Effect of enhanced coagulation by KMnO(4) on the fouling of ultrafiltration membranes.

Pre-coagulation enhanced by KMnO(4) before ultrafiltration (KCUF) was compared with normal pre-coagulation by alum (CUF) in the ultrafiltration of water from the Songhua River, China. The trans-membrane pressure (TMP) with KCUF was much lower than that when alum alone was used. With KCUF a slower increment of TMP occurred, even under conditions of high river water turbidity. The results also showed that the removal of COD, UV(254) and TOC was appreciably higher after adding 0.5mg/L KMnO(4) compared with CUF. Although assimilable organic carbon (AOC) was increased by permanganate treatment, the AOC of the permeate from KCUF was nearly the same as that from CUF, showing that the cake layer on the surface of KCUF membrane could adsorb small molecules more effectively than that of CUF. This result was confirmed by the apparent molecular weight (MW) distribution measured by size exclusion chromatography (SEC). It was shown that flocs formed by KMnO(4) and alum were larger than those formed only by alum, causing higher removal of flocs and higher permeation flux. Lower NOM was found in the permeate from the KCUF systems because oxidation and adsorption of organic matter on the flocs occurred. The membrane was partly clogged by organic matter or other materials including some small flocs.

Membrane coagulation bioreactor (MCBR) for drinking water treatment.

In this paper, a novel submerged ultrafiltration (UF) membrane coagulation bioreactor (MCBR) process was evaluated for drinking water treatment at a hydraulic retention time (HRT) as short as 0.5h. The MCBR performed well not only in the elimination of particulates and microorganisms, but also in almost complete nitrification and phosphate removal. As compared to membrane bioreactor (MBR), MCBR achieved much higher removal efficiencies of organic matter in terms of total organic carbon (TOC), permanganate index (COD(Mn)), dissolved organic carbon (DOC) and UV absorbance at 254nm (UV(254)), as well as corresponding trihalomethanes formation potential (THMFP) and haloacetic acids formation potential (HAAFP), due to polyaluminium chloride (PACl) coagulation in the bioreactor. However, the reduction of biodegradable dissolved organic carbon (BDOC) and assimilable organic carbon (AOC) by MCBR was only 8.2% and 10.1% higher than that by MBR, indicating that biodegradable organic matter (BOM) was mainly removed through biodegradation. On the other hand, the trans-membrane pressure (TMP) of MCBR developed much lower than that of MBR, which implies that coagulation in the bioreactor could mitigate membrane fouling. It was also identified that the removal of organic matter was accomplished through the combination of three unit effects: rejection by UF, biodegradation by microorganism and coagulation by PACl. During filtration operation, a fouling layer was formed on the membranes surface of both MCBR and MBR, which functioned as a second membrane for further separating organic matter.

[Identification and PAC Adsorption of Foulants Responsible for Irreversible Fouling During Ultrafiltration of Dongjiang River Water].

Foulants responsible for hydraulic irreversible fouling in Dongjiang River water were identified by ultrafiltration process and their removal by powdered activated carbon (PAC) adsorption treatment was investigated using fluorescent excitation emission matrix and parallel factor analysis (EEM-PARAFAC). A correlation analysis was then carried out for samples between the maximum fluorescence intensities (Fmax) of three PARAFAC components after PAC adsorption and the surface properties of corresponding PAC samples. The results showed that two humic-like (C1 and C3) and one tryptophan-like fluorescent components were obtained through PARAFAC analysis, in which tryptophan-like component C2 was found to be the main substance in hydraulic irreversible foulants extracted from fouled membrane. Furthermore, the results of correlation analysis suggested that microspore area of PAC correlated with PAC adsorption of tryptophan-like fluorescent components, which played an important role in irreversible fouling. Both BET and mesopore+macropore area of PAC correlated with its adsorption of humic-like fluorescent components. The result provided support for selecting PAC in PAC-ultrafiltration hybrid process, which would be more effective for fouling control.

[Effects of Pretreatment on Hydraulic Irreversible Membrane Fouling During Ultrafiltration Short Process: A Pilot Study].

