This study investigated the application of a conductive material, granular activated carbon (GAC), as an approach to improve anaerobic lipid degradation and methane production. Anaerobic biomethane ...potential (BMP) assays were performed in 120 ml batch anaerobic digestion (AD) vials using 5 gVS/L anaerobic sludge as inoculum. Different BMP assays were carried out testing the impact of increasing GAC concentrations (0–33 g/L), use of different sludge types (granular vs. crushed), different substrates (oleate C18:1, butter and dairy wastewaters) and different temperatures (15, 37 and 55 °C). Experimental results and model fitting showed that addition of GAC supports faster methane production, i.e. the lag-phase decreased by 2–1000% depending on the GAC concentration and AD temperature. GAC addition also showed faster consumption of both volatile fatty acid and long-chain fatty acid, particularly palmitate (C16:0). Thermodynamic modelling suggested that GAC-induced direct interspecies electron transfer is kinetically superior to conventional indirect hydrogen transfer during AD of oleate. However, when the GAC concentration exceeded 8.0 g/L, there was a 20–50% decrease in the maximum methane production compared to the control. Overall, GAC supplementation has a significant potential to improve the digestion of lipid-rich wastewater which benefits design of modern bioenergy systems.
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•Granular activated carbon (GAC) addition improved AD of lipid-rich wastewaters.•Addition at 33.0 g/L GAC decreased the lag-phase time by 1000%.•Adding more than 8.0 g/L GAC lowered the maximum methane production by 20–50%.•Consumption of volatile fatty acids increased 2–5 fold with GAC addition.•Degradation rates of long-chain fatty acids increased by 50% with GAC addition.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
We performed a transcriptome-based bioassay (TSB assay) using human hepatoma HepG2 cells to evaluate the potential toxicity of whole wastewater effluents from two membrane bioreactors (MBRs) and a ...conventional activated sludge process (AS). The biologically active agent(s) in the wastewater effluents were characterized based on expression of the marker genes (i.e., CYP1A1, AKR1B10, GCLM and GPX2) selected by DNA microarray analysis, after the wastewater effluent samples were concentrated by a reverse osmosis (RO) membrane and further fractionated by various manipulations. The qPCR assay of marker genes demonstrated that the induction of CYP1A1 and GPX2 was mitigated after passing through C18 and chelate columns. In addition, clear induction of CYP1A1 was observed in the smallest size fraction with 1 k Da or smaller organic molecules in all the tested effluents. These results together with the water quality data of the fractionated samples suggested that responsible constituents for potentially adverse and abnormal transcriptomic responses in HepG2 could have hydrophobic nature and act with metal-dissolved organic matter (DOM) complexes in 1 k Da or smaller size fraction. Although DOM is known to play two contradictory roles as a protector and an inducer of toxicants, our present study indicated the DOM in wastewater effluent, particularly humic substances with acidic nature, functioned as a toxicity inducer of residual chemicals in the effluents. This study provided a new insight into the nature of “toxic unknowns” in the wastewater effluents, which should be monitored whole through the reclamation process and prioritized for removal.
•Whole effluents toxicity from MBRs was assessed based on transcriptome-based bioassay.•Characteristics of “toxic unknowns” were investigated based on expression of the marker genes after fractionation.•Responsible constituents could be hydrophobic and act with metal-DOM complexes (<1 k Da).•Acidic humic substances may act as an inducer of effluent toxicity.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•Two reactor configurations were compared for the removal of SeO42−, SO42− and Ni2+.•SO42− addition significantly enhanced the SeO42− and total Se removal in a BTF.•Ni2+ addition ...decreased SeO42− and SO42− removal by >30% in both the BTF and UASB.•UASB showed a faster recovery from Ni2+ inhibitory effects compared to the BTF.•Formation of Se-S and Ni-S minerals was detected in both the biofilm and granules.
