activated carbon/ultrafiltration (PAC/UF). EE2 was easily adsorbed by PAC. The adsorption of EE2 fitted the Freundlich model well. The influences of initial EE2 concentration, filtration rate, PAC dose, natural organic matter (NOM), and sodium dodecyl benzene sulfonate (SDBS) were investigated. The EE2 concentration and filtration rate had no significant effect on EE2 removal, whereas the addition of PAC had a significant effect on EE2 removal. The removal rate of EE2 increased dramatically from 7.01% to 80.03% as the PAC dose was increased from 0 to 10 mg/L. Both SDBS and NOM decreased the EE2 removal efficiency. The removal efficiency of EE2 in the PAC/UF process decreased from 86.77% to 42.64% as the SDBS concentration was increased from 0 to 50 mg/L. It was concluded that activated carbon adsorption and PAC/UF can be used for the effective removal of EE2 from water.Keywords: 17-α-ethynylestradiol, adsorption, ultrafiltration, PAC/UF process, removal efficienc

Evaluation of DNA Extraction Methods for the Analysis of Microbial Community in Biological Activated Carbon

It is difficult to isolate DNA from biological activated carbon (BAC) samples used in water treatment plants, owing to the scarcity of microorganisms in BAC samples. The aim of this study was to identify DNA extraction methods suitable for a long-term, comprehensive ecological analysis of BAC microbial communities. To identify a procedure that can produce high molecular weight DNA, maximizes detectable diversity and is relatively free from contaminants, the microwave extraction method, the cetyltrimethylammonium bromide (CTAB) extraction method, a commercial DNA extraction kit, and the ultrasonic extraction method were used for the extraction of DNA from BAC samples. Spectrophotometry, agarose gel electrophoresis and polymerase chain reaction (PCR)-restriction fragment length polymorphisms (RFLP) analysis were conducted to compare the yield and quality of DNA obtained using these methods. The results showed that the CTAB method produce the highest yield and genetic diversity of DNA from BAC samples, but DNA purity was slightly less than that obtained with the DNA extraction-kit method. This study provides a theoretical basis for establishing and selecting DNA extraction methods for BAC samples

Bromate Ion Formation in Dark Chlorination and Ultraviolet/Chlorination Processes for Bromide-Containing Water

Bormate (BrO3-) is a carcinogenic chemical produced in ozonation or chlorination of bromide-containing water. Although its formation in seawater with or without sunlight has been previously investigated, the formation of bromate in dilute solutions, particularly raw water for water treatment plant, is unknown. In this article, the results of bench scale tests to measure the formation rates of bromate formation in dilute solutions, including de-ionized water and raw water from Yangtze River, were presented in dark chlorination and ultraviolet (UV)/chlorination processes. And the effects of initial pH, initial concentration of NaOCl, and UV light intensity on bromate formation in UV/chlorination of the diluted solutions were investigated. Detectable bromate was formed in dark chlorination of the two water samples with a relatively slow production rate. Under routine disinfecting conditions, the amount of formed bromate is not likely to exceed the national standards (10 μg/L). UV irradiation enhanced the decay of free chlorine, and, simultaneously, 6.6%-32% of Br- was oxidized to BrO3-. And the formation of bromate exhibited three stages: rapid stage, slow stage and plateau. Under the experimental conditions (pH = 4.41-11.07, CCl2= 1.23-4.50 mg/L), low pH and high chlorine concentration favored the generation of bromate. High light intensity promoted the production rate of bromate, but decreased its total generation amount due to acceleration of chlorine decomposition

Stability of Newfound Nitrogenous Disinfection by-Products Haloacetamides in Drinking Water

The conversion of drinking water disinfection process from free chlorine to mono-chloramine reduces the formation of trihalomethanes (THM), but increases the concentration of nitrogenous disinfection by-products (N-DBP), especially five new haloacetamides (HAcAm) including monochloroacetamide (MCAcAm), dichloroacetamide (DCAcAm), trichloroacetamide (TCAcAm), monobromoacetamide (MBAcAm) and dibromoacetamide (DBAcAm). Among these HAcAms, DCAcAm and TCAcAm are normally present in drinking water at a higher concentration. The hydrolysis characteristics with different pH values and chlorination characteristics under different chlorine dosages of HAcAm were studied by combination with linear free-energy relationship (LFER). Based on the hydrolysis and chlorination characteristics of HAcAm, the reaction pathways of hydrolysis and chlorination for HAcAm were also investigated by detection of final product haloacetic acids (HAA). The results indicated that DCAcAm reacted slowly with water in highly acidic condition (pH=4) but was stable at pH 5 within 7 d reaction time. Acid environment can not cause TCAcAm hydrolysis reaction. Obvious hydrolysis reactions of DCAcAm and TCAcAm were discovered in alkaline conditions, which followed the first order reaction. The water sample containing DCAcAm and TCAcAm could be preserved by adjusting pH to 5. The use of chlorine disinfection and increment of chlorine dosage caused the amount of THM and HAA to go up in drinking water, however, it maybe resulted in the decrease of N-DBP such as HAcAm. Trichloroacetic acid (TCAA) was produced rapidly by TCAcAm hydrolysis at pH 10. For chlorination of TCAcAm, relatively stable Cl-N-TCAcAm was produced from a reaction between TCAcAm and HOC1, then continued to generate TCAA and NHCl2 at a higher concentration of HOC1

