岩心钻探施工中绳索取心液动潜孔锤的应用价值分析

岩心钻探是当前获取地下地质资料最为完成及最为直接的方法,尤其在深部探测工程中具有重要意义。从当前来看,常规的绳索取心技术具有较低的钻进效率,且刻取岩石的表面积较大,制约了其推广应用。为了充分发挥绳索取心技术的优势,创新一种新的岩心钻探方法——绳索取心液动潜孔锤。本文特对绳索取心液动潜孔锤的应用做详细探讨,以望对该技术有更为全面的了解。     

2-Methylisoborneol and geosmin uptake by organic sludge derived from a recirculating aquaculture system

In a previous study on a recirculating fish culture system, levels of geosmin and 2-methylisoborneol were found to decrease when culture water was recirculated through the anaerobic sludge digestion treatment stage of the system. This finding led us to the present study in which the geosmin and 2-methylisoborneol removal capacity of the sludge derived from this treatment stage was examined in vitro. It was found that reduction of off-flavor compounds by the sludge was mediated by both chemical/physical sorption and biological degradation. At geosmin and 2-methylisoborneol concentrations within the range of those experienced in fish culture systems, chemical/physical sorption by the sludge was found to account for a 93% reduction in geosmin and a 79% reduction in 2-methylisoborneol from the overlying water within 48 h of incubation. Combined with the biological degradation taking place in the sludge, a complete removal of these compounds from the water phase occurred within 9 days of incubation. By means of repeated washing of the geosmin and 2-methylisoborneol contaminate sludge with clean water, relatively small amounts of these compounds were released from the sludge, a possible indication for the fact that absorption, rather than adsorption, underlies the chemical/physical removal process.     

Repeated phosphate removal from recirculating aquaculture system using cyanobacterium remediation and chitosan flocculation

Unicellular cyanobacterium Synechocystis sp. was used for phosphate removal in a recirculating aquaculture system. The cell harvesting was performed using chitosan solution in this study. The parameters (i.e. cell density, pH of cell suspension and chitosan concentration) affecting the flocculation efficiency of chitosan were investigated. With the optimal condition, the repeated flocculation for phosphate removal in a photobioreactor was demonstrated. The results show that the flocculation efficiency of chitosan depends on cell density, pH of cell suspension and chitosan concentration. The optimal flocculation process could be accomplished by adjusting the pH to 7.2 before adding 20 mg/L chitosan followed by pH adjustment to 7.5. With single inoculation, the sequential process of phosphate removal using cyanobacterial uptake followed by cell flocculation using chitosan with the optimal condition in the photobioreactor was successfully achieved for 12 cycles with water from a recirculating fish tank.     

Impact of water boundary layer diffusion on the nitrification rate of submerged biofilter elements from a recirculating aquaculture system

Total ammonia nitrogen (TAN) removal by microbial nitrification is an essential process in recirculating aquaculture systems (RAS). In order to protect the aquatic environment and fish health, it is important to be able to predict the nitrification rates in RAS's. The aim of this study was to determine the impact of hydraulic film diffusion on the nitrification rate in a submerged biofilter. Using an experimental batch reactor setup with recirculation, active nitrifying biofilter units from a RAS were exposed to a range of hydraulic flow velocities. Corresponding nitrification rates were measured following ammonium chloride, NH₄Cl, spikes and the impact of hydraulic film diffusion was quantified.The nitrification performance of the tested biofilter could be significantly increased by increasing the hydraulic flow velocity in the filter. Area based first order nitrification rate constants ranged from 0.065 m d⁻¹ to 0.192 m d⁻¹ for flow velocities between 2.5 m h⁻¹ and 40 m h⁻¹ (18 °C). This study documents that hydraulic film diffusion may have a significant impact on the nitrification rate in fixed film biofilters with geometry and hydraulic flows corresponding to our experimental RAS biofilters. The results may thus have practical implications in relation to the design, operational strategy of RAS biofilters and how to optimize TAN removal in fixed film biofilter systems.     