Pilot-scale performances for ultrafiltration of Dongjiang river water without and with micro-coagulation and coagulation-adsorption-sedimentation pretreatments were conducted to investigate the effects of pretreatments on hydraulic irreversible fouling of ultrafiltration short processes. Scanning electron microscope (SEM) imaging, high performance size exclusion chromatography (HPSEC) and fluorescence excitation-emission matrix (EEM) were employed to identify foulants responsible for irreversible fouling during ultrafiltration with and without pretreatments. The results showed that the hydraulic irreversible fouling rate was 0.16 kPa·d-1 with micro-coagulation pretreatment at 10 L·(m2·h)-1, while the rate without pretreatment was 0.32 kPa·d-1 at the same flux. Meanwhile, the fouling rate with coagulation-adsorption-sedimentation pretreatment was almost zero at the same flux. Furthermore, when the flux increased to 17 L·(m2·h)-1, the irreversible fouling was not observable with coagulation-adsorption-sedimentation pretreatment (backwashing every 24 hours). Properties of foulants from external membrane and internal membrane after backwashing showed that the protein-like and fulvic-like substances were responsible for irreversible fouling in Dongjiang river water. Furthermore, structural alteration of cake layer resulted in less cake resistance and higher backwash efficiency after micro-coagulation pretreatment, leading to less irreversible fouling. Coagulation-adsorption-sedimentation pretreatment decreased irreversible fouling with higher removal efficiency of protein-like and fulvic substances, which were the foulants responsible for irreversible fouling during ultrafiltration. Both micro-coagulation and coagulation-adsorption-sedimentation pretreatments decreased irreversible fouling during ultrafiltration short process.

Effects of chlorine content and position of chlorinated phenols on their oxidation kinetics by potassium permanganate.

Chlorine content and position of chlorinated phenols have many significant effects on the reactivity of oxido-reduction. The effects of chlorine content and position of chlorinated phenols on their oxidation kinetics by potassium permanganate were evaluated through different kinetics studies. Since chlorine was an electron withdrawing atom, the substitution of chlorine on the aromatic ring decreased the oxidation rate constant by sigma-electron withdrawing conductive effect. The substitution of chlorine at ortho or para position on the aromatic ring increased the oxidation rate constant by pi-electron donating conjugative effect, and the conjugative effect could counteract the negative impact of the conductive effect to some extent. On the other hand, the substitution of chlorine at ortho position on the aromatic ring decreased the oxidation rate constant by steric hindrance effect. The oxidation rate constants of phenol and chlorinated phenol studied decreased as follow order: 4-chlorophenol > 2,4-dichlorophenol > phenol > 2,6-dichlorophenol.

Fouling of ultrafiltration membrane by algal-rich water: effect of kalium, calcium, and aluminum.

Algae are commonly aquatic plants showing generally negatively charged. The fouling behavior of hollow-fiber ultrafiltration membrane by algal-rich water could be therefore influenced by various cations (K(+), Ca(2+), and Al(3+)) and their doses. Microcystis aeruginosa solution was used as the feed solution to study the fouling in detail. Constant flux experiments were performed with a laboratory-scale experiment. Increasing the concentrations of calcium and aluminum had a significant impact on alleviating membrane fouling and increasing flux recovery by backwashing, especially for calcium. However, kalium ion had little influence on the membrane filtration. Based on the measurement of MW distribution and zeta potential, charge neutralization was proposed to be the primary aggregation mechanism for calcium, in contrast to precipitate coverage and sweep flocculation for aluminum. It was demonstrated that the fouling layer became more loose and porous in the presence of Ca(2+) and Al(3+), respectively, which can be identified by scanning electron microscope (SEM). However, SEM also proved that the two additives damaged the cell walls and caused the intercellular organic matter released to different extents.

Measuring the activity of heterotrophic microorganism in membrane bioreactor for drinking water treatment.

In order to quantify the activity of heterotrophic microorganism in membrane bioreactor (MBR) for drinking water treatment, biomass respiration potential (BRP) test and 2,3,5-triphenyl tetrazolium chloride-dehydrogenase activity (TTC-DHA) test were introduced and modified. A sludge concentration ratio of 5:1, incubation time of 2h, an incubation temperature that was close to the real operational temperature, and using a mixture of main AOC components as the substrate were adopted as the optimum parameters for determination of DHA in drinking water MBR. A remarkable consistency among BDOC removal, BRP and DHA for assessing biological performance in different MBRs was achieved. Moreover, a significant correlation between the BRP and DHA results of different MBRs was obtained. However, the TTC-DHA test was expected to be inaccurate for quantifying the biomass activity in membrane adsorption bioreactor (MABR), while the BRP test turned out to be still feasible in that case.

