Potential for methane production from anaerobic co-digestion of swine manure with winery wastewater

This work examines the methane production potential for the anaerobic co-digestion of swine manure (SM) with winery wastewater (WW). Batch and semi-continuous experiments were carried out under mesophilic conditions. Batch experiments revealed that the highest specific methane yield was 348 mL CH₄ g⁻¹ COD added, obtained at 85.4% of WW and 0.7 g COD g⁻¹ VS. Specific methane yield from SM alone was 27 mL CH₄ g⁻¹ COD added d⁻¹. Furthermore, specific methane yields were 49, 87 and 107 mL CH₄ g⁻¹ COD added d⁻¹ for the reactors co-digesting mixtures with 10% WW, 25% WW and 40% WW, respectively. Co-digestion with 40% WW improved the removal efficiencies up to 52% (TCOD), 132% (SCOD) and 61% (VSS) compared to SM alone. These results suggest that methane can be produced very efficiently by the co-digestion of swine manure with winery wastewater.     

Biodegradation by activated sludge and toxicity of tetracycline into a semi-industrial membrane bioreactor

Much attention has been devoted recently to the fate of pharmaceutically active compounds such as tetracycline antibiotics in soil and water. Tetracycline (TC) biodegradability by activated sludge derived from membrane bioreactor (MBR) treating swine wastewater via CO₂-evolution was evaluated by means of modified Sturm test, which was also used to evaluate its toxicity on carbon degradation. The impact of tetracycline on a semi-industrial MBR process was also examined and confronted to lab-scale experiments. After tetracycline injection in the pilot, no disturbance was detected on the elimination of organic matters and ammonium (nitrification), reaching after injection 88% and 99% respectively; only denitrification was slightly affected. Confirming the ruggedness and the superiority of membrane bioreactors over conventional bioreactors, no toxicity was observed at the considered level of TC in the pilot (20 mg TOC L⁻¹), while at lab-scale sodium benzoate biodegradation was completely inhibited from 10 mg TOC L⁻¹ TC. The origin of the activated sludge showed a significant impact on the performances, since the ultimate biodegradation was in the range −50% to −53% for TC concentrations in the range 10–20 mg TOC L⁻¹ with conventional bioreactor sludge and increased to 18% for 40 mg TOC L⁻¹ of TC with activated sludge derived from the MBR pilot. This confirmed the higher resistance of activated sludge arising from membrane bioreactor.     

Aerobic granular sludge formation for high strength agro-based wastewater treatment

The present study investigates the formation of aerobic granular sludge in sequencing batch reactor (SBR) fed with palm oil mill effluent (POME). Stable granules were observed in the reactor with diameters between 2.0 and 4.0 mm at a chemical oxygen demand (COD) loading rate of 2.5 kg COD m⁻³ d⁻¹. The biomass concentration was 7600 mg L⁻¹ while the sludge volume index (SVI) was 31.3 mL g SS⁻¹ indicating good biomass accumulation in the reactor and good settling properties of granular sludge, respectively. COD and ammonia removals were achieved at a maximum of 91.1% and 97.6%, respectively while color removal averaged at only 38%. This study provides insights on the development and the capabilities of aerobic granular sludge in POME treatment.     

Influence of carbon source and inoculum type on anaerobic biomass adhesion on polyurethane foam in reactors fed with acid mine drainage

This paper analyzes the influence of carbon source and inoculum origin on the dynamics of biomass adhesion to an inert support in anaerobic reactors fed with acid mine drainage. Formic acid, lactic acid and ethanol were used as carbon sources. Two different inocula were evaluated: one taken from an UASB reactor and other from the sediment of a uranium mine. The values of average colonization rates and the maximum biomass concentration (C_max) were inversely proportional to the number of carbon atoms in each substrate. The highest C_max value (0.35 g TVS g⁻¹ foam) was observed with formic acid and anaerobic sludge as inoculum. Maximum colonization rates (v_max) were strongly influenced by the type of inoculum when ethanol and lactic acid were used. For both carbon sources, the use of mine sediment as inoculum resulted in a v_max of 0.013 g TVS g⁻¹ foam day⁻¹, whereas 0.024 g TVS g⁻¹ foam day⁻¹ was achieved with anaerobic sludge.     

