GB2213811A

GB2213811A - Purification of water for ponds or tanks containing fish

Info

Publication number: GB2213811A
Application number: GB8822398A
Authority: GB
Inventors: Malcolm Graham Goodson
Original assignee: Individual
Current assignee: Individual
Priority date: 1987-09-27
Filing date: 1988-09-23
Publication date: 1989-08-23
Also published as: GB8822398D0; GB8722662D0

Abstract

Water purification apparatus for ponds or tanks containing fish comprises a spiral/vortex settler 1 having means 5a for effecting physical flocculation of particulate matter by promoting particle to particle contact. The said means may comprise brushes or a loose or geometrically formed matrix of inert material. Water is introduced through a tangential inlet 2 and withdrawn through filters 12. <IMAGE>

Description

PURIFICATION OF WATER FOR PONDS AND TANKS CONTAINING FISH This invention relates to the purification of water from ponds or tanks containing fish. Certain aspects of the invention may also be applicable to other applications.

The principal by-products of fish production in enclosed systems are 1 Ammonia and other nitrogenous compounds.

2 Suspended solids (Settleable).

3 Suspended solids (Non-Settleable).

4 Soluble and insoluble organic matter.

Ammonia is highly toxic to fish even at very low concentration. About 70X of the ammonia produced by fish is excreted into solution at the fish gills, but the remaining 30X is contained in the protein content of the suspended solids. This is not released immediately into the water but is produced gradually through the biological decomposition of the protein to amino acids and then to ammonia.

A pond purification system may include a biological treatment section for the removal of the ammonia. Thus the effective removal of suspended solids is fundamental in minimizing the size of the biological purification system.

In the past solids have been removed using a variety of settlement devices of various sizes and configurations.

Sedimentation basins, similar to those employed in sewage and water treatment have been widely used, but these need to be large to be effective, providing up to lhr retention of the flow from the fish tank. Thus a typical pond of 10 cubic metres capacity, with a recycle flow of 5 cubic metres per hour would need 5 cubic metres of settlement capacity. Recently attempts have been made to reduce the volume of tankage required for settlement. My UK specification number 1594832, for example, provides a means of settlement integrally within the tank used for holding fish. More recentLy 'accelerated' separators have been proposed to treat fish tank effluent operating on the vortex or hydroclone principles. The advantage of such units is that they are very compact occupying only 1.5 - 2% of the area required by more conventional settling basins.

The main disadvantage of accelerated vortex-type separators, however, is that they operate best at a fairly constant flow rate when they will remove a large proportion of solids within a limited particle size range. It is seldom possible to arrange for such constant flow conditions in practical aquaculture applications, and accordingly there is often a loss of solids removal efficiency with the carry-over into the effluent of a Large proportion of the mid-small particle size solids.

An object of the present invention is to provide a method and apparatus for the purification of water from ponds or tanks containing fish offering improvements in relation to one or more of the matters discussed above, or generally.

According to the invention there is provided a method and apparatus for the p u r i f i c a t'i on of water from ponds or tanks as defined in the accompanying claims.

In an embodiment described below, certain aspects of spiral, vortex, or hydroclone separators, which provide for the separation of solids from fluids. are modified so as to give enhanced removal of solids, and, if required, in addition, provision is made for integral biological purification of soluble and insoluble organic and inorganic matter contained in the fluid stream being treated. The embodiment provides for improved solids capture within a vortex separator tank, and in some circumstances in addition can also provide biological treatment of the separator effluent.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which : Fig 1 shows a plan view indicating the spiral path of water within a vortex separator; Fig 2 shows an elevation view of a vortex separator; Figs 3 and 4 show elevation views of two embodiments of means for promoting physical flocculation of particles; Fig 5 shows the apparatus of Fig 3 mounted in the separation tank of Fig 2; and Figs 6 and 7 show, in views corresponding, respectively, with Figs 2 and 1, a further embodiment of the invention.

One embodiment of a separator for increasing capture of solids is best described by reference to Figs 1 and 2.

The vortex settlement chamber (1) is a conically bottomed tank. The water to be treated enters chamber (1) tangentially through pipe (2) creating a liquid spiral.

The rotational flow causes heavy particulate materials to move outward toward the conical w a II s (3). S p i r a 1 f 10 w moves downward at the outer wall and upward near the centre. Captured solids are moved downward to the apex of the cone, whilst cleaned water flows in the upward spiral (4) towards the outlet pipe (5). Captured solids accumulate in the apex of the cone from where they can be removed continuously or intermittently via pipe (6) either by gravity or with the assistance of a pump. Intermittent removal will cause consolidation of the captured solids thereby reducing the quantity of liquor for disposal.

However the frequency of removal should not be so long as to allow substantial accumulation of solids in the cone apex, otherwise there will occur re-entrainment of solids in the effluent spiral causing a reduction in solids removal efficiency.

