好氧颗粒污泥形成机制初步探讨

在生物水处理技术中,好氧颗粒污泥有很好的应用前景.好氧颗粒污泥是在好氧条件下自发形成的生物自固定颗粒,具有较高的生物量、良好的沉淀性能和在高容积负荷条件下降解高浓度有机废水的良好生物活性.它的形成机制初步认为是SBR运行模式、胞外多糖及水力剪切力等共同作用的结果.文章综述了SBR运行模式中选择压、周期性的好氧饥饿对颗粒污泥形成的作用,以及胞外多糖、水力剪切力对好氧颗粒污泥形成与稳定性关系的重要影响.     

Preliminary Studies on Converting Agricultural Waste into Biodegradable Plastics,Part I: Corn Distillers’ Dry Grain

Distillers dry grain (DDG) was derivatized either by carboxymethylation, glutaration, maleiation, phthallation, or succination in order to produce anionic materials suitable for complexation with soy protein isolate. Infrared spectroscopy confirmed that derivatization of DDG by all reagents was successful. Blending of derivatized anionic products with soy protein resulted in instant precipitation of gels. The gels were centrifuged, molded, and dried into solid pellets with tensile strengths as high as 1.67MPa, suggesting that these materials could be promising as biodegradable structural materials. Infrared spectroscopy suggested the possibility of complexes forming between soy protein isolate and each of the derivatized DDG samples.     

Photosensitized Oxidation of Cyanide in Aqueous Solutions of Photoactive Modified Hydroxyethylcellulose

Novel water-soluble polymeric photosensitizers based on a natural polymer, naphthalene-modified hydroxyethylcellulose (HENC), were obtained and used for the photooxidation of cyanide. The reaction leads to the formation of cyanate. The process occurs via photoinduced electron transfer from CN⁻ to the naphthalene or naphthoquinone polymeric chromophores. The kinetics of the reaction depend on the degree of substitution of HENC, its concentration, and pH of the solution. The polymers can be easily removed after reaction as prolonged irradiation leads to their photodegradation.     

生物去除H2S废气装置中EPS的提取和分析方法

为了研究生物滴滤塔去除H2S的生物膜降解机理,采用超声波法剥落滴滤塔内填料上的生物膜,在超声25 min时可以获得较好的提取效果;采用苯酚硫酸法测定胞外聚合物多糖时回收率为98.1%,具有较好地稳定性,简单、方便。     

污泥中蛋白质和多糖的分布对脱水性能的影响

为研究污泥中蛋白质和多糖的组成及空间分布对污泥可脱水性的影响,采用高温（55℃）及pH 10.0和pH 5.5控制条件,进行污泥水解酸化试验;通过离心和超声波法,对污泥中蛋白质和多糖在污泥粘液层、松散附着胞外聚合物层、紧密粘附胞外聚合物层及细胞相层的分布,并对污泥脱水性能（以毛细吸水时间表征）作了跟踪监测.结果表明,污泥中蛋白质和多糖主要分布在细胞相层.在酸性条件下（pH 5.5）,污泥高温水解酸化（第0～15 d）使其毛细吸水时间比原污泥稍大,而最终（第20 d）稍低;在碱性条件下（pH 10.0）的污泥水解酸化,则使污泥毛细吸水时间远大于原污泥.统计分析结果表明,污泥脱水性能主要受粘液层的可溶性蛋白质和蛋白质/多糖影响,几乎不受污泥中的蛋白质、多糖和蛋白质/多糖及其它EPS层中的化学组分的影响.     

Effect of proteins, polysaccharides, and particle sizes on sludge dewaterability

Four batch experiments of hydrolysis and acidification were carried out to investigate the distributions of proteins (PN) and polysaccharides (PS) in the sludge, the PN/PS ratio, the particle sizes, and their relationship with sludge dewaterability (as determined by capillary suction time, CST). The sludge flocs were stratified through centrifugation- and ultrasound-based method into four fractions: (1) slime, (2) loosely bound extracellular polymeric substances (LB-EPS), (3) tightly bound EPS (TB-EPS), and (4) pellet. The results showed that PN was mainly partitioned in the pellet (80.7%) and TB-EPS (9.6%) fractions, while PS distributed evenly in the four fractions. During hydrolysis and acidification, PN was transferred from the pellet and TB-EPS fractions to the slime fraction, but PS had no significant transfer trends. The mean particle sizes of the sludge flocs decreased with hydrolysis and acidification. The pH had a more significant influence on the dewaterability of sludge flocs than temperature. Sludge dewaterability during hydrolysis and acidification processes greatly deteriorated from 9.7 s at raw sludge to 340–450 s under alkaline conditions. However, it was just slightly increased under acidic conditions. Further investigation suggested that CST was a ected by soluble PN, soluble PN/PS, and particle sizes of sludge flocs, but was a ected slightly by total PN, PS, or PN/PS in the whole sludge flocs and other fractions (except slime).     

