Comparison of membrane fouling in ultrafiltration of down-flow and up-flow biological activated carbon effluents

The UF membrane fouling by down- and up-flow BAC effluents were compared. Up-flow BAC effluent fouled the membrane faster than down-flow BAC effluent. The combined effects dominated irreversible fouling. The extent of fouling exacerbated by inorganic particles was higher. The TMP, permeate flux, and normalized membrane flux during 21 days of UF of DBAC and UBAC effluents. Fouling during ultrafiltration of down- and up-flow biological activated carbon effluents was investigated to determine the roles of polysaccharides, proteins, and inorganic particles in ultrafiltration membrane fouling. During ultrafiltration of down- flow biological activated carbon effluent, the trans-membrane pressure was≤26 kPa and the permeate flux was steady at 46.7 L?m⁻²?h⁻¹. However, during ultrafiltration of up-flow biological activated carbon effluent, the highest trans-membrane pressure was almost 40 kPa and the permeate flux continuously decreased to 30 L?m⁻²?h⁻¹. At the end of the filtration period, the normalized membrane fluxes were 0.88 and 0.62 for down- and up-flow biological activated carbon effluents, respectively. The membrane removed the turbidity and polysaccharides content by 47.4% and 30.2% in down- flow biological activated effluent and 82.5% and 22.4% in up-flow biological activated carbon effluent, respectively, but retained few proteins. The retention of polysaccharides was higher on the membrane that filtered the down- flow biological activated effluent compared with that on the membrane that filtered the up-flow biological activated carbon effluent. The polysaccharides on the membranes fouled by up-flow biological activated carbon and down- flow biological activated effluents were spread continuously and clustered, respectively. These demonstrated that the up-flow biological activated carbon effluent fouled the membrane faster. Membrane fouling was associated with a portion of the polysaccharides (not the proteins) and inorganic particles in the feed water. When there was little difference in the polysaccharide concentrations between the feed waters, the fouling extent was exacerbated more by inorganic particles than by polysaccharides.     

Coagulation of colloidal material in surface waters: the role of natural organic matter

Organic matter has a great influence over the fate of inorganic colloids in surface waters. The chemical nature and structure of natural organic matter (NOM) will be an important factor in determining whether colloids will be stabilised or destabilised by NOM. Under environmentally relevant conditions, the ubiquitous fulvic acids are likely to be responsible for coating and imparting a negative charge to colloids. If the adsorbed polyelectrolyte coating produces an increase in absolute surface potential, it will act to stabilise colloids in the water column. On the other hand, colloidal organic carbon, especially chain-like structures, has been shown to be involved in the aggregation of inorganic colloids through the formation of bridges. It is highly probable that both adsorption and bridging flocculation are occurring simultaneously in the natural aquatic environment. The importance of each process depends directly on the nature and concentration of organic matter in the system and indirectly on the productivity of the lake, its hydrological pathways, temporal variations, temperature, etc. The present paper reports such results and emphasises the need to discriminate the different kinds of NOM.     

黄精多糖对果蝇寿命的影响

水提法从黄精属的一种（Ｐｄｙｇｏｎａｔｕｍ ｓｐ．）分离得到一种含糖为９６．２５％的黄精多糖（Ｐｏｌｙｇｏｎａｔｕｍ ｐｏｌｙｓａｃｃｈａｒｉｄｅ，简称ＰＰ）。ＰＰ经ＵＶ－２４０紫外分光光度计扫描，其特征吸收率为２００ｎｍ，无蛋白质（２８０ｎｍ）和核酸（２６０ｍｎ）的特征吸收峰。浓度分别为０．０５％、０．５％、２％的ＰＰ哺养果蝇（６０ｄ）的实验结果表明：三种浓度组两性果蝇的平均寿命和最高寿命均明显     

Membrane fouling in ultrafiltration of natural water after pretreatment to different extents

The combined fouling during ultrafiltration(UF) of surface water pretreated to different extents was investigated to disclose the roles of polysaccharides, proteins, and inorganic particles in UF membrane fouling. Both reversible and irreversible fouling decreased with enhanced pretreatment(biologically active carbon(BAC) treatment and sand filtration). The sand filter effluent fouled the membrane very slowly. The UF membrane removed turbidity to less than 0.1 nephelometric turbidity unit(NTU), reduced polysaccharides by 25.4%–29.9%, but rejected few proteins. Both polysaccharides and inorganic particles were detected on the fouled membranes, but inorganic particles could be effectively removed by backwashing. The increase of turbidity in the sand filter effluent to 3.05 NTU did not significantly increase the fouling rate, but an increase in the turbidity in the BAC effluent to6.11 NTU increased the fouling rate by more than 100%. The results demonstrated that the polysaccharide, not the protein, constituents of biopolymers were responsible for membrane fouling. Membrane fouling was closely associated with a small fraction of polysaccharides in the feed water. Inorganic particles exacerbated membrane fouling only when the concentration of fouling–inducing polysaccharides in the feed water was relatively high. The combined fouling was largely reversible, and polysaccharides were the predominant substances responsible for irreversible fouling.     

