Low-temperature biodegradation of aniline by freely suspended and magnetic modified Pseudomonas migulae AN-1.

Aniline is of great environmental concern with regards to widespread occurrence in water and soil and increasing threat into the life forms. Bioremediation involving the use of degrading bacterium in the removal of aniline is the most promising process, yet inhibited under low temperature usually. In the present study, a new psychrotrophic bacterial strain isolated from groundwater, designated AN-1, was shown to be capable of aniline degradation in a concentration range of 135-2202 mg L(-1) within 72 h at 10 °C. Strain AN-1 was proposed to be a Pseudomonas migulae group of bacteria based on the evolutionary relationship and the morphological and biochemical characteristics. The pH, NaH2PO4, and aniline concentration were used as independent variables to optimize the aniline removal by AN-1 at 10 °C, and a statistically significant (R (2) = 0.9230, p < 0.005) quadratic polynomial mathematical model was suggested. Moreover, an efficient biocomposite by assembling Fe3O4 nanoparticles onto the surface of AN-1 cells was constructed. Compared with free cells, the microbial cell/Fe3O4 biocomposite had the same biodegradation activity but exhibited remarkable reusability. This study highlights AN-1 might be a promising candidate for aniline removal from wastewater at low temperatures.

Phytoremediation potentiality of garlic roots for 2,4-dichlorophenol removal from aqueous solutions.

2,4-Dichlorophenol (2,4-DCP) is considered as an important pollutant because of its high toxicity and wide distribution in wastewaters. Innocuous remediation technologies have been studied for the removal of this pollutant. This study investigated the feasibility of using garlic roots as a plant system for the removal of 2,4-DCP. The optimal conditions for its removal were established based on orthogonal experiments (OA25 matrix). Significant factors that affect removal efficiency, arranged from high to low importance, include pH, reaction time, 2,4-DCP concentration, and H2O2 concentration. In addition, garlic roots could be re-used for as much as three consecutive cycles. The decrease in pH and the increase of Cl(-) ion content in the post-removal solutions indicated that 2,4-DCP dehalogenation occurred during transformation. Changes in the deposition pattern of lignin in roots exposed to 2,4-DCP suggested that several of the products deposited were lignin-type polymers. The acute toxicity test revealed that the post-removal solutions were less toxic than the parent solutions. Therefore, garlic roots have considerable potential to effectively and safely remove 2,4-DCP from wastewater.

[Efficiency analysis of two-stage SBR for phosphorus nitrogen and organic substrate removal].

Taking simulated domestic sewage as treatment object, the characteristics of separate-stage phosphorus, organic substrate and nitrogen removal were studied in two-stage SBR by contrast experiment and mechanism analysis under the normal temperature, its efficiency-predominance was analyzed. The results indicate that the heterotrophic PAOs and nitrobacteria can be dominant growth in individual reactor respectively, under the effluent quality is more superior, the treatment efficiency is one time higher than that in the single SBR by controlling the sludge age (the phosphorus removal stage 5-7 d, the nitrogen removal stage about 50 d). The two-stage SBR can relieve the attack of organic load to nitrification process effectively, its nitrogen removal stage (SBR2) can still maintain stable nitrification rate under the higher COD concentration and the final effluent of the system is easy and stable to reach national standards (TP < or = 0.5 mg x L(-1)). In addition, the nitrogen removal stage (SBR2) of two-stage SBR not only can maintain nitrobacteria predominant, but also can cultivate heterotrophic bacteria which can remove difficult degraded organic substrate, that results in lower COD concentration than in the single's at the end of nitrification.

[Natural attenuation of BTEX in the underground environment].

It was found that the naturally attenuation of BTEX occurred. In this process, volatilization and biodegradation are the important mechanisms. Taking benzene for example, at the concentration of 11.40 mg/L, the relative proportions of volatilization and biodegradation accounting for natural degradation were 16.36% and 4.91%. Comparatively, at the concentration of 3.30 mg/L for toluene, the relative proportions of volatilization and biodegradation accounting for natural degradation were 11.04% and 41.50%. It demonstrated that different components of BTEX had different attenuation trends. Furthermore, the higher the concentration of BTEX was, the faster the BTEX volatilized, and more important volatilization was. The effect of biodegradation on toluene was more efficiency, whose proportion accounting for natural degradation was 41.50%, and xylene only occupied 8.49%, while, benzene and ethylbenzene were hardly degraded.

[Study on performance of double mineral base liner using modified bentonite as active material].

The absorbing capacity of clay,roasting bentonites by 450 degrees C and dual-cation organobentonites of the pollutions in landfill leachate was compared through static experiment, and investigations were conducted into availability of controlling the permeating of landfill leachate and feasibility of removing the main pollutants in leachate on the double mineral base liners of clay/roasting bentonites by 450 degrees C and clay/dual-cation organobentonites by using nice landfill leachate as the filter fluid. Experiment indicated that the adsorption equilibrium time of landfill leachate in clay, roasting bentonites by 450 degrees C and dual-cation organobentonites was 24 h; the absorbing capacity of roasting bentonites by 450 degrees C and dual-cation organobentonites was larger than that of clay. Simultaneous the penetration coefficients of the two liners were respective 1.31 x 10(-8) cm x s(-1) and 2.80 x 10(-8) cm x s(-1); Double mineral base liners of clay/roasting bentonites by 450 degrees C owned larger absorbing capacity of NH4+, however, double mineral base liners of clay/dual-cation organobentonites had strong absorbing capacity of organic pollutants and the attenuation rate of COD was 33.82% higher than the other. Conclusion was drawn that different types of modified bentonite should be chosen as "the active layer" according to different styles of landfill pollutants.

[Isolation, identification and degradation characterization of a polychlorinated biphenyls-degrading bacterium Pseudomonas sp. DN2].

A polychlorinated biphenyls-degrading bacterium DN2, using biphenyl as sole carbon source and energy source, was isolated from long-term PCBs-contaminated soil. Through morphological observation and sequence analysis of 16S rDNA, the strain was identified as Pseudomonas sp.. By identification of bphA1 core segment of biphenyl dioxygenase (BPDO) and enzyme activity assay of 2, 3-dihydroxybiphenyl-1,2-dioxygenase, the PCBs/biphenyl degradation-related genes in the bacterium was confirmed. Using GC-MS and resting cells PCBs degradation capacity test, the strain could remove 67% of the Aroclor 1242 in 3 days with 30%-90% of degradation rate of Aroclor 1242 congeners, which can contribute to the in situ bioremediation for the PCBs contaminated field.