Pentachlorophenol (PCP) dechlorination in horizontal-flow anaerobic immobilized biomass (HAIB) reactors

This study verifies the potential applicability of horizontal-flow anaerobic immobilized biomass (HAIB) reactors to pentachlorophenol (PCP) dechlorination. Two bench-scale HAIB reactors (R1 and R2) were filled with cubic polyurethane foam matrices containing immobilized anaerobic sludge. The reactors were then continuously fed with synthetic wastewater consisting of PCP, glucose, acetic acid, and formic acid as co-substrates for PCP anaerobic degradation. Before being immobilized in polyurethane foam matrices, the biomass was exposed to wastewater containing PCP in reactors fed at a semi-continuous rate of 2.0 μg PCP g⁻¹ VS. The applied PCP loading rate was increased from 0.05 to 2.59 mg PCP l⁻¹ day⁻¹ for R1, and from 0.06 to 4.15 mg PCP l⁻¹ day⁻¹ for R2. The organic loading rates (OLR) were 1.1 and 1.7 kg COD m⁻³ day⁻¹ at hydraulic retention times (HRT) of 24 h for R1 and 18 h for R2. Under such conditions, chemical oxygen demand (COD) removal efficiencies of up to 98% were achieved in the HAIB reactors. Both reactors exhibited the ability to remove 97% of the loaded PCP. Dichlorophenol (DCP) was the primary chlorophenol detected in the effluent. The adsorption of PCP and metabolites formed during PCP degradation in the packed bed was negligible for PCP removal efficiency.     

The effect of electrodialytic treatment and Na2H2EDTA addition on methanogenic activity of copper-amended anaerobic granular sludge: treatment costs and energy consumption

The effect of electrodialytic treatment in terms of a current density, pH and Na₂H₂EDTA addition on the methanogenic activity of copper-amended anaerobic granular sludge taken from the UASB reactor from paper mill was evaluated. Moreover, the specific energy consumption and simplified operational and treatment costs were calculated. Addition of Na₂H₂EDTA (at pH 7.7) to copper-amended sludge resulted in the highest microbial activity (62 mg CH₄-COD g VSS⁻¹ day⁻¹) suggesting that Na₂H₂EDTA decreased the toxic effects of copper on the methanogenic activity of the anaerobic granular sludge. The highest methane production (159 %) was also observed upon Na₂H₂EDTA addition and simultaneous electricity application (pH 7.7). The energy consumption during the treatment was 560, 840, 1400 and 1680 kW h m⁻³ at current densities of 0.23, 0.34, 0.57 and 0.69 mA cm⁻², respectively. This corresponded to a treatment costs in terms of electricity expenditure from 39.2 to 117.6 € per cubic meter of sludge.     

Kinetic study and oxygen transfer efficiency evaluation using respirometric methods in a submerged membrane bioreactor using pure oxygen to supply the aerobic conditions

The performance of a wastewater bench-scale ultrafiltration membrane bioreactor (MBR) treatment plant using pure oxygen to supply the aerobic conditions for 95 days was studied. The results showed the capacity of the MBR systems to remove organic material under a hydraulic retention time of 12 h and a sludge retention time of 39.91 days. Aeration represents its major power input; this is why the alpha-factor of the aeration and kinetic parameters (design parameters) were determined when the mixed liquid suspended solids (MLSS) was increased from 3420 to 12,600 mg/l in order to understand the system. An alpha-factor in the range 0.462-0.022 and the kinetic parameters measured with the respirometric method (K_M of 73.954-3.647 mg/l, k_d of 0.0142-0.104 day⁻¹, k_H of 0.1266-0.655 day⁻¹, and the yield mean coefficient of 0.941) were obtained. Our study suggested significant changes in the behaviour of the biological system when the concentration of MLSS was increased.     