Life Cycle Assessment of Polysaccharide Materials: A Review

Apart from conventional uses of polysaccharide materials, such as food, clothing, paper packaging and construction, new polysaccharide products and materials have been developed. This paper reviews life cycle assessment (LCA) studies in order to gain insight of the environmental profiles of polysaccharide products (e.g. viscose or natural fibre polymer composites) in comparison with their conventional counterparts (e.g. cotton or petrochemical polymers). The application areas covered are textiles, engineering materials and packing. It is found that for each stage of the life cycle (production, use phase and waste management) polysaccharide-based end products show better environmental profiles than their conventional counterparts in terms of non-renewable energy use (NREU) and greenhouse gas (GHG) emissions. Cotton is an exception, with high environmental impacts that are related to the use of fertilisers, herbicides, pesticides and high water consumption. The available literature for man-made cellulose fibres shows that they allow to reduce NREU and GHG emissions in the fibre production phase. No study has been found for the fabric production and the use phase of man-made cellulose textiles.

黄精多糖对老龄大鼠衰老生理生化指标的影响

以水提法从黄精（Ｐｏｌｙｇｏｎａｔｕｍｓｐ）中得到的粗多糖成分（ＰＰ）进行了老龄大鼠的衰老生理生化指标测定试验．两种剂量的ＰＰ灌喂老龄大鼠１ｍｏ后，测定其１２项衰老生理生化指标：胸腺指数和脾脏指数，外周血淋巴细胞ＡＮＡＥ活性，红细胞、视网膜、晶体核、晶体皮质的ＳＯＤ活性，心脏、血浆中过氧化脂质含量，肝脏、肾脏中脂褐质含量及脑中Ｂ型单胺氧化酶活性．结果表明：除胸腺指数、血浆中过氧化脂质含量无显著性变化外，其他１０项指标均有明显的改善作用；试验结果经统计学处理有显著性差异．     

Studies on materials containing polysaccharides as soil amendments 1: effects on animal waste water purification in a potting experiment

A potting experiment was carried out to determine the effects of soil amendments containing polysaccharides and earthworms on a land application system for the purification of animal waste water. The following soil amendments were used: purified Konjak powder (KP, powder containing glucomannan made from the root system of devil's tongue, Amorphophalus rivieri Dur.), crystallized cellulose (CC), and a mixture of the two (MX). These soil amendments were added to the pots, and then Chrysanthemum corondria were planted in the earthworm pots (A pots), the nonearthworm pots (B pots), and the control pots (C pots); the first two plots received primary-treated animal waste water, and the other one received tap water. The following items were then measured: pH, electrical conductivity, chemical oxygen demand (COD_Mn), total nitrogen (TN), total phosphorus, the volume of drained water from each pots, the height and dry matter weight of plants, and the water permeability into the soil. The MX-A pots, i.e., the pots containing both soil amendments and earthworms, gave good results, especially for water permeability, plant growth, the purification of COD_Mn, and TN. These results suggest that the presence of soil amendments and earthworms may enhance the improvement of water quality in land application systems using vegetation. Received: December 9, 1998 / Accepted: February 8, 2000     

Biochemical responses of the freshwater microalga Dictyosphaerium sp. upon exposure to three sulfonamides

Sulfonamides (SAs) are common antimicrobial drugs, which are frequently detected in surface water systems, and are difficult to degrade, posing a potential threat to the aquatic environment. However, little is known about the potential adverse effects of SAs on non-target organisms (e.g., microalgae) in the aquatic ecosystem. In this study, the effect of SAs (sulfadiazine (SD), sulfamerazine (SM1), and sulfamethazine (SM2) at 1, 5, 20, and 50 mg/L concentrations, respectively) on the freshwater microalga Dictyosphaerium sp. was investigated, with respect to changes of biomass and chlorophyll a content and induction of extracellular polymer substances (EPS), including protein and polysaccharide contents. At the same time, the residue of SAs was determined. The results showed that Dictyosphaerium sp. was tolerant to the three SAs, and the chlorophyll a content in Dictyosphaerium sp. significantly decreased on day 7, followed by a “compensation phenomena”. The increase in protein and polysaccharide contents played a defensive role in Dictyosphaerium sp. against antibiotic stress, and there was a strong positive correlation between polysaccharide contents and antibiotic concentrations. Dictyosphaerium sp. exhibited 35%–45%, 30%–42%, and 26%–51% removal of SD, SM1, and SM2, respectively. This study is helpful to understand the changes of EPS in the defense process of microalgae under the action of antibiotics, and provides a new insight for the ecological removal of antibiotic pollution in natural surface water system.