The photocatalytic degradation of a local South Africa oil refinery wastewater was conducted under UV radiation using an aqueous catalyst of titanium dioxide (TiO2), Degussa P25 (80% anatase, 20% rutile) in suspension. the experiment was carried out in a batch aerated photocatalytic reactor based on a central composite design (CCD) and analyzed using response surface methodology (RSM). The effects of three operational variables viz. TiO 2 dosage (2-8 g/L), runtime (30-90 minutes), and airflow rate (0.768-1.48 L/min) were examined for the removal of phenol and soap oil and grease (SOG). The data derived from the CCD, and the successive analysis of variance (ANOVA) showed the TiO 2 dosage to be the most influential factor, while the other factors were also significant (P < 0.0001). Also, the ANOVA test revealed the second-order of tio 2 dosage and runtime as the main interaction factors on the removal efficiency. To maximize the pollutant removal, the optimum conditions were found at runtime of 90 minutes, TiO 2 dosage of 8 g/L, and an aeration flow rate of 1.225 L/min. Under the conditions stated, the percentage removal of phenol (300 ± 7) and SOG (4000 ± 23) were 76% and 88% respectively. At 95% confidence level, the predicted models developed results were in reasonable agreement with that of the experimental data, which confirms the adaptability of the models. The first-order kinetic constants were estimated as 0.136 min −1 and 0.083 min −1 for SOG and phenol respectively. Photocatalysis has attracted worldwide interest due to its potential to use solar energy not only to solve environmental problems but also to provide renewable and sustainable energy 1,2. However, the ever-increasing demand for good water quality and oil refinery products have become expensive commodities with major challenges, which requires thoughtful attention 3,4. Oily waste from petroleum refinery has aliphatic and phenolic compounds, are considerably carcinogenic and toxic to the ecosystem and human health, and therefore their removal from wastewater is of global concern 3,5,6. The tox,icity and extreme instability of oily waste make them not degradable easily, this pose a significant threat to the water bodies and soil 5-7. Meanwhile, the processing of crude oil consumes large volumes of water and generates about 0.4-1.6 times the amount of crude oil processed as oil refinery wastewater (ORW) 8-10. The discharge of ORW with adequate or no treatment, due to their inertness, endocrine-disrupting abilities, and carcinogenic behaviour could also affect water bodies and soil profile negatively 9-11. Therefore, there is the need to develop sustainable and eco-effective methods to mitigate the oily pollutants from the ORW, to produce clean water and a sustainable environment 12. In this case, the photocatalysis technology was considered. Unfortunately, the production of polluted wastewater (ORW) is based on the raw crude oil type, plant configuration, and operational procedure, which varies in physicochemical parameters as compared to urban wa...
This study aimed at isolating filamentous bacteria from full-scale activated sludge processes and studying them in pure culture. Three cultures were isolated using conventional microbiological techniques. The isolates were positively identified as Gordonia amarae, Thiothrix nivea and Type 1863/Acinetobacter spp., using fluorescent in situ hybridization (FISH) with 16S rRNA-targeted oligonucleotide probes. However, a 'morphological shift' from filamentous to single-cell form was observed in pure culture. The application of fluorescent in situ hybridization (FISH) showed filamentous bacteria to be much more diverse in their ability to adapt to their changing enviroments. Pure culture studies of filamentous bacteria form the basis for application in full-scale activated sludge plants. It therefore remains important that the taxonomic status of filamentous bacteria be determined.
The identification and ch;iracterization of filamentous bacteria and their association with specific plant operating conditions and influent characteristics has been hampered because of morphological variations and differences between process configurations. A study was conducted to isolate and characterize the predominant filamentous bacteria observed in a foaming activated sludge treatment plant. The predominant foam-forming filament was isolated and characterized using microscopic, biochemical and molecular techniques. The phylogenetic analysis of the 16S rRNA gene confirmed that it was Nocardia farcinica, a typical filamentous foam-foaming pathogenic bacterium which is not widely reported outside of South Africa. The bacterium used a variety of substrates for its growth and showed greater affinity to larger and slowly biodegradable compounds. The N. farcinica grew well at temperatures ranging from 12 to 30 C in R2A medium and with a pH ranging from 5.5 to 8.0 and an NaCl concentration of 1 to 5%. This range of conditions shows that A' , farcinica can withstand extreme conditions, which results in its proliferation in foaming samples. Water Environ. Res., 83, 527 (2011).
A Kubotatrade mark submerged membrane bio-reactor was applied to treat wastewater from a sugar manufacturing industry. To achieve optimal results, fundamental and extended understanding of the microbiology is important. Fluorescence in situ hybridization was used to evaluate the microbial community present. The majority of cells visualized in the sludge flocs by staining with the DNA fluorochrome DAPI, hybridized strongly with a bacterial probe. Probes specific for the alpha-, beta-, and gamma-subclasses of proteobacteria and high G + C Gram positive bacteria were used to characterize the community structures by in situ hybridization. Sampling was carried out over 12 weeks and samples were fixed with 4% paraformaldehyde for gram positive organisms and ice cold ethanol for gram negative organisms. The activated sludge population usually constitutes about 80 to 90% of proteobacteria. However, in this study it was found that a relatively small amount of proteobacteria was present within the system. No positive hybridization signal was observed with any of the applied eubacterial family- level probes.
The activated sludge process is the mostl used biological treatment process. Engineers and microbiologists are constantly seeking ways to improve process efficiency, which can be attributed to the increasing demand for fresh water supplies and proper environmental management. Since the inception of the activated sludge process, bulking and foaming have been major problems affecting its efficiency. Filamentous bacteria have been identified as the primary cause of bulking and foaming. Numerous attempts have been made to resolve this problem. Some of these attempts were effective as interim measures but failed as long term control strategies. The identification of filamentous bacteria and the study of their physiology have been hampered by the unreliability of conventional microbiological techniques. This is largely due to their morphological variations and inconsistent characteristics within different environments. To fully understand their role in promoting bulking and foaming, filamentous bacteria need to be characterized on a molecular level. The aim of this study was, therefore, to identify filamentous bacteria in pure culture with the purpose of validating these findings to the physiological traits of the pure cultures when they were isolated. Fourteen different filamentous cultures were used for this study. The cultures were identified using specific oligonucleotide probes via fluorescent in situ hybridisation and nucleotide sequencing. Prior to sequencing, an agarose gel and a denaturing gradient gel Electrophoresis profile were determined for each isolate. The various techniques were optimised specifically for the filamentous isolates. The isolates were identified as Gordonia amarae, Haliscomenobacter hydrossis, Acinetobacter sp./Type 1863, Type 021N, Thiothrix nivea, Sphaerotilus natans and Nocardioform organisms.
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