[show abstract][hide abstract] ABSTRACT: The production of ligninolytic enzymes and protease by Phanerochaete chrysosporium was investigated under different culture conditions. Different amounts of medium were employed in free and immobilized culture, together with two kinds of medium with different C/N ratios. Little lignin peroxidase (LiP) (< 2 U/L) was detected in free culture with nitrogen-limited medium (C/N ratio: 56/2.2, in mmol/L), while manganese peroxidase (MnP) maximum activity was 231 and 240 U/L in 50 and 100 ml medium culture, respectively. Immobilized culture with 50 ml nitrogen-limited medium gave the highest MnP and LiP production with the maximum values of 410 and 721 U/L separately on the day 5; however, flasks containing 100 ml nitrogen-limited medium only produced less MnP with a peak value of 290 U/L. Comparatively, carbon-limited medium (C/N ratio: 28/44, in mmol/L) was adopted in culture but produced little MnP and LiP. Medium type had the greatest impact on protease production. Large amount of protease was produced due to glucose limitation. Culture type and medium volume influence protease activity corporately by affecting oxygen supply. The results implied shallow immobilized culture was a possible way to gain high production of ligninolytic enzymes.
Journal of Environmental Sciences 02/2008; 20(1):94-100. · 1.77 Impact Factor
[show abstract][hide abstract] ABSTRACT: White rot fungi is capable of oxidizing many persistent organic pollutants including dyes. The application of the fungi has been limited for wastewater treatment under non-sterile conditions due to the contamination by bacteria and other micro-organisms. We developed a treatment approach by using immobilized white rot fungi Phanerochaete chrysosporium to degrade reactive dye K-2BP under non-sterile condition. Four different inert carriers were tested for immobilization of the white rot fungi with orthogonal experiments in comparison with suspension culture. The activity of manganese peroxidase (MnP) was used for the evaluation of oxidization performance in order to understand whether contamination of bacteria and other micro-organisms was suppressed. Under non-sterile conditions, the immobilized fungal cultures successfully restrained the growth of microzymes, coccies, and bacillus but suspension culture was highly contaminated with poor MnP activity. Under non-sterile conditions, higher MnP enzymatic activity (690U/L vs. 125U/L), higher decolorization efficiency (93.5% vs. 15%) and shorter reaction period (3 days vs. 6 days) were achieved in immobilized cultures in comparison with suspension culture. With the immobilized fungal cultures, no difference was observed under non-sterile and sterile conditions for the degradation of reactive dye K-2BP.
Process Biochemistry - PROCESS BIOCHEM. 01/2008; 43(9):937-944.
[show abstract][hide abstract] ABSTRACT: In order to explore ways for the application of white rot fungus in dye effluent treatment under non-sterile conditions, experiment
on decolorization of reactive brilliant red was carried out, employing nitrogen-limited and carbon-limited medium with C/N
ratio of 56/2.2 and 28/44 (in mmol/L), respectively. The results showed that the decolorization rate reached 92% while culturing
white rot fungus with nitrogen-limited medium; however, the decolorization process ended in carbon-limited medium (n(C)/n(N) = 28/44) because of bacterial contamination. In addition, pH rose up to 9.31 after 4 d of decolorization, which was caused
by bacterial contamination in the carbon-limited system. Therefore, it is concluded that nitrogen-limited medium can inhibit
bacterial growth to some extent while carbon-limited medium is more easily contaminated by bacteria. Nitrogen-limited medium
is more suitable in culture of white rot fungus for decolorization of reactive dye. Medium with the ability of inhibiting
yeast growth should be developed by adjusting other components of nitrogen-limited medium.
