A comparative study of biodegradability of a carcinogenic aromatic amine (4,4'-diaminodiphenylmethane) with OECD 301 test methods.

4,4'-Diaminodiphenylmethane (MDA) is a widely used compound in industries. Studies on the biodegradability of MDA are necessary for environmental hazard identification and risk assessment. Previous studies have suggested that MDA was not readily biodegradable. In the present study, three batches of biodegradation tests (OECD 301A, B, D and F tests) were performed on MDA in June, August and December of 2012. MDA was found to be readily biodegradable and produced colored intermediates in the 301A, B and F test systems. MDA biodegradation measurements were consistent among the three batches of tests. Differences in the extent of biodegradation determined in different methods originated from different test conditions and assessment endpoints. The 301D test has stringent test conditions and is usually performed on chemicals that are toxic to microorganisms, so the test results obtained from 301D tests are less meaningful for evaluating the biodegradability of MDA. The low MDA biodegradation measurements in the 301B tests compared to the 301A and F tests were due to the assessment method, which did not account for MDA incorporation into biomass in its calculation of CO2 formation rate. The differences in the biodegradation rates, as measured by the different OECD 301 test systems, could also be related to the structure and properties of the chemical. For test substances that can be assessed by all OECD 301 test methods, the highest biodegradation values may be obtained from the 301A and F test methods. This study provides new information to assess the environmental fate in the risk assessment of MDA.

[Analysis of microbial community variation in the domestication process of sludge in a sulfate-reducing reactor].

The variations of microbial community in the sludge of sulfate-reducing UASB during domestication period were analyzed by PCR-DGGE technique. The results showed that the diversity of microbial community was strongly related to the sulfate reduction and COD removal performance. The sulfate reduction rate of the reactor was about 95% when the Shannon index of microbial community was higher than 3.45. The preponderant bands in DGGE figure were excised and cloned, and the sequencing analysis indicated there were Firmicutes, Proteobacteria, Deinococcus-Thermus and Chloroflexi in the sludge, which accounted for 50.0%, 28.6% 14.3% and 7.1% of the total sequences of samples, respectively. The anaerobic fermentative bacteria of Clostridium sp. were predominant in the whole domestication period, but the predominant species was changing. Some anaerobic bacteria like Chloroflexi sp. and Geopsychrobacter sp. were detected to be dominant species, which then disappeared along with further domestication, but anaerobic bacteria Geobacter sp. became gradually predominant in the domestication process. Species of Desulfovibrio sp. were detected to be predominant only in the last two phases of domestication.

[Nitrogen removal performance of ANAMMOX ABR process in tannery wastewater treatment].

Anaerobic ammonium-N removal from tannery wastewater was investigated using a lab-scale anaerobic baffled reactor (ABR). The results indicated that ABR could be used as a good anaerobic ammonium oxidation reactor, the stable and effective performance of ammonium-N and COD removal from tannery wastewater was demonstrated in the ANAMMOX ABR. When the NH4(+) -N concentration of the influents were in the range of 25.0 mg x L(-1) to 76.2 mg x L(-1) and COD ranged from 131 mg x L(-1) to 237 mg x L(-1), under the volumetric loading of 0.05 kg x (m3 x d)(-1) to 0.15 kg x (m3 x d)(-1), the NH4(+)-N and COD of the effluents were from 0.20 mg x L(-1) to 7.12 mg x L(-1) and from 35.1 mg x L(-1) to 69.2 mg x L(-1), respectively, and the removal efficiency of NH4(+) -N and COD were 90.8% to 99.6% and 66.9% to 74.7%, respectively. In addition, the brown-red, brown-yellow, red granular sludges were developed in ABR. SEM observation confirmed the presence of ANAMMOX bacteria in granular sludge of all four compartments of ANAMMOX ABR. According to FISH results, ANAMMOX bacteria had grown in all four compartments to various degrees during the acclimatization and running process, the percentage of ANAMMOX bacteria in sludge increased from 4% to 9%, 8%, 12% and 30% in compartment 1, compartment 2, compartment 3 and compartment 4, respectively, and a higher population percentage of ANAMMOX bacteria existed in the rear than in the front compartments.

Rhizobium borbori sp. nov., aniline-degrading bacteria isolated from activated sludge.

