WO1987002595A1

WO1987002595A1 - Means for purifying water and use of the means

Info

Publication number: WO1987002595A1
Application number: PCT/SE1986/000500
Authority: WO
Inventors: Hans Eriksson
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-10-31
Filing date: 1986-10-31
Publication date: 1987-05-07
Anticipated expiration: 1988-04-30
Also published as: SE8505141D0; EP0243441A1; ES2002908A6; AU6593586A; SE8505141L

Abstract

Sewage disposal works for waste water take up considerable space and are expensive since the through-flow time is long and considerable resources are required to remove the sedimentation. The present invention provides a purification means (1) in the form of a continuous filter cloth which collects particles and oil above a certain viscosity limit and replaces mechanical means now in use, thus considerably reducing the costs entailed in a sewage disposal plant. The purification means (1) replaces or relieves one or more of the purification steps.

Description

Means for purifying water and us of the means

The present invention relates to a means for purifying water in sewage disposal plants, certain washing facilities or other facilities where water or some other liquid is polluted by particles and/or oil.

A plant for purifying waste water comprises one or more purification steps. Purification may be carried out by mechanical, biological and/or chemical means. Before reaching these steps the waste water generally passes through a course grid to remove any large particles. An aerated sand trap follows, where sedimentation of heavier particles occurs and these are removed mechanically, usually by means of scrapers and pumps. Sedimentation also occurs in subsequent basins, after which organic sub¬ stances are broken down by oxidation with oxygen from the air and bac¬ terial activity. Chemicals may be added as nutrient for bacteria cultures and to cause flocculation.

A sewage disposal plant is usually dimensioned for 4-5 times the normal quantity of water. When heavy rains occur or when snow is melting, oil- which has become lodged in the drainage system may be released. Oil spills due to some other cause seem to occur in municipal wastewater treatment plants on average about once or twice a year. Oil in sufficient quan¬ tities can put the biological purification system out of function for up to a month. If the quantity of water exceeds the capacity of the plant, unpurified water is released to the receiver, which is a drawbac if this has low capacity. Furthermore, oil released from the wastewater system has been known to incur expensive clearance efforts over vast expanses of water.

It is known to replace mechanical sedimentation basins by other mecha¬ nical purification steps, such as drum filters. These have relatively large openings and tend to break up particles so that they cannot be filtered out. They are also subject to wear. They only separate out oil when it has formed stable emulsion lumps. The present invention offers a solution to the problem by replacing basins and mechanical arrangements for both sand trap and pre-sedimentation. Considerable space is saved. Furthermore, long delays for sedimentation to take place are avoided in one or more purifying steps, thus increasing the through-flow rate of the wastewater and thereby the purification capacity in comparison with a conventional wastewater disposal plant. The need is also reduced for bulky and expensive tools and instruments to deal with the sludge which has settled in a basin. Oils over a certain viscosity are also removed from the water. Organic material is to a certain extent removed from the wastewater, thus facilitating subsequent purification steps.

In relation to the space it requires, and its cost, the means has a large capacity. It can be applied in an overflow channel in the event of considerable quantities of water, thus enabling the wastewater exceeding the plant capacity to also be cleaned to a considerable extent.

The means according to the present invention comprises a continuous filter oloth movable in a substantially vertical plane, inclined in the direction of flow of the wastewater. The waste filtered from the liquid and remaining on the filter cloth is transported upwardly out of the water and removed at the upper end of the device.

Additional features of the present invention are revealed in the fol- lowing claims.

The present invention will be described below with reference to the accom¬ panying drawings, in which

Figure 1 is a block diagram showing the purification steps in a con¬ ventional wastewater disposal plant and Figure 2 shows a means according to the invention.

Figure 1 shows the flowchart for a conventional purification plant, the arrows 20, 30, 40, 50 and 60 showing through-flow of the water. A waste- water disposal plant may consist of one or more of the blocks shown in Figure 1. The wastewater first passes a course grid and sand trap 22, where solid particles down to a certain size are removed depending on the dimensions of the grid opening. The water 30 then passes sedimentation basins 32. In the next step the water 40 is cleaned by biological means 42. Oxygen from the air is added as shown by the arrow 41, and sludge is removed at 43. Part of the sludge 43 is returned through pipe 44 to the biological cleaning step 42 in order to return the bacteria cultures. The water 50 leaving this stage is purified by means of flocculation, using chemicals and sedimentation 52. The arrow 51 indicates the addition of chemicals. The sludge 53 is separated off and the purified water 60 can be re-used or supplied to a receiver.

