WO2010061033A1

WO2010061033A1 - Equipment for improving the efficiency of clarification basins

Info

Publication number: WO2010061033A1
Application number: PCT/FI2008/000131
Authority: WO
Inventors: Vesa Leppanen
Original assignee: Vesa Leppanen
Priority date: 2008-11-26
Filing date: 2008-11-26
Publication date: 2010-06-03

Abstract

The invention concerns an accessory for the improvement of the separation efficiency of clarification basins (10) used for the cleaning of liquids. The accessory (12) is based on flotation and can be retrofitted onto the clarification basin. The invention is distinguished by its equipment (12), which is placed inside an existing clarification basin (10) to form part of the discharge flow channel (11 ) for the liquid to be cleaned (C). While passing through the equipment (12), impurities (B2) that have not been separated during the previous clarification process-those in their second phase-are separated from the liquid to be cleaned (C). While flowing through the equipment (12), bubbles, which comprise gas released from a so-called dispersion fluid (D) and formed by means of a compressed air controlled clog-proof nozzle (13), and whose size can be adjusted by means of the control pressure (15) of the nozzle to conform to the impurities (B2) that occur in the cleaning process, are mixed into the liquid to be cleaned (C). When rising to the surface, these bubbles adhere to impurities (B2) that have passed through the clarification process, and lift them to the surface of the tank (12), where they can be collected by familiar methods, e.g. raking or bleeding.

Description

EQUIPMENT FOR IMPROVING THE EFFICIENCY OF CLARIFICATION BASINS

This invention concerns an accessory for the improvement of the separation efficiency of clarification basins used for cleaning liquids. The accessory is based on flotation and can be retrofitted into the clarification basin.

The cleaning of various liquids, such as municipal raw water and wastewater, industrial process water and wastewater, and others, often includes the separation of solids, or impurities, which occur in some other phase.Such a cleaning process also aims at removing harmful dissolved material from liquids by first precipitating them into solid particles. The most conventional way of removing substances that occur in another phase is to allow them to descend to the bottom of suitable clarification basins. Then the impurities are raked or drained.

This conventional method may include various disrupting factors. Liquids may contain chemical or mechanical components that prevent the formation of suspended material which can be precipitated; the solid particles formed may too small; or impurities may form a sludge which is impossible to remove through sedimentation, e.g. due to its low density. In such cases, liquids can be cleaned by means of a well-known method, flotation, whereby small gas bubbles lift impurities to the surface, where they are collected.

There are several ways of forming these bubbles. The most traditional way is to use pressure to dissolve gas into the liquid. This releases the fluid pressure, and the gas bubbles discharge in accordance with Henry's law, familiar from the world of physics. When the gas bubbles are fed into the liquid, they adhere to the impurities and lift them to the surface. Evenjhis method has its flaws, and the success of flotation is considerably dependent on the size of the gas bubbles. The smaller the bubbles, the smaller the impurity particles to which the gas bubbles adhere. Larger impurity particles may require larger gas bubbles. Another potential problem arises in the number of bubbles produced. The number of gas bubbles produced through various common release methods using dissolved gas, e.g. ejectors, nozzles and pressure liberators, may be too small with respect to the stream flow. If you wish to increase the amount of gas bubbles, any increase in the number and size of pressure liberators will correspondingly increase costs. An economical flotation process that operates in an optimal way is therefore required, for easy and economical integration into an existing clarification system for the removal of foreign matter that has passed through clarification.

Flotation is a significantly more effective way of removing suspended matter from liquids than clarification; it requires just a fraction of the volume and surface area of clarification based on gravity. Only 10% of the volume and surface area is required compared to the volume of a corresponding clarification basin. In addition, investment costs are often considerably smaller.

The purpose of this invention is to introduce equipment that can be placed inside an existing clarification system by using 5 to 10% of the volume and surface area of the existing clarification basin, while in many cases improving the separation efficiency and capacity at least twofold.

The invention is distinguished by its equipment, e.g. a tank which is placed inside an existing clarification basin to form part of the discharge flow channel allowing the liquid to be cleaned. While passing through the equipment, the impurities that have not been separated in the previous clarification process- those in their second phase-are separated from the liquid to be cleaned. Meanwhile, the bubbles, which are formed from gas released from a so-called dispersion fluid by means of a compressed air controlled clog-proof nozzle, and whose size can be adjusted by means of the nozzle's control pressure to conform to the impurities that occur in the cleaning process, are mixed into the liquid to be cleaned. When rising to the surface, the bubbles adhere to impurities that have passed through the clarification process, and lift them to the surface, where they can be collected by well-known methods, e.g. raking or bleeding. EXPLANATORY SECTON

The invention is described in the accompanying explanatory section, which is based on FIG 1 and FIG 2 (also included). Although the accompanying explanation presents just one implementation method, the solution has many variants that can be considered as falling under the scope of this invention.

