Microbial Bioremediation and Different Bioreactors Designs Applied

Microbial remediation of pollutants involves the use of microorganisms to degrade pollutants either completely to water and carbon dioxide (for organic pollutants) or into less toxic forms. In the case of nonbiodegradable inorganic compounds, bioremediation takes the form of bioaccumulation or conversion of one toxic species to a less toxic form for example Cr(VI) is converted to less toxic (III). Bioremediation is considered an environmentally friendly way for pollution clean-up. Microbial clean up can be applied in situ (in place of contamination) or ex situ (off the site of contamination). In situ remediation in the natural environment is deemed slow and often times difficult to control and optimize the different parameters affecting the bioremediation. To this end, use of engineered bioreactors is preferred. Engineered bioreactors providing for optimum conditions for microbial growth and biodegradation have been developed for use in bioremediation processes to achieve the different desired remediation goals. Bioreactors in use range in mode of operation from batch, continuous, and fed batch bioreactors and are designed to optimize microbial processes in relationship to contaminated media and nature of pollutant. Designed bioreactors for bioremediation range from packed, stirred tanks, airlift, slurry phase, and partitioning phase reactors amongst others

An assessment of the physicochemical properties and toxicity potential of carwash effluents from professional carwash outlets in Gauteng Province, South Africa

The assessment of the quality of carwash effluents has received scant attention as a potential source of public and environmental health hazard in South Africa as demonstrated by the lack of literature in this subject. The physicochemical quality and potential ramifications of carwash effluents on receiving waterbodies were investigated in this study. Grab effluent samples were collected from six carwash outlets in Gauteng Province of South Africa and analysed for selected physicochemical qualities including biological oxygen demand (BOD), oil and grease, total petroleum hydrocarbons-gasoline range organics (TPH-GRO), pH, dissolved oxygen (DO), total solids (TS) and total dissolved solids (TDS), electrical conductivity (EC), nutrients (nitrates, nitrites and phosphates), anionic surfactants and heavy metals (zinc [Zn], copper [Cu], lead [Pb] and chromium [Cr]). Further, the toxicity potential of the effluent samples was assessed using organisms from four trophic levels ranging from Selenastrum capricornutum (primary producer), Daphnia magna (primary consumer), Poecilia reticulata (secondary-tertiary consumer) and Vibrio fischeri (decomposer). High pollutant levels were observed in all effluents with BOD ranging from 27±2.1 to 650±4.9 mg/l, TDS from 362±8.5 to 686±8.5 mg/l, GRO-TPH from 0.01±0.0 to 7.6±0.2 mg/l, DO from 0.0 to 0.1 mg/l, Zn from 0.79±0.08 to 20±2.12 mg/l, Cu from 0.77±0.03 to 13±0.71 mg/l and oil and grease from 12±2.8 to 43±2.1 mg/l. Ammonium concentrations ranged from 0.4±0.1 to 75±6.4 mg/l; turbidity from 109±0.7 to 4000±29.7 mg/l, anionic surfactants from 1.4±0.1 to 5.8±0.3 mg/l and TPH from < 0.01 to 7.6 mg/l. Toxicity assessment assays resulted in 100% mortality for fish and Daphnia after 96 and 24 h respectively and significant bioluminescence and growth reduction in Vibrio fischeri and algae after 15 min and 72 h respectively. Most of the measured physicochemical parameters were in concentrations above the Environmental Management Agency (EPA) stipulated guidelines. Additionally, the effluents demonstrated acute toxicity against all four test species.UNISA-WiREnvironmental Science

Screening and evaluation of some green algal strains (Chlorophyceae) isolated from freshwater and soda lakes for biofuel production

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An evaluation of the bacterial diversity at Tshipise, Mphephu and Sagole hot water springs, Limpopo Province, South Africa

Tshipise, Mphephu and Sagole are thermal hot water springs in the Limpopo Province of South Africa with temperatures of 58, 43 and 45°C; and pH of 8.85, 8.08 and 9.70, respectively. The bacterial diversity of the hot water springs was determined by pyrosequencing of the two 16S rRNA hypervariable regions V1-3 and V4-7. Analyses of the community DNA revealed that bacterial populations as detectable by the V1-3 or V4-7 region, respectively were dominated by the Bacteriodetes and Proteobacteria for Mphephu, and Proteobacteria and Cyanobacteria for both Tshipise and Sagole. The major differences in the bacterial diversity between the springs was that no Cyanobacteria were detected for Mphephu and the level of Bacteriodetes detected for both Tshipise and Sagole was much lower compared to the levels detected at Mphephu. The Firmicutes were detected at all the springs but at a much lower abundance compared to the other main phyla detected. Various other phyla were detected at the hot springs at levels below 0.20% of the total sequences obtained. It is interesting that very diverse bacterial genera exist in the three hot water springs studied.This research was supported through a grant from Water Research Commission (WRC, SA, Project K5/1959/1).http://www.academicjournals.org/AJM