Treatment of industrial wastewater with two-stage constructed wetlands planted with Typha latifolia and Phragmites australis

Industrial wastewater treatment comprises several processes to fulfill the discharge permits or to enable the reuse of wastewater. For tannery wastewater, constructed wetlands (CWs) may be an interesting treatment option. Two-stage series of horizontal subsurface flow CWs with Phragmites australis (UP series) and Typha latifolia (UT series) provided high removal of organics from tannery wastewater, up to 88% of biochemical oxygen demand (BOD₅) (from an inlet of 420 to 1000 mg L⁻¹) and 92% of chemical oxygen demand (COD) (from an inlet of 808 to 2449 mg L⁻¹), and of other contaminants, such as nitrogen, operating at hydraulic retention times of 2, 5 and 7 days. No significant (P < 0.05) differences in performance were found between both the series. Overall mass removals of up to 1294 kg COD ha⁻¹ d⁻¹ and 529 kg BOD₅ ha⁻¹ d⁻¹ were achieved for a loading ranging from 242 to 1925 kg COD ha⁻¹ d⁻¹ and from 126 to 900 kg BOD₅ ha⁻¹ d⁻¹. Plants were resilient to the conditions imposed, however P. australis exceeded T. latifolia in terms of propagation.     

A novel multifunctional cellulolytic enzyme screened from metagenomic resources representing ruminal bacteria

Metagenomic resources representing ruminal bacteria were screened for novel exocellulases using a robotic, high-throughput screening system, the novel CelEx-BR12 gene was identified and the predicted CelEx-BR12 protein was characterized. The CelEx-BR12 gene had an open reading frame (ORF) of 1140 base pairs that encoded a 380-amino-acid-protein with a predicted molecular mass of 41.8 kDa. The amino acid sequence was 83% identical to that of a family 5 glycosyl hydrolase from Prevotella ruminicola 23. Codon-optimized CelEx-BR12 was overexpressed in Escherichia coli and purified using Ni–NTA affinity chromatography. The Michaelis–Menten constant (K_m value) and maximal reaction velocity (V_max values) for exocellulase activity were 12.92 μM and 1.55 × 10⁻⁴ μmol min⁻¹, respectively, and the enzyme was optimally active at pH 5.0 and 37 °C. Multifunctional activities were observed against fluorogenic and natural glycosides, such as 4-methylumbelliferyl-β-d-cellobioside (0.3 U mg⁻¹), CMC (105.9 U mg⁻¹), birch wood xylan (132.3 U mg⁻¹), oat spelt xylan (67.9 U mg⁻¹), and 2-hydroxyethyl-cellulose (26.3 U mg⁻¹). Based on these findings, we believe that CelEx-BR12 is an efficient multifunctional enzyme as endocellulase/exocellulase/xylanase activities that may prove useful for biotechnological applications.     

Effect of high external pressures on the vibrational spectra of crystalline dichloro(1,5-cycloctadiene)platinum(II), Pt(η-C8H12)Cl2

The effects of high external pressures on the principal IR and Raman bands of crystalline dichloro(1,5-cycloctadiene)platinum(II), Pt(COD)Cl₂ (COD = η⁴-C₈H₁₂), have been investigated for pressures up to ∼30 kbar by diamond-anvil cell microspectroscopy. This square-planar Pt(II) complex does not undergo any pressure-induced structural change throughout the pressure range investigated and the pressure dependences (dν/dP) for the vibrational modes range from −0.18 to 0.79 cm⁻¹ kbar⁻¹. The negative dν/dP value observed for the IR band at 1426 cm⁻¹ (−0.18 cm⁻¹ kbar⁻¹) suggests that this band is chiefly associated with a CC stretching mode of the Pt-COD group. This observation provides yet another indication that high-pressure vibrational spectroscopy may indeed be a general method for establishing the presence of π-backbonding in organometallic complexes, such as metal carbonyls and alkenes.     

Molecularly-imprinted microspheres for selective extraction and determination of melamine in milk and feed using gas chromatography–mass spectrometry

