Iodinated trihalomethanes formation in iopamidol-contained water during ferrate/chlor(am)ination treatment.

Iopamidol is a commonly used iodinated X-ray contrast media in medical field, and its residue in water can react with disinfectants to form highly toxic iodinated disinfection by-products (I-DBPs). This study investigated the degradation of iopamidol and formation of DBPs, especially iodinated trihalomethanes (I-THMs), during ferrate (Fe(VI)) pre-oxidation and subsequent chlor(am)ination under raw water background. It was found that iopamidol degradation efficiency in raw water by Fe(VI) at pH 9 could reach about 80%, which was much higher than that at pH 5 and pH 7 (both about 25%). With Fe(VI) dose increasing, iopamidol removal efficiency increased obviously. During the iopamidol degradation by Fe(VI), IO3- was the dominant product among all the iodine species. After pre-treated by Fe(VI), yields of THM4 and I-THMs can be reduced in subsequent chlor(am)ination. Besides, pH was a crucial factor for Fe(VI) pre-oxidition controlling DBPs. With the pH increasing from 5 to 9, the yield of THM4 kept increasing in subsequent chlorination but showed the highest amount at pH 6 in subsequent chloramination. The yield of I-THMs increased first and then decreased with the increase of pH in both subsequent chlorination and chloramination. I-THM concentrations in chlorinated samples were lower than chloraminated ones under acidic conditions but became higher under neutral and alkaline conditions. The total CTI of THMs during Fe(VI)-chloramination was higher than that during Fe(VI)-chlorination under neutral condition, but sharply decreased under alkaline conditions. In summary, Fe(VI)-chloramination subsequent treatment under alkaline conditions should be an effective method for iopamidol removal and DBP control.

[Sorption mechanism of ofloxacin by carbon nanotubes].

Sorption of ofloxacin (OFL) by carbon nanotubes is an effective method to control its fate in aquatic environment. The sorption process of OFL by mixed acid-treated and non-treated multi-walled carbon nanotubes was discussed. Sorption kinetics, sorption isotherm, desorption, sorption thermodynamics and effect of pH were investigated. The results indicated that the sorption kinetics followed the pseudo-second order kinetics model. The equilibrium sorption capacity of OFL on MWCNTs-O was higher. The sorption isotherm could be fitted by both the Langmuir and Freundlich models. The equilibrium sorption capacity dropped when the pH of aqueous solution was in the range of 6.0 to 10.0. Obvious desorption hysteresis was observed during the desorption experiments, especially on MWCNTs-O. Sorption thermodynamics analysis showed that the interactions between the OFL and sorbents were mainly between molecules. More oxygen-containing functional groups introduced on MWCNTs provided OFL molecules with more sorptive sites, which facilitated the generation of hydrogen bonds, a relatively strong interaction. The hydrogen bonds dominated the sorption process of OFL by MWCNTs/MWCNTs-O, explaining the experimental phenomena.

[Phosphorus removal characteristics by aerobic granules in normal molasses wastewater after anaerobic treatment].

COD decreased obviously in normal molasses wastewater after anaerobic treatment, however, concentrations of nitrogen and phosphorus were still higher in the effluent which seriously damaged the ecological balance. In this study, aerobic granules cultivated in sequencing batch airlift reactor (SBAR) were carried out for treating the effluent; phosphorus removal processes and characteristics were discussed as well. The mean diameter of aerobic granules cultivated by multiple carbon sources (acetate, propionate and butyrate) was 1.7 mm. The average phosphorus removal efficiency was 90.9% and the level of phosphorus in effluent was only 1.3 mg x L(-1); TP released per COD consumed was 0.571 and the specific rate of TP released was 5.73 mg x (g x h)(-1). NO3(-) -N usage of phosphorus accumulating organisms (PAOs) improved during denitrifying process because the concentration of propionate and butyrate increased in multiple carbon sources which means the phosphorus uptake efficiency increased when per NO3(-) -N consumed. Phosphorus content represented a stronger correlation with magnesium, calcium and ferrum contents in aerobic granules and their extracellular polymeric substances (EPS), the phosphorus adsorption by EPS could enhance phosphorus removal. 61.9% of phosphorus accumulating organisms were denitrifying phosphorus accumulating organisms in aerobic granules and TP uptake per NO3(-) -N consumed was 1.14 which was higher than that of aerobic granules only cultivated by acetate.

Comparative performance between intermittently cyclic activated sludge-membrane bioreactor and anoxic/aerobic-membrane bioreactor.