Evaluation of the Digestibility of Attached and Suspended Growth Sludge in an Aerobic Digester for a Small Community

The aerobic sludge digestion process for waste sludge generated from suspended biomass (i.e., activated sludge process, ASP) and attached biomass (i.e., moving bed bioreactor, MBBR and modified packed bed biofilm, PBBR) reactors in a residential complex were analyzed. The rate of digestion with respect to different sludge characteristics generated through these various treatment processes were examined; the results revealed that waste sludge from ASP took 16 days to achieve complete digestion while MBBR and PBBR took nine and seven days, respectively. The most important factors influencing the sludge digestion such as sludge volume index (SVI), mixed liquor suspended solid (MLSS), and mixed liquor volatile suspended solid (MLVSS) were examined. The ASP which had the highest initial MLSS and MLVS took a longer time for digestion. Aerobic sludge digestion in all the treatment reactors was studied under laboratory scale conditions in batch experimentation to evaluate sludge characteristics and the rate of digestion as well as through a continuous bench scale pilot system to optimize the process parameters. Removal efficiencies of volatile solids (VS) 90.71% in ASP, 84.27% in MBBR and 84.07% in PBBR in aerobic digestion during batch mode were also observed. The study revealed that the aerobic sludge digestion process utilized in curbing sludge is not feasible application for a small community due to very long digestion times and a large amount of space although Packed Bed Biofilm (PBBR) used the lowest time (seven days) compared to the other systems

Targeted 16S rRNA amplicon analysis reveals the diversity of bacterial communities in carwash effluents

Follow the DOI link at the top of the record to access the full-text on the publisher's websiteThis study aimed to analyze the bacterial diversity in carwash effluents and to determine their potential for use in microbial degradation of environmental contaminants. Nine carwash effluent samples were collected for physicochemical and bacterial community diversity analysis using multi-digital probes and 16S rRNA gene amplicon sequencing respectively. The pH of all effluent samples was neutral to slightly alkaline. Oil and grease concentrations ranged from 15.3 to 49.7 mg/L. 16S gene amplicon sequencing of the nine samples produced 45,934-sequence reads, which translated to 13 bacterial phyla, 26 classes, and 43 genera. The most dominant phyla were Proteobacteria, Bacteroidetes, Firmicutes, and Fusobacteria. Canonical correspondence analysis (CCA) showed that the distribution of the phyla Proteobacteria, Bacteroidetes, Acidobacteria, and Verrucomicrobia was influenced by the presence of oil and grease, total petroleum hydrocarbons-gasoline range organics (GRO-TPH), and metals species (Pb, Cu, and Zn). The dominant bacterial genera found in the present study were previously proven to biodegrade hydrocarbons, and their presence in carwash effluents could bode well for in situ natural bioremediation of these contaminated sites.University Of South AfricaEnvironmental Science

Assessing the Potential of Some Freshwater and Saline Microalgae as Biodiesel Feedstock

Microalgae have attracted a major interest in biofuel, food and feed stock sectors as they can accumulate lipids, proteins and carbohydrates in large amounts within short periods of time. The selection of the most suitable algal species for biofuel production is based on key parameters such as lipids, fatty acids composition and characteristics. This paper describes the bioprospecting and molecular screening of 21 microalgal strains isolated from different fresh and saline water habitats by analysing their biomass, lipids and fatty acid profiles, used for estimating biodiesel properties. Biomass productivity amongst the strains varied from 142.5±13.4 to 622.8±14.0 mg/L. Seven strains viz. Acutodesmus sp. TST2, Scenedesmus sp. PK1, Desmodesmus armatus TTT1, Desmodesmus armatus FW005, Neochloris sp. RP2, Stichococcus bacillaris LU1 and Hegewaldia sp. LC1 showed a lipid mass fraction of >25% on a dry basis. Fatty acid profiling showed that fatty acids with carbon chain length of C16–C18 such as palmitic, oleic and linoleic acids were major fatty acids in all the isolated species. Three strains viz. Acutodesmus sp. TST2, Stichococcus bacillaris LU1 and Hegewaldia sp. LC1 accumulated high lipid content (>28% dwt), with higher levels of fatty acid profiles of C16–C18 (>70%) indicating their potential as sources of biodiesel with suitable biodiesel properties of high cetane number (57–59), low viscosity (4.73–4.85 mm2/s), lower iodine value (54.4–68.5 gl2/100 g), relative cloud point 9–13 °C) and negative cold filter plugging point (–2 to –6 °C) in accordance with international standards

Heavy metal reduction for different fill ratio percentages of media.

<p>Heavy metal reduction for different fill ratio percentages of media.</p