Science in China Series B Chemistry 09/2007; 50(5):718-724. · 1.20 Impact Factor
[show abstract][hide abstract] ABSTRACT: Sludge reduction in a conventional activated sludge (CAS) process combined with a recycled sludge reactor where Tubifex tubifex (one of Oligochaeta) was inoculated was investigated in this study. The results showed sludge production could be reduced through T. tubifex's predation on sludge in the recycled sludge reactor. The sludge reduction rate of T. tubifex (R) was from 0.18 to 0.81 mg-VSS mg-Tubifex(-1) d(-1). The sludge reduction capacity of the recycled sludge reactor E was from 650 to 1080 mg-VSS L(-1) d(-1). The optimum density of T. tubifex was 2500 mg L(-1) and the optimum sludge recycled ratio was 1. The existence of T. tubifex did not affect COD and NH(4)(+)-N removals in the process, but led to a slight decrease in TP removal. SVI almost did not change when the T. tubifex density was lower than 3300 mg L(-1). The LC50 values on T. tubifex of copper and ammonia were 2.5 and 880 mg L(-1), respectively, both of which were higher than those on Aeolosoma hemprichi.
Journal of Biotechnology 02/2007; 127(3):443-51. · 3.18 Impact Factor
[show abstract][hide abstract] ABSTRACT: Membrane separation was employed in a novel photocatalytic oxidation slurry reactor to conserve catalyst. This paper reports some critical operational conditions of this reactor. While fine-bubble aeration served to suspend the catalyst, introducing an intermittent coarse bubbling under the membrane during operation was vital to counteract TiO2 catalyst entrapment on membrane surface. Circulation flow in the reactor was also found to have certain effect on counteracting the dropping out of catalyst. A submerged membrane module with a pore size of 0.1μm successfully conserved the powdered catalysts within the reactor after 2 days’ preluding filtration. As for pollutant removal, membrane filtration and circulation flow had no effect, whereas increase in gas holdup had. Running the reactor to treat model pollutant dissolved in tap water revealed that calcium carbonate both deactivated the catalyst and contributed to membrane fouling, suggesting that water hardness and alkalinity deserves appropriate treatment to warrant a good performance of such a reactor.
Separation and Purification Technology - SEP PURIF TECHNOL. 01/2007; 55(2):165-172.
[show abstract][hide abstract] ABSTRACT: Microcystins (MCs) are a group of closely related toxic cyclic heptapeptides produced by common cyanobacteria, which cause
lots of accidents and threatens human health. In this paper, an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA)
was established and used to detect microcystin-LR (MC-LR) in drinking and surface waters. The concentration of coating antigen
was 5 μ/mL, the dilution of monoclonal antibody MC10E7 was 1:3 000, the dilution of enzyme tracer (goat anti-mouse IgG-peroxidase)
was 1:3 000, the standard concentration of MC-LR ranged from 0.001 μg/L to 30 μg/L, and o-phenylenediamine was used as substrate. The assay showed high relativity with high performance liquid chromatography (HPLC)
with a correlation coefficient of more than 99%. The relative standard deviation was less than 10%, the detection limit was
achieved down to 0.01 μg/L and up to 5.1 μg/L. The quantitative detection range was from 0.03 μg/L to 3 μg/L, and the antibody
had high specificity for [4-arginine] microcystins. It performed well in spite of the influence of the real samples.
Frontiers of Environmental Science & Engineering in China 01/2007; 1(3):329-333. · 0.75 Impact Factor
[show abstract][hide abstract] ABSTRACT: The resistance analyses for recirculated membrane bioreactor by the resistance-in-series model and the modified gel-polarization model respectively were extended to the turbulent ultrafiltration system. The experiments are carried out by dye wastewater in a tubular membrane module, it is found that the permeate fluxes are predicted very well by these models for turbinate systems. And the resistance caused by the concentration polarization is studied; the gel layer resistance is the most important of all the resistances.
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.] 12/2006; 27(11):2344-9.
[show abstract][hide abstract] ABSTRACT: Spatial distributions of ammonia oxidizing bacteria (AOB) and nitrobacteria in a renovated suspended carrier biofilm reactor (SCBR) were investigated by using fluorescence in situ hybridization (FISH) with 16S rRNA oligonucleotide probes in combination with confocal laser scanning microscopy (CLSM). Three bench-scale structurally identical SCBR reactors were operated under different ratios of COD to NH4(+) -N in influents, 5, 10 and 15, respectively. Each SCBR reactor was consisted of a 6 L of aeration basin and a 2L of clarifier, with the hydraulic retention time (HRT) of 1.0h. The monitoring results showed that the thickness of biofilm in the SCBR was about 80 to 120 micron. Both the total amount of AOB and nitrobacteria decreased with depth in biofilm, most of the nitrification bacteria communities lied in the upper layer of biofilm, about 20 to 30 micron. The proportion of AOB to all bacteria in biofilm decreased when the ratio of COD to NH4(+) -N increased.