During various phases, the bulk of foreign matter in the liquid (A) sinks through gravity based clarification to the bottom of the clarification basin (10) in the form of sludge (B), as shown in FIG 1. Depending on the density of the liquid to be cleaned (A) and the impurities in various phases, the sinking speed may vary and part of the foreign matter (B2) may rise to the surface. Typically, the largest and heaviest particles sink quickly to the bottom in the form of sludge (B), and the lightest ones sink last, as shown in FIG 1. Thus, the final result depends on the size of the clarification basin (10) and the velocity of flow of the liquid to be cleaned (A). There are several well-known methods of removing foreign matter from the clarification basin (10). The principle underlying the recovery of cleaned liquid (C) is to capture it where the liquid (C) is at its cleanest, i.e. free from impurities in their second phase (B2). The outlet union (1 1) can be a tube, a canal or an overflow chute. In FIG 1, the outlet union is a tube.

However, impurities (B2) can pass through the clarification. In accordance with this invention, equipment (12) which does not disturb the operation of the clarification basin is installed into the outlet union (11). With the help of the equipment (12), impurities (B2) that have passed through can be removed by means of a more efficient flotation method than normal

In one application of the invention (FIG 1), the exiting cleaned liquid (C), still containing impurities (B2), some of which did not settle to the bottom or which were light enough to re-ascend to the surface, is conducted to the clearing basin

(10), or into the tank (12) installed in the outlet union (11), where its flow rate is changed by means of the dimensioning of the tank (12), and where gas bubbles are mixed into it by means of a nozzle (13) (FIG 2). This nozzle has a control system that allows the regulation of the size of the gas bubbles. The dispersion fluid (D) that contains the dissolved gas required by the nozzle (13) is produced by means of any known gas dissolution method.

One application of the nozzle (13) in accordance with the invention is shown in

FIG 2. The function of the nozzle (13) is to form an adjustable opening (14) that allows the delivery of a sufficient amount of pressurized dispersion fluid (D) to treat the total amount of liquid (A) to be cleaned. It is possible to feed gas containing pressurized dispersion fluid (D) from various directions (16) into the nozzle (13) according to the required amount of dispersion fluid (D) and its required delivery direction. Since the dispersion fluid (D) fed into the nozzle (13) from various directions is under the same pressure, the pressure release of the various dispersion fluid flows (16) can be regulated using the same back pressure (15), so that, in accordance with Bernoulli's equation, the opening (14) inside the nozzle is the same everywhere. In the discharge slots (17), the released gas bubbles are always the same size, which can be regulated by means of the back pressure (15).

The back pressure (15) used to define the size of the pressure release opening (14) is fed into a seal (E) made of a flexible matter. In accordance with

Bernoulli's equation, the size of the opening (14) is the same everywhere.

The impurities and gas bubbles produced using the nozzle (13) adhere to one another inside the tank (12), and flow through it. While thus flowing through the tank (12), the gas bubbles lift the impurities (B2) to the top of the tank, where the impurities are separated and removed. In any case, the top of the tank (12) must be closed somehow, since clarification basins (10) are often in an outdoor location, and rain can prevent the successful operation of flotation. In addition, the tank (12) can be immersed in the clarification basin (10), if necessary. The tank (12) can be placed in clarification basins (10) of all shapes and sizes. The initial cost of a solution based on the invention is considerably more economical than purchasing a clarification basin and flotator separately.

Naturally, while FIG 1 and FIG 2 show just one variant of the invention, it can have many which equally form part of the invention.

For example, the addition of chemicals and polymerization agents to the liquid to be cleaned, and generally used in connection with the clarification process, can be applied as part of the solution described above, and can be considered as pertaining to the invention and as recognised techniques in this sense.

Moreover, methods of removing impurities formed in the tank are also recognised techniques. While other applications can also be added or performed in a different way, they too would then be included within the scope of the invention.

Claims

PATENT CLAIMS

1) Equipment (12) for the improvement of the separation efficiency of clarification basins (10), k n o w n for the fact that fluid (C) cleaned in a clarification basin (10) is fed into the equipment (12) installed in the existing clarification basin (10) in connection with its outflow (C).

2) Equipment (12) described in the patent claim, for the improvement of the separation efficiency of clarification basins (10), k n o w n for the fact that the equipment (12) can be installed in a clarification basin (10) of any form.

3) The equipment (12) described in patent claims 1 - 2 for the improvement of the separation efficiency of clarification basins (10), k n o w n for the fact that the equipment (12) is a covered tank (12) that can be installed on the surface or under the surface of a clarification basin (10).

4) The equipment (12) described in patent claims 1 - 3 for the improvement of the separation efficiency of clarification basins (10), k n o w n for the fact that the equipment (12) is equipped with a nozzle (13, FIG 2), whereby the size and number of gas bubbles that clean the liquid (A) can be regulated.

5) The equipment (12) described in patent claims 1 - 4 for the improvement of the separation efficiency of clarification basins (10), k n o w n for the fact that the equipment (12) handles all of the flow (C) fed into it.