Microbial Biotreatment of Actual Textile Wastewater in a Continuous Sequential Rice Husk Biofilter and the Microbial Community Involved

<div><p>Textile dying processes often pollute wastewater with recalcitrant azo and anthraquinone dyes. Yet, there is little development of effective and affordable degradation systems for textile wastewater applicable in countries where water technologies remain poor. We determined biodegradation of actual textile wastewater in biofilters containing rice husks by spectrophotometry and liquid chromatography mass spectrometry. The indigenous microflora from the rice husks consistently performed >90% decolorization at a hydraulic retention time of 67 h. Analysis of microbial community composition of bacterial 16S rRNA genes and fungal internal transcribed spacer (ITS) gene fragments in the biofilters revealed a bacterial consortium known to carry azoreductase genes, such as <i>Dysgonomonas</i>, and <i>Pseudomonas</i> and the presence of fungal phylotypes such as <i>Gibberella</i> and <i>Fusarium</i>. Our findings emphasize that rice husk biofilters support a microbial community of both bacteria and fungi with key features for biodegradation of actual textile wastewater. These results suggest that microbial processes can substantially contribute to efficient and reliable degradation of actual textile wastewater. Thus, development of biodegradation systems holds promise for application of affordable wastewater treatment in polluted environments.</p></div

Microbial decolorization in the biofilter.

<p>Degradation of textile wastewater in reactors at steady state from 190 to 750nm; wastewater: TWW line, reactor 1: line 1, reactor 2: line 2, reactor 3: line 3, reactor 4: line 4, reactor 5 line 5. The vertical line marks the lambda max.</p

Phylogenetic tree of 16S rRNA gene sequences.

<p>Maximum-Likelihood based phylogenetic tree of 16S rRNA gene sequences obtained from DGGE bands and reference bacteria. Scale bar represent 0.1 nucleotide substitutions per site. Bold face text denote DGGE bands from this study and asterisks (*) denote phylotypes identified in (1). Parenthesis indicates GenBank accession number.</p

Experimental design.

<p>Biofilter set-up with anaerobic reactors R1, R2, R3, R4 and the aerobic R5 in series. The biobed in the reactors is supported by a net with a free water volume in the bottom.</p

DGGE gel image of fungal community composition in the experiments.

<p>Reactor 1 (R1- D20), reactor 1 26 days later at steady state (R1-D46) and rice husks (R.H).</p

Characteristics of textile effluent and treated water.

<p>Characteristics of textile effluent and treated water.</p

Identification of sequenced Fungi ITS regions.

<p>Identification of sequenced Fungi ITS regions.</p

DGGE gel image of bacterial community composition in the experiments.

<p>Reactor 1–5 on day 20 (R1-R5 D20), reactor 1–5 on day 46 steady state (R1-R5 D46) and rice husks (R.H).</p

Image_3_Seasonal Dynamics in Carbon Cycling of Marine Bacterioplankton Are Lifestyle Dependent.TIF

Although free-living (FL) and particle-attached (PA) bacteria are recognized as ecologically distinct compartments of marine microbial food-webs, few, if any, studies have determined their dynamics in abundance, function (production, respiration and substrate utilization) and taxonomy over a yearly cycle. In the Baltic Sea, abundance and production of PA bacteria (defined as the size-fraction >3.0 μm) peaked over 3 months in summer (6 months for FL bacteria), largely coinciding with blooms of Chitinophagales (Bacteroidetes). Pronounced changes in the growth efficiency (range 0.05–0.27) of FL bacteria (defined as the size-fraction <3.0 μm) indicated the magnitude of seasonal variability of ecological settings bacteria experience. Accordingly, 16S rRNA gene analyses of bacterial community composition uncovered distinct correlations between taxa, environmental variables and metabolisms, including Firmicutes associated with elevated hydrolytic enzyme activity in winter and Verrucomicrobia with utilization of algal-derived substrates during summer. Further, our results suggested a substrate-controlled succession in the PA fraction, from Bacteroidetes using polymers to Actinobacteria and Betaproteobacteria using monomers across the spring to autumn phytoplankton bloom transition. Collectively, our findings emphasize pronounced seasonal changes in both the composition of the bacterial community in the PA and FL size-fractions and their contribution to organic matter utilization and carbon cycling. This is important for interpreting microbial ecosystem function-responses to natural and human-induced environmental changes.</p

Image_5_Seasonal Dynamics in Carbon Cycling of Marine Bacterioplankton Are Lifestyle Dependent.TIF

Although free-living (FL) and particle-attached (PA) bacteria are recognized as ecologically distinct compartments of marine microbial food-webs, few, if any, studies have determined their dynamics in abundance, function (production, respiration and substrate utilization) and taxonomy over a yearly cycle. In the Baltic Sea, abundance and production of PA bacteria (defined as the size-fraction >3.0 μm) peaked over 3 months in summer (6 months for FL bacteria), largely coinciding with blooms of Chitinophagales (Bacteroidetes). Pronounced changes in the growth efficiency (range 0.05–0.27) of FL bacteria (defined as the size-fraction <3.0 μm) indicated the magnitude of seasonal variability of ecological settings bacteria experience. Accordingly, 16S rRNA gene analyses of bacterial community composition uncovered distinct correlations between taxa, environmental variables and metabolisms, including Firmicutes associated with elevated hydrolytic enzyme activity in winter and Verrucomicrobia with utilization of algal-derived substrates during summer. Further, our results suggested a substrate-controlled succession in the PA fraction, from Bacteroidetes using polymers to Actinobacteria and Betaproteobacteria using monomers across the spring to autumn phytoplankton bloom transition. Collectively, our findings emphasize pronounced seasonal changes in both the composition of the bacterial community in the PA and FL size-fractions and their contribution to organic matter utilization and carbon cycling. This is important for interpreting microbial ecosystem function-responses to natural and human-induced environmental changes.</p