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.] 12/2006; 27(11):2358-62.
[show abstract][hide abstract] ABSTRACT: Three bio-methods for sludge reduction including aerobic digestion, anaerobic digestion and predation by T. tubifex were investigated. The sludge reduction rates in 24h by predation of T. tubifex, anaerobic digestion and aerobic digestion were 0.13 mg x (mg x d)(-1), 0.09 mg x (mg x d)(-1) and 0.03 mg x (mg x d)(-1) respectively, when sludge concentration was 2500 mg x L(-1). T. tubifex could destroy the cell membrane of the bacteria in a short time, which could increase the sludge reduction rate when anaerobic digestion was adopted after the predation of T. tubifex. Using the T. tubifex to reduce sludge for 12h combined with anaerobic digestion for 36h could reduce sludge by 30%, and the sludge reduction rate was 0.25 mg x (mg x d)(-1). If the initial sludge concentration increased, the time of predation by T. tubifex should be extended.
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.] 12/2006; 27(11):2339-43.
[show abstract][hide abstract] ABSTRACT: Microcystins (MCs) are a group of closely related toxic cyclic heptapeptides produced by common cyanobacteria (blue-green algae), and microcystin-leucine-arginine (MC-LR) is among the most frequent and most toxic microcystin congeners. In this study, a free amino group was introduced to MC-LR at its seventh amino acid residue with 2-mercaptoethylamine, and the product aminoethyl-MC-LR was coupled to bovine serum albumin (BSA) and horseradish peroxidise (HRP) by glutaraldehyde to be complete antigen (MC-LR-BSA) and labelled hapten (MC-LR-HRP), respectively. Polyclonal antibodies against MC-LR were generated by immunization with MC-LR-BSA. A direct competitive enzyme-linked immunosorbent assay (dc-ELISA) was established to detect the MCs in waters, which showed a good cross-reactivity with MC-LR, MC-RR, MC-YR, MC-LF, MC-LW and nodularin, and have a detection limit for MC-LR 0.12 microg L(-1), the 50% inhibition concentration (IC50) for MC-LR was 0.63+/-0.06 microg L(-1) and the quantitative detection range was from 0.17 to 2.32 microg L(-1), the analysis result of water samples showed good recovery and reliability. So the comprehensive and reliable dc-ELISA will well potentially suit for sensitive analysis for total MCs in drinking as well as resource water samples.
[show abstract][hide abstract] ABSTRACT: In situ bioremediation is a safe and cost-effective technology for the cleanup of contaminated sites, but its remediation rate is usually very slow. This study attempted to accelerate the process of bioremediation by employing non-uniform electrokinetic transport processes to mix organic pollutants and degrading bacteria in soils under in situ conditions (namely, in situ bioelectrokinetic remediation) by use of an electrode matrix and a rotational operation mode. A bench-scale non-uniform electrokinetic system with periodic polarity-reversal was developed for this purpose, and tested by using a sandy loam spiked with phenol as a model organic pollutant. The results demonstrated that non-uniform electrokinetic processes could enhance the in situ biodegradation of phenol in the soil, the efficiency of which depended upon the operational mode of the electric field. Compared with the unidirectional operation and the bidirectional operation, the rotational operation could effectively stimulate the biodegradation of phenol in the soil if adopting appropriate time intervals of polarity-reversal and electrode matrixes. A reversal interval of 3.0 h and a square-shaped electrode matrix with four electrode couples appeared appropriate for the in situ biodegradation of phenol, at which a maximum phenol removal of 58% was achieved in 10d and the bioremediation rate was increased about five times as compared to that with no electric field applied. The results also showed that adopting a small polarity-reversal interval and an appropriate electrode array could produce a high and uniform removal of phenol from the soil. It is believed that in situ bioelectrokinetic remediation holds the potential for field application.