Molecularly-imprinted polymers in the form of microspheres were synthesized using the dispersion polymerization protocol; cyromazine was used as dummy template, while methacrylic acid, ethylene glycol dimethacrylate and acetonitrile (MeCN) were used as functional monomer, cross-linker, and porogen, respectively. When compared with the non-imprinted polymer, the molecularly-imprinted polymers (MIPs) showed outstanding affinity toward melamine in MeCN with a maximum binding concentration (B_max) of 53.20 nmol mg⁻¹ MIPs, imprinting effect of 4.6, and a dissociation constant (K_d) of 90.45 μM. After optimization of the molecularly-imprinted solid-phase extraction conditions, a new method was developed to determine the melamine in milk and feed with gas chromatography–mass spectrometry. The performance of this method has been evaluated in the tainted milk and feed in terms of recovery, precision, linearity, the limit of detection (LOD) and limit of quantitation (LOQ). Recovery ranged in samples from 93.1 to 101.3% with intra-day and inter-day relative standard deviation values below 5.34%. The LOD and LOQ of melamine in milk and feed were 0.01 μg mL⁻¹ (μg g⁻¹) and 0.05 μg mL⁻¹ (μg g⁻¹), respectively.     

Correlation between fouling propensity of soluble extracellular polymeric substances and sludge metabolic activity altered by different starvation conditions

Soluble extracellular polymeric substances (EPSs) cause membrane fouling in membrane bioreactors (MBRs), correlated with MBR sludge characteristics. Effects of F/M ratios on the evolution of soluble EPSs, fouling propensity of supernatants, and sludge metabolic activity were measured in this study in a two-period sequencing batch reactor (SBR). The experimental results show that fouling propensity was directly correlated with soluble-EPS concentration and composition. Sludge that had entirely lost active cells by long-term starvation released 64.4 ± 0.9 mg/L of humic acids, which caused a rapid increase in membrane resistance (40.67 ± 2.24 × 10¹¹ m⁻¹) during fouling tests. During short-term starvation, induced by incubation at a normal to low F/M ratio of 0.05 d⁻¹, sludge can use previously secreted utilization-associated products (UAPs) to maintain endogenous respiration. Therefore, the strategies of accumulating sludge and prolonging sludge retention time in MBRs may create long-term starvation and promote membrane fouling.     

The antioxidant effect of the mesoionic compound SYD-1 in mitochondria

The sydnone SYD-1 (3-[4-chloro-3-nitrophenyl]-1,2,3-oxadiazolium-5-olate] possesses important antitumor activity against Sarcoma 180 and Ehrlich tumors. We previously showed that SYD-1 depresses mitochondrial phosphorylation efficiency, which could be involved in its antitumoral activity. Considering the important role of mitochondria in the generation of reactive oxygen species (ROS) and the involvement of ROS in cell death mechanisms, we evaluated the effects of SYD-1 on oxidative stress parameters in rat liver mitochondria. SYD-1 (0.5 and 0.75 μmol mg⁻¹ protein) inhibited the lipoperoxidation induced by Fe³⁺/ADP-oxoglutarate by approximately 75% and promoted total inhibition at the highest concentration tested (1.0 μmol mg⁻¹ protein). However, SYD-1 did not affect lipoperoxidation started by peroxyl radicals generated by α-α′-azodiisobutyramidine dihydrochloride. The mesoionic compound (0.25–1.0 μmol mg⁻¹ protein) demonstrated an ability to scavenge superoxide radicals, decreasing their levels by 9–19%. The activities of catalase and superoxide dismutase did not change in the presence of SYD-1 (0.25–1.0 μmol mg⁻¹ protein). SYD-1 inhibited mitochondrial swelling dependent on the formation/opening of the permeability transition pore induced by Ca²⁺/phosphate by approximately 30% (1.0 μmol mg⁻¹ protein). When Ca²⁺/H₂O₂ were used as inducers, SYD-1 inhibited swelling only by approximately 12% at the same concentration. NADPH oxidation was also inhibited by SYD-1 (1.0 μmol mg⁻¹ of protein) by approximately 48%. These results show that SYD-1 is able to prevent oxidative stress in isolated mitochondria and suggest that the antitumoral activity of SYD-1 is not mediated by the increasing generation of ROS.     

