[Enhanced Removal of Herbicide 2,4-dichlorophenoxyacetic Acid and Simultaneous Power Generation in Microbial Fuel Cells]

This study investigated the effects of a widely used herbicide 2,4-dichlorophenoxyacetic acid on power generation, pollutants removal from microbial fuel cells (MFCs) and microbial community changes, and also explored anode pre-aeration for enhanced 2,4-D removal and power generation. The results showed that when 2,4-D was inputted to the anode chamber of MFCs which was previously enriched with acetate sodium as the fuel, the voltage output and power density declined and the internal resistance increased apparently. The maximum power density declined to 0.057 W·m^-2 in the presence of 300 mg·L^-1 2,4-D comparing to 0.151 W·m^-2 obtained with acetate alone (850 mg·L^-1), and the internal resistance increased from 524 Ω to 1230 Ω correspondingly. To accelerate 2,4-D removal rate and reduce its inhibition to anode exoelectrogens, 6h pre-aeration was applied to the anode chamber. Fast removal of 2,4-D was achieved during aeration period and simultaneous high maximum voltage output (0.42-0.47 V) was obtained. Anode microbial community changed after 2,4-D addition and several 2,4-D degrading bacteria and 2,4-D tolerant exoelectrogen were enriched. MFCs could be used for 2,4-D removal and simultaneous power generation through anode pre-aeration.

[Adsorption of Cu2+ by xanthate-functionalized waste sludge]

Waste sludge from waste water treatment plants was treated with the carbon disulfide in alkaline medium to prepare xanth, aiming to explore an efficient way to recycle waste sludge. Fourier transform infrared spectroscopy (FTIR) was applied to characterize the sludge. Batch experiments were conducted to investigate the adsorption property of Cu2+ as well as effecting factors including pH and initial concentration of Cu2+ . Results show that the chemical modification introduces sulfur groups successfully and the adsorption capacity of xanthate-functionalized sludge increases by 20.6%- 46. 9% comparing to the pristine waste sludge. The Cu2+ removal efficiency of xanthate-functionalized sludge reaches 96.7% when the initial concentration of Cu2+ is 25 mgL-1. The adsorption process can attain equilibrium within 3 hours and kinetics is found to be best-fit the Pseudo-second-order equation. The process is jointly controlled by film diffusion and intraparticle diffusion. Both Langmuir model and Freundlich model can describe the adsorption, process well. The maximum adsorption capacity given by the Langmuir model is 142.92 mgg-1 at 25 degree C (pH = 5). Adsorption capacity increases with pH value (1-5) and initial Cu2+ concentration. The xanthate-functionalized sludge can be used as high performance adsorbents to recycle waste resources.

[Isolation, identification of two aerobic denitrifiers and bioaugmentation for enhancing denitrificaition of biofilm under oligotrophic conditions]

Two aerobic denitrifying bacteria were isolated from the sludge of municipal wastewater treatment plant by enrichment, preliminary screening with BTB culture medium and the denitrification potential test and identified through 16S rDNA sequence analysis. Then they were bioaugmented to oligotrophic biofilm system respectively, aiming to enhance the denitrification capacity. The two strains were identified as Pseudomonas aeruginosa and Pseudomonas putida respectively. They could remove 78% or 82% of the total nitrogen in the simulate wastewater when existed alone. And the total nitrogen removal efficiency of the biofilm system reached 68% and 64% after bioaugmentation with two trains, increased by 47% and 43% compared to the control, respectively. Meanwhile, the ammonia nitrogen was nearly 100% removed. It can be concluded that two aerobic denitrifiers can enhance the denitrification of biofilm system significantly under oligotrophic conditions and will not inhibit the nitrification process, therefore can help biofilm system achieve simultaneous nitrification and denitrification.