Adsorption of Perchlorate from Water Using Calcined Iron-Based Layered Double Hydroxides

In this study, a new calcined iron-based layered double hydroxide material was synthesized to adsorb perchlorate from water. The MgFe-CO 3 layered double hydroxides (MgFe-LDH) were prepared at pH 9-10 and with different molar Mg/Fe ratios (2-5) using a co-precipitation method, and then calcined at a temperature range of 300-900°C. Results showed that the best synthesis conditions to maximize the perchlorate adsorption capacity of the calcined MgFe-CO 3 layered double hydroxide (MgFe-CLDH) were the calcination temperature of 550°C and [Mg]/[Fe]=3. Furthermore, the adsorbents and their adsorption products were characterized by X-ray, FT-IR and thermogravimetric analyses. The layered double hydroxide structures in the adsorbent were lost during calcination at 550°C, but were reconstructed subsequent to adsorption of perchlorate, indicating that the \u27memory effect\u27 appeared to play an important role in perchlorate adsorption. The perchlorate adsorption pattern was well described by the pseudo-second-order kinetic model, while the Freundlich isotherm provided the best fitting of adsorption isotherms with the experimental data at chemical equilibrium at 25°C. Indeed, an initial solution pH of 4-10, a higher adsorbent dose, and a lower initial perchlorate concentration typically favored the removal of perchlorate from water. Furthermore, co-existing anions, including PO 4 3-, SO 4 2-, Cl - and NO 3 -, inhibited the perchlorate adsorption, to different degrees. At 25°C, MgFe-3 CLDH=1.33g/L (calcination temperature=550°C and [Mg]/[Fe]=3), and the initial solution pH of 4-10, 2000μg/L of perchlorate was almost all adsorbed within 720min. This study demonstrated that the new calcined iron-based layered double hydroxide was a promising adsorbent for control of the perchlorate pollution in water

Influencing Factors and Kinetic Studies of Imidacloprid Degradation by Ozonation

Batch kinetic tests in ozonation of imidacloprid from water were performed in this study. The pseudo-first-order rate constant of imidacloprid degradation was increased from 0.079 to 0.326 min−1 with the increasing pH from 6.02 to 8.64 at an average ozone dose of 1.149 mg L−1. When the alkalinity was increased from 0 to 250 mg L−1 NaHCO3, the pseudo-first-order rate constants decreased from 0.121 to 0.034 min−1. These results suggested that the predominant oxidant gradually switched from ozone to hydroxyl radicals (.OH)) with the increase in solution pH. The secondary rate constant kO3-Imid (10.92 ± 0.12 M−1s−1) for the reaction of imidacloprid and molecular ozone was determined at pH 2.0 and in the presence of 50 mM ter-butyl alcohol (p-chlorobenzoic acid, pCBA), respectively. An indirect competition method was used to determine the secondary rate constant for .OH oxidation of imidacloprid in the presence of pCBA as the reference compound. The rate constants k.OH-imid were estimated to range 2.65–3.79 M−1s−1 at pH 6.02–8.64. Results obtained from this study demonstrate that ozonation appears to be an effective method to remove imidacloprid from water

Powder Activated Carbon Pretreatment of a Microfiltration Membrane for the Treatment of Surface Water

This study focused on the effect of powder activated carbon (PAC) adsorption on microfiltration (MF) membrane performance. The results showed that PAC pretreatment offered high organic matter removal rates for both dissolved organic carbon (DOC) and ultraviolet absorbance at 254 nm (UV254) during 10–200 mg/L PAC dosage. The removal efficiencies of organic matter by MF membrane filtration decreased with the increase of organic matter removal rate by PAC adsorption. PAC mainly removed organic matter of about 3 kDa molecular weight (MW). MF membrane maintained more than 5 kDa MW organic matter on the membrane after PAC adsorption. The results of membrane filtration indicated that PAC pretreatment slightly promoted membrane flux, regardless of PAC dosage. It seems that the organic matter fouling membrane was concentrated in more than 3 kDa MW. PAC removed markedly less than 3 kDa MW organic matter and had less effect on more than 3 kDa organic matter. Thus, PAC cannot reduce membrane fouling