Figure 2 shows the means 1 according to the invention, for purifying wastewater A. The means 1 consists of a continuous filter cloth 2 which moves clockwise in a vertical plane in a channel having vertical sides and a horizontal bottom. The filter cloth rests on rollers 6,7,8,9_. or metal rods in a frame which can be lifted out of the water, and is driven by a roller above the water. The filter cloth 2 is deflected so as to form an upper part moving in upward direction, an upper part moving in downward direction and a lower part moving in downward direction. The lower, downwardly moving part may be divided into several sections as is indi¬ cated by the roller 9. The upwardly moving part of the filter cloth 2 is inclined in the direction of flow of the water. The type of means normally used for such filters are provided to control its tension prevent imbalance. If necessary rubber seals may rest on the filter to form a seal between the filter and the bottom and sides of the channel. Any sludge remaining on the filter can be removed by a scraper 3 and/or nozzles 4 for pressurized air or water directed towards the clean side of the filter. The sludge removed from the filter falls down onto a conveyor 12 moving transversely to the filter cloth, preferably a conveyor consisting of the same type of filter cloth as the inclined filter cloth. The sludge is thus drained at the same time. The rinsing water is collected in a trough located below the conveyor and is returned to the channel upstream of the purification means, or continues to the next purification step. The sludge is carried further for processing. The filter cloth dimen- sions, the mesh size, inclination and speed of travel of the cloth, the latter preferably being variable, should be adjusted to the quantity of water, the concentration and nature of the contaminants in the waste¬ water, pressure drop and the degree of purity required for the water leaving the means.

The wastewater A is supplied on top of the upper part of the upwardly moving filter cloth 2. Sludge is deposited on the filter cloth 2 and when the sludge on the filter reaches the upper, downwardly moving portion, it is scraped off by the scraper 3. The sludge scraped off is then treated in a special arrangement. Of course the scraper 3 may be located at some other point along the filter cloth. However, it is preferable for it to be located at a raised part of the means 1, i.e. to the right in Figure 2. After the scraping means, water or possibly an organic solution is lushed through the cloth 2 from the uncoated side, from nozzles 4. The nozzle arrangement 4 is preferably located at the downwardly moving, lower por¬ tion of the cloth 2.

The cloth 2 is dimensioned to deal with a predetermined quantity of sludge, estimated by calculation. "Sludge" is used here in its widest sense and may cover inorganic or organic waste. The cloth may be up to 15 m in width, but in most cases a width of one or two meters is suffi¬ cient. For small quantities of water, for instance from automobile washing facilities, cloth widths of less than a meter may be suitable. The mesh, wire dimension and weave should be suited to the composition of the wastewater and the required degree of purification. Examples of

2 standard mesh sizes are 0.5-2 mm . The wire dimension may be varied.

2 With a mesh size of 1 mm , for instance, the wire dimensioned might be

0.8 mm. The filter cloth may also be in two layers. It should preferably be made of synthetic fibres since oil and biological substances adhere better than to metal. This type of cloth can also be used for polluted liquids consisting of or containing acid or lye. A filter cloth according to the invention treats the contaminating particles gently so that they are not disintegrated, thus achieving efficient purification of the wastewater. The means according to the invention may constitute a separate purifi¬ cation unit for cleaning wastewater from automobile workshops, automobile washing facilities and other industrial applications. The means may also form part of a sewage disposal plant, for instance, where it may replace or supplement one or more cleansing steps. It preferable replaces the mechanical cleansing step, i.e. the step designated 32 in Figure 1. Besides the above-mentioned advantages of the means according to the invention, its superior ability to deal with oily waste should also be emphasized.

Claims

- 8CLAIMS

1. A means for purifying waste liquid, c h a r a c t e r i s e d by a continuous filter cloth

(2) movable in a substantially vertical plane*, inclined in the direction of flow of the liquid, the waste filtered from the liquid (a) and remaining on the filter cloth being transported in an upward direction and removed at the upper end of the device (1).

?. A means according to claim 1, c h a r a c t e r i s e d in that the purified water (B) is transferred to a subsequent purification step or to a receiver.

3. A means according to claims 1 and 2, c h a r a c t e r i s e d in that the waste remaining on the ζilter cloth is removed by means of a scraping arrangement (3), blast air, rinsing with liquid (4) and/or the like.

4. The use of a means according to one or more of the preceding claims for purifying waste water in a sewage disposal plant, c h a - r a c t e r i s e d in that the means (1 ) replaces or supplements one or more of the purification steps in the plant.

5. - - .The .use of. a means according to claim 4, c h a r a c ¬ t e r i s e d in that the means (1) is connected in series or in paral¬ lel with the purification steps which are to be replaced or supplemented.

6. The use of means according to claims 4 and 5, c h a r a c ¬ t e r i s e d in that the means (1) replaces or supplements one or more purification steps.

7. The use of a means according to any of claims 1 to 3 for purifying the waste liquid from washing facilities such as automobile-washing facilities and gasoline stations, whereby oily waste is removed.