[Microbial ecology analysis of the biofilm from two biological contact oxidation processes with different performance]

This study investigated the performance of one-step aerobic biological oxidation process and anoxic/aerobic two-step biological oxidation process treating modeled river water containing low carbon and rich ammonia. Biofilm microbial ecology was analyzed with multiple molecular technologies including PCR-DGGE, FISH/CLSM and FISH/FCM to investigate the succession of bacteria community and space distribution along with abundance of the main functional bacteria, and to research the micro-influential factors and the mechanism of different biological contact oxidation processes for their performance. Results showed that two-step contact oxidation process achieved higher removal percentage than that of the one-step process, with COD and NH4(+) -N removal enhanced about 10% and 32%-59%, respectively. A much thicker biofilm was obtained by the one-step process compared to the two-step process, and nitrobacterium was mainly distributed in the depth of 180-200 microm and 105-125 microm, respectively. PCR-DGGE results found that the two-step process demonstrated less microbial diversity than that of the one-step process, FISH/FCM results showed that ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) abundance increased in the two-step process with the increase of operation time, while that of the one-step process declined. Experiment results demonstrate that functional partitioning of the anoxic-aerobic two-step biological contact oxidation process could be in favor for harvesting nitrobacteria and other special bacteria in different reactor spaces, which can improve removal efficiency for organics and ammonia finally.

[Bioaugmentation of bioreactors with a pJP4 receiving transconjugant to enhance the removal of 2,4-D]

The paper first investigated horizontal transfer of a conjugative plasmid pJP4 to two pure strains of E. coli DH5alpha and Alcaligenes sp., and a mixed culture of aerobic granular sludge, respectively. With a pJP4 receiving transconjugant Alcaligenes sp. :: pJP4 as the bioaugmented bacteria, bioaugmentation experiments were conducted in an aerobic granular sludge reactor and a biofilm reactor, respectively, to enhance the removal of a recalcitrant compound 2,4-dichlorophenoxyacetic acid(2,4-D). Results showed that pJP4 successfully transferred to E. coli DH5alpha, Alcaligenes sp. and the mixed culture of aerobic granules. For the aerobic granular sludge reactor operated in semi-continuous mode and fed with 2,4-D sole carbon source wastewater, bioaugmentation with Alcaligenes sp. : : pJP4 increased 2,4-D average removal rate significantly with an enhancement of 12% -1 498%. For the biofilm reactor operated in sequence batch mode and fed with mixed carbon sources wastewater, supplementation of the transconjugant reduced system start-up time greatly from 16 d to 5 d. It is a feasible strategy to obtain special degradative transconjugants through gene augmentation and put them into bioreactor as bioaugmentation agent to enhance the removal of some specific pollutants.

[Power generation from glucose and nitrobenzene degradation using the microbial fuel cell]

By constructing a dual-chamber microbial fuel cell (MFC), experiments were carried out using an initial glucose concentration of 1 000 mg/L with different nitrobenzene (NB) concentrations (0, 50, 150 and 250 mg/L) as the MFC's fuel. Results showed that with an external resistance of 1 000 omega, the initial glucose concentration of 1 000 mg/L and the initial NB concentrations of 0, 50, 150, 250 mg/L, the operation periods were 55.7, 51.6, 45.9 and 32.2 h, respectively, the maximum voltage outputs were 670, 597, 507, and 489 mV, the maximum volumetric power densities were 28.57, 20.42, 9.29, and 8.47 W/m3, and the electric charges were 65.10, 43.50, 35.48, and 30.32 C. The MFC could use the NB and glucose mixtures as fuel and generated stable electricity outputs. The degradation rates of NB in the MFC in all cases reached up to 100% and COD removals in the MFC were 87% - 98%. However, the electricity generation was negligible when using 250 mg/L NB as the sole fuel. Denaturing gradient gel electrophoresis (DGGE) profiles demonstrated that the presence of NB resulted in changes of the dominant bacterial species on the electrodes.

[Electricity generation and quinoline degradation of pure strains and mixed strains in the microbial fuel cell]

Microbial flora composition of microbial fuel cells (MFC) is important to the electricity generation. Four bacterium strains Q1, b, c and d which represent all different morphology of culturable bacterium were isolated from a MFC using 200 mg x L(-1) quinoline as the fuel and operating for at least 210 days. Strains Q1, c and d were Pseudomonas sp. based on 16S rDNA sequence analysis, while strain b was Burkholderia sp. Double-chamber MFCs using 200 mg x L(-1) quinoline and 300 mg x L(-1) glucose as the fuel and potassium ferricyanide as the electron acceptor were constructed. Results showed that strain b, c and d were non-electrogenesis. The electrical charges of MFC inoculated electrogenesis strain Q1 with non-electrogenesis strain b, c and d respectively were 3.00, 3.57 and 5.13C, and the columbic efficiency were 3.85%, 4.59% and 6.58%, which were all lower than that inoculated with pure Q1, because of the interspecific competition of electrogenesis and non-electrogenesis bacteria. Combinations of Q1 with the other three strains respectively resulted in 100% of quinoline degradation rates within 24h, which is better than pure cultures, that is, mixed microbial populations perform better in MFC when complex organics are used as the fuel. GC/MS analyses showed that only 2(1H)-quinolinone and phenol existed in the effluent of the MFC, which was inoculated with only Q1 or mixed bacteria.

