[Show abstract][Hide abstract] ABSTRACT: 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.
[Show abstract][Hide abstract] ABSTRACT: In this paper, a novel process of recycling alum sludge with powdered active carbon (PAC) was evaluated for drinking water treatment under various conditions. Results of this study indicated that the removal of turbidity, DOC and UV254 from simulated raw water by recycling alum sludge with PAC could reach up to 89.2%, 52.7% and 60.1%, respectively, which were better than that of recycling alum sludge alone, and it may be due to the adsorption of PAC which existed in mixed sludge. Turbidity of raw water had an important impact on the recycle of alum sludge with the PAC process, which is better to be applied in treating raw water with turbidity less than 100 NTU. In addition, the optimal pH for humic acid removal by recycling alum sludge with PAC was approximately 5. It was postulated that combination of adsorption and sweeping by hydroxide precipitates and the adsorption of PAC existing in mixed sludge played a key role in the enhancement of turbidity and organic matter removal.
Desalination and water treatment 01/2011; 25:170-175. · 0.85 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Ultrafiltration is a promising process to produce qualified drinking water. The application of ultrafiltration for drinking water production has undergone accelerated development during the past decade. Membrane fouling may be the main obstacle for wider implementation of ultrafitration, which usually causes higher costs of energy, operation, and maintenance. Fouling is formed due to pore blocking, pore stricting and cake formation. Pretreatments (e.g. coagulation, adsorption, and pre-oxidation) can in various degrees alleviate the fouling by pre-reacting with the foulants in the feed water. However, adverse effects from the pretreatment are also claimed. Moreover, modest operation methods (e.g. running modes, rinsing modes, chemical cleaning, and air scouring) can effectively obtain the fouling reduction. In this report, fouling control in ultrafiltration technology for drinking water production is reviewed in terms of different effective pretreatments and operation methods. Specific mechanisms and future research required are also discussed based on the literature reviewed.
[Show abstract][Hide abstract] ABSTRACT: Effect of operating conditions on the fouling of immersed ultrafiltration(UF) membrane for the Suzhou Internal River was investigated with a pilot scale study. Results show that fouling could be reduced by both the continuous aeration and intermittent aeration, while the aeration intensity should be selected reasonably. Fouling could be reduced by intermittent filtration only due to the decrease of the filtration duration, but the combination of aeration and intermittent filtration could have better control of fouling. The transmembrane pressure (TMP) of UF operation could be significantly reduced by coagulation pretreatment and the combination of coagulation, aeration and backwashing could have better mitigation of membrane fouling in the real application of immersed UF.
[Show abstract][Hide abstract] ABSTRACT: 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.
Water Science & Technology 01/2011; 64(7):1497-502. · 1.10 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: 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.
Water Research 09/2010; 45(2):819-27. · 4.66 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this paper, the influences of air bubbling mode, air flow rate, air bubble size and feed water quality on the membrane fouling of immersed hollow-fiber (HF) membrane for ultrafiltration of river water were investigated. The membrane was operated in the intermittent suction mode of 9min on/1min off. The results showed that continuous air bubbling was more effective for mitigating membrane fouling than intermittent bubbling (1min on/9min off in the study) at the same air flow rates of 1.0, 2.5, 5.0, and 7.5m3/m2h, respectively. Furthermore, an optimum air flow rate was observed for immersed HF membrane system when considering the alleviating effect on membrane fouling and energy consumption simultaneously, with the optimum value determined as 5.0m3/m2h in this investigation. It was also found that the smaller the air bubble was (4dia of 3.5, 5.0, 6.5, and 8.0mm were investigated), the more effective the air bubbling would be for mitigating the membrane fouling of immersed HF membrane. However, even if air bubbling was performed, eliminating membrane foulants from the feed water before ultrafiltration was still necessary for the reduction of membrane fouling.
[Show abstract][Hide abstract] ABSTRACT: An integrative membrane coagulation adsorption bioreactor (MCABR) with simultaneous dosing of polyaluminium chloride (PACl, 10 mg/L) as the coagulant and powdered activated carbon (PAC, 8 mg/L) as the adsorbent into the bioreactor was put forward and investigated for the drinking water treatment from slightly polluted surface water. The MCABR exhibited excellent capacity for the removal of organic matter even at a low hydraulic retention time of 0.5 h. As for DOC, UV254, TOC, CODMn, THMFP, HAAFP, BDOC and AOC, the removal efficiencies by the MCABR reached to 63.2, 75.6, 68.3, 72.7, 55.3, 56.2, 67.4 and 75.5%, respectively. In the MCABR, four kinds of mechanisms, i.e. separation by the membrane, biodegradation by micro-organisms, coagulation by PACl, and adsorption by PAC jointly contributed to the removal of dissolved organic matter (DOM), with their respective contributions of 11.1, 8.3, 24.6 and 19.2% in DOC removal, and 11.4, 5.0, 38.1 and 21.1% in UV254 removal. Furthermore, scanning electronic microscopy (SEM) and confocal laser scanning microscopy (CLSM) observations showed that a sludge layer was formed on the membrane surface in the MCABR, which was demonstrated to provide additional rejection for DOM in the mixed liquor, especially for the organic molecules of 3000–300 Da.
[Show abstract][Hide abstract] ABSTRACT: 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.
Water Research 09/2009; 44(1):59-68. · 4.66 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: 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.
[Show abstract][Hide abstract] ABSTRACT: 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.
Huan jing ke xue= Huanjing kexue / [bian ji, Zhongguo ke xue yuan huan jing ke xue wei yuan hui "Huan jing ke xue" bian ji wei yuan hui.] 06/2009; 30(5):1381-5.
