RU2279408C2 - Apparatus for biological purification of sewage water - Google Patents

Abstract

FIELD: liquid aeration equipment for saturation of liquid with air oxygen to provide for biological purification of sewage water in municipal and industrial water purifying constructions.

SUBSTANCE: apparatus has aeration tank with aeration unit made in the form of ejector with aeration pipe fixed at ejector outlet end and having diameter d, and sewage water feeding and discharging pipes. Branch pipe inserted into inlet part of aeration pipe is (0.5-0.2)d long and is equipped with (0.3-0.5)d high guiding protrusions formed as cylindrical spirals adapted for causing silt mixture to circulate by cavitation at G=0.01-0.05 to provide for intensive dispersion therein of bubbles of air sucked by ejector, and uniform distribution of air bubbles across section of silt mixture flow.

EFFECT: increased efficiency and stability of biochemical purification of sewage water.

1 dwg

Description

1. The technical field

The invention relates to techniques for aeration of a liquid and its saturation with atmospheric oxygen for biochemical treatment of wastewater in municipal and industrial wastewater treatment plants.

2. The prior art

A known aerator for biological wastewater treatment, containing a hollow shaft with a drive vertically mounted in a tank with treated water, a rotor consisting of upper and lower disks with blades between them (RU No. 2021979, IPC ⁷ : C 02 F 3/12, 1991 .).

The disadvantages of the known aerator are low productivity due to the high resistance of the air entering the aerator along the path, the lack of sending to the rotor of the upper layers of water enriched with air oxygen, the presence of an oil seal working in the water and intensively worn out, respectively, a short resource and the aerator cannot operate at high pressures.

A combined device for biochemical wastewater treatment is known, which contains a biofilter with an irrigation system located above the sump aeration tank with feed pipes for jet aeration of liquids, a circulation pump that supplies sewage to aeration pipes, inside the upper part of which there are guide protrusions in the form of spirals (RU No. 2220915, IPC ⁷ : C 02 F 3/00, 3/02, 2001).

The known device does not have rotating elements for the formation of vortex funnels (the twisting of the liquid is carried out as it passes along the guiding protrusions in the form of a cylindrical spiral), thereby increasing the efficiency of saturation of the liquid with oxygen in the irrigation system, in which drops of water fall in the form of rain, with a significant improvement reliability indicators.

However, the placement of the guiding protrusions in front of the aerator itself provides only a swirling of the fluid flow to form a compact jet, when it falls onto the reflector it is crushed into individual drops (the smaller the drops, the larger their total surface through which the aeration of the liquid occurs), which entails the following disadvantages of the known device:

- passive saturation of the droplets of the liquid stream with atmospheric oxygen for a limited period of time (while they are in the air);

- significantly increases the size and cost of the aeration device;

- the operation of crushing liquid droplets is more energy intensive compared to crushing air bubbles due to a significant difference in the density of the media;

- the known system does not provide sufficient uniformity of droplet sizes of the entire flow of the processed fluid.

The closest in design and achieved effect, which we adopted as a prototype, is a device for biochemical wastewater treatment, containing a housing with an aeration unit, an ejector and pipelines supplying and discharging wastewater (AS USSR No. 812759, IPC ³ : C 02 F 3/20, 1979).

The disadvantages of the prototype are low efficiency and stability.

3. Disclosure of invention

The task of the invention is to increase the efficiency and stability of biochemical wastewater treatment.

The problem is solved in that in a device for biochemical wastewater treatment, containing an aeration tank with an aeration unit, made in the form of an ejector with an aeration pipe attached to its outlet, and pipelines supplying and discharging waste water, according to the invention, a pipe is installed inside the aeration pipe inlet length (0.5 ÷ 2.0) d with guiding protrusions of height (0.3 ÷ 0.5) d in the form of cylindrical spirals causing cavitation in the circulating silt mixture with G = 0.01 ÷ 0.05, providing intensive dispersion there is a bubble in it air, sucked in by the ejector, and a uniform distribution of the latter over the cross section of the flow of sludge mixture.

Design description

The drawing shows a tower-type aeration tank water-jet aeration unit in the form of a supply pipe 1, an ejector 2 and an aeration pipe 3, with a pipe 4 fixed in its inlet part, inside of which guide projections 5 are installed in the form of cylindrical spirals causing cavitation with G in the circulating silt mixture = 0.01 ÷ 0.05, providing intensive dispersion in the stream of bubbles of air sucked in by the ejector, and a uniform distribution of the latter over the cross section of the flow of the sludge mixture. The pipe 4 can be mated to the aeration pipe 3 by means of flanges.

