Sewage treatment by a low energy membrane bioreactor

A new membrane bioreactor (MBR) was developed for treatment of municipal wastewater. The MBR was mainly made up of an activated sludge reactor and a transverse flow membrane module, with an innovative configuration being in application between them. As a result, the transverse flow membrane module and low recirculation flow rate created advantages, such as lower energy consumption and more resistance to membrane fouling. The total energy consumption in the whole system was tested as 1.97+/-0.74 kWh/m(3) (permeate) while using periodical backwash with treated water and backflush with mixed liquor daily, being in the same level as a submerged membrane bioreactor, reported to be 2.4 kWh/m(3) (permeate). Energy consumption analysis in the system shows that the membrane module was more energy consuming than the other four parts listed as pump, aeration, pipe system and return sludge velocity lose, which consumed 37.66-52.20% of the total energy. The effluent from this system could be considered as qualified for greywater reuse in China, showing its potential application in the future.     

Electrostatics of a simple membrane model using Green''s functions formalism.

The electrostatics of a simple membrane model picturing a lipid bilayer as a low dielectric constant slab immersed in a homogeneous medium of high dielectric constant (water) can be accurately computed using the exact Green's functions obtainable for this geometry. We present an extensive discussion of the analysis and numerical aspects of the problem and apply the formalism and algorithms developed to the computation of the energy profiles of a test charge (e.g., ion) across the bilayer and a molecular model of the acetylcholine receptor channel embedded in it. The Green's function approach is a very convenient tool for the computer simulation of ionic transport across membrane channels and other membrane problems where a good and computationally efficient first-order treatment of dielectric polarization effects is crucial.     

The general membrane equilibrium equation: Its simple derivation and some of its biological implications

On the basis of thermodynamic considerations, expressions for the relation between thei-th andj-th ions and solvent separated into subsystems by a semi-permeable membrane are derived. From this basic equation expressions for the transfer of solvent attending solute changes are developed. The application of these expressions to biological systems involving solvent transfer, as in cellular growth, chloride shift in the red blood cell, imbibition of water into cells is discussed.     

黑豹麻醉意外抽搐并休克抢救一例

黑豹属食肉目、猫科,是国家一类保护野生动物,具有极高的观赏和科研价值。1999年3月26日,我园在对一例患尾部脱毛的成年黑豹麻醉检查时,该黑豹出现全身肌肉强直性痉孪、口吐白沫,持续时间达2小时,最后演变成休克达9小时。通过及时全面的抗休克治疗使该黑豹恢复了健康。国内曾经对大熊猫麻醉意外休克及抢救有所报道,但都未见有抽搐症状。黑豹的麻醉、抽搐、休克、抢救情况目前国内还未见有报道,现介绍如下。1　基本情况雌性黑豹,4岁,体重60ｋｇ左右,外观健壮,食欲和大小便正常。1998年底发现尾部脱毛,口服药物治疗后疗效较差。1999年3月初发…     

A simple model analysis of product transfer through a non-impervious enzymic membrane

Summary Taking into account substrate diffusion limitations, computer simulation profiles of product distribution on both sides of a porous enzymic membrane are presented. In compartmentalized enzyme membrane systems like biosensors, the geometry of the system, membrane characteristics and hydrodynamic conditions play a prominent role in the product distribution relative to the substrate diffusional limitations.     

Quantitative characterization of a biological membrane by means of its spatial autocovariance.

Profiles for the exoplasmic face (EF) of the freeze-fractured plasma membrane from the root storage tissue of red beets are reconstructed by microdensitometry of micrographs of surface-shadowed-platinum carbon replicas. Autocovariance functions (ACFs) are computed from those profiles. The initial portions of the ACFs have a Gaussian form whose parameters (root mean square surface roughness and autocovariance length) are estimated. The parameter estimates are used to show that the pits on the EF faces are in good complementarity with the intramembrane particles seen on the complementary protoplasmic fracture faces.     

Purification of brush border membrane by thiocyanate treatment

Rat small intestinal brush border membranes are purified from brush borders by homogenization in relatively high concentrations of thiocyanate salts (0.56 m LiSCN, 0.41 m NaSCN, or 0.52 m KSCN), removal of this salt, and differential centrifugation to separate cytoskeletal material from membranes. The marker enzyme, sucrase, is enriched 98-fold in the final membranes over the starting homogenate of intestinal scrapings at a yield of about 20%. The isolated membranes are capable of secondary active sodium-dependent glucose transport as demonstrated by sodium gradient-supported overshooting glucose uptake.     

Evidence for a simple Cl conductance pathway in nutrient membrane of frog stomach

A decrease in nutrient Cl⁻ results in an increased negativity of the nutrient relative to the secretory side. The possibility emerged that Cl⁻ transport could be attributed to a neutral mechanism involving Cl⁻ in the nutrient membrane coupled to a simple Cl⁻ conductance pathway in the secretory membrane. The decrease in PD (potential difference) with a decrease in nutrient Cl⁻ could arise from a decrease in cellular Cl⁻ so that the ratio of Cl⁻ in cell to Cl⁻ in secretory solution was decreased. Experiments were designed to determine whether there was a need to assume a simple Cl⁻ conductance pathway. A 10-fold decrease in Cl⁻ gave in HCO₃⁻-containing nutrient solutions a PD decrease of 20 mV, in HCO₃⁻-free nutrient solutions, a PD decrease of 13.5 mV, and in HCO₃⁻-free and Na⁺-free solutions, a PD decrease of 6.7 mV. The decrease of 6.7 mV could not be attributed to a neutral Cl⁻HCO₃⁻ exchanger or a NaCl symport. Also there was no evidence for a KCl symport from changes in Cl⁻ in presence and absence of K⁺. It followed that the decrease of 6.7 mV provided evidence for a simple Cl⁻ conductance pathway in the nutrient membrane.     

Rationalization of membrane protein crystallization with polyethylene glycol using a simple depletion model

Based on the importance of crystallizing membrane proteins in a rational way, cytochrome bc(1) complex (BC1) was crystallized using polyethylene glycol (PEG) as a sole crystallization agent. Interaction between protein-detergent complexes of BC1 was estimated by dynamic light scattering, and was compared with the numerical calculation using the Derjaguin-Landau-Verwey-Overbeek potential plus a depletion potential, without considering specific surface properties of the protein-detergent complexes. The experiments and calculation were found to be consistent and we obtained a relation between PEG molecular weight M and the range of depletion zone delta as delta approximately M(0.48+/-0.02). The stability of liquid phase of BC1 solutions was controlled by a ratio of (the range of depletion zone)/(the radius of a BC1 particle), which was consistent with recent theoretical predictions. The crystallization was most successful under a condition where the stability of the liquid phase changed from stable to unstable. The PEG molecular weight that fulfilled this condition coincided with the one used empirically to crystallize BC1 in the past by a number of groups. These results are compared to the fact that membrane proteins were often successfully crystallized close to the detergent cloud point.