Pilot Study of Ultrafiltration-Nanofiltration Process for the Treatment of Raw Water from Huangpu River in China

Pilot-scale test was carried out to evaluate the performance of a combined ultrafiltration (UF)-nanofiltration (NF) membrane process for the treatment of raw water from Huangpu River, Shanghai, in China. Results showed that UF could significantly remove turbidity, iron and manganese, and also could retain a part of high molecular weight (MW) organic compounds. Subsequently, NF could further reject low MW organics and inorganic salts, and ensured the treated water to reach the Standards for Drinking Water Quality in China. It seemed that 90 L/m2&#183h was an appropriate permeate flux for UF system when the raw water was directly filtered by UF membrane, the addition of coagulant (alum or ferric chloride) was not preferable to mitigate the fouling of the UF membrane. After near 120 days operation, the permeate flux of NF could be main-tained at 24-25 L/m2&#183h steadily, and no chemical clean was required.

Degradation of bisphenol-A using ultrasonic irradiation assisted by low-concentration hydrogen peroxide

This study investigated the degradation of bisphenol-A （BPA） by ultrasonic irradiation in the presence of different additives （H2O2, air bubbles and humic acid） under various operating conditions, i.e., ultrasonic frequency, power intensity and power density. The results demonstrated that the BPA degradation followed pseudo first-order kinetics under different experimental conditions. The optimum power intensities were 0.9, 1.8, and 3.0 W/cm2 at the frequencies of 400, 670, and 800 kHz, respectively. At the fixed frequency （800 kHz）, the degradation rate of BPA was shown proportional to the increase of power density applied. With this manner, the BPA sonolysis could be facilitated at H202 dosage being lower than 0.1 mmol/L; while BPA degradation was hindered at H202 concentration in excess of 1 mmol/L. Additionally, BPA removal was shown to be inhibited by the presence of aeration and humic acid during ultrasonic irradiation. The present study suggested that the degradation rate of BPA assisted by ultrasonic irradiation was influenced by a variety of factors, and high BPA removal rate could be achieved under appropriate conditions.

Perchlorate removal using granular activated carbon supported iron compounds: Synthesis, characterization and reactivity

Synthesis and use of the iron compounds supported on granular activated carbon （ICs/GAC） have shown significant environmental implications for perchlorate （ClO4^- ） removal. ICs/GAC was synthesized via hydrolyzing FeSO 4 ·7H2O on GAC, reduced by NaBH 4 solution in polyethylene glycol 6000 and ethanol solution, dried in vacuum condition and exposed to air. Synthesized ICs/GAC was characterized using transmission electron micrograph （TEM）, Brunauer-Emmett-Teller, X-ray photoelectron spectroscopy （XPS）. ICs/GAC was determined to be containing a large amount of FeOHSO 4 , Fe2O3 and a small amount of zero-valent iron （ZVI） nanoparticles according to TEM and XPS measurements. Batch static kinetic tests showed that 97% of ClO4^- was removed within 10 hr at 90°C and 86% of ClO4^- was removed within 12 hr at 25°C, at ICs/GAC dosage of 20 g/L. The experimental results also showed that FeOHSO 4 and Fe 2 O 3 nanoparticles have the function of perchlorate adsorption and play important roles in ClO4^- removal. The activation energy （E a ） was determined to be 9.56 kJ/mol.

Characteristics and model studies for fluoride and arsenic adsorption on goethite

Fluoride and arsenic are major anionic elements of concern in drinking water treatment. The effects of contact time, pH, surface loading and ionic strength on adsorption of fluoride and As（V） were investigated using batch methods. Adsorption of fluoride and As（V） onto goethite obeyed a pseudo second-order rate law. Through experimental data and adsorption kinetic analysis, the affinity of As（V） onto goethite was stronger than fluoride. Fluoride and As（V） uptake by goethite all decreased with pH increasing at the same surface loading; however, ionic strength had slight influence on their adsorption. A surface sites-species model was used to quantify the adsorption of fluoride and As（V） onto goethite as function of pH and surface loading. This model can satisfactorily predict their adsorption characteristics with several adsorption constants.

Removal of phenol by powdered activated carbon adsorption

In this study, the adsorption performance of powdered activated carbon （PAC） on phenol was investi- gated in aqueous solutions. Batch adsorption studies were performed to evaluate the effects of various experimental parameters like PAC type, PAC dose, initial solution pH, temperature and pre-oxidation on the adsorption of phenol by PAC and establish the adsorption kinetics, thermo- dynamics and isothermal models. The results indicated that PAC adsorption is an effective method to remove phenol from water, and the effects of all the five factors on adsorption of phenol were significant. The adsorption rate of phenol by PAC was rapid, and more than 80% phenol could be absorbed by PAC within the initial 10 min. The adsorption process can be well described by pseudo- second-order adsorption kinetic model with rate constant amounted to 0.0313, 0.0305 and 0.0241 mg.μg .min -1 with coal, coconut shell and bamboo charcoal. The equilibrium data of phenol absorbed onto PAC were analyzed by Langmuir, Freundlich and Tempkin adsorp- tion isotherms and Freundlich adsorption isotherm model gave the best correlation with the experimental data. Thermodynamic parameters such as the standard Gibbs free energy （△G0）, enthalpy （△H0） and entropy （△S0） obtained in this study indicated that the adsorption of phenol by PAC is spontaneous, exothermic and entropy decreasing.