[Show abstract][Hide abstract] ABSTRACT: 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.
Huan jing ke xue= Huanjing kexue / [bian ji, Zhongguo ke xue yuan huan jing ke xue wei yuan hui "Huan jing ke xue" bian ji wei yuan hui.] 04/2009; 30(3):761-4.
[Show abstract][Hide abstract] ABSTRACT: The mini-pilot experiments of submerged membrane bioreactor (sMBR) for the drinking water treatment from a slightly polluted surface water supply was conducted for more than 110 days, with a hydraulic retention time of 0.5 h. Perfect ammonia removal (by 89.4%) were achieved by the sMBR through the biological nitrification. However, the capacity of the sMBR for organic matter removal was demonstrated to be low. The average removal efficiencies for TOC, CODMn, DOC, UV254, and corresponding THMFP and HAAFP were 28.6%, 33.5%, 21.5%, 15.1%, 34.1% and 24.7%, respectively, though much higher removal of 51.7% and 54.9% were obtained for BDOC and AOC, respectively. A sludge layer was observed on the UF membrane surface in the sMBR. The sludge layer could provide additional filtration for dissolved organic matter (DOM) in the mixed liquor, especially for organic molecules in the range of 5000–500 Da. Fractionation of DOM indicated that the sludge layer together with the UF membrane had the ability to reject hydrophobic neutrals, hydrophobic acids, and weakly hydrophobic acids by 45.0%, 42.7% and 48.1%, respectively; whereas hydrophobic bases and hydrophilic organic matter were separated mainly by the UF membrane, with the efficiencies of 11.3% and 14.6%, respectively.
[Show abstract][Hide abstract] ABSTRACT: Polyaluminium chloride (PAC) synthetic water was selected as a coagulant and kaolin suspension particles as objects to be
removed. Online instruments such as the turbidimeter and particle counter were employed to monitor the flocculation process
online and collect test data. The aim of the experiments was to study the dynamic distribution characteristics of suspension
particles in the flocculation process. The 3D flow field in the reacting vessel was also simulated at different slow stirring
speeds. The experiments showed that particle collision and aggregation in the flocculation process is in compliance with the
Sutherland cluster aggregation model. This study further indicated that under appropriate hydrodynamic conditions, the distribution
of turbulent flow in the reactor could be improved to increase the odds of effective particle collision and restrain the breakup
of formed flocs by vortex shearing force. A good flocculation effect could therefore be produced.
Journal of Zhejiang University - Science A: Applied Physics & Engineering 01/2009; 10(9):1350-1358. · 0.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The efficiency of chlorine and chloramines disinfection on biofilm development in a simulated drinking water distribution
system was investigated by using heterotrophic bacterial spread plate technique. The experiments were carried out with four
annular reactors (ARs) with stainless steel (SS) or copper (Cu) material slides. The results showed that there were fewer
bacteria attached to Cu slides without a disinfectant compared with those attached to SS slides. When the water was disinfected
with chloramines, the heterotrophic plate counts (HPCs) on the biofilm attached to the Cu slides were significantly lower
(by 3.46 log CFU/cm2) than those attached to the SS slides. Likewise, the biofilm HPC numbers on the Cu slides were slightly lower (by 1.19 log
CFU/cm2) than those on the SS slides disinfected with chlorine. In a quasi-steady state, the HPC levels on Cu slides can be reduced
to 3.0 log CFU/cm2 with chlorine and to about 0.9 log CFU/cm2 with chloramines. The addition of chloramines resulted in a more efficient reduction of biofilm heterotrophic bacteria than
did chlorine. We concluded that the chlorine and chloramines levels usually employed in water distribution system were not
sufficient to prevent the growth and development of microbial biofilm. The combination of copper pipe slides and chloramines
as the disinfectant was the most efficient combination to bring about diminished bacterial levels.
Journal of Zhejiang University - Science A: Applied Physics & Engineering 01/2009; 10(5):725-731. · 0.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: 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.
Huan jing ke xue= Huanjing kexue / [bian ji, Zhongguo ke xue yuan huan jing ke xue wei yuan hui "Huan jing ke xue" bian ji wei yuan hui.] 01/2009; 29(12):3372-5.
[Show abstract][Hide abstract] ABSTRACT: Effects of PAC and alum sludge generated from water treatment process on the effluent quality and fouling of immersed UF membrane were systematically investigated with representative source of natural water and the efficiency of coagulation, PAC adsorption and RPAS to treat natural surface water prior to UF were compared. It was found that the average turbidity removal by RPAS could reach up to 80.2%, and the turbidity removal of immersed membrane UF was independent of the influent, which could be kept at 99%. Particulates were reduced after being pre-treated by different processes, and particles with sizes ranging from 0.5 to 3.5μm and larger than 13.5μm were effectively removed by RPAS. UF coupled with RPAS pre-treatment got the best removal for DOM compared to other processes with average DOC and UV254 removal 54.1% and 47.2% due to the high removal in the influent of UF. The residual alum content in the effluent of RPAS with UF was less than coagulation and bacteria were almost all removed by membrane. The membrane-fouling was mitigated by pre-treatment processes at different degrees, TMP of UF coupled with RPAS process was relatively stable in 15d of run, the adsorption of PAC and large number of Al(OH)3 complexes and precipitates for the foulant molecules might be an important mechanism.
[Show abstract][Hide abstract] ABSTRACT: 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.
Water Research 09/2008; 42(14):3910-20. · 4.66 Impact Factor