[show abstract][hide abstract] ABSTRACT: Using micorfauna to reduce excess sludge is a potentially effective ecological technology and scaling the rate of sludge reduction rate is the first step. A method to scale the rate of sludge reduction caused by microfauna was proposed, and comparison of sludge reduction rates induced by four microfaunas was carried out. The principle of this method is based on the change of carbon forms. The rate of sludge reduction was correlated with the rate at which solids were changed into liquid and gas. Four microfaunas, including Aeolosoma hemprichi, Daphnia magna, Tubifex tubifex and Physa acuta, were cultured with sterilized sludge in a covered sterilized bottle and were then isolated from the atmosphere above the liquid phase. The rates of sludge reduction using the four microfaunas were 0.8, 0.18, 0.54 and 0.1 mg-sludge/(mg-Microfauna d), respectively, changing with the microfaunas' phylum or class and body size. Based on the change of carbon (C) forms, the proposed method produced accurate results similar to those produced using the direct measuring method.
[show abstract][hide abstract] ABSTRACT: In this study, sludge reduction in a conventional activated sludge (CAS) process where Aeolosoma hemprichi (one species of oligochaeta) was inoculated as a micro-fauna was tested. The factors affecting the growth of A. hemprichi and the influence of A. hemprichi on treatment performance were investigated. The observed specific growth rate of A. hemprichi decreased at lower SRT, and the SRT at which A. hemprichi would be totally exhausted was estimated about 3 days. Obvious appearance of A. hemprichi was observed when the F/M ratio was lower than 0.7 mg-COD/(mg-VSS day). A. hemprichi grew independent of sludge concentration when SS concentration was higher than 300 mg-VSS/L, and more easily predated on sludge floes with higher protein content or smaller particle size. The apparent sludge yield was found to have a negative correlation with the density of A. hemprichi in the CAS reactor. The relative sludge reduction by A. hemprichi was estimated to be about 39–65%, and the apparent sludge reduction rate per unite weight of A. hemprichi was from 0.53 to 6.32 mg-VSS/(mg-A. hemprichi day). The existence of A. hemprichi was beneficial to stabilize the sludge settleability and TP removal but did not affect COD and NH4+-N removals in the process. The results indicated that using A. hemprichi to reduce sludge in wastewater treatment was feasible.
[show abstract][hide abstract] ABSTRACT: To achieve a stable performance during long-term operation of biofiltration process, the effect and control of excess biomass accumulation should be investigated in detail. In this study, a biofilter treating gaseous toluene was operated continuously under different operating conditions for more than 270 days. Decrease in toluene removal efficiency and increase in pressure drops of the filter bed were simultaneously observed during the operation period due to excess biomass accumulation. The distributions of toluene concentration and gas pressure suggested that more biomass would accumulate in the inlet section. By carbon balance analysis, the variation of the biomass concentration in the biofilter was calculated. The variation of the biofilter performance and the biomass concentration demonstrated that 10,000 g C m−3 might be a critical biomass concentration for the biofilter to maintain a stable operation. An evaluation equation based on biomass growth kinetics was successfully established and used to estimate the stable-run time of a biofilter under different VOCs loadings. Bed mixing was found to be able to remove approximately 4000 g VSS m−3 of excess biomass and could also recover the performance of the biofilter.
[show abstract][hide abstract] ABSTRACT: In vitro degradation of synthetic dyes by ligninolytic enzymes from white rot fungi is one potential way to deal with dye pollution compared with decolorization by conventional biological treatment. In this work, production of the ligninolytic enzymes was carried out at C/N ratios of 28/44 mM and 56/2.2 mM in nonimmersed liquid culture of Phanerochaete chrysosporium. In vitro decolorization of one industrial azo dye, Reactive brilliant red K-2BP, by crude lignin peroxidase (LiP) and manganese peroxidase (MnP) obtained under carbon and nitrogen limitation respectively, was examined and compared for their degradation characteristics. Both decolorization by LiP and MnP were sensitive to pH, peaking around pH 3.0, and improved at higher enzyme activities. Decolorization by LiP can be enhanced to the greatest degree (89%) with higher addition of H2O2 and veratryl alcohol, whereas decolorization by MnP was optimized only with a suitable dose of H2O2 (0.1 mM) and decreased by the addition of Mn2+. Decolorization declined at high dye concentrations; LiP was able to decolorize a dye concentration of 60 mg/l and below to no less than 85%, and MnP of 10 mg/l to a maximum of 71%. Decolorization by LiP and MnP together was somewhat lower than that by LiP alone. It is suggested that the optimization of the H2O2 supply was mainly responsible for a high efficiency in continuous dye degradation by crude LiP and MnP.
