Behavior of Decayed Spruce (Picea abies) during Kraft Pulping

This study indicated that by applying an improved classification system to decayed large-diameter Norway spruce (Picea abies) wood, its use as raw material for kraft pulping without loss of pulp quality could be essentially increased. This is based on the fact that although the cooking yield of decayed spruce material which has been sorted according to these new recommendations is somewhat lower and Kappa number higher than those of sound wood material, the greatest part of the decayed stem (the outer part of the stem) contains long-fiber wood material which produces pulp of good quality. Therefore, large-diameter spruce logs can also be separately used, for example, in the manufacture of reinforcement pulp.     

A priori risk-informed approach to ensure the compliance with discharge limits for liquid radioactive effluent to be discharged from APR 1400

ABSTRACT

In order to develop a methodology to guarantee the conformance to operational discharge limits for liquid effluent from a NPP at an early stage of design, a risk-informed approach was proposed and its applicability was verified for APR 1400. Existing methodology to calculate risk-based detection limit for a single radionuclide was improved by incorporating a new model to derive more realistic pathway dose factors. A new simple expression was also proposed to adjust risk-based detection limits for multiple radionuclides mixture if necessary. In addition, a new procedure to warrant the compliance with discharge limits by controlling detection limits of only a few principal radionuclides was established in accordance with risk-informed concept. Through case studies for APR 1400 to be commissioned at a hypothetical site, it was shown that calculated pathway dose factors are more realistic for majority of radionuclides. It also turns out that neither present detection limits nor unadjusted risk-based detection limits can be justified when the radionuclide composition is unknown, however further adjustment of detection limits or increasing additional dilution factor resolves the problem. Finally, ten principal radionuclides were identified and shown to be enough for liquid effluent control at APR 1400 from a risk-informed point of view.     

In-situ methane enrichment of biogas from anaerobic digestion of palm oil mill effluent by addition of zero valent iron (ZVI)

Palm oil mill effluent (POME) is a wastewater effluent that is generated from palm oil milling. Treatment of POME, especially using biological treatment methods, is a challenge as it contains high amounts of organic and sulfur compounds, and it is highly acidic. In this research, the effects of zero-valent iron (ZVI) on the enhancement of methane production from POME via anaerobic digestion were investigated. Furthermore, to identify the reactor operation modes that were suitable for the addition of ZVI, anaerobic digestion of POME was tested in three reaction configurations: batch reactor, fed-batch reactor, and continuous stirred-tank reactor (CSTR). In the batch mode, where acidic POME was fed with 16 g/L of ZVI dose just once, methane production increased by 74%. However, as the oxidation of ZVI under anaerobic conditions led to the production of hydroxyl ions, the pH of the medium continuously increased from approximately 7 to 9, which is not suitable for methanogenesis. In the fed-batch mode that involved intermittent feeding of acidic POME, the pH of the culture media was maintained at 6.8. This is because the extra hydroxyl ions generated from the oxidation reaction of ZVI tended to neutralize the acids in the feeding substrate. In addition, ZVI promoted the production of methane from POME and increased the average methane content in biogas from 62% to 76%. In the CSTR mode, which involved continuous feeding of acidic POME, ZVI increased methane production by 86% (from 1.79 to 3.32 L/day), methane content in biogas from 60 to 75%, and total chemical oxygen demand (tCOD) removal efficiency from 78 to 89 to 88–95%. Thus, the addition of ZVI can be a potential strategy for in-situ methane enrichment of biogas by anaerobic digestion of POME. This is because ZVI acts as a buffer for acid generation and provides extra electrons, ferrous ions, and ferric ions, which promote key microbial activities in the anaerobic digestion process.     

柠条的纤维特性及其双螺杆CMP制浆性能研究

以柠条为原料，分析了其化学组分和纤维形态，并探讨了柠条双螺杆CMP法的制浆工艺以及浆料的纤维形态和成纸的物理性能。研究结果表明：与针、阔叶木相比，柠条原料中纤维素和综纤维素质量分数较低，苯醇抽出物和热水抽出物质量分数较高，柠条纤维长度总体偏短，木质部和皮部的纤维质量平均长度分别为0.621和0.819 mm，还存在部分杂细胞。采用3.5% Na₂SO₃和1.5% NaOH常温预浸12 h、90℃汽蒸1 h后再用双螺杆挤浆机在质量分数35%下进行搓丝，并结合高浓盘磨机磨浆，所得CMP浆得率可达73%。柠条CMP浆基本保持了纤维原有的长度，质量平均长度达0.650 mm，长宽比为32.7，纤维解离较好，但分丝帚化情况不理想，含有部分纤维束和杂细胞。当加拿大游离度为300 mL时，柠条CMP浆成纸的环压强度指数和松厚度较高，分别为8.67（N·m）/g和2.56 cm³/g，抗张指数为19.6（N·m）/g，本色浆白度较高，达50%（ISO）。柠条CMP浆适合配抄瓦楞原纸等包装用纸，漂白后可配抄新闻纸和白板纸。     

Application of thermophilic temperatures,low hydraulic retention times and high recycling of de-gassed effluent for higher biohydrogen production

This study investigated the external operational factors that would reduce the thermodynamic constrains preventing the simultaneous achievement of high hydrogen productivities (HPs) and hydrogen yields (HYs) in the bioreactor. At hydraulic retention time (HRT) of 1, the maximum HPs and HYs achieved was 35 L H₂/h and 3.91 mol H₂/mol glucose, respectively. At this stage, the bacterial granules occupied approximately 75% of the bioreactor and consisted of the settled biomass density of 40.6 g/L (settled granule bed height = 13.8 cm). The formation of bacterial granules improved the bioreactor performance and resulted in higher substrate conversion efficiency (95%), nutrient influent (7.5 L/h) and de-gassed effluent recycle rates (3.5 L/min). In conclusion, this study demonstrated that high nutrient influent and high de-gassed effluent recycle rates reduced the thermodynamic constrains preventing the achievement of higher H₂ productivities in the bioreactor system.     