Situated above the vortex chamber (1) at a sufficient height so as not to impair the vortex spiral, is a flocculating zone (7).

Certain types of solids are amenable to flocculation This process causes agglomeration of discrete particles into larger particles, which improves the efficiency of any subsequent solids removal process, for example, mechanical filtration. Flocculation processes may be divided into three categories : 1 Chemical Flocculation achieved by adding certain chemicals (Coagulants).

2 Physical Flocculation achieved by physically encouraging particle-to-particle contact.

3 Biological Flocculation - a phenomenon exhibited by a wide variety of organisms in the presence of a sufficient concentration of solids.

This invention employs the physical and biological flocculation mechanisms.

The media used in the flocculation zone may be provided by a variety of physical forms but essentially consists of a loose or geometrically formed matrix of inert material arranged to create converging and diverging flow patterns which will have the effect of encouraging particle-to-particle contact and then entraining the agglomerated particles so produced within the matrix of the media. One such media was included in my UK patent application number 8718479 (Strand Flocculator). Another suitable flocculating medium is brushes illustrated by Fig 3. These could be formed from filaments of any natural or synthetic fibre or alternatively be made by crimping sheet material onto a central longitudinal rod. (Fig 4).

Fig 5 illustrates an embodiment of the invention using brushes.

Effluent containing residual solids passes from the vortex chamber (1) into the brush flocculating chamber (7).

The brushes (8) may be suspended vertically from rods (9) to hang in chamber (7). A sufficient density of brushes is provided to ensure that all the flow must pass through the brushes matrix, causing eddy formation, particle-toparticle contact and flocculation solids then being entrained within the brush matrix.

It is inevitable in any system treating an organic or inorganic effluent that some degree of biological flocculation and biological purification of the waste will occur on the flocculating media. In the treatment of fish tank waste this will achieve a reduction in the biochemical oxygen demand and in the ammonia, nitrite levels in the water.

This aspect can be enhanced by using high specific surface medias in the flocculating section (7) such as open cell foam sheets, strands or particles; random-pack or geometrically formed high voidage ( > 60X) plastic packings, open fibre matting, sea shells and other high voidage medias.

Furthermore additional removal of solids can be achieved by causing the effluent from the flocculating/biological treatment section (7) to be drawn by gravity or by pumping through a mechanical filtration medium. For example cartridges or sheets made from opencell foam or open fibres matting. An embodiment of this concept is illustrated in Figs 6 and 7 where bed (7) consists of randomly placed plastic media of normal size 2Omm diameter x 2Omm long supported on a grid (10).- Water passing thro-ugh this bed is drawn by pump (11) through an assembly of open-cell foam cartridges (12) prior to return of the flow to the fish tank. With this arrangement it is possible to use this same pump (11) also for periodically sucking the solids accumulated in the apex of the vortex chamber and discharging these solids to waste as shown by pipe line branches (13) to (14).

Claims

1 A method of purifying water for ponds or tanks containing fish comprising subjecting the water to the action of a spiral, vortex or hydroclone separator, characterised by the further step of subjecting the water to the action of means for effecting physical flocculation of particulate matter by promoting particle-to-particle contact.

2 A method according to claim 1 characterised in that said water is caused in said further step to move in converging and diverging flow patterns to promote said particle-to-particle contact.

3 A method according to claim 1 or claim 2 characterised in that said further step is effected in a region of the same tank or chamber in which said spiral separation is effected, said further step being carried out above the region in which said spiral step is effected.

4 A method of purifying water from ponds or fish tanks containing fish substantially as described herein with reference to the accompanying drawings.

5 Apparatus for purifying water for ponds or tanks containing fish comprising means for effecting spiral or vortex or hydroclone separation, characterised by the provision of means for effecting physical flocculation of particlate matter by promoting particle-to-particle contact

6 Apparatus according to claims 5 characterised in that said means for effecting physical flocculation comprises means for create converging and diverging water flow patterns.

7 Apparatus according to claim 5 or claim 6 characterised in that said means for effecting physical flocculation comprises a loose or geometrically formed matrix of inert material.

8 Apparatus according to claim 7 characterised in that said means for effecting physical flocculation comprises filaments or strands.

9 Apparatus according to claim 8 characterised in that said means for promoting physical flocculation comprises brushes.

10 Apparatus for use in the purification of water for ponds or tanks containing fish substantially as described herein with reference to and as shown in the accompanying drawings.

11 A method of purifying water comprising subjecting the water to spiral or vortex or hydroclone separation, characterised by the further step of subjecting the water to means for promoting physical flocculation of particulate matter by encouraging particle-to-particle contact.

12 Apparatus for purifying water comprising sprial or vortex or hydroclone separation means, characterised by the provision of means for promoting physical flocculation by encouraging particle-to-particle contact of particulate matter within the water.