[show abstract][hide abstract] ABSTRACT: The poor mobility of organic pollutants in contaminated sites frequently results in slow remediation processes. Organics, especially hydrophobic compounds, are generally retained strongly in soil matrix as a result of sorption, sequestration, or even formation into non-aqueous-phase liquids and their mobility is thus greatly reduced. The objective of this study was to evaluate the feasibility of using non-uniform electrokinetic transport processes to enhance the mobility of organic pollutants in unsaturated soils with no injection reagents. Phenol and 2,4-dichlorophenol (2,4-DCP), and kaolin and a natural sandy loam soil were selected as model organics and soils, respectively. The results showed that non-uniform electrokinetics can accelerate the desorption and movement of phenol and 2,4-DCP in unsaturated soils. Electromigration and electroosmotic flow were the main driving forces, and their role in the mobilization of phenol and 2,4-DCP varied with soil pH. The movement of 2,4-DCP in the sandy loam towards the anode (about 1.0 cmd(-1)V(-1)) was 1.0-1.5 cmd(-1)V(-1) slower than that in the kaolin soil, but about 0.5 cmd(-1)V(-1) greater than that of phenol in the sandy loam. When the sandy loam was adjusted to pH 9.3, the movement of phenol and 2,4-DCP towards the anode was about twice and five times faster than that at pH 7.7, respectively. The results also demonstrated that the movement of phenol and 2,4-DCP in soils can be easily controlled by regulating the operational mode of electric field. It is believed that non-uniform electrokinetics has the potential for practical application to in situ remediation of organics-contaminated sites.
[show abstract][hide abstract] ABSTRACT: In situ bioremediation is an attractive and often cost-effective technology for the cleanup of organics-contaminated sites, but it often requires extended treatment time under field conditions. This study explored the feasibility of using non-uniform electrokinetic transport processes to enhance in situ bioremediation. A bench-scale non-uniform electrokinetic system with periodic polarity-reversal was developed for this purpose, and tested by using a sandy loam spiked with phenol as a model organic pollutant. The results demonstrated that non-uniform electrokinetic processes could accelerate the movement and in situ biodegradation of phenol in the soil. Bidirectional operation enhanced the phenol biodegradation more effectively than unidirectional operation. At the same time, a smaller polarity-reversing interval induced a higher and more uniform removal of phenol from the soil. The results also showed that reversing the polarity of electric field applied could maintain the soil pH and moisture, but it increased the consumption of electricity.
Journal of Hazardous Materials 06/2005; 121(1-3):187-94. · 3.93 Impact Factor
[show abstract][hide abstract] ABSTRACT: A renovated suspended carrier biofilm reactor was investigated for its capability of carbon oxidation and nitrification. The carrier used was polyvinyl chloride cylinder with 2.5 mm diameter and 2.5–3.0 mm height. The carrier filling ratio, which is defined as the volume ratio of carrier to the whole reactor, is a key characteristic parameter for the new reactor. The operational experiments under different carrier filling ratio ranging from 10 to 75% were conducted. Meanwhile, the pollutant removal rate and behaviour of the microorganisms, such as biomass and specific oxygen utilization rate (SOUR) activity, were monitored and analyzed. The results showed that when the influent chemical oxygen demand (COD) and ammonia was about 200 and 20 mg/l, hydraulic retention time of 1.0 h, the optimum carrier concentration was about 50%with the average COD and ammonia removal rate about 70 and 30%, respectively.
Process Biochemistry 05/2005; 40(9):2992-3001. · 2.44 Impact Factor