V2O5/RGO/Pt nanocomposite on oxytetracycline degradation and pharmaceutical effluent detoxification

The cover image is based on the Research Article V₂O₅/RGO/Pt nanocomposite on oxytetracycline degradation and pharmaceutical effluent detoxification by Mohan, H et al., DOI: 10.1002/jctb.6238 .

     

Performance optimization of microbial electrolysis cell (MEC) for palm oil mill effluent (POME) wastewater treatment and sustainable Bio-H2 production using response surface methodology (RSM)

Microbial electrolysis cells (MECs) are a new bio-electrochemical method for converting organic matter to hydrogen gas (H₂). Palm oil mill effluent (POME) is hazardous wastewater that is mostly formed during the crude oil extraction process in the palm oil industry. In the present study, POME was used in the MEC system for hydrogen generation as a feasible treatment technology. To enhance biohydrogen generation from POME in the MEC, an empirical model was generated using response surface methodology (RSM). A central composite design (CCD) was utilized to perform twenty experimental runs of MEC given three important variables, namely incubation temperature, initial pH, and influent dilution rate. Experimental results from CCD showed that an average value of 1.16 m³ H₂/m³ d for maximum hydrogen production rate (HPR) was produced. A second-order polynomial model was adjusted to the experimental results from CCD. The regression model showed that the quadratic term of all variables tested had a highly significant effect (P < 0.01) on maximum HPR as a defined response. The analysis of the empirical model revealed that the optimal conditions for maximum HPR were incubation temperature, initial pH, and influent dilution rate of 30.23 ^°C, 6.63, and 50.71%, respectively. Generated regression model predicted a maximum HPR of 1.1659 m³ H₂/m³ d could be generated under optimum conditions. Confirmation experimentation was conducted in the optimal conditions determined. Experimental results of the validation test showed that a maximum HPR of 1.1747 m³ H₂/m³ d was produced.     

Feasibility of Ni/Ti and Ni/GF cathodes in microbial electrolysis cells for hydrogen production from fermentation effluent: A step toward real application

The low cost, low over-potential loss, good catalytic properties for hydrogen evolution reaction (HER), high corrosion stability, commercially available, and could be applied in pH-neutral solution and ambient temperature are important properties for the cathode materials when it is applied in microbial electrolysis cell (MEC) technology. This study has two-pronged objectives: the first is to investigate the feasibility of titanium (Ti) and graphite felt (GF) coated with nickel (Ni), and the second is to generate hydrogen from the fermentation effluent (FE). The electrodeposition (ED) method was used to deposit Ni catalyst onto Ti (Ni/Ti) and GF (Ni/GF) surfaces. The scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy were used to characterize the cathode morphology and element composition. The catalytic properties of Ni/Ti and Ni/GF could be evaluated using the linear sweep voltammetry tests. The maximum volumetric H₂ production rates of MEC using Ni/Ti and Ni/GF cathodes were obtained at 0.39 ± 0.01 and 0.33 ± 0.03 m³ H₂ m⁻³ d⁻¹ respectively. The Ni/Ti and Ni/GF cathodes could be used as alternative cathodes while producing hydrogen from FE.     

Identification and cultivation of hydrogenotrophic methanogens from palm oil mill effluent for high methane production

By means of biorefinery, biogas production through anaerobic digestion is one of the most common treatments of wastewater in the palm oil industry. After biogas production, the treated palm oil mill effluent (POME) is generally discharged into the environment. However, certain level of hazardous compounds still exists in the treated wastewater, which can lead to the pollution of water bodies. In this study, we have investigated the dynamics of volatile organic acids dwelling in consecutive POME treatment lagoons as well as identified, and categorized, microbial species responsible for the treatment process. Bacteria and methanogens, both hydrogenotrophic and acetoclastic, related to methane production were identified using mcrA and 16S rRNA genes specific primers. Two hydrogenotrophic methanogens, Methanoculleus marisnigri and Methanoculleus chikugoensis, were found abundant in accordance with high formate concentration throughout the process of anaerobic digestion. This study has also isolated eight consortia of microbes that yielded different methane productions by utilizing formate as the substrate in the synthetic medium. The consortia of a group, containing M. marisnigri, M. chikugoensis, uncultured bacteria, Aminobacterium sp., and Ruminobacillus xylanolyticum, produced the highest methane yield of 259 mL/g COD after 25 days of incubation in the laboratory. The findings from this study are contributing to optimize and increase biogas production in POME, which will allow higher efficiency in palm oil mill wastewater treatment.