Simultaneous biotreatment of Polycyclic Aromatic Hydrocarbons and dyes in a one-step bioreaction by an acclimated Pseudomonas strain

Demonstration of a plant-microbe integrated system for treatment of real-time textile industry wastewater

The real-time textile dyes wastewater contains hazardous and recalcitrant chemicals that are difficult to degrade by conventional methods. Such pollutants, when released without proper treatment into the environment, impact water quality and usage. Hence, the textile dye effluent is considered a severe environmental pollutant. It contains mixed contaminants like dyes, sodium bicarbonate, acetic acid. The physico-chemical treatment of these wastewaters produces a large amount of sludge and costly. Acceptance of technology by the industry mandates that it should be efficient, cost-effective and the treated water is safe for reuse. A sequential anaerobic-aerobic plant-microbe system with acclimatized microorganisms and vetiver plants, was evaluated at a pilot-scale on-site. At the end of the sequential process, decolorization and total aromatic amine (TAA) removal were 78.8% and 69.2% respectively. Analysis of the treated water at various stages using Fourier Transform Infrared (FTIR), High Performance Liquid Chromatography (HPLC)) Gas Chromatography-Mass Spectrometry (GC-MS) Liquid Chromatography-Mass Spectrometry (LC-MS) indicated that the dyes were decolourized and the aromatic amine intermediates formed were degraded to give aliphatic compounds. Scanning Electron Microscope (SEM) and Atomic Force Microscopy (AFM) analysis showed interaction of microbe with the roots of vetiver plants. Toxicity analysis with zebrafish indicated the removal of toxins and teratogens.

Bioaugmentation Treatment of a PAH-Polluted Soil in a Slurry Bioreactor

A bioslurry reactor was designed and used to treat loamy clay soil polluted with polycyclic aromatic hydrocarbons (PAHs). To this end, biostimulation alone, or combined with bioaugmentation with two bacterial strains (Rhodocccus erythropolis and Pseudomonas stuzeri) previously isolated from the polluted site, was applied. The PAH concentrations decreased notably after 15 days in all of the treatments. The concentrations of the two- and three-ring compounds fell by >80%, and, remarkably, the four- to six-ring PAHs also showed a marked decrease (>70%). These results thus indicate the capacity of bioslurry treatments to improve, notably, the degradation yields obtained in a previous real-scale remediation carried out using biopiles. In this sense, the remarkable results for recalcitrant PAHs can be attributed to the increase pollutants’ bioavailability achieves in the slurry bioreactors. Regarding bioaugmentation, although treatment with R. erythropolis led to a somewhat greater reduction of lighter PAHs at 15 days, the most time-effective treatment was achieved using P. stutzeri, which led to an 84% depletion of total PAHs in only three days. The effects of microbial degradation of other organic compounds were also monitored by means of combined qualitative and quantitative gas chromatography mass spectrometry (GC–MS) tools, as was the evolution of microbial populations, which was analyzed by culture and molecular fingerprinting experiments. On the basis of our findings, bioslurry technology emerges as a rapid and operative option for the remediation of polluted sites, especially for fine soil fractions with a high load of recalcitrant pollutants.

Biodegradation of Congo red dye in a moving bed biofilm reactor: Performance evaluation and kinetic modeling

The biodegradation of Congo red dye was performed using polyurethane foam-polypropylene immobilized Bacillus sp. MH587030.1 in a moving bed biofilm reactor (MBBR). The central composite design (CCD) based response surface methodology (RSM) was used to optimize the process parameters; pH, Congo red concentration, and media filling ratio, and optimum conditions were observed to be 7.0, 50 mg/L, and 45%, respectively in batch MBBR. At optimum condition, MBBR was operated in continuous mode at different flow rates (25-100 mL/h) over a period of 564 h. The maximum removal efficiency (RE) and elimination capacity (EC) were obtained as 95.7% and 57.6 mg/L·day, respectively under steady-state. The kinetics of Congo red biodegradation at various flow rates were evaluated by a modified Stover-Kincannon model, and kinetic constants; K_B and U_max were found to be 0.253 g/L·day and 0.263 g/L·day, respectively.

A novel comparative study of modified carriers in moving bed biofilm reactor for the treatment of wastewater: Process optimization and kinetic study

In this work, modified plastic carriers; polypropylene (PP), low-density polyethylene- polypropylene (LDPE-PP), and polyurethane foam-polypropylene (PUF-PP) were developed and used in moving bed bioreactor (MBBR) for the wastewater treatment containing naphthalene. To optimized the process parameters using response surface methodology (RSM), two numerical variables; pH (5.0-9.0) and hydraulic retention time (HRT) (1.0-5.0 day) along with the type of carriers (PP, LDPE-PP, and PUF-PP) were selected as a categorical factor. At 7.0 pH and 5 days HRT, maximum removal efficiencies were observed to be 72.4, 84.4, and 90.2% for MBBR packed with PP, LDPE-PP, and PUF-PP carriers, respectively. Gas chromatography-mass spectrometry (GC-MS) analysis reveals catechol and 2-naphthol were observed as intermediate metabolites for naphthalene degradation. Modified Stover-Kincannon model was applied for biodegradation kinetic and constants were observed as U_max: 0.476, 0.666, and 0.769 g/L.day and K_B: 0.565, 0.755, and 0.874 g/L.day for PP, LDPE-PP, PUF-PP, respectively.

Bioremoval of priority polycyclic aromatic hydrocarbons by a microbial community with high sorption ability

The treatment of large volumes of wastewater during oil refining is presently a challenge. Bioremediation has been considered an eco-friendly approach for the removal of polycyclic aromatic hydrocarbons (PAHs), which are one of the most hazardous groups of organic micropollutants. However, it is crucial to identify native PAH-removing microorganisms for the development of an effective bioremediation process. This study reports the high potential of an anaerobic microbial consortium enriched from a petrochemical refinery wastewater to remove two priority PAHs-acenaphthene and phenanthrene. Seventy-seven percent of acenaphthene was removed within 17 h, whereas phenanthrene was no longer detected after 15 h. Bioremoval rates were extremely high (0.086 and 0.156 h^-1 for acenaphthene and phenanthrene, respectively). The characterization of the microbial communities by next-generation sequencing and fluorescence in situ hybridization showed that the PAH-removing consortium was mainly composed by bacteria affiliated to Diaphorobacter and Paracoccus genera, independently of the PAH tested. Moreover, besides biodegradation, biosorption was a relevant mechanism involved in the removal of both PAHs, which is an important finding since biosorption is less expensive than biodegradation and can be carried out with dead biomass. Although biodegradation is the most commonly reported biological mechanism for PAH removal, this study demonstrated that biosorption by this microbial community may be extremely efficient for their removal. Given the outstanding ability of this microbial consortium to quickly remove the compounds addressed, it could be further applied for the bioremediation of PAHs in refinery wastewaters and other contaminated environments.

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

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 Dysgonomonas, and Pseudomonas and the presence of fungal phylotypes such as Gibberella and Fusarium. 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.