Occurrence of aliphatic hydrocarbons in water, suspended particulate matter and sediments of Daliao River system, China

In August of 2005 a study was carried out to evaluate contamination of aliphatic hydrocarbons(AHc) in water, suspended particulate matter (SPM) and sediments from Daliao River system composed of the Hun River, Taizi River, and Daliao River in a heavy industrial area of northeast of China. The content of AHc ranged from 13.39 to 283.62 microg L(-1) in surface water, from 22.68 to 5,725.36 microg g(-1) in dry SPM, and from 61.37 to 229.42 microg g(-1) in dry sediments. High hydrocarbon levels were generally found in the areas associated with high anthropogenic impact and port activities. The calculated hydrocarbon indexes suggest that the stations with petrogenic sources and biogenic origin predominance would constitute aliphatic hydrocarbons for the river system. Hierarchical cluster analysis (HCA) of aliphatic hydrocarbons is correspondence with hydrocarbons indexes results.

[Plasmid pJP4 mediated gene horizontal transfer in a biofilm system and its effect on 2, 4-D degradation]

With plasmid pJP4 (which contains functional gene cluster (tfd) encoding 2,4-D degradation) carrying genetic microorganism Pseudomonas putida SM1443:: gfp2x (pJP4:: dsRed) as the donor strain, events of plasmid mediated gene horizontal transfer and its effect on 2,4-D degradation was investigated in a biofilm system operated under fed-batch mode. The surviving status of the functional gene element in the gene-augmented system and effects of gene-augmentation on microbial community structure were also investigated. Results showed that introduction of pJP4 carrying strain to the biofilm system with 2, 4-D (initial concentration at 170 mg/L +/- 10 mg/L) as the sole carbon source could enhance the degradation of 2, 4-D. Enhancement was slight during the initial stage of operation, but it increased with increasing of fed batch runs. Difference in 2, 4-D average degradation rate between gene-augmented system and the control system achieved up to 13.3 mg/(L x h) at most. Through detecting functional gene tfdB and reporter gene gfp, pJP4 mediated gene horizontal transfer to the bacteria on biofilm was further approved. Effects of gene augmentation on microbial community structure was analyzed by PCR-DGGE analysis, and results showed that relatively higher stability of microbial community was maintained for the gene-augmented biofilm system compared to the control system when facing 2,4-D shock loadings.

[Plasmid pJP4 mediated gene-augmentation in different systems and its effect on 2,4-D biodegradation]

With pJP4 plasmid carrying genetic engineering bacteria Pseudomonas putida SM1443 :: gfp2x (pJP4 :: dsRed) as the donor, horizontal gene transfer of pJP4 plasmid in 4 isolated pure strains was investigated, and effects of the donor bacteria inoculation on the removal of the target pollutant 2,4-dichlorophenoxyacetic acid (2,4-D) was studied through conducting gene augmentation in activated sludge, biofilm, aerobic granular sludge and river sediment system, respectively. Results showed that plasmid pJP4 could transfer from Pseudomonas putida SM1443 to a broad spectrum of bacteria. Inoculation of pJP4 plasmid carrying donor bacterium apparently promoted the degradation of 2,4-D for all the above four systems. For the activated sludge system (2,4-D initial concentration at 450 mg/L), 66% and 54% removal of 2,4-D was achieved after 143.5 h reaction for the gene augmented and control system, respectively. For the biofilm system with 2,4-D initial concentration at 180 mg/L, 2,4-D removal percentage at 113 h was 99% and 61%, respectively. For aerobic granular sludge system (2,4-D initial concentration at 160 mg/L), 2,4-D was nearly completely removed by 62 h in the gene-augmented system, while the control system only degraded 26% at 66 h. For the system with sediment (2,4-D initial concentration at 2 mg/L), 93% and 69% removal of 2,4-D was obtained at 344 h reaction for the gene augmented and control system, respectively. Confocal laser scanning microscopy (CLSM) analysis revealed the formation and presence of transconjugants in different gene augmentation systems.