Three aniline-degrading bacteria, strains DN316(T), DN316-1 and DN365, were isolated from activated sludge. According to 16S rRNA gene sequence-based phylogenetic analysis, the isolates belonged to the genus Rhizobium, with Rhizobium ( = Agrobacterium) radiobacter LMG 140(T) as the closest relative, with 96.5 % sequence similarity. Phylogenetic analysis of the representative strain DN316(T) using sequences of the glnA, thrC and recA genes and the 16S-23S intergenic spacer region confirmed the phylogenetic arrangement obtained from analysis of the 16S rRNA gene. DNA-DNA relatedness between DN316(T) and R. radiobacter LMG 140(T) was 43.7 %, clearly indicating that the representative strain DN316(T) represents a novel species. Phenotypic and biochemical characterization of the isolates and insertion sequence-PCR fingerprinting patterns showed several distinctive features that differentiated them from closely related species. The major components of the cellular fatty acids were C(18 : 1)ω7c (57.10 %), C(16 : 0) (11.31 %) and C(19 : 0) cyclo ω8c (10.13 %). Based on our taxonomic analysis, the three isolates from activated sludge represent a novel species of the genus Rhizobium, for which the name Rhizobium borbori sp. nov. is proposed. The type strain is DN316(T) ( = CICC 10378(T)  = LMG 23925(T)).

[Isolation and characterization of a sulfate reducing Citrobacter sp. strain SR3].

A sulfate reducing bacterium, designated strain 'SR3', was isolated from sludge of a sulfate-reducing up-flow anaerobic sludge bed (UASB) reactor for treating high concentration sulfate wastewater. It was identified as Citrobacter sp. based upon the phenotypic-characteristics and physiological properties as well as the analysis of the sequence of 16S rDNA. The strain could reduce sulfate under anaerobic and micro-aerobic conditions. The dissimilatory sulphite reductase gene (dsr) was also amplified from this strain's genomic DNA using specific dsr gene primers. In aerobic conditions, the strain couldn't reduce sulfate, but exhibited a highest growth rate. In anaerobic conditions, the optimal growth conditions for this stain were temperature 37 degrees C and initial pH 8.0. Under this conditions,the strain could reduced both SO4(2-) and Cr(VI) at initial Cr(VI) concentrations of 0.4-0.8 mmol synchronously. Its tolerance ability to Cr(VI) concentrations reaches 1.0 mmol. This is the first report about an facultative anaerobe with sulfate reducing function and dissimilatory sulphite reductase gene (dsr).

[Changes of sludge characteristic in start-up process of UASB treatment for highly sulfate-containing wastewater].

Changes of sludge characters in a sulfate-reducing UASB reactor during the 243 day of domestication process were tracking comparison. Results showed the average diameter of granular sludge in initial domestication stages decreased to 0.99 mm compared with 1.82 mm of incubating sludge, but which was found to be increasing along with the enhance of the loading rate of reactor, the shorten of HRT, and the acceleration of hydraulic up-flow velocity. N2 stripping was used to remove H2S produced in the reactor, and the average diameter of granular sludge increased to 1.51 mm quickly when N2 stripping with the flux of 60 mL x min(-1) was used, but it decreased when the flux of N2 improved to 100 mL x min(-1). Differences in average diameter among granular sludges in different height of the reactor became unconspicuous through continuous stripping. Changes in the MLVSS and the ratio of (MLVSS/MLSS) displayed similar trends, for which firstly decreased in the earlier period then increased to 33.59 g x L(-1) and went up to 49.72 g x L(-1) steadily in the later stage, and then raised from 0.36 to 0.50 subsequently. Sulfate reduction efficiency improved from 30% to 95%, which was strongly correlated with the MLVSS (r = 0.918, p = 0.003). Scanning electron microscope analysis showed inoculating sludge was coarse and incompact, and with the dominant species of filamentous bacteria, bacillus, cocci, but granular sludge with dense microorganism community structure were observed, and in which vibrio and bacillus were the dominant species.

[Isolation and characterization of a facultative anaerobic aniline-degrading bacterium].

An aniline-degrading bacterium (designated strain AN29) was isolated from dyeing wastewater process (anaerobic baffled reactor, ABR) with the capability of utilizing aniline as sole carbon source and nitrogen source. It was identified as Pseudomonas sp. based upon the phenotypic properties and a partial analysis of the 16S rDNA. The strain could degrade aniline under the aerobic and anaerobic conditions, the optimal initial pH 6.5 - 8.0, a temperature of 37 degrees C, and initial aniline concentrations of 500 - 2 000 mg/L with maximum concentration of 4 000 mg/L respectively.

[Isolation and characterization of two aniline-degrading strains and compare of functional genes].

Two aniline-degrading bacterial strains, AN30 and DN425, were isolated from activated sludge of textile-printing wastewater treatment plant and identified as Pseudomonas sp. and Shewanella sp. , respectively. Under shaking condition, 250 mg/L aniline was removed 96.1% and 13.8% within 72h by strains AN30 and DN425, respectively. Under static condition, their degrading rates were 39.6% and 8.6% , respectively. Under static condition, the decolorizing rate of strain DN425 reached 96% for azo dye Great Red GR in 4h, exhibiting a remarkable color removal capability. However, strain AN30 was not capable of decolorizing Great Red GR. With two sets of specific primers for tdnQ gene and fre gene, the two genes were detected by PCR amplification. The results indicated the two strains possess both tdnQ gene and fre gene.