Kinetics of electro-oxidation of ammonia-N, nitrites and COD from a recirculating aquaculture saline water system using BDD anodes

The viability of the electro-oxidation technology provided with boron doped diamond (BDD) electrodes for the treatment and reuse of the seawater used in a Recirculating Aquaculture System (RAS) was evaluated in this work.The influence of the applied current density (5-50 A m⁻²) in the removal of Total Ammonia Nitrogen (TAN), nitrite and chemical oxygen demand (COD) was analyzed observing that complete TAN removal together with important reductions of the other considered contaminants could be achieved, thus meeting the requirements for reuse of seawater in RAS systems.TAN removal, mainly due to an indirect oxidation mechanism was described by a second order kinetics while COD and nitrite removal followed zero-th order kinetics. The values of the kinetic constants for the anodic oxidation of each compound were obtained as a function of the applied current density (k_TAN = 7.86 × 10⁻⁵·exp(6.30 × 10⁻² J); k₂NO = 3.43 × 10⁻² J; k_COD = 1.35 × 10⁻² J). The formation of free chlorine and oxidation by-products, i.e., trihalomethanes (THMs) was followed along the electro-oxidation process. Although a maximum concentration of 1.7 mg l⁻¹ of total trihalomethanes was detected an integrated process combining electrochemical oxidation in order to eliminate TAN, nitrite and COD and adsorption onto activated carbon to remove the residual chlorine and THMs is proposed, as an efficient alternative to treat and reuse the seawater in fish culture systems. Finally, the energy consumption of the treatment has been evaluated.     

Establishment of a real-time PCR method for quantification of geosmin-producing Streptomyces spp. in recirculating aquaculture systems

Geosmin and 2-methylisoborneol (MIB) have been associated with off-flavour problems in fish and seafood products, generating a strong negative impact for aquaculture industries. Although most of the producers of geosmin and MIB have been identified as Streptomyces species or cyanobacteria, Streptomyces spp. are thought to be responsible for the synthesis of these compounds in indoor recirculating aquaculture systems (RAS). The detection of genes involved in the synthesis of geosmin and MIB can be a relevant indicator of the beginning of off-flavour events in RAS. Here, we report a real-time polymerase chain reaction (qPCR) protocol targeting geoA sequences that encode a germacradienol synthase involved in geosmin synthesis. New geoA-related sequences were retrieved from eleven geosmin-producing Actinomycete strains, among them two Streptomyces strains isolated from two RAS. Combined with geoA-related sequences available in gene databases, we designed primers and standards suitable for qPCR assays targeting mainly Streptomyces geoA. Using our qPCR protocol, we succeeded in measuring the level of geoA copies in sand filter and biofilters in two RAS. This study is the first to apply qPCR assays to detect and quantify the geosmin synthesis gene (geoA) in RAS. Quantification of geoA in RAS could permit the monitoring of the level of geosmin producers prior to the occurrence of geosmin production. This information will be most valuable for fish producers to manage further development of off-flavour events.     

The method of computing a water-treatment filter with the account of media granulometric composition

We have developed a method of computing main technological parameters for the operation of a water-treatment filter including the time of the media protective effect and the time of filter operation until the achievement of the maximum head, taking into account the granulometric composition of the media. The theory of filtration and the method of technological simulation of this process developed by Mints are behind the computation method.     

某黑色金属熔炼炉循环冷却水系统设计

介绍了某特殊行业废旧污染黑色金属熔炼处理中心的中频无心感应熔炼炉循环冷却水系统设计,针对工程所在地的气候条件及水质等确定循环冷却水系统的工艺流程、运行控制方式,并结合现场实际运行情况对运行及处理效果进行了评价和分析,得出了一些有参考价值的结论。     

Fate and microbiological effects of furazolidone in a marine aquaculture sediment.

Furazolidone is used in the treatment of bacterial diseases in farmed fish. During application a large proportion of the administered drug reaches the environment directly or via feces. The persistence and metabolism of furazolidone in sediment from a Norwegian salmon farm is described. Furazolidone, in contrast to oxytetracycline and oxolinic acid, is actively metabolized by microorganisms in the sediment. The main metabolite is 3-(4-cyano-2-oxobutylidene-amino)-2-oxazolidone. This is a well known metabolite of the degradation of furazolidone in mammals, fish and Escherichia coli. 3-(4-Cyano-2-oxobutylideneamino)-2- oxazolidone had no detectable antibacterial activity. The half-life of furazolidone in the sediment at 4 degrees C was calculated to be 18 h.     

多类型支护体系在工程中的应用

根据工程地质勘察报告,介绍了基坑支护结构区段划分方法及结构设计要点,并按照动态设计、信息化施工的原则,对基坑工程实施了现场监测,提出了基坑开挖过程中发生应急事件的处理措施,以供参考。     

集体建设用地及其房屋的法律制度

1999年1月1日生效的《土地管理法》和同年5月6日国务院办公厅《关于加强土地转让管理严禁炒卖土地的通知》就明确规定：“农村集体土地使用权不得出让、转让或出租用于非农业建设;