A process of intermittently cyclic activated sludge-membrane bioreactor (ICAS-MBR) was developed to enhance the performance of biological phosphorus removal (EBPR), which was constructed under sequencing anoxic/anaerobic/aerobic condition. The performance between ICAS-MBR and conventional anoxic/aerobic-membrane bioreactor (A/O-MBR) in terms of phosphorus removal, nitrification performance and microbial aspects were investigated in this study. The experimental results indicated that the phosphorus removal efficiency in ICAS-MBR process increased from 65% to 83% when compared with A/O-MBR. It was also found that the COD removal efficiencies of the two processes were over 94%, and NH(4)(+)-N and TN average removal efficiencies were 96% and 69% in ICAS-MBR and 96% and 78% in A/O-MBR, respectively. Furthermore, micrographs observation obtained confirmed the succession and diversification of microorganisms in the two systems followed a similar regularity.

[Pollution removal efficiency of powdered activated carbon and microfiltration integrated process].

The removal effects by PAC-MF integrated system for organic matters, pesticides and ammonia-nitrogen are introduced. The separate contribution of PAC, microorganism and MF in the system are detailed quantitatively. The results indicate that the average removal rates of the integrated process for TOC, UV254, THMFP and HAAFP are 73.56%, 96.75%, 77.64%, 83%, respectively, and 95.1% for pesticides dichlorvos, 98% for ammonia-nitrogen. The results illustrate that PAC significantly reduces the membrane organic burden to 28.32% of the direct membrane filtration without PAC; and carbon layer on the surface of membrane has the removal effect for pollutants. Moreover, the PAC used in high concentration can largely improve its adsorption performance for ammonia-nitrogen, whose removal rate is 44.5%.

[Quantitative investigation on flocculation and destruction of poly-silicic-ferric (PSF) coagulant].

An inorganic polymer, poly-silicic-ferric (PSF) coagulant was prepared using water glass, FeSO4 x 7H2O and NaClO3 by copolymerization. A comparison of coagulation performance, distribution of residual flocs in finished water and influence of turbulent shear force on the flocs between PSF and polyferric aluminum (PFA) was explored by jar tests and particle counter approach. The results indicate that PSF has superior removal of COD at higher dose to PFA. Flocculating speed should not be much higher or lower when using PSF as coagulant in treating surface water, and excellent coagulation efficiency can be obtained by the close cooperation of flocculation speed with flocculation time, that is, higher flocculation speed should be consistent with shorter flocculation time. The PFA flocs are much easier destructed than PSF flocs when increasing the turbulent shear force, and the destructed PSF flocs tend to be more easily re-coupled than PFA flocs. From the order magnitude, the flocculation coefficient KA of PSF is from 10(-2) to 10(-3), in comparison with the destruction coefficient KB from 10(-7) to 10(-8). For particles whose size is smaller than 2 microm, KA of PSF is 4 order magnitude more than that of PFA, and KB of PSF is almost the same to that of PFA; while for the other particles, KA of PSF is 2 order magnitude more than that of PFA, and KB of PSF is almost ten times smaller than that of PFA.

Reaction mode between Si and Fe and evaluation of optimal species in poly-silicic-ferric coagulant.

A kind of Fe-polysilicate polymer, poly-silicic-ferric (PSF) coagulant was prepared by co-polymerization (hydroxylation of mixture of Fe3+ and fresh polysilicic acid (PS)), in which PSF0.5, PSF1 or PSF3 denotes Si/Fe molar ratio of 0.5, 1 or 3, respectively. The effects of Si/Fe ratio and reaction time (co-polymerization time or aging time) on the reaction mode between Si and Fe were studies, and the optimal species of PSF was evaluated by pH change during the preparation of PSF and coagulation tests. The results showed that the characteristics of PSF are largely affected by both reaction time and Si/Fe ratio. PSF is found to be a essential complex of Si, Fe, and many other ions. The reaction mode between Si and Fe differs with various Si/Fe ratios. The pH of PSF0.5, PSF1 or PSF3 tended to be stable when reaction time is 10, 25 or 55 min, respectively, which is almost consistent with the time reaching the relative stable morphology that is just the optimal species of higher coagulation efficiency. The optimal reaction time reaching optimal species can be evaluated by measuring the pH change during the polymerization process.

[Analysis of reaction process between Si and Fe in poly-silicic-ferric sulfate (PSF) coagulant].