Acid mine drainage and mining wastewaters contain, depending on the source, elevated concentrations of metals, e.g. nickel (Ni2+), and oxyanions, e.g. selenate (SeO42−) and sulfate (SO42−). This study compared the performance of two reactor configurations, a biotrickling filter (BTF) and an upflow anaerobic sludge blanket (UASB) reactor, for the treatment of model mining wastewater contaminated with SeO42−, SO42− and Ni2+. The Se removal efficiency of the BTF biofilm was improved by >70% in the presence of SO42−. In contrast, the Se removal performance of the UASB reactor was not affected by the presence of SO42−. The addition of Ni2+ decreased the oxyanion (SO42− and SeO42−) removal efficiency of both the BTF and UASB reactor by >30%. However, the UASB reactor recovered more quickly (∼10 days after Ni2+ addition) from Ni2+ toxicity as compared to the BTF (∼22 days after Ni2+ addition). A Ni2+ removal efficiency of more than 80% was achieved for both the BTF and UASB reactor. Ni2+ was mainly removed via sulfidic (HS−) precipitation by forming nickel sulfide (Ni3S4). Scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDX) and powder X-ray energy diffraction (P-XRD) revealed entrapped Se and selenium monosulfide (SeS) in the biofilm and granules of both reactor configurations, which could be potentially recovered for further reuse applications. This study demonstrated that the feed wastewater characteristics and the reactor configuration are key factors in achieving an efficient treatment of Se-laden mine drainage wastewater.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Fermentation processes have been shown to be a good approach to food waste (FW) management. Among the commodities that can be bioproduced by using FW as an organic substrate and exploiting its ...biodegradability, there is lactic acid (LA). LA has gained the interest of research because of its role in the production of polylactic acid plastics. In this study, the influence of the HRT (2-5 days) used during the fermentation of the liquid fraction (∼12-13 g COD/L) of FW on LA yield and concentration was investigated. Moreover, the changes in the chemical composition (in terms of carbohydrates and organic metabolites concentration) of the influent occurring in the feeding tank were monitored and its influence on the downstream fermentation process was examined. High instability characterized the reactor run with the optimal production yield obtained on day 129 at an HRT 2 days with 0.81 g COD/g COD. This study shows the importance of the fluctuating composition of FW, a very heterogeneous and biologically active substrate, for the LA fermentation process. The non-steady state fermentation process was directly impacted by the unstable influent and shows that a good FW storage strategy has to be planned to achieve high and constant LA production.
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BFBNIB, GIS, IJS, KISLJ, NUK, PNG, UL, UM, UPUK
AbstractThe synthetic strong base anion-exchange resin Amberlite IRA-900 was investigated for its adsorption capacity to simultaneously remove selenate (SeO42−) and sulfate (SO42−) from single and ...binary anion solutions at pH 7.5 and 20°C. At an initial SeO42− and SO42− concentration of 428.9 and 1,441.1 mg/L, respectively, IRA-900 adsorbed 85 (±1)% SeO42− and 75 (±5)% SO42− from single anion solutions at 2% (w/v) resin dosage. In binary anion solutions, a 20% decrease for both the SeO42− and SO42− adsorption efficiency was observed. Batch kinetic experimental data indicated that the adsorption rate of IRA-900 for both SeO42− and SO42− in the single and binary anion solutions fitted well to the pseudo-second-order kinetic model (R2=0.99). The modified Langmuir isotherm complete competition model best fitted the experimental data for binary anion solutions, showing 24% and 10% average relative error from theoretical calculations for SeO42− and SO42−, respectively. Exhausted resin was regenerated for the next cycle of adsorption using either 0.25 or 0.5 M HCl for 20 min and was tested for 30 adsorption-desorption cycles. Results showed that the resin was suitable for reuse at an optimal adsorption-desorption of 6 cycles without compromising the removal efficiencies. Efficient and fast adsorption of both SeO42− and SO42− is promising for developing an IRA-900 based ion-exchange process for the remediation of Se-contaminated (waste)waters.
