Mechanical aeration separation

Jet Aerators. Jet aerators are a cross between the diffused and mechanical aerators. Air and water are pumped separately under the water surface into a mixing chamber and ejected as a jet at the bottom of the tank or pond (Fig. 3f). Jet aerators are suited for deep tanks and have only moderate cost. Disadvantages include high operational costs, limitations caused by tank geometries, and nozzles that can clog. Additionally, they require blowers. 

Conventional—This type includes an aeration basin, a clarifier, and a sludge recycle system. The recycle sludge (RAS) and influent enter the aeration basin at the inlet and leave the basin in the opposite or outlet end. The solids in the mixed liquor get separated out in the clarifier and are recycled back to the aeration basin. Aeration in the basin can be achieved by diffused air or mechanical aerations. 

Complete Mix—The influent and the RAS are introduced at several points in the center of the aeration basin from a header or central channel. Effluent fi om the aeration basin is collected from both sides of the basin by means of two effluent channels. A clarifier is used to separate the solids in the basin effluent before the sludge is recycled back to the head of the system. Excess sludge is sent to the sludge handling facility of the treatment plant. Aeration can be accomplished by diffused air or mechanical aeration. 

Comminution Shredding. A mechanical treatment process which cuts large pieces of waste into smaller pieces so that they won t plug pipes or damage equipment. Contact stabilization Contact stabilization is a modification of the conventional activated sludge process. In contact stabilization, two aeration tanks are used. One tank is for separate reaeration of the return sludge for at least four hours before it is permitted to flow into the other aeration tank to be mixed with the primary effluent requiring treatment. 

This process, according to the manufacturer,54 has been developed in such a way that space requirements are kept to a minimum. A BIOPAQ IC reactor is used as the initial step in the treatment process. The name of this anaerobic reactor is derived from the gas-lift driven internal circulation that is generated within a tall, cylindrical vessel. These reactors have been operational in the paper industry since 1996. The second step in the purification process is a mechanically mixed and aerated tank. The aerating injectors can be cleaned in a simple way without the need to empty the aeration tank. Potential scaling materials are combined into removable fine particles. At the same time, the materials that may cause an odor nuisance are oxidized into odorless components. The process can be completed by a third and a fourth step. The third step focuses on suspended solids recovery and removal. The fourth step is an additional water-softening step with lamella separation and continuous sand filters in order to produce fresh water substitute. The benefits claimed by the manufacturer are as follows54 ... 

The silver is dissolved from the ore by an aqueous solution of a salt, and then precipitated as metal or sulphide. The cyanide process2 is the most important of the lixiviation methods, its application having been considerably extended in recent years, especially in Mexico. The ore is very finely crushed with cyanide solution in a stamp-mill, and the sludge produced submitted to agitation and aeration in contact with cyanide solution. The liquid is separated from the ore by the aid of mechanical filters, and the silver precipitated from the clear solution by addition of zinc in the form of dust or shavings. The product is smelted with nitre, and is sometimes refined by blowing air through the molten mass. 

Entrainment Most fluidized bed reactors employ one or more cyclone, either inside the freeboard region at the top of the vessel or located externally, to capture entrained solids that are then returned continuously to the base of the fluidized bed via a standpipe and a mechanical (e.g., slide) valve or aerated nonmechanical valve (see Ref. ° for details of solid return systems). A flapper gate, acting as a check valve, is commonly employed to prevent backflow of gas up the standpipe. While cyclones are by far the most popular, other gas-solid separators like impingement separators, electrostatic precipitators, filters, and scrubbers are sometimes provided, especially as second- or third stage separators. 

During the above described milling process a separate pile of approximately 4,000 kg. was used for our study. Temperatures in different points of the pile were measured periodically. A significant drop in this variable was the setting moment to further aerate the pile by mechanical means. 

There are two basic designs of floatation cells mechanical and pneumatic. Mechanical cells are the most common design and generally use a stator with an overhead-driven rotor to circulate the slurry medium (pulp) and also to provide air dispersion and bubble shear see Figure 4.11. Aeration may be self-induced or introduced from an external air source, and the froth is removed using peripheral launders. Pneumatic cells make use of aeration and hydrodynamics to circulate and suspend the pulp as well as achieving froth separation. 

A global analysis of all radionuclides, as well as of non-radioactive constituents, can be performed by taking microsamples from the fuel pellet, e. g. by mechanical drilling or by an ultrasonic technique. By using sophisticated sampling techniques, a local resolution on the order of 300 pm is possible. In order to determine the fission gas contents, the microsamples are dissolved under vacuum in de-aerated nitric acid the released gases are collected and analyzed by mass spectrometry. Other constituents are determined by an appropriate separation and measurement method as an example, determination of in such microsamples by neutron activation analysis is described in Section 3.2.3.3. 

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