A new inorganic polymer coagulant, poly-silic-ferric sulfate (PSF) with various Si/Fe ratios (PSF0.5, PSF1 and PSF denote Si/Fe molar ratios of 0.5, 1 and 3, respectively), was prepared using water glass, ferrous sulfate and sodium chlorate by co-polymerization, and pH value was measured during the preparation process. The influence of both Si/Fe ratio and reaction time (polymerization time) on the complexation process (bonding mode) between Si and Fe was explored with many analytical methods (such as X-ray diffraction (XRD), ultraviolet/visible absorption (UVA) scanning, transmission electron microscope (TEM), photon correlation spectra (PCS) and infrared spectrum (IR) using PSF samples taken from different reaction time at different Si/Fe ratios. The results show that the characteristics of PSF are largely influenced by both reaction time and Si/Fe ratios. PSF is found to be a complexation compound of Si, Fe and many other ions, instead of a simple mixture of raw materials. The complexation process between Si and Fe may be different from various Si/Fe ratios, namely, the bonding rate, bonding mode and the stability of the bond between Si and Fe are different from various Si/Fe ratios: the polymer based on Si-O-Fe-O-Fe-O-Si bond may be formed at low Si/Fe ratio, in comparison with that based on Si-O-Fe-O-Si-O-Si bond at high Si/Fe ratio; the formation rate of Fe-O-Fe bond is rapid and there may be a mutual acceleration between Fe-O-Fe bond and Si-O-Fe bond, while the formation rate of Si-O-Si is slow and maybe there is a mutual retardation between Si-O-Fe bond and Si-O-Si bond; the stability of Fe-O-Fe bond is weaker than that of Si-O-Fe or Si-O-Si bond.

[Research of performances for the organic membrane modified by inorganic material].

Nano-sized alumina particles as inorganic additive were dispersed in the poly (vinylidene fluoride) uniformly to prepare organic-inorganic composite membranes. Contact angle between water and the membrane surface were measured by contact angle measurement in order to characterize the hydrophilicity changing of the membrane surface. The membrane surface structures, porous distribution on the membrane surface, the cross-sectional structures and nanometer particles distribution were examined by confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) respectively. Membrane properties were characterized by ultrafiltration (UF) experiments in terms of water flux and antifouling properties. Membranes mechanical performances were measured by omnipotence electronic intensity measuring instrument (W-56). Experiments indicate that Al2 O3 -PVDF composite membranes exhibit significant differences in surface hydrophilicity properties, flux, and intensity and antifouling performances due to nano-sized particles addition.

Comparing results of cultured and uncultured biological methods used in biological phosphorus removal.

Increasing attention has been paid to phosphate-accumulating organisms (PAOs) for their important role in biological phosphorus removal. In this study, microbial communities of PAOs cultivated under different carbon sources (sewage, glucose, and sodium acetate) were investigated and compared through culture-dependent and culture-independent methods, respectively. The results obtained using denaturing gradient gel electrophoresis (DGGE) of polymerase chain reaction-amplified 16S rDNA fragments revealed that the diversity of bacteria in a sewage-fed reactor (1#) was much higher than in a glucose-fed one (2#) and a sodium acetate-fed one (3#); there were common PAOs in three reactors fed by different carbon sources. Five strains were separated from three systems by using a phosphate-rich medium; they were from common bacteria isolated and three isolates could not be found in DGGE profile at all. Two isolates had good phosphorus removal ability. When the microbial diversity was studied, the molecular biological method was better than the culture-dependent one. When phosphorus removal characteristics were investigated, culture-dependent approach was more effective. Thus a combination of two methods is necessary to have a comprehensive view of PAOs.

Role of extracellular exopolymers on biological phosphorus removal.

Three sequencing batch reactors supplied with different carbon sources were investigated. The system supplied with glucose gained the best enhanced biological phosphorus removal although all of the three reactors were seeded from the same sludge. With the measurement of poly-beta-hydroxyalkanoate (PHA) concentration, phosphorus content in sludge and extracellular exopolymers (EPS) with scanning electron microscopy (SEM) combined with energy dispersive spectrometry (EDS), it was found that the biosorption effect of EPS played an important role in phosphorus removal and that the amount of PHA at the end of anaerobic phase was not the only key factor to determine the following phosphorus removal efficiency.

[Co-digestion of waste activated sludge and kitchen garbage].

The effects of mixture ratio and hydraulic retention time on mesophilic co-digestion of waste activated sludge and kitchen garbage were investigated, and the mixtures having the ratios of 75%:25%, 50%:50% and 25%:75% on a TS basis, operated at the HRTs of 10d, 15d and 20d. In all the digesters, with an OLR 1.53-5.63 g/(L x d), there were no indication of failure, such as low pH, insufficient alkalinity, ammonia inhibition and accumulation of VFAs. The optimum operating conditions of all the digesters were found to be a mixture of 50%:50% in terms of the stability and performance, buffer capacity was the highest. The volatile solid removal efficiency, specific methane production and methane content in this condition achieved 51.1%-56.4%, 0.353-0.373 L/g and 61.8%-67.4%.