Food waste (FW) generation has become one of the largest environmental concerns for human society. Thanks to its chemical features and its high biodegradability, FW can be used as starting platform ...to produce biocommodities. Lactic acid (LA) is one of those chemicals that is gaining the attention of industry and research for its important role in polylactic acids production. To exploit better the organic content of FW, several FW pretreatments have been proposed in the literature, though none of them were aimed at influencing LA fermentation. Thermal and ultrasonic pretreatment effects on solubilization rates and LA production yields have been investigated in this batch study. The highest solubilization rate was achieved with 30 minutes ultrasonic pretreated FW resulting in a 15% increment in soluble COD (sCOD). The highest LA yield was obtained after 90-minute thermal pretreatment at 80 and 100°C at a yield of 0.49 g LA•g COD−1. This study shows that ultrasonic pretreatment generally performed better than thermal pretreatment when considering the increase in sCOD but caused a reduction in LA concentrations and yields after fermentation with high production of ethanol. The opposite trend was recorded in the thermal pretreated incubations, in which LA was present for 50% of the sCOD with higher LA concentrations of 2.90 g COD•L−1.
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NUK, OILJ, SAZU, UKNU, UL, UM, UPUK
Lactic acid production through fermentation is an established technology, however, improvements are necessary to reduce the process costs and to decrease its market price. Lactic acid is used in many ...industrial sectors and its market has increased in the last decade for its use as the raw material for polylactic acid product. Using food waste as a cheap and renewable substrate, as well as fermentation at uncontrolled pH, helps to make the production cheaper and to simplify the downstream purification process. Lactic acid production at acidic conditions and the role of varying organic loading rate (OLR) and hydraulic retention time (HRT) were tested in two different semicontinuous batch fermentation systems. Reactor performances indicated that lactic acid fermentation was still possible at pH < 3.5 and even up to a pH of 2.95. The highest lactic acid production was recorded at 14-day HRT, 2.14 g VS/L·day OLR, and pH 3.11 with a maximum lactic acid concentration of 8.72 g/L and a relative yield of 0.82 g lactate/g carbohydrates. The fermentation microbial community was dominated by
Lactobacillus
strains, the organism mainly responsible for lactic acid conversion from carbohydrates. This study shows that low pH fermentation is a key parameter to improve lactic acid production from food waste in a semicontinuous system. Acidic pH favored both the selection of
Lactobacillus
strains and inhibited VFA producers from utilizing lactic acid as primary substrate, thus promoting the accumulation of lactic acid. Finally, production yields tend to decrease with high OLR and low HRT, while lactic acid production rates showed the opposite trend.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
This study investigated the potential of granular activated carbon (GAC) supplementation to enhance anaerobic degradation of dairy wastewater. Two sequential batch reactors (SBRs; 0.8 L working ...volume), one control and another amended with GAC, were operated at 37°C and 1.5–1.6 m/h upflow velocity for a total of 120 days (four cycles of 30 days each). The methane production at the end of each cycle run increased by about 68%, 503%, 110%, and 125% in the GAC‐amended SBR, compared with the Control SBR. Lipid degradation was faster in the presence of GAC. Conversely, the organic compounds, especially lipids, accumulated in the absence of the conductive material. In addition, a reduction in lag phase duration by 46%–100% was observed at all four cycles in the GAC‐amended SBR. The peak methane yield rate was at least 2 folds higher with GAC addition in all cycles. RNA‐based bacterial analysis revealed enrichment of Synergistes (0.8% to 29.2%) and Geobacter (0.4% to 11.3%) in the GAC‐amended SBR. Methanolinea (85.8%) was the dominant archaea in the biofilm grown on GAC, followed by Methanosaeta (11.3%), at RNA level. Overall, this study revealed that GAC supplementation in anaerobic digesters treating dairy wastewater can promote stable and efficient methane production, accelerate lipid degradation and might promote the activity of electroactive microorganisms.
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BFBNIB, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
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