The optimal design length of the pipe 4, on which the guide protrusions are mounted, is (0.5 ÷ 2.0) of its diameter (d). The range parameters are established by optimizing two conditions: the minimum hydraulic resistance to the fluid flow and the dimensions of the devices that determine the energy consumption for pumping the fluid and the cost of structures, i.e. the planned technical result is achieved only within the specified range.

The angle of the helical line of a cylindrical spiral with the longitudinal axis of the aeration pipe 3 is selected from the condition for the formation of low-efficiency cavitation in the circulating sludge mixture with G = 0.01 ÷ 0.05, where there is no cavitation below the lower limit of the range, and above - cavitation reaches dangerous values for structural elements devices.

The height of the straightening protrusions is (0.3 ÷ 0.5) d, which allows twisting into the vortex funnels of the entire fluid flow, with their minimum thickness selected from the conditions of strength and corrosion resistance of the material. In practice, with sufficient corrosion resistance of the material (for example, titanium), the thickness of the protrusions can be as small as 1.0 mm, which with sufficient strength of the protrusions 5 practically does not affect the live section of the pipe 4.

4. Description of the operation of the device

A device for biochemical wastewater treatment works as follows. Returned activated sludge is pumped from the secondary sludge pump to an aeration tank, for example a tower type, via a supply pipe 1, on which an ejector 2 is installed as an aerator, where air is sucked into the pumped sludge mixture. Having entered the aeration pipe 3, the sludge-air flow forms, due to the interaction with the pipe 4 containing the protrusions 5 in the form of cylindrical spirals, vortex funnels with the smallest air bubbles dispersed into the liquid into which air cavities created in the stream by the ejector 2 are crushed. At the same time, uniform distribution occurs air bubbles over the flow cross section. At the same time, due to the increase in the total surface of air bubbles uniformly distributed in the liquid volume, the efficiency of the mass transfer process between the gas-liquid phases is increased, the result of which is the increased solubility of air oxygen in the sludge mixture and the active oxidation (neutralization) of harmful impurities.

4. Technical Results

The inventive step of the claimed proposal lies in the fact that the proposed combination of features provides a new technical result compared to known devices in which guiding protrusions or mixers of a different type in biofilter irrigation systems are placed in front of the ejector and are designed to form a compact jet incident on the reflector, providing crushing it into separate drops, which are sprayed in all directions, saturated with atmospheric oxygen before contact with the attached biofilm Coy on loading biofilters. In the claimed proposal, in which the mixer is placed after the ejector, instead of crushing the liquid into droplets, air bubbles are already dispersed, already involved in the liquid flow due to the low-intensity cavitation formed in the stream during its interaction with the spirals. This, firstly, increases the utilization of oxygen in the air; secondly, it allows to obtain a high concentration of dissolved oxygen in the treated wastewater, providing a high rate of oxidation of wastewater pollution, and thirdly, it allows to reduce the intensity of the flotation process in tower aeration tanks that occurs in the presence of free (undissolved) air bubbles.

In addition, the dispersion of air is less energy intensive than crushing water, and due to the fact that it occurs directly in the pipeline, oxidation of the bulk of the contaminants is ensured during transportation of the liquid to be cleaned, which is also less energy intensive than in the prototype and does not block anaerobic processes in the lower biocenosis layer of devices for biochemical wastewater treatment.

In the known device, twisting the fluid flow in the pipe with a spiral provides the tangential component of its spray at the outlet through the holes in the side walls of the pipe, due to which the liquid jets are crushed and create an extensive area of irrigation.

In the claimed proposal, the twisting of the fluid flow in the pipe provides new properties. Due to centrifugal forces (centrifugal moment of inertia I _xy = Σm _k x _k y _k , where m _k is the mass of the medium’s points, x _k , y _k are the coordinates of the points) and Coriolis forces (F _k = m _k 2 ω _per ν _rel Sinα , where ω _lane is the angular velocity, α is the angle between the relative velocity vector ν _rel and the axis around which the reference frame rotates) large air bubbles are crushed and mixed over the entire flow section.

The claimed proposal is industrially applicable and has significantly higher efficiency and stability compared to known devices due to structural simplicity, the ability to integrate into existing water treatment systems, the absence of moving elements and minor hydraulic losses.

Claims (1)

A device for biochemical wastewater treatment containing an aeration tank with an aeration unit made in the form of an ejector with an aeration pipe attached to its outlet with a diameter d, and pipelines supplying and discharging waste water, characterized in that a pipe length is installed inside the inlet of the aeration pipe ( 0.5 ÷ 0.2) d with guiding protrusions of height (0.3 ÷ 0.5) d in the form of cylindrical spirals causing cavitation in the circulating silt mixture with G = 0.01 ÷ 0.05, providing intensive dispersion in it air bubbles sucked in ejector, and uniform distribution of the latter over the cross section of the flow of the sludge mixture.