Characteristics of adsorbents made from biological, chemical and hybrid sludges and their effect on organics removal in wastewater treatment.

Meso-macropore adsorbents were prepared from biological sludge, chemical sludge and hybrid sludge of biological and chemical sludges, by chemically activating with 18.0 M H(2)SO(4) in the mass ratio of 1:3, and then pyrolyzing at 550 °C for 1 h in anoxic atmosphere. The physical and chemical characteristics of the sludge-based adsorbents were examined in terms of surface physical morphology, specific surface area and pore size distribution, aluminum and iron contents, surface functional groups and crystal structure. Furthermore, the adsorption effect of these adsorbents on the organic substances in wastewater was also investigated. The results indicated that the adsorption capacities of the sludge-based adsorbents for UV(254) were lower than that of commercial activated carbon (AC), whereas the adsorption capacities of the adsorbents prepared from hybrid sludge (HA) and chemical sludge (CA) for soluble COD(Cr) (SCOD(Cr)) were comparable or even higher than that of the commercial AC. The reasons might be that the HA and CA possessed well-developed mesopore and macropore structure, as well as abundant acidic surface functional groups. However, the lowest adsorption efficiency was observed for the biological sludge-based adsorbent, which might be due to the lowest metal content and overabundance of surface acidic functional groups in this adsorbent.

Consecutive chemical cleaning of fouled PVC membrane using NaOH and ethanol during ultrafiltration of river water.

Chemical cleaning of fouled hollow-fiber polyvinyl chloride (PVC) membrane with the consecutive use of NaOH and ethanol during ultrafiltration of river water was investigated in the study. Results showed that through the chemical cleaning with 1% NaOH for 30min, a negative cleaning efficiency of -14.6% was observed for the PVC membrane. This might be due to the increase of membrane hydrophobicity, which was reflected by the increase of contact angle from 69.7 degrees to 87.6 degrees . On the other hand, the cleaning efficiency of 85.1% was obtained by the consecutive cleaning with 30min of 1% NaOH and 30min of ethanol. Individual ethanol cleaning could remove 48.5% of the irreversible resistance, indicating that NaOH cleaning also made its contribution (36.6%) to the removal of membrane foulants. Scanning electronic microscopy (SEM) and atomic force microscopy (AFM) analyses demonstrated that both NaOH and ethanol were not only able to eliminate the foulants on membrane surface, but also able to remove the in-pore fouling of the PVC membrane. The synergetic effects for removing membrane foulants were observed between the NaOH and ethanol. Furthermore, ethanol could also restore the hydrophilicity of the membrane by decreasing the contact angle from 87.6 degrees to 71.4 degrees . Considering that ethanol is easy to be used and reclaimed, the consecutive chemical cleaning by alkali and ethanol is recommended for PVC membrane in filtration of surface water.

[Oxidization characteristic of chlorine on the biofilm in simulated drinking water distribution system].

In the article, the inactivation effect of chlorine on E. coli biofilm and the influence of chlorine oxidization on the contents of assimilable organic carbon (AOC), microbially available phosphorus (MAP) and bacterial regrowth potential (BRP) was investigated in the simulated drinking water distribution system. Results showed that chlorine resulted in more efficient reduction on suspended E. coli than did in biofilm. The inactivation effect of E. coli was influenced by chlorine concentration. Likewise, higher chlorine concentration resulted in more E. coli inactivation rate at the same CT (chlorine concentration multiply by time) value, when biofilm was oxidized by chlorine. Concentrations of AOC and MAP in bulk water increased owing to organic substance dissolved from biofilm. The AOC concentration increased from 20.78 microg/L to 120.17 microg/L, and the MAP was increased from 0.11 microg/L to 0.17 pg/L, and the Chlorine oxidization enhanced BRP concentration in the bulk water. BRP reached maximum at 1.10 x 10(7) CFU/mL when chlorine concentration was 1.0 mg/L, CT value was 100 mg x min/L.

