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Research Publications (Water and Wastewater Technology)

Permanent URI for this collectionhttp://ir-dev.dut.ac.za/handle/10321/841

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Author: search.filters.author.Tawfik, Ahmed

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    Polyhydroxyalkanoates production from fermented paperboard mill wastewater using acetate-enriched bacteria
    (Springer-Verlag Berlin Heidelberg, 2017) Farghaly, Ahmed Mustafa; Enitan, Abimbola Motunrayo; Kumari, Sheena K.; Bux, Faizal; Tawfik, Ahmed
    The aim of the study was to investigate the use of dark fermented paperboard mill wastewater (PMW) containing volatile fatty acids for polyhydroxyalkanoates (PHA) production. Six sequencing batch reactors (SBRs) were initially fed with synthetic feed containing acetate and operated at different organic loading rates (OLRs) of 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 gCOD l-1 day-1 for PHA-storing bacteria enrichment. The maximum PHA content and yield (YPHA/S) were 67.44 ± 5.88 % and 0.45 ± 0.39 C-mol C-mol-1 at OLR of 1.5 gCOD l-1 day-1, respectively. The synthetic feed was replaced by dark fermented PMW effluent rich in acetate, butyrate, propionate, and lactate at the accumulation stage resulting in a PHA content and yield of 58.57 ± 4.02 % and 0.46 ± 0.09 C-mol C-mol-1, respectively. The maximum specific PHA production rate max ) amounted to 0.29 ± 0.1 C-mol C-mol-1 X-1 h-1.(qPHA Illumina MiSeq sequencing of bacterial 16S rRNA gene showed that Proteobacteria and Bacteroidetes increased from 37.4 to 77.6 % and from 2.49 to 17.66 % at enrich-ment and accumulation stages, respectively. Actinobacteria (15.44 %), Chloroflexi (8.15 %), Planctomycetes (7.46 %), and Acidobacteria (6.0 %) were detected at the enrichment SBRs.
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    Pathways of 3-biofules (hydrogen, ethanol and methane) production from petrochemical industry wastewater via anaerobic packed bed baffled reactor inoculated with mixed culture bacteria
    (Elsevier, 2016) Elreedy, Ahmed; Tawfik, Ahmed; Enitan, Abimbola Motunrayo; Kumari, Sheena K.; Bux, Faizal
    Simultaneous production of 3-biofuels (hydrogen, ethanol and methane) as by-products of the biodegra-dation of petrochemical wastewater containing MEG via anaerobic packed bed baffled reactor (AnPBBR), was extensively investigated. A four-chambered reactor supported by polyurethane sheets, was operated at a constant hydraulic retention time (HRT) of 36 h and different organic loading rates (OLRs) of 0.67, 1, 2 and 4 gCOD/L/d. The maximum specific H2 and CH4 production rates of 438.07 ± 43.02 and 237.80 ± 21.67 ml/L/d were respectively achieved at OLR of 4 gCOD/L/d. The residual bio-ethanol signif-icantly increased from 57.15 ± 2.31 to 240.19 ± 34.69 mg/L at increasing the OLR from 0.67 to 4 gCOD/L/d, respectively. The maximum MEG biodegradability of 98% was attained at the lowest OLR. Compartment-wise profiles revealed that the maximum H2 and ethanol production were achieved at HRT of 9 h (1st compartment), while the CH4 production was peaked at HRTs of 27 and 36 h (last two compartments). Kinetic studies using Stover–Kincannon and completely stirred tank reactor (CSTR) in series models were successfully applied to the AnPBBR overall and compartment-to-compartment performance, respectively. The economic evaluation strongly revealed the potentials of using AnPBBR for simultaneous treatment and bio-energy production from petrochemical wastewater as compared to the classical anaerobic baffled reactor (ABR). Microbial analysis using Illumina MiSeq sequencing showed a diversity of bacterial com-munity in AnPBBR. Proteobacteria (36.62%), Firmicutes (20.85%) and Bacteroidetes (3.44%) were the most dominant phyla.
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    Continuous biohydrogen production from starch wastewater via sequential dark-photo fermentation with emphasize on maghemite nanoparticles
    (Elsevier, 2015) Nasr, Mahmoud; Tawfik, Ahmed; Ookawara, Shinichi; Suzuki, Masaaki; Kumari, Sheena K.; Bux, Faizal
    Hydrogen production from starch wastewater via sequential dark-photo fermentation process was investigated. Two anaerobic baffled reactors (ABRs) were operated in parallel at an OLR of 8.11 ± 0.97 g-COD/L/d, and a HRT of 15 h. ABR-1 and ABR-2 was inoculated with pre-treated sludge and sludge immobilized on maghemite nanoparticles, respectively. Better hydrogen yield of 104.75 ± 12.39 mL-H2/g-COD-removed was achieved in ABR-2 as compared to 66.22 ± 4.88 mL-H2/g-COD-removed in ABR-1. The effluent of ABR-2 was used for further hydrogen production by photo fermentation in ABR-3. An overall hydrogen yield of 166.83 ± 27.79 mL-H2/g-COD-removed was achieved at a total HRT of 30 h. 16S rRNA phylogeny showed that Clostridium and Rhodopseudomonas palustris species were dominant in ABR-1, ABR-2 and ABR-3, respectively.
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    Effect of thermal pre-treatment on inoculum sludge to enhance bio-hydrogen production from alkali hydrolysed rice straw in a mesophilic anaerobic baffled reactor.
    (Taylor & Francis, 2013) Bux, Faizal; Kumari, Sheena K.; Tawfik, Ahmed; El-berry, Haitham
    The effect of thermal pre-treatment on inoculum sludge for continuous H2 production from alkali hydrolysed rice straw using anaerobic baffled reactor (ABR) was investigated. Two reactors, ABR1 and ABR2, were inoculated with untreated and thermally pre-treated sludge, respectively. Both reactors were operated in parallel at a constant hydraulic retention time of 20 h and organic loading rate ranged from 0.5 to 2.16 g COD/L d. The results obtained indicated that ABR2 achieved a better hydrogen conversion rate and hydrogen yield as compared with ABR1. The hydrogen conversion rates were 30% and 24%, while the hydrogen yields were 1.19 and 0.97 mol H2/mol glucose for ABR2 and ABR1, respectively. Similar trend was observed for chemical oxygen demand (COD) and carbohydrate removal, where ABR2 provided a removal efficiency of 53±2.3% for COD and 46±2% for carbohydrate. The microbial community analysis using 16S rRNA phylogeny revealed the presence of different species of bacteria, namely Clostridium, Prevotella, Paludibacter, Ensifer, and Petrimonas within the reactors. Volatile fatty acids generated from ABR1 and ABR2 were mainly in the form of acetate and butyrate and a relatively low fraction of propionate was detected in ABR1. Based on these results, thermal pre-treatment of inoculum sludge is preferable for hydrogen production from hydrolysed rice straw.