[Factors influencing bacterial cell-surface hydrophobicity and bacterial adhesion ratio to activated sludge flocs]

With four different strains as the model, effects of different culture medium on cell-surface hydrophobicity (CSH) were investigated, and the relationship between CSH, contact time and adhesion of bacteria to activated sludge flocs was correlated. Results showed that culture medium, culture time and the characteristic of strain itself influenced the CSH of bacteria, and initial CSH, contact time was closely related to bacterial adhesion ratio in activated sludge system. When contact time was relatively short (< 14 h), initial CSH was the main factor influencing bacterial adhesion ratio. A critical value existed for CSH, similar bacterial adhesion ratio was obtained below the critical value; beyond the value, bacterial adhesion ratio was greatly enhanced, which indicated that only strains with initial CSH beyond the critical value could adhere to activated sludge flocs rapidly. When contact time was long enough (> or = 38 h), contact time became the main factor influencing adhesion. When the inoculated bacteria thoroughly adhered to sludge flocs by pre-contact, nutrient supplementation and changing oxygen providing mode did not cause the release of adhered bacteria again.

[Contamination characters of polycyclic aromatic hydrocarbons in Daliao River system of China]

With GC/MS, a quantitative study was made on the polycyclic aromatic hydrocarbons (PAHs) in the surface water and suspended particulates in Daliao River system, with their spatial distribution and sources investigated. The results showed that the total PAHs concentration ranged from 946.1 to 13 448.5 ng x L(-1) in surface water, and from 317.5 to 238 518.7 ng x g in suspended particulates. The PAHs concentration was decreased in the order of Taizi River > Daliao River > Hunhe River. The PAHs in surface water were dominated by 3-5 rings, while those in suspended particulates were dominated by 2 rings. The calculated ratios of selected PAHs suggested that the discharges from municipal, petrochemical and steel industrial wastewater, and the atmospheric fallout might be the important PAHs sources, and the contamination sources of PAHs were the mixture of petrogenic and pyrolytic inputs. In comparing with other river and marine systems in the world, Daliao River system had higher concentrations of PAHs in its surface water and suspended particulates, and thus, presented certain ecological risk.

[Distribution characteristics of organochlorine pesticides in river surface sediments in Song-Liao watershed]

With gas chromatography-electron capture detector (GC-ECD), this paper analyzed 13 kinds of organochlorinae pesticides (OCP) in surface sediments collected from 22 sites of Song-Liao water system. The results showed that the total concentration of OCP varied from 3.06 to 23.24 ng x g(-1) in Daliao River system and from 4.26 to 18.45 ng x g(-1) in Songhuajiang River system. The most dominant OCP pollutant in the sediments in Song-Liao Watershed was HCH, but there existed different pollution tendency in the two subsystems. In Songhuajiang River, there were also relatively high concentrations of DDT. High concentration gamma-HCH was observed among the isomers of HCH in the whole watershed, which exceeded the initial affecting concentration and could potentially do toxic effect on the water creatures.

[Study on the treatment of aromatic hydrocarbon containing wastewater by an anaerobic filter reactor under denitrifying condition]

With benzene, naphthalene and biphenyl as the model aromatic hydrocarbon, the treatment of aromatic hydrocarbon containing wastewater by an anaerobic filter (AF) reactor operated in continuous mode and under denitrifying condition were conducted. With glucose as the supplemented carbon, the influence of C/N ratio on the degradation of organic compounds was also investigated. Results showed that the AF reactor could degrade these aromatic hydrocarbons effectively under above mentioned conditions. When the influent COD concentration was 1 000 mg/L, and benzene, naphthalene and biphenyl concentration was 60 mg/L, the removal efficiency for COD and aromatic hydrocarbons was 90% and 84%, respectively. Benzene was more easily degraded than naphthalene and biphenyl under denitrifying condition. When C/N was in the range 5 - 30, benzene removal percentage was always at about 90% , and C/N ratio did not have obvious effect on the degradation of benzene. The degradation of naphthalene and biphenyl and total COD was greatly influenced by C/N. When C/N was 15, the highest removal percentage was achieved and it was 90%, 78% and 82% for COD, naphthalene and biphenyl, respectively.