Pre-oxidation with KMnO4 changes extra-cellular organic matter's secretion characteristics to improve algal removal by coagulation with a low dosage of polyaluminium chloride

Microcystis aeruginosa was used to study the effect of KMnO4 pre-oxidation on algal removal through coagulation with polyaluminium chloride （PAC）.KMnO4 pre-oxidation improved the coagulation efficiency of algal at a low dosage of PAC.The optimal KMnO4 feeding period was in the stationary growth phase of Microcystis aeruginosa.KMnO4 traumatized the algal cells and stimulated cellular release of organic matter,contributing to the pool of extra-cellular organic matter （EOM）.KMnO4 also decomposed EOM,especially small molecular weight EOM.Lower concentrations of KMnO4,such as 2 mg/L,induced algae cells to produce moderate amounts of new EOM with molecular weights of 11,280,and 1500 kDa.These relatively large molecules combined easily with PAC,promoting coagulation and removal of algae.High concentrations of KMnO4 lysed algae cells and produced much high-molecular-weight EOM that did not enhance flocculation by PAC at lower dosages.

Adsorption of humic acid from aqueous solution on bilayer hexadecyltrimethyl ammonium bromide-modified zeolite

Surfactant-modified natural zeolites(SMNZ)with different coverage types were prepared by loading hexadecyltrimethyl ammonium bromide(HTAB)onto the surface of a natural zeolite.The adsorption behavior of humic acid(HA)on SMNZ was investigated.Results indicate that the adsorbent SMNZ exhibited a higher affinity toward HA than the natural zeolite.HA removal efficiency by SMNZ increased with HTAB loading.Coexisting Ca2+in solution favored HA adsorption onto SMNZ.Adsorption capacity decreased with an increasing solution pH.For typical SMNZ with bilayer HTAB coverage,HA adsorption process is well described by a pseudo-second-order kinetic model.The experimental isotherm data fitted well with the Langmuir model.Calculated maximum HA adsorption capacities for SMNZ with bilayer HTAB coverage at pH 5.5 and 7.5 were 63 and 41 mg·g^(-1),respectively.E2/E3(absorbance at 250 nm to that at 365 nm)and E4/E6(absorbance at 465 nm to that at 665 nm)ratios of the residual HA in solution were lower than that of the original HA solution.This indicates that the HA fractions with high polar functional groups,low molecular weight(MW),and aromaticity had a stronger tendency for adsorption onto SMNZ with bilayer HTAB coverage.Results show that HTABmodified natural zeolite is a promising adsorbent for removal of HA from aqueous solution.

Characterization of typical taste and odor compounds formed by Microcystis aeruginosa

Production and characteristics of typical taste and odor （T＆O） compounds by Microcystis aeruginosa were investigated. A few terpenoid chemicals, including 2-MIB, β-cyclocitral, and β-ionone, and a few sulfur compounds, such as dimethyl sulfide and dimethyl trisulfide, were detected. β-Cyclocitral and β-carotene concentrations were observed to be relevant to the growth phases of Microcystis. During the stable growth phase, 41-865 fg/cell of β-cyclocitral were found in the laboratory culture. β-Cyclocitral concentrations correlated closely with β-carotene concentrations, with the correlation coefficient R2 = 0.96, as it is formed from the cleavage reaction of β-carotene. For dead cell cases, a high concentration of dimethyl trisulfide was detected at 3.48-6.37 fg/cell. Four T＆O compounds, including β-cyclocitral, β-ionone, heptanal and dimethyl trisulfide, were tested and found to be able to inhibit and damage Microcystis cells to varying degrees. Among these chemicals, β-cyclocitral has the strongest ability to quickly rupture cells.

Formation of THMs and HANs during bromination of Microcystis aeruginosa

Bromine-contained disinfectants and biocides are widely used in swimming pools, recreational waters and cooling towers. The objective of this study was to evaluate the formation of thrihalomethanes （THMs） and haloacetonitriles （HANs） and their cytotoxicity in algae solutions during free bromine disinfection. Disinfection by-products formation potential experiments were conducted using model solutions containing 7 mg/L （as total organic carbon） Microcystis aeruginosa cells. Effects of free bromine dosage, pH and ammonia were investigated. The results showed that brominated disinfection by-products were the major products when free bromine was applied. The total THMs formed during bromination was much as that formed during chlorination, whereas HANs were elevated by using bromination instead of chlorination. Dibromoacetonitrice （C2H2NBr2 ） and bromoform （CHBr3 ） were the only detected species during free bromine disinfection. The production of C2H2NBr2 and CHBr 3 increased with disinfectant dosage but decreased with dosing ammonia. CHBr3 increased with the pH changing from 5 to 9. However, C2H2NBr2 achieved the highest production at neutral pH, which was due to a joint effect of variation in hydrolysis rate and free bromine reactivity. The hydrolysis of C2H2NBr2 was base-catalytic and nearly unaffected by disinfectant. Finally, estimation of cytotoxicity of the disinfected algae solutions showed that HANs formation was responsible for the majority of toxicity. Considering its highest toxicity among the measured disinfection by-products, the elevated C2H2NBr2 should be considered when using bromine-related algaecide.

Modeling the aqueous reaction kinetics of estriol with ferrate

In this study the aqueous oxidation kinetics of estriol(E3)by potassium ferrate(K_(2)FeO_(4)),a chemical for its strong oxidizing power and for producing a coagulant from its reduced state(i.e.Fe(III)),was evaluated in the range of pH 8–12 with different molar ratios of the reactants.As the degree of Fe(VI)protonation varies with the solution pH,it was found that afirst order model was not suitable to describe the oxidation reaction.This paper describes a theoretical representation that closely models the reaction kinetics of E3 and ferrate.From this modeling,the reaction rates of HFeO_(4)^(-) and FeO_(4)^(2-) with E3 have been determined.The results show that the reactivity of HFeO–with dissociated and undissociated E3 is greater than that4 of FeO_(4)^(2-),and that E3 is more reactive in its dissociated state.