[Mechanism of natural organic matter removal by potassium permanganate composite enhanced coagulation].

Streaming current technique, fluctuation of transmitted light technique, molecular weight distribution and XAD resin adsorption technique were used to study the mechanism of natural organic matter removal by potassium permanganate composite (PPC) enhanced coagulation. Results showed that natural organic matter removal efficiency increased 13% by 0.75 mg/L potassium permanganate composite enhanced coagulation compared with that of alum coagulation alone. Streaming current indicated that potassium permanganate composite decreased the organic matter stability by reducing the surface negative charge, and the SC value increased from 55.2 to 61.4, 69.6 and 87.0 by addition of 0.50, 0.75 and 1.0 mg/L PPC. Coagulation index R indicated both nascent manganese dioxide and subsidiaries played an important role in potassium permanganate composite enhanced coagulation process. Potassium permanganate composite enhanced coagulation increased the removal efficiency of lower molecular weight and hydrophilic organic matter compared with alum coagulation, and hydrophilic organic matter can be reduced from 1.9 mg/L to 1.32 mg/L by the addition of 0.75 mg/L potassium permanganate composite.

Hybrid process of BAC and sMBR for treating polluted raw water.

The hybrid process of biological activated carbon (BAC) and submerged membrane bioreactor (sMBR) was evaluated for the drinking water treatment from polluted raw water, with the respective hydraulic retention time of 0.5 h. The results confirmed the synergetic effects between the BAC and the subsequent sMBR. A moderate amount of ammonium (54.5%) was decreased in the BAC; while the total removal efficiency was increased to 89.8% after the further treatment by the sMBR. In the hybrid process, adsorption of granular activated carbon (in BAC), two stages of biodegradation (in BAC and sMBR), and separation by the membrane (in sMBR) jointly contributed to the removal of organic matter. As a result, the hybrid process managed to eliminate influent DOC, UV(254), COD(Mn), TOC, BDOC and AOC by 26.3%, 29.9%, 22.8%, 27.8%, 57.2% and 49.3%, respectively. Due to the pre-treatment effect of BAC, the membrane fouling in the downstream sMBR was substantially mitigated.

[Effect of chloramines disinfection for biofilm formation control on copper and stainless steel pipe materials].

Two rotating annular bioreactors (RABs) with copper and stainless steel pipe materials were adopted in the study, the effects of these two pipe materials and chloramines disinfection on biofilms formation in drinking water distribution system were evaluated. The maximum viable bacterial number in biofilm of copper and stainless steel reached 5.5 x 10(3) CFU/cm2 and 2.5 x 10(5) CFU/cm2 at 18th and 21st day without chloramines, and the viable bacterial number at the apparent steady state was 1.0 x 10(3) CFU/cm2 and 1.3 x 10(5) CFU/cm2 respectively. It was obvious that the biomass on copper materials was lower than that of the stainless steel. The maximum viable bacterial on copper and stainless steel under chloramines was 5.0 x 10(2) CFU/cm2 and 5.0 x 10(4) CFU/cm2, which was one order of magnitude lower than that of without chloramines, and its number was 10 CFU/cm2 and 3.5 x 10(4) CFU/cm2 at the steady state. These results illustrated that chloramines had apparent ability in controlling biomass when the biofilm was on steady states, especially for copper material. There was exponential relationship between biomass in biofilm and residue chloramines, which meant less biomass with more chloramines, synergistic effects were observed between chloramines and copper materials on biomass in biofilms inactivation.

[Mechanism and promotion effect of K+ on yield of Fe(VI)].

