Characterization of date palm lignocellulosic by-products and self-bonded composite materials obtained thereof

In the present work, we investigated the possibility of valorizing four date palm tree by-products: leaflets, rachis, leaf sheath and fibrillum as self-bonded materials. First, their chemical composition and morphological properties were studied and showed high neutral detergent fiber values for all samples (65–91%) as normally required for self-bonding adhesion. Particleboard composites were then manufactured by thermopressing without any pretreatment or addition of synthetic binders. The properties of the resulting composites were assessed using bending test, internal bonding measurement, thickness swelling, water absorption and dynamical mechanical analysis. The fibrillum, leaflets and rachis based- composites have sufficient modulus of rupture to meet the Japanese Industrial Standard. However, only the fibrillum panels meet the French Standards. Furthermore, the results of dynamic mechanical analysis of leaflets composites reveal a relaxation peak which could be attributed to higher molecular weight carbohydrates. These preliminary results will allow to discriminate the various sources of fibrous particles on the same tree and to choose adequate preprocessing for further research.     

Mathematical modelling for biohydrogen production by Clostridium beijerinckii

Hydrogen is an energy source that can be produced by Clostridium sporogenes microorganism. In the present work, modeling of dark fermentation using Clostridium beijerinckii and dextrose as substrate was performed to evaluate how the gases and liquid by-products affect the biological process. A mathematical model was developed according to ADM1. The developed model takes into account biochemical reactions, physicochemical equilibrium as well as mass transfer processes during dark fermentation. Findings revealed that Clostridium beijerinckii reached a yield as high as 3.58 mol of H₂/mol of dextrose and generates by-products in the aqueous phase that may either be used as raw materials in a chemical process. Clostridium beijerinckii is very sensitive to acid media (pH < 5.0) and shows a low rate of biohydrogen production (even the absence of metabolic activity) at pH lower than 4.5. The developed model is able to predict (R² > 0.95) dextrose consumption profile, cumulative biohydrogen production and the maximum concentrations of liquid by-products.     

Effect of air-drying temperature on physico-chemical properties of dietary fibre and antioxidant capacity of orange (Citrus aurantium v. Canoneta) by-products

Dehydration promoted important modifications affecting both the physico-chemical properties of dietary fibre (DF) and the antioxidant capacity of orange by-products (peel and pulp remaining after juice extraction). The significance of such changes was largely dependent on the air-drying temperature used (from 30 °C to 90 °C). The major modifications on the DF components were observed when either extended drying periods, i.e. at lower temperatures, or elevated drying temperatures were applied. Dehydration around 50–60 °C apparently promoted the minor disruption of cell wall polymers, in particular of pectic substances. Pulp samples exhibited higher values of swelling (SW) and fat adsorption capacity (FAC) than those derived from orange peel. Although, significant decreases in water retention capacity (WRC), FAC and solubility values were detected for both by-products as the air-drying temperature increased. The antioxidant capacity associated to dehydrated citrus by-products was significantly higher for orange peel than for pulp samples. In general, the by-products studied proved to be quite resistant to the different heat treatments applied within the range of 40–70 °C. In overall, the study shows that, in order to preserve either the DF quality and/or the antioxidant capacity, air-drying temperature should be controlled since both types of compounds, DF components and antioxidants, might be degraded or modified either when extended drying periods and/or high drying temperatures are applied.     

Modeling dichloroacetic acid formation from the reaction of monochloramine with natural organic matter

A kinetic model was developed to predict dichloroacetic acid (DCAA) formation in chloraminated systems. Equations describing DCAA formation were incorporated into an established comprehensive monochloramine-natural organic matter (NOM) reaction model. DCAA formation was theorized to be proportional to the amount of NOM oxidized by monochloramine and described by a single dimensionless DCAA formation coefficient, theta(DCAA) (M(DCAA)/M(DOC(ox)). The applicability of the model to describe DCAA formation in the presence of six different NOM sources was evaluated. DCAA formation could be described by considering a single NOM source-specific value for theta(DCAA) over a wide range of experimental conditions (i.e., pH, NOM, free ammonia, and monochloramine concentrations). DCAA formation appears to be directly proportional to the amount of active chlorine (monochloramine and free chlorine) that reacted with the NOM under these experimental conditions. Values of theta(DCAA) for all six NOM sources, determined by nonlinear regression analysis, varied from 6.51 x 10(-3) to 1.15 x 10(-2) and were linearly correlated with specific ultraviolet absorbance at 280 nm (SUVA(280)). The ability to model monochloramine loss and DCAA formation in the presence of NOM provides insight into disinfection by-product (DBP) formation pathways under chloramination conditions. The subsequent model and correlations to SUVA has the potential to aid the water treatment industry as a tool in developing strategies that minimize DBP formation while maintaining the microbial integrity of the water distribution system.     

饮用水消毒副产物的去除途径及进展

饮用水使用氯消毒产生的消毒副产物对人类健康带来了极大危害。本文介绍了饮用水消毒副产物的形成原因及影响因素,并从选择优质水源、降低消毒副产物的前体物质、替换传统的消毒剂、去除已生成的消毒副产物四个方面论述和比较了饮用水中消毒副产物的各种去除途径及进展,指出了在去除消毒副产物方面存在的问题。     

寒冷地区高天然有机物水库水源水消毒工艺

为保障城市居民饮用水水质安全,以东北某寒冷地区低温、低浊、高色度、富含天然有机物磨盘山水库水源水为研究对象,分别采用不同消毒方式,如液氯、次氯酸钠和氯胺研究其在常规净水处理工艺中的消毒方法.结果表明:液氯和次氯酸钠消毒会导致三氯乙醛的生成;然而,采用氯胺消毒,当次氯酸钠和硫酸铵的投加比例为4∶1时(2 mg/L∶0.46 mg/L),能够显著降低水中消毒副产物,特别是三氯乙醛的质量浓度,且消毒持续时间更长,保证了其对管网水的稳定消毒效果.氯胺消毒方式在减小饮用水消毒副产物方面明显优于常规液氯和次氯酸钠消毒,各项消毒指标均满足《生活饮用水卫生标准》(GB5749—2006)的要求,解决了管网水三氯乙醛超标的问题.     

水的耗氧量的卫生学意义

水的耗氧量是评价水质有机物污染的重要项目之一。它与水的异臭 ,氯化消毒副产物 ,Ames致突变试验中回复突变率 (MR) ,水的致癌性呈正相关关系 ,而且其检测方便 ,应作为水厂日常净水控制项目之一。     

论当前在饮用水消毒领域内的研究工作方向

本文通过阅读大量国内外有关饮用水消毒技术资料,较全面的分析,总结了现在国内外有关饮用水领域的研究工作方向和正在研究的问题,主要从几个方面：饮用水生物控制发展方向、消毒前水质体物特性的研究、消毒剂和消毒工艺的研究、利用各种检测方法对消毒副产物进行鉴别分析的研究、控制去除消毒副产物的研究和饮用水生物稳定性的研究等进行了论述。     

水中痕量亚硝胺类消毒副产物的分析测试技术

亚硝胺类消毒副产物由于其潜在的高致癌风险正引发国内外水处理领域的极大关注。水中痕量亚硝胺的定量分析测试技术是开展各项研究工作的基础。介绍了水中常见亚硝胺消毒副产物主要单体物质的基本特征;探讨了识别定量分析水中亚硝胺消毒副产物所面临的主要困难和关键问题;从样品的预处理技术和测试技术两个方面论述了目前水中痕量亚硝胺消毒副产物定量分析的主要进展。