Aerobic biological treatment of thermophilically digested sludge

Aerobic biological treatment of digested sludge was studied in a continuously operated laboratory set-up. An aerated reactor was filled with thermophilically digested sludge from the Moscow wastewater treatment plant and inoculated with special activated sludge. It was then operated at the chemostat mode at different flow rates. Processes of nitrification and denitrification, as well as dephosphatation, occurred simultaneously during biological aerobic treatment of thermophilically digested sludge. Under optimal conditions, organic matter degradation was 9.6%, the concentrations of ammonium nitrogen and phosphate decreased by 89 and 83%, respectively, while COD decreased by 12%. Dewaterability of digested sludge improved significantly. The processes were found to depend on hydraulic retention time, oxygen regime, and temperature. The optimal conditions were as follows: hydraulic retention time 3-4 days, temperature 30-35 degrees C, dissolved oxygen levels 0.2-0.5 mg/L at continuous aeration or 0.7-1 mg/L at intermittent aeration. Based on these findings, we propose a new combined technology of wastewater sludge treatment. The technology combines two stages: anaerobic digestion followed by aerobic biological treatment of digested sludge. The proposed technology makes it possible to degrade the sludge with conversion of approximately 45% volatile suspended solids to biogas, to improve nitrogen and phosphorus removal in reject water from sludge treatment units, and to achieve removal of malodorous substances after 8-9 days of anaerobic-aerobic sludge treatment.     

Anaerobic thermophilic digestion of sewage sludge with a thickened sludge recycle

The process of anaerobic thermophilic digestion of municipal wastewater sludge with a recycled part of thickened digested sludge, was studied in semi-continuous laboratory digesters. This modified recycling process resulted in increased solids retention time (SRT) with the same hydraulic retention time (HRT) as compared with traditional digestion without recycling. Increased SRT without increasing of HRT resulted in the enhancement of volatile substance reduction by up to 68% in the reactor with the recycling process compared with 34% in a control conventional reactor. Biogas production was intensified from 0.3 L/g of influent volatile solids (VS) in the control reactor up to 0.35 L/g VS. In addition, the recycling process improved the dewatering properties of digested sludge.     

A new real-time retinal tracking system for image-guided laser treatment

A new system is proposed for tracking sensitive areas in the retina for computer-assisted laser treatment of choroidal neovascularization (CNV). The system consists of a fundus camera using red-free illumination mode interfaced to a computer that allows real-time capturing of video input. The first image acquired is used as the reference image and utilized by the treatment physician for treatment planning. A grid of seed contours over the whole image is initiated and allowed to deform by splitting and/or merging according to preset criteria until the whole vessel tree is demarcated. Then, the image is filtered using a one-dimensional Gaussian filter in two perpendicular directions to extract the core areas of such vessels. Faster segmentation can be obtained for subsequent images by automatic registration to compensate for eye movement and saccades. An efficient registration technique is developed whereby some landmarks are detected in the reference frame then tracked in the subsequent frames. Using the relation between these two sets of corresponding points, an optimal transformation can be obtained. The implementation details of proposed strategy are presented and the obtained results indicate that it is suitable for real-time location determination and tracking of treatment positions.     

Development of a root feeding system based on a fiber ion-exchange substrate for space plant growth chamber "Vitacycle"

Selecting a plant root nutrient delivery system is one of the key aspects of designing root modules for space plant growth chambers. This article examines a number of the nutrient delivery systems and shows the most suitable technique for providing nutrients to roots in microgravity, which to date are ion-exchange artificial soils. In addition, this article characterizes the ion composition and hydrophysical parameters of a new Russian artificial ion charged fiber substrate, BIONA-V3. The BIONA-V3 substrate is comprised of ion-exchange resin fibers. The experimental data concerning the effects of anionic and cationic components on plant biomass is presented. Preliminary experiments with BIONA-V3 showed that 1 kg of dry BIONA-V3 produces up to 2.4 kg (fresh mass) of cabbage leaf or 180 g of dry plant mass per 1 dm3 of the substrate. Therefore, the root zone volume can be as small as 120 cm3 per plant. Further optimizing the nutrient composition of the resin fibers can increase space plant growth chamber productivity.     