The mechanism and promotion effects of K+ on the yield of Fe(VI) were studied during the reaction of forming ferrate. The experiment results showed that K+ is far better than Na+ for the preparation of Fe(VI) at temperatures higher than 50 degrees C. The optimal temperature for the preparation of Fe(VI) with K+ is 65 degrees C. During the reaction, the yield of ferrate increases with the concentration of K+, and the promotion effect of K+ is obviously with ferric nitrate dosage increase. The Fe(VI) concentration prepared with 4.4 mol/L KOH is 0.05 mol/L at 85 g/L ferric nitrate; and which achieves 0.15 mol/L when added 2 mol/L K+. The promotion effect of K+ on the yield of ferrate is remarkable when ferric nitrate dosage is higher than 75 g/L, reaction temperature is below 55 degrees C and ClO(-) concentration is lower than 1.16 mol/L. The K+ can substitute for partly alkalinity and reduce the concentration of OH(-) in the reaction solution. During the reaction, the K+ can enwrap around FeO4(2-) that can reduce the contact between Fe(3+) and FeO4(2-), and decrease the catalysis effect of Fe(3+) on FeO4(2-). At the same time, K+ can react with FeO4(2-) to form solid K4FeO4, whichwill lower the Fe(VI) concentration, decrease the decomposition rate of Fe(VI), enhance the stability and improve the yield of Fe(VI).

Salicylate-spectrophotometric determination of inorganic monochloramine.

On the basis of classical Berthelot reaction, a simple salicylate-spectrophotometric method was developed for quantitative determination of inorganic monochloramine in water samples. With the catalysis of disodium pentacyanonitrosylferrate(III), inorganic monochloramine reacts with salicylate in equimolar to produce indophenol compound which has an intense absorption at 703nm. Parameters that influence method performance, such as pH, dosage of salicylate and nitroprussiate and reaction time, were modified to enhance the method performance. By using this method, inorganic monochloramine can be distinguished from organic chloramines and other inorganic chlorine species, such as free chlorine, dichloramine, and trichloramine. The molar absorptivities of the final products formed by these compounds are below +/-3% of inorganic monochloramine, because of the alpha-N in them have only one exchangeable hydrogen atom, and cannot react with salicylate to produce the indophenol compound. The upper concentrations of typical ions that do not interfere with the inorganic monochloramine determination are also tested to be much higher than that mostly encountered in actual water treatment. Case study demonstrates that the results obtained from this method are lower than DPD-titrimetric method because the organic chloramines formed by chlorination of organic nitrogenous compounds give no response in the newly established method. And the result measured by salicylate-spectrophotometric method is coincident with theoretical calculation.

[Study on adsorption of bisphenol A from aqueous solution on modified activated Carbons].

A commercial activated carbon (WV A1100) was modified with nitric acid, sodium hydroxide and thermal treatment in an atmosphere of N2. Several techniques were used to characterize the physicochemical properties of these materials including BET, XPS, pH(PZC) and Boehm titration. The results indicated that the specific surface area of the W20 remarkably decreased after oxidized by nitric acid. But the amount of surface acidic oxygen-containing functional groups of the oxidized sample increased compared to the W20 and resulting in the points of zero charge (pH(PZC)) changed from 4.95 to 1.50. The changes of surface chemical properties of thermal treatment and sodium hydroxide treatment were opposite to the oxidized sample, as a result, the pH(PZC) of them was changed to near pH 7.0. However, a 43.81% surface area of W20 was also diminished by thermal treatment. Furthermore, the results of BPA adsorption indicated that the oligomerization of BPA on the surface of activated carbon could not be formed through oxidative coupling reactions in the presence of dissolved oxygen. And the data of BPA adsorption on original sample, thermal and sodium hydroxide treatment sample were fitted to the Langmuir isotherm model well. Whereas the Freundlich isotherm model described the adsorptive behavior of the oxidized sample better. In addition, the adsorption capacity of thermal treatment sample was the highest and its saturated adsorption capacity reached 526.32 mg/g. The value was three times higher than that of the oxidized sample. Combined with the results of characterization, it was found that the hydrophobic nature and zero of net charge density of carbon surface were the main factors to affect the BPA adsorption on activated carbons and the adsorption is based on pi-pi theory.

[Characteristic of natural organic matter removal by ferric and aluminium coagulation].

Natural organic matter removal efficiency and characteristic by ferric chloride and aluminium sulphate were studied. Results showed that ferric chloride was effective in natural organic matter removal when coagulant dosage was higher than 15 mg/L, while aluminium was effective at lower dosage. The TOC of water was reduced to 4.19 mg/L and 9 mg/L at a dosage of 10 mg/L for aluminium sulphate and ferric chloride respectively, while TOC was reduced to 2.44 mg/L and 1.69 mg/L at the dosage of 20 mg/L. Ferric chloride decreased pH sharply than aluminium sulphate which made hydrolysate more positive and attachable for natural organic matter. UV254 and SUVA results showed that ferric chloride removed more conjugate structure materials and unsaturated band contents than aluminium. Ferric chloride was more effective in reducing lower molecular weight organic matter and hydrophilic substances than aluminium, when the dosage of coagulant was 20 mg/L, the removal efficiency of relative molecular weight below 10 000 was 16.4% and 6.1% respectively, while aluminum was more effective in high molecular weight matter removal than ferric chloride.