The influenced of PAC, zeolite, and Moringa oleifera as biofouling reducer (BFR) on hybrid membrane bioreactor of palm oil mill effluent (POME)

The main objective of this work was to determine the effectiveness of various biofouling reducers (BFRs) to operational condition in hybrid membrane bioreactor (MBR) of palm oil mill effluent (POME). A series of tests involving three bench scale (100 L) hybrid MBR were operated at sludge retention times (SRTs) of 30 days with biofouling reducer (BFR). Three different biofouling reducers (BFRs) were powdered actived carbon (PAC), zeolite (Ze), and Moringa oleifera (Mo) with doses of 4, 8 and 12 g L⁻¹ respectively were used. Short-term filtration trials and critical flux tests were conducted. Results showed that, all BFRs successfully removed soluble microbial products (SMP), for PAC, Ze, and Mo at 58%, 42%, and 48%, respectively. At their optimum dosages, PAC provided above 70% reductions and 85% in fouling rates during the short-term filtration and critical flux tests.     

Laboratory scale examination of the effects of overloading on the anaerobic digestion by glycerol

The anaerobic digestion of pure glycerol, which produces a baseline acetic acid to propionic acid ratio of 0.2, was studied in laboratory scale reactors (3 l working volume) at mesophilic temperature (37 °C) with 3000 mg chemical oxygen demand (COD) l⁻¹d⁻¹. During the experiment tVFA and C2-C6 VFA analysis and daily biogas yield measurement were carried out. Following 10 days of a 15% d⁻¹ increase in the organic loading rate (OLR) of 3.0-10.5 g COD l⁻¹d⁻¹, the concentration of propionic acid increased to 6200-8000 mg l⁻¹. Then the inoculum was divided into three parts feeding with 100% glycerol, 50% glycerol + 50% acetic acid, and 50% glycerol + 50% thick stillage, (presented in % of 2.60 g COD l⁻¹d⁻¹ OLR), respectively. The application of co-substrates reduced the recovery period by 5 days compared to feeding with pure glycerol. When the reactors were loaded with glycerol again (10% OLR raise per day) the previously applied co-substrates had a positive effect on the VFA composition and the biogas yield as well.     

Nitrogen nutrition of Canna indica: Effects of ammonium versus nitrate on growth, biomass allocation, photosynthesis, nitrate reductase activity and N uptake rates

The effects of inorganic nitrogen (N) source (NH₄⁺, NO₃⁻ or both) on growth, biomass allocation, photosynthesis, N uptake rate, nitrate reductase activity and mineral composition of Canna indica were studied in hydroponic culture. The relative growth rates (0.05-0.06 g g⁻¹ d⁻¹), biomass allocation and plant morphology of C. indica were indifferent to N nutrition. However, NH₄⁺ fed plants had higher concentrations of N in the tissues, lower concentrations of mineral cations and higher contents of chlorophylls in the leaves compared to NO₃⁻ fed plants suggesting a slight advantage of NH₄⁺ nutrition. The NO₃⁻ fed plants had lower light-saturated rates of photosynthesis (22.5 μmol m⁻² s⁻¹) than NH₄⁺ and NH₄⁺/NO₃⁻ fed plants (24.4-25.6 μmol m⁻² s⁻¹) when expressed per unit leaf area, but similar rates when expressed on a chlorophyll basis. Maximum uptake rates (V_max) of NO₃⁻ did not differ between treatments (24-35 μmol N g⁻¹ root DW h⁻¹), but V_max for NH₄⁺ was highest in NH₄⁺ fed plants (81 μmol N g⁻¹ root DW h⁻¹), intermediate in the NH₄NO₃ fed plants (52 μmol N g⁻¹ root DW h⁻¹), and lowest in the NO₃⁻ fed plants (28 μmol N g⁻¹ root DW h⁻¹). Nitrate reductase activity (NRA) was highest in leaves and was induced by NO₃⁻ in the culture solutions corresponding to the pattern seen in fast growing terrestrial species. Plants fed with only NO₃⁻ had high NRA (22 and 8 μmol NO₂⁻ g⁻¹ DW h⁻¹ in leaves and roots, respectively) whereas NRA in NH₄⁺ fed plants was close to zero. Plants supplied with both forms of N had intermediate NRA suggesting that C. indica takes up and assimilate NO₃⁻ in the presence of NH₄⁺. Our results show that C. indica is relatively indifferent to inorganic N source, which together with its high growth rate contributes to explain the occurrence of this species in flooded wetland soils as well as on terrestrial soils. Furthermore, it is concluded that C. indica is suitable for use in different types of constructed wetlands.     