Effect of components in activated sludge liquor on membrane fouling in a submerged membrane bioreactor.

By a membrane bioreactor with a settle tank in long-term operation and batch experiments, the effects of flocs, soluble microorganism products (SMPs) and metal ions in activated sludge liquor on membrane fouling were investigated. The results showed that foulants absorbed each other and formed a fouling layer as a "second membrane" influencing the permeability of the membrane. The "gel layer" caused by SMPs and "cake layer" by flocs showed great differences in morphology by analysis of scanning electron microscope and atomic force microscope. The "gel layer" was more compact and of poor permeability. When the membrane flux was 40 L/(m(2) x h), the rate of membrane fouling caused by supernatant (0.011 MPa/h) was greater than that by sludge liquor (0.0063 MPa/h). SMPs played very important roles on membrane fouling. In the bulking sludge, with SMPs increasing, the rate of membrane fouling (0.0132 MPa/h) was faster. While after flocculation of the SMPs, the rate of fouling decreased to 0.0034 MPa/h. Flocs could keep holes in their overlaps. They could alleviate membrane fouling by preventing the SMPs directly attaching on membrane surface.

Flux enhancement during ultrafiltration of produced water using turbulence promoter.

Concentration polarization and membrane fouling remain one of the major hurdles for the implementation of ultrafiltration of produced water. Although many applications for ultrafiltration were already suggested, only few were implemented on an industrial scale. Among those techniques, turbulence promoter can be more simple and effective in overcoming membrane fouling and enhancing membrane flux. As for the result that turbulence promoter increase fluid velocity, wall shear rates and produce secondary flows or instabilities, the influence of turbulence promoter was investigated on permeate flux during produced water ultrafiltration and the potential application of this arrangement for an industrial development. Experimental investigations were performed on 100 KDa molecular weight cut-off PVDF single-channel tubular membrane module using four kinds of turbulence promoters. It is observed that the significant flux enhancement in the range of 83%-164% was achieved while the hydraulic dissipated power per unit volume of permeate decreased from 31%-42%, which indicated that the using of turbulence promoter is more efficient than operation without the turbulence promoter. The effects of transmembrane pressure and cross-flow velocity with and without turbulence promoter were studied as well. Among the four kinds of turbulence promoters, winding inserts with 20.0 mm pitch and 1.0 mm wire diameter showed better performances than the others did.

[Analysis of solid-liquid oxidizing poly silicic ferric sulfate (PSF-I)].

A new type of inorganic coagulant, solid-liquid oxidative poly silicic ferric sulfate (PSF-I), was prepared by adding KMnO4 and stabilizer M to poly silicic ferric sulfate (PSF). The species characteristics of PSF-I, the filtrate of PSF-I and PSF with spectrophotometer, and coagulation performance of PSF-I and the filtrate of PSF-I with jar tests were explored, respectively. Coagulation efficiency of PSF-I was studied compared to that of PSF and poly ferric sulfate (PFS), and the effect of storage time on coagulation performance of PSF-I was investigated. The results show that KMnO4 added to PSF modifies the microstructure of PSF, increasing species size of PSF and making UVA characteristic peaks of Fe3+ ion in PSF-I higher than that in PSF. There exists KMnO4 unattached in PSF-I. The solid phase in PSF-I is a kind of primary nucleus for building up flocs. The optimal dosage with PSF-I is 9 mg x L(-1), in comparison with 12 mg x L(-1) by PSF-I filtrate. The removal of natural organic matters (NOM) is not only caused by adsorption/charge-neutralization and co-precipitation but also by oxidization using PSF-I as coagulant, while to PSF and PFS, adsorption/charge-neutralization and co-precipitation is the only coagulation mechanism.

Analysis of phosphate-accumulating organisms cultivated under different carbon sources with polymerase chain reaction-denaturing gradient gel electrophoresis assay.

To investigate the microbial communities of microorganisms cultivated under different carbon sources, three sequencing batch reactors were operated. They were supplied with sewage, glucose and sodium acetate as carbon sources respectively and showed high phosphorus removal performance. The results of denaturing gradient gel electrophoresis (DGGE) of polymerase chain reaction-amplified (PCR) 16S rDNA fragments demonstrated that beta-protebacteria, Actinomyces sp. and gamma-protebacteria only exited in 1 # reactor. The microbiological diversity of 1 # reactor exceeded the other two reactors. Flavobacterium, Bacillales, Actinomyces, Actinobacteridae and uncultured bacteria (AF527584, AF502204, AY592749, AB076862, AJ619051, AF495454 and AY133070) could be detected in the biological phosphorus removal reactors.