[Image and coagulation behavior of colloidal hydrated manganese dioxide flocculate particles].

The structure and image of colloidal hydrated manganese dioxide flocculate particles and the electrical charge characteristic of colloidal hydrated manganese dioxide were studied by transmission electron microscope (TEM) and zeta potential (ZP) measurement. The surface chemistry characteristic of colloidal hydrated manganese dioxide was characterized by IR spectra and XRD technology etc. Then the coagulating property and behavior of the colloidal hydrated manganese dioxide produced by KMnO4 were also studied by jar test. The results show that the colloidal hydrated manganese dioxide shows negative electricity in doubly distilled water and raw water. The diameter of the particles is about 10 nm and its flocculate shows network structure which benefits to adsorbing-bridging in doubly distilled water. It has abundant surface hydroxyl radical and its specific surface is 151.422 m2/g. It belongs to delta-MnO2. So it exhibits surface chemistry of excellent removal pollutants. It gives best coagulation efficiency and good effect of removal organic pollutants to raw water in a low dosage.

[Ozonation of representative endocrine disruptors (EDs) in water].

The effects of ozone dose, bicarbonate concentration and pH on endocrine disruptors(EDs) removal, such as E1, E2, EE2, DES and 4-n-NP, were investigated through batch experiment. The results indicated that the removal rates were enhanced by increasing ozone dose, and O3 exposures of only 63.6 microg/L were calculated to achieve > or = 92.0% EDs removal efficiency. The presence of bicarbonate (0 - 100 mg/L) inhibited EDs ozonation. Furthermore, the EDs removal rates increased significantly as pH increased. The five apparent rate constants (20 degrees C +/- 0.5 degrees C) of ozone with the five EDs were in the range of (1.67 - 3.89) x 10(6)L (mol s) (-1) at neutral pH (pH approximately 7.0) and (0.93 approximately 1.75) x 10(9) L (mol s)(-1) at basic pH (pH > 10.6). It was indicated that the five EDs were removed rapidly by O3 in water. At the same time, the elementary reaction ozone rate constants (20 degrees C +/- 0.5 degrees C) were calculated, and the reactivity of ozone with ionized EDs [i.e. 1.21 x 10(9) - 3.81 x 10(9) L (mol s)(-1)] was 10(3) - 10(4) times higher than with neutral EDs [i.e. 7.62 x 10(5) - 2.55 x 10(6) L (mol s)(-1)]. The comparative test of EDs ozonation under different water quality conditions indicated that the removal rates of EDs in filtrated water and river water were reduced 26.5% - 50.3% and 57.3% - 72.0% respectively compared with the case using ultrapurified water as the background. It showed that organics in real water would compete with EDs for ozonation.

[Effects of potassium permanganate on natural organic matter chlorination activity].

Effects of potassium permanganate (PP) oxidation on natural organic matter(NOM) chlorination activity was studied in the article. Natural organic matter was separated into humic acid (HA), fulvic acid(FA), hydrophilic acid(HPIA) and non-hydrophilic acid (HPI-NA) fraction four fractions by XAD resin adsorption technique. Potassium permanganate oxidation alone increased HA and HPIA chlorination activity and decrease that of FA and HPI-NA. The chlorination activity of HA and HPIA were increased by 39.3% and 13.8% by 0.75 mg/L. potassium permanganate, but the chlorination activity of FA and HPI-NA were decreased by 33.6% and 46.9%. SUVA results showed that potassium permanganate increase FA and HPIA unsaturated band contents, and decreased that of FA and HPI-NA. Compared with coagulation, potassium permanganate combined with coagulation can decrease the trihalomethanes of HA, FA, HPIA and HPI-NA by 9.1,15.7,7.2 and 14.7 per cent compared with that of coagulation alone.