Electricity generation in single-chamber microbial fuel cells using a carbon source sampled from anaerobic reactors utilizing grass silage

Production of electricity from samples obtained during anaerobic digestion of grass silage was examined using single-chamber air-cathode mediator-less microbial fuel cells (MFCs). The samples were obtained from anaerobic reactors at start-up conditions after 3 and 10 days of operation under psychrophilic (15 °C) and mesophilic (37 °C) temperatures. Electricity was directly produced from all samples at a concentration of 1500 mg COD L⁻¹. Power density obtained from the samples, as a sole carbon source, ranged from 56 ± 3 W m⁻³ to 31 ± 1 W m⁻³ for the mesophilic and psychrophilic samples, respectively. Coulombic efficiencies ranged from 18 ± 1% to 12 ± 1% for the same samples. The relationship between the maximum voltage output and initial COD concentration appeared to follow saturation kinetics at the external resistance of 217 Ω. Chemical oxygen demand (COD) removal was over 90% and total phenolics removal was in the range of 30-75% for all samples tested, with a standard amount of 60 mg L⁻¹ total phenolics removed for every sample. Our results indicate that generating electricity from solution samples of anaerobic reactors utilizing grass silage is possible, opening the possibility for combination of anaerobic digestion with MFC technology for energy generation.     

Quantification of metabolic limitations during recombinant protein production in Escherichia coli

Escherichia coli is one of the major microorganisms for recombinant protein production because it has been best characterized in terms of molecular genetics and physiology, and because of the availability of various expression vectors and strains. The synthesis of proteins is one of the most energy consuming processes in the cell, with the result that cellular energy supply may become critical. Indeed, the so called metabolic burden of recombinant protein synthesis was reported to cause alterations in the operation of the host's central carbon metabolism.To quantify these alterations in E. coli metabolism in dependence of the rate of recombinant protein production, ¹³C-tracer-based metabolic flux analysis in differently induced cultures was used. To avoid dilution of the ¹³C-tracer signal by the culture history, the recombinant protein produced was used as a flux probe, i.e., as a read out of intracellular flux distributions. In detail, an increase in the generation rate rising from 36 mmol_ATP g_CDW⁻¹ h⁻¹ for the reference strain to 45 mmol_ATP g_CDW⁻¹ h⁻¹ for the highest yielding strain was observed during batch cultivation. Notably, the flux through the TCA cycle was rather constant at 2.5 ± 0.1 mmol g_CDW⁻¹ h⁻¹, hence was independent of the induced strength for gene expression. E. coli compensated for the additional energy demand of recombinant protein synthesis by reducing the biomass formation to almost 60%, resulting in excess NADPH. Speculative, this excess NADPH was converted to NADH via the soluble transhydrogenase and subsequently used for ATP generation in the electron transport chain. In this study, the metabolic burden was quantified by the biomass yield on ATP, which constantly decreased from 11.7 g_CDW mmol_ATP⁻¹ for the reference strain to 4.9 g_CDW mmol_ATP⁻¹ for the highest yielding strain. The insights into the operation of the metabolism of E. coli during recombinant protein production might guide the optimization of microbial hosts and fermentation conditions.     

Feasibility of biogas production from anaerobic co-digestion of herbal-extraction residues with swine manure

The objective of this work was to examine the feasibility of biogas production from the anaerobic co-digestion of herbal-extraction residues with swine manure. Batch and semi-continuous experiments were carried out under mesophilic anaerobic conditions. Batch experiments revealed that the highest specific biogas yield was 294 mL CH₄ g⁻¹ volatile solids added, obtained at 50% of herbal-extraction residues and 3.50 g volatile solids g⁻¹ mixed liquor suspended solids. Specific methane yield from swine manure alone was 207 mL CH₄ g⁻¹ volatile solid added d⁻¹ at 3.50 g volatile solids g⁻¹ mixed liquor suspended solids. Furthermore, specific methane yields were 162, 180 and 220 mL CH₄ g⁻¹ volatile solids added d⁻¹ for the reactors co-digesting mixtures with 10%, 25% and 50% herbal-extraction residues, respectively. These results suggested that biogas production could be enhanced efficiently by the anaerobic co-digestion of herbal-extraction residues with swine manure.