外加营养源作用下微生物黏结剂对土壤团聚体的影响

通过室内培养实验研究了外加营养源条件下微生物黏结剂(真菌菌丝和微生物胞外多糖)对土壤稳定性的影响以及微生物在不同粒径团聚体中的分布.所加营养源分别为葡萄糖(以C计)和硝酸铵(以N计),实验周期为30 d.实验设计包括对照(0.5 mg.g-1)、CN5(0.5 mg.g-1,0.1 mg.g-1,C/N=5)、CN10(0.5 mg.g-1,0.05 mg.g-1,C/N=10)3个水平.结果表明,3个处理的土壤呼吸速率十分接近,最大值都在3.10 mg.(h.kg)-1左右,说明无机氮肥的施加短期内对葡萄糖的矿化作用不明显.除培养第5 d CK的大团聚体形成量(15.67%)显著低于CN5(25.32%)和CN10(24.63%)外,其余培养期间3个处理的团聚体含量总体无显著性差异,表明本实验中葡萄糖对微生物的影响较大,覆盖了施加无机氮的影响,从而导致团聚体含量之间差异不显著.     

含水介质中胞外聚合物的影响因素研究

明确含水介质中微生物胞外聚合物(EPS)生成量的影响因素,是解决含水层生物堵塞的关键问题.本文在现场样品采集和微生物培养的基础上,通过砂柱试验模拟人工回灌过程,系统研究了进水碳、氮、磷浓度、盐度和温度对含水介质中EPS组成和含量的影响.结果表明,砂柱中EPS最主要的成分为多糖和蛋白质,其中多糖占总量的72%~99%;砂柱生物堵塞程度与介质上附着的EPS含量呈正相关关系,当回灌水碳、氮、磷浓度、盐度和温度分别为50 mg·L-1、5 mg·L-1、1 mg·L-1、0.5%和30℃时,微生物EPS生成量最高,砂柱渗透系数降低最显著,堵塞程度最严重.此外,碳、磷浓度、盐度和温度是影响EPS生成量的主要因素,而氮浓度对其影响不大;碳浓度和盐度对EPS中多糖、蛋白质的组成影响较大,而氮、磷以及温度则影响不明显.     

Review of konjac glucomannan

The paper reviews the solution and gelling properties of konjac glucomannan (KGM) and its interactions with other hydrocolloids such as xanthan and carrageenan for food applications. Research activities in the area of KGM processing in environmentally friendly aqueous environments have been discussed for coatings and packaging applications. Guest Editor: Heidi Schreuder-Gibson, U.S. Army Natick RD&E Center, Kansas Street, Natick, Massachusetts 01760-5020     

Sorption of 1-naphthol by plant cuticular fractions

The contribution of aliphatic-rich plant biopolymer to sorption of hydrophobic organic compounds is significantly important because of their preservation and accumulation in the soil environment,but sorption mechanism is still not fully understood.In this study, sorption of 1-naphthol by plant cuticular fractions was examined to better understand the contributions of respective fraction.Toward this end,cuticular materials were isolated from the fruits of tomato by chemical method.The tomato cuticle sheet consisted of waxes (6.5 wt%),cuticular monomer (69.5 wt%),and polysaccharide (24.0 wt%).Isotherms of l-naphthol to the cuticular fractions were nonlinear (N value (0.82-0.90)) at the whole tested concentration ranges.The KodKow ratios for bulk cuticle (TC1),dewaxed cuticle (TC2),cutin (TC4),and desugared cuticle (TC5) were larger than unity,suggested that tomato bulk cuticle and cutin are much powerful solption medium.Sorption capability of cutin (TC4) was 2.4 times higher than the nonsaponifiable fraction (TC3).The 1-naphthol interactions with tomato cuticular materials were governed by both hydrophobic-type interactions and polar (H-bonding) interactions. Removal of the wax and polysaccharide materials from the bulk tomato cuticle caused a significant increase in the sorption ability of the cuticular material.There was a linear negative trend between K_(oc) values and the amount of polysaccharides or fraction's polarities ((N O)/C);while a linear positive relationship between K_(oc) values and the content of cutin monomer (linear R~2=0.993) was observed for present in the cuticular fractions.Predominant sorbent of the hydrophobic organic compounds (HOCs) in the plant cuticular fraction was the cutin monomer,contributing to 91.7% of the total sorption of tomato bulk cuticle.