Numerical study of passive Q switching of a Tm:YAG laser with a Ho:YLF solid-state saturable absorber

In a previous work [Appl. Phys. Lett. 65, 3060 (1994)] we experimentally demonstrated that passive Q switching of a 2,017-nm, flashlamp-pumped Tm,Cr:YAG laser with a Ho:YLF saturable absorber could be obtained with an internal focusing lens. We numerically investigate the optical performance of the Ho:YLF Q-switched Tm:YAG laser system by solving the coupled rate equations. The simulation results indicate that the results obtained numerically are in good agreement with those obtained experimentally. With typical laser configuration, a Q-switched laser pulse of 35 mJ in 30 ns is obtained.     

油田注水射流泵添加防腐剂

在俄罗斯的Tananykskoye油田注水中,Orenburgneft公司试用射流泵添加防腐剂向地层注水。由于这种泵没有传动部分,而用泵喷射出的工作液进行密封与机械泵相比较具有重量轻、直径小、设备简单和成本低的优点。Orenburgneft公司与英国JKX油气公司共同研制出这种协调式射流泵(见图1)。     

Box model investigation of the effect of soot particles on ozone downwind from an urban area through heterogeneous reactions

Soot can provide additional surface area where heterogeneous reactions can take place in the atmosphere. These reactions are dependent on the number of reactive sites on the soot surface rather than the soot surface area per se. A box model, MOCCA, is used to investigate the effects of introducing heterogeneous reactions on soot into air parcel passing over an urban area and traveling downwind. The model was run at two soot mass concentrations of 2 microg/m3 and 20 microg/m3 with a surface density of n-hexane and decane. Signifcant change in gasphase concentration was only observed for the higher soot concentration. Due to the noncatalytic nature of the heterogeneous reactions, soot sites are rapidly consumed, and soot site concentrations are greatly reduced shortly after emissions are turned off. Notable changes in gaseous concentrations due to the introduction of heterogeneous reactions are not observed in the urban setting. The impact of heterogeneous reactions is more evident after emissions are turned off (i.e. downwind from the urban center). These changes are minimal for the condition that used n-hexane surface density. For conditions that used decane soot, NOx concentrations showed a slight increase, with NO being higher in the daytime and NO2 at night. The maximum O3 reduction observed when using the higher soot concentration is 7 ppb, downwind of the urban center. Change in O3 concentration was less than 1 ppb when using the lower soot loading. The observed effects of heterogeneous reactions on soot decrease with time.     

Track membranes with embedded semiconductor nanocrystals: structural and optical examinations

We studied the optical properties of poly(ethylene terephthalate) ion track membranes of 1.5, 0.5 and 0.05?μm?pores impregnated with luminescent semiconductor CdSe/ZnS nanocrystals of different diameters (2.5 and 5?nm). The nanocrystals were embedded from their colloidal solutions in toluene by the immersion of a membrane in a colloidal solution. Localization of quasi-isolated weakly interacting CdSe/ZnS nanocrystals in a loosened layer on the track pore wall surface along with the existence of empty pores was demonstrated. We observed also the spatial separation of nanocrystals of 2.5 and 5?nm in size along the 50?nm pores.     

采用驯化细菌从含金黄铁矿尾渣中浸出金

含金硫化物矿石在其硫化物晶格中常含有细分散的金和其它贵金属颗粒。由于贵金属颗粒被包裹,因此,这类矿石难于用常规的提取方法进行处理,致使金属常常残留于尾渣中而被弃失。本工作研究了在使用普通的提取技术(例如氰化法)之前,先采用生化浸出法对这类难处理的尾渣进行预处理的可能性。将含金黄铁矿的Leadville金矿尾渣先用泡沫浮选法浮选富集。在氰化浸出前,黄铁矿精矿用驯化12个星期的氧化铁硫杆菌进行不同周期的处理。氰化浸出前精矿经生化浸出处理可使金的提取率从32％提高到95％,银的提取率从48％提高到大于98％。