AU2015282359B2 - Aeration entrainment, fractionation and mixing system and a method of using same - Google Patents

Abstract

The invention relates to a system for the aeration, fractionation and mixing of waste water containing organic material. The system includes an effluent tank with plurality of effluent conduits extending into it, wherein each conduit has an external housing, an aeration vent connected or otherwise linked to the external housing, an internal housing disposed within the external housing, and an outlet, wherein the outlet has adjacent first, second, and third sections. The internal housing terminates proximate the first section of the outlet while its second section is of reduced cross sectional area relative to the first section, and the third section has an increased cross sectional area relative to the second section. Although not limited to this use, the system has particular application for aeration of dairy effluent storage tanks to help minimise odour. 29 u '-I im WL H3 D fN La C3H U-Q CoD r3 U 1/6

Description

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AERATION ENTRAINMENT, FRACTIONATION AND MIXING SYSTEM AND A METHOD OF USING SAME TECHNICAL FIELD

The invention relates to a system for the aeration, fractionation and mixing of waste water

containing organic material. Although not limited to this use, the invention has particular

application for aeration of dairy effluent storage tanks to help minimise odour.

BACKGROUND ART

It is common practice on many dairy farms to collect effluent from dairy sheds for the purpose of

redistributing it on pasture as a fertiliser to encourage plant growth. This effluent, which consists

primarily of animal faeces and urine together with wash down water from the dairy shed, is usually

stored in large effluent tanks or ponds before it is redistributed.

As will be appreciated, dairy effluent will contain a large amount of bacteria of varying types. While

in storage these bacteria, and other microorganisms, will begin to break down and consume the

organic elements of the effluent.

Dairy effluent has particularly high Biochemical Oxygen Demand (BOD); this means that aerated

bacteria requires a large supply of dissolved oxygen to digest the organic material of the effluent.

However, this is not an issue for bacteria which is anoxic or anaerobic, which require little or no

oxygen.

A major issue with effluent tanks and ponds on dairy farms is the odour that is generated by anoxic

or anaerobic bacterial action. These odours are gases produced as a bi-product of the digestion

process by which the bacteria consume the organic compounds within the effluent and can be

quite unpleasant for nearby residents. Examples of these smelly gases include hydrogen sulphides and acids such as butyric or lactic acids. [he problem worsens when the ettluent is particularly turbid with high amounts of suspended solids present.

This odour problem becomes even more problematic in warmer weather as heat reduces the

available oxygen. As oxygen levels within the effluent become depleted, an effluent tank can

quickly become a largely anoxic or anaerobic environment, promoting growth and reproduction of

bacteria that prefer these conditions. Consequently, this can result in an increase in emissions of

odorous gases.

It will then be appreciated that an aerobic environment is preferred for effluent tanks and ponds to

encourage the growth and proliferation of aerobic or facultative bacteria (the latter type can live in

both aerobic and anaerobic environments) that prefer these conditions, thereby reducing the

potential for the stored effluent to give off offensive odours. Reducing the turbidity of the effluent

is also helpful in creating an environment favourable to aerobic or facultative bacteria.

At present, arrangements to help achieve this include the use of stirring or agitation apparatus to

mix and turn over the contents of the effluent tank or pond. Such apparatus are well known in the

art and helps to mix the effluent and introduce oxygen. Examples of such apparatus are

manufactured and/or distributed by the likes of Nevada (www.nevadanz.co.nz) and Midwest

Machinery (www.midwestmachinery.co.nz).

These devices are intended to promote an increase in the presence of aerated bacteria which not

only digests the organic material of the effluent, but also other bacteria thus contributing to a

relative aerobic environment. This also results in less odours being generated by the effluent.

However, these stirring or agitation apparatus have their problems. They employ moving and

rotating parts which can be dangerous should a user fall into the tank. Pontoon-type stirrers,

which float in the centre of the effluent tank, also require cabling and/or wires which may be an electrical hazard.

The action of these devices tend to be confined to the upper depths of the effluent tanks, leaving

the lower depths, closer to the base of the tank, relatively untouched. Often organic material in

these lower levels will settle out as sediment at the base of the tank and become highly anaerobic.

Furthermore, stirring alone does not always help in the reduction of odorous gases. Often, an

outcome of the stirring or agitation action is that it simply introduces new food for the anoxic or

anaerobic bacteria already present in the effluent. The oxygen introduced is insufficient to foster

significant development and growth of the desirable, aerobic, bacteria. This is particularly the case

in the extremely oxygen depleted waste water found in the lower parts of the effluent tank.

Consequently, a stirring or agitation system does not always result in a significant reduction in the

presence of foul smelling odours from stored effluent.

When applied to pasture, the soil quality can be affected with high amounts of nitrogen, sodium

and phosphorous present. The loading of the soil with the effluent can mean that there is a greater

likelihood of it leaching into waterways as surface runoff, with a detrimental effect on water

quality.

All references, including any patents or patent applications cited in this specification are hereby

incorporated by reference. No admission is made that any reference constitutes prior art. The

discussion of the references states what their authors assert, and the applicants reserve the right

to challenge the accuracy and pertinency of the cited documents. It will be clearly understood

that, although a number of prior art publications may be referred to herein, this reference does not

constitute an admission that any such documents form part of the common general knowledge in

the art, in New Zealand or in any other country.

Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising", and the like, are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense, that is to say, in the sense of "including, but not limited to".

It is an object of the present invention to address the foregoing problems or at least to provide the

public with a useful choice.

Further aspects and advantages of the present invention will become apparent from the ensuing

description which is given by way of example only.

DISCLOSURE OF THE INVENTION

According to one aspect of the present invention there is provided an aeration, fractionation and

mixing system for an effluent tank, wherein the system includes:

a plurality of effluent conduits into the tank, wherein each conduit includes:

an external housing;

an aeration vent connected or otherwise linked to the external housing;

an internal housing disposed within the external housing, and

an outlet, wherein the outlet has adjacent first, second, and third sections;

characterised in that

the internal housing terminates proximate the first section of the outlet, and wherein the second

section is of reduced cross sectional area relative to the first section, and the third section has an

increased cross sectional area relative to the second section.

According to another aspect of the present invention there is provided a kitset for an aeration,

fractionation and mixing system for an effluent tank, wherein the system includes:

a tank to contain effluent; a plurality o ettluent conduits into the tank, wherein each conduit includes: an external housing; an aeration vent connected or otherwise linked to the external housing; an internal housing disposed within the external housing, and an outlet, wherein the outlet has adjacent first, second, and third sections; characterised in that the internal housing terminates proximate the first section of the outlet, and wherein the second section is of reduced cross sectional area relative to the first section, and the third section has an increased cross sectional area relative to the second section.

According to yet another aspect of the invention, there is provided an effluent conduit for an

aeration, fractionation and mixing system for an effluent tank, the effluent conduit including:

an external housing;

an aeration vent connected or otherwise linked to the external housing;

an internal housing disposed within the external housing, and

an outlet, wherein the outlet has adjacent first, second, and third sections;

characterised in that

the internal housing terminates proximate the first section of the outlet, and wherein the second

section is of reduced cross sectional area relative to the first section, and the third section has an

increased cross sectional area relative to the second section.

The invention provides a fractionation, mixing and aeration system (and apparatus) which introduces and entrains oxygen into ettluent and mixes it in order to help create an aerobic environment which is detrimental to the growth and development of any anoxic or anaerobic bacteria which may be present. This consequently reduces the odour that may be generated by the effluent as it is broken down by aerobic bacteria.

The invention also helps breakdown suspended solids by creating a cavitation effect that

fractionates its organic matter content as the effluent/oxygen mixture is passed through the

system (fractionation should be understood to mean the separation of the organic matter into

smaller components). This breakdown of the organic matter content of the suspended solids

present in effluent helps to reduce its turbidity and is also more favourable to facilitating an

aerobic environment. It also exposes more surface area of the solid to bacterial action and

increases oxygen uptake.

Reference shall now be made throughout the remainder of the specification to the effluent being

mixed and fractionated as being derived from dairy farms, and in particular, from milking sheds of

said dairy farms.

However, it is possible that the invention may have applications to other industries in which waste

water contains a high amount of organic matter. For example, the invention may be used with

waste waters from attaboirs, vineyards and piggeries or even domestic housing which does not

have access to municipal waste water treatment plants.

An effluent tank should be understood to be a large vessel into which effluent is introduced and

stored for later redistribution according to the requirements of the user. The tank may also need

to comply with any local or national guidelines, standards and/or practices.

The effluent tank may be an in-ground tank which, to reduce risk of leakage, may be lined or

unlined, depending on the material from which it is constructed. In its crudest form, the effluent tank may simply be a hole in the ground with a lining ot a suitable material, such as plastics material to prevent leaching of effluent into the substrate. Effectively, this is an effluent pond.

In preferred embodiments, the effluent tank is an above-ground tank with a lining. The applicant

produces a range ofsuch tanks.

In preferred embodiments of the invention, the effluent tank is fabricated from plastics material,

such as high density polyethylene (HDPE) although this is not meant to be limiting, and designed

such that in use it is situated above ground (or it may be in ground, depending on the requirements

of the user). There may also be additional reinforcing components such as stainless steel or

aluminium to support the walls and be part of the panels of the tank. An example of an effluent

tank that may be adapted for use in the present invention is described in New Zealand Patent No.

560570.

However, this is not meant to be limiting and in some embodiments, the effluent tank may be

formed from cementitious material or the like.

The present invention may be used with effluent tanks of a variety of sizes although it is envisaged

that the larger the tank, the greater the number of effluent conduits that will be required.

A typical effluent tank is generally circular in plan view but this is not meant to be limiting. Some

tanks may be substantially square or rectangular. However, the applicant does prefer a

substantially circular tank for reasons that will be apparent from the ensuing discussion.

The tank should be understood to have a base having a perimeter and in its circular form, a

continuous wall running the perimeter of the base. In tanks having defined sides, each side will

have a wall.

The effluent tank should be understood to include a plurality of effluent conduits by which the

effluent is introduced into the tank. These effluent conduits are linked directly or indirectly to a supply o ettluent by an external pump or the like to provide the necessary pressure to deliver the effluent from its source, which in preferred embodiments is the milking shed of the farm on which the invention is to be used, to the effluent tank. It will be appreciated that this means no wires or cables need to enter the effluent tank itself thereby eliminating a potential electrical hazard.

The effluent conduit should be understood to be a substantially pipe-like structure, which in

preferred embodiments of the invention passes through the walls of the effluent tank. Persons

skilled in the art will appreciate that washers and the like may be required to help seal the passage

of the effluent outlet where it passes through the walls of the effluent tank.

However, in some embodiments of the invention, the conduit may enter over the walls of the tank.

It will be appreciated that this means that the effluent conduit may include bends to get around

the corners where the walls meet the bottom of the tank. This may be particularly useful in

situations where the effluent conduit is being retrofitted to existing effluent ponds or concrete

tanks.

In use, at least a portion of the effluent conduit, including the outlet, runs substantially horizontally

along or proximate the bottom of the effluent tank. It is preferable to have the outlet close to the

bottom of the tank so that as effluent is discharged, the resulting turbulence helps keeps the

organic material within the effluent suspended as much as possible.

It will be appreciated that the size of the tank may determine the length of the portion of the

effluent conduit that is in the tank itself. As will be apparent from the following discussion on how

the invention works, the length of the effluent conduit has to be sufficient that it extends a

reasonable distance either towards the centre of the tank (or at an angle) in order to achieve the

desired effect.

Reference shall now be made to the effluent conduit being a pipe.

Ihe relative dimensions at the pipe, and indeed the ettluent conduit and its outlet, will ultimately

depend on the requirements of the user, the size of the tank, and the volume of effluent, and this

will be apparent to a person skilled in the art.

In preferred embodiments of the invention, the pipe is made of plastics material such as polyvinyl

chloride (PVC), High Density Polyethylene (HDPE), stainless steel or other suitably robust materials

readily apparent to a person skilled in the art. As parts of the invention may be exposed to sunlight

to extended periods of time, the pipe may be UV resistant for sake of longevity. Alternatively, the

pipe may be formed from a metal such as stainless steel.

The effluent conduit includes an outlet through which effluent is allowed to exit the pipe and into

the tank. The pipe may be relatively elongate, and thus the outlet is directed towards the centre or

middle of the effluent tank. However, if the pipe is at an angle relative to the centre of the tank, it

may be possible that it may be shorter. Ultimately, the length is dependent on the desired

performance requirements.

However, in some embodiments of the invention, the pipe may extend into the effluent tank

somewhat on an angle or tangent and thus the outlet is offset from the centre or middle of the

tank. The size of the tank may have a bearing on the extent of the angle; the larger the tank, the

more likely the pipe may be on an angle as this helps with mixing.

It will be appreciated that the effluent conduit has an upstream end and a downstream end; the

effluent and oxygen flows from the upstream end, where the conduit enters the effluent tank

through its walls or over the sides, to the downstream end where the effluent is discharged via the

outlet.

It should be appreciated that the walls of the pipe is the external housing of the effluent conduit.

The pipe also includes an internal housing, which in its simplest form is simply a pipe of a smaller diameter than the external housing. Essentially, the ettluent conduit has two pipes, one (the internal housing) disposed within the other (the external housing).

Preferably, the effluent is passed through this internal housing while oxygen is passed in the space

between the internal and external housings. It will be created that a suction or vacuum effect is

created as effluent is discharged from the internal housing thereby drawing oxygen into the

external housing and entraining it with the effluent.

In preferred embodiments, the internal housing is connected to the supply of effluent. It will be

appreciated that this means in these embodiments, the internal housing passes through the walls

of the effluent tank.

However, this arrangement may be reversed in some embodiments and oxygen is allowed to pass

through the internal housing with effluent being passed exterior of it. However, this may be more

complicated to manufacture.

It should be noted that the invention does not require cabling or wires into the effluent tank itself

in order for it to be used. This is in contrast with conventional stirrers which do require an external

source of power into the effluent tank in order to work.

In preferred embodiments of the invention, the pipe forming the internal housing is made of a

metal such stainless steel pipe. However, it is possible that plastics material such as PVC, HDPE, or

other materials readily apparent to a person skilled in the art may be used to form the internal

housing.

The effluent conduit also includes an aeration vent. It will be understood that the aeration vent

provides a route for environmental oxygen to enter the effluent conduit and eventually become

entrained and mixed with the effluent being discharged into the effluent tank. As discussed above,

as effluent is discharged from the internal effect a suction effect is created and this draws environmental oxygen into the ettluent conduit.

The aeration vent is an elongate hollow structure such as a rigid or flexible pipe or hose which, in

use, extends vertically upwards from the effluent conduit. In preferred embodiments, the aeration

vent is formed from plastics material such as PVC or HDPE.

The aeration vent has two ends; the first end (the bottom end) is connected to the effluent

conduit. This may be achieved using a hub-like structure to ensure adequate sealing between the

join of the effluent conduit and the aeration vent. Persons skilled in the art will readily appreciate

other ways by which the aeration vent may be connected to the effluent conduit.

The other (or top) end of the aeration vent is open to allow environmental oxygen to be drawn in.

However, in preferred embodiments of the invention, it may include an open frame work or mesh

structure to act as a guard and prevent large airbourne debris and detritus entering the aeration

vent.

The length of the aeration vent will depend on the dimensions of the tank but persons skilled in the

art will appreciate that in use, the aeration vent must extend higher than the depth of the stored

effluent when the effluent tank is at capacity storage. Otherwise effluent may enter the aeration

vent.

Preferably, the aeration vent extends higher than the walls of the effluent tank but it may also be

substantially at the same height as the walls of the tank (or even below if the tank has emergency

drainage outflows near the top of the walls such that effluent levels cannot reach the top edge of

the walls).

In some embodiments, the aeration vent may even be configured to pass through a sealed opening

in the walls near the top of the tank. Therefore, in these embodiments, the top end of the aeration

vent opens externally of the wall. The advantage of this is that the entire tank may then be covered it desired. It can also mean that environmental oxygen can still be drawn in even it the ettluent reaches a height that covers the portion of the aeration vent that is within the effluent tank.

Effectively, the aeration vent needs to be ducted into the effluent conduit such that air can flow

from the open end into the space between the external and internal housings.

As will be appreciated from the preceding discussion, the effluent conduit has an upstream end,

which is proximate the walls of the effluent tank.

In preferred embodiments of the invention, the aeration vent is connected to the effluent conduit

proximate the walls of the effluent tank. This is so that the aeration vent, which may be relatively

elongate depending on the depth of the effluent tank, can be provided with some external support,

such as brackets or the like, that is mounted to the walls. However, this is not meant to be limiting

and the aeration vent may be positioned further downstream along the effluent conduit, closer to

the centre of the effluent tank.

However, it must be connected to the effluent conduit upstream of, or at least proximate to, the

open end of the internal housing.

The pipe (the external housing) includes an outlet. The outlet may be continuous with the pipe or

alternatively may be a separate component which is mounted to the open end of the pipe using

complementary screw threads or adhesives or the like.

The outlet has an opening which effectively is the downstream or open end of the effluent conduit

in use.

The outlet should be understood to include at least three distinct sections of differing cross

sectional areas. The aspect ratios, that is to the say the length and/or diameter of each distinct

section relative to adjacent or other sections of the effluent conduit, are important to the

functioning of the invention. The relative dimensions of each section will ultimately depend on the requirements at the user, the volume o ettluent, and pressure delivery. Persons skilled in the art will readily appreciate that the respective sections of the outlet may be up-scaled ordownsized as appropriate.

These distinct sections, adjacent or otherwise continuous with each other, are important in helping

with the entrainment of oxygen within the effluent being discharged into the effluent tank. The

configuration of the outlet is also important in creating a cavitation effect that acts to break down

and fractionate suspended solids, thereby helping to reduce the turbidity of the effluent.

In some respects, the first and third sections of the outlet may be thought of as a compression

chamber and expansion chamber respectively.

The first section of the outlet is its upstream end; the third section is its downstream or open end.

It should be understood that the first and third sections are tapered along their respective lengths,

i.e. their cross-sectional area decreases/increases along their length.

The first section tapers to a reduced diameter relative to the pipe. It should be appreciated that

the internal housing terminates within this first section of the outlet, i.e. the internal housing

opens within the first section. It will be understood that this means that the external housing

extends further downstream relative to the internal housing.

Ideally, the opening of the internal housing is closer to the upstream end of the first section rather

than the downstream end. This gives some time for the effluent and oxygen to become

pressurised as the first section tapers towards its downstream end.

Thus, in preferred embodiments of the invention, the first section of the outlet is where oxygen

introduced via the aeration vent passes through the space between the pipe and the internal

housing meets the effluent exiting the internal housing.

The gradual reduction in diameter of the first section of the outlet causes an acceleration and subsequent increase in pressure o ettluent and oxygen passes downstream though this section towards the opening of the outlet. Effectively, the effluent/oxygen mixture becomes compressed or pressurised.

In preferred embodiments of the present invention, the angle of the taper of the first section of

the outlet is consistent along its length. However, this is not strictly necessary and the degree of

tapering may change along the length of the first section. For example, the degree of tapering at

the upstream end of the first section may be relatively minimal initially but drastically increases as

it approaches the downstream end of the first section. This may have the effect of a more rapid

acceleration of the effluent/oxygen mixture.

The second section of the outlet has a substantially consistent diameter along its length. Persons

skilled in the art will appreciate that strict compliance with a constant diameter is not essential and

that there may be some slight variance in the diameter of the second section along its length.

This section provides a short time period in which the oxygen becomes entrained within the

effluent as the mixture flows downstream towards the opening of the outlet. The longer the

length of the second section, the more entrained the oxygen becomes.

The third section expands from a cross-sectional area which is, at the upstream end that is adjacent

or otherwise continuous with the second section, the same as that of the section to a larger cross

sectional area at its downstream end.

The transition from a relatively small cross-sectional area to a larger one has the effect of reducing

the pressure of the flow of effluent and entrained oxygen passing through the outlet as it flows

towards the opening. This allows the effluent/oxygen mixture to effectively expand.

This reduces the pressure of the effluent/oxygen mixture, creating a cavitation effect as the

entrained oxygen bubbles implode. This implosive or blasting force helps to break up and tractionate suspended solids present in the ettluent. In some embodiments ot the invention, the downstream end of the third section of the outlet includes the open end of the outlet.

However, in particularly preferred embodiments of the invention, the outlet may include a fourth

section adjacent to the third section.

This fourth section includes the opening of the outlet. Like the third section, it expands from a

relatively small cross-sectional area, corresponding to the diameter of the downstream end of the

third section of the outlet, to a larger cross-sectional area. This further reduces the pressure and

assists the cavitation achieved resulting in more fully aerated effluent entering the effluent tank

and improved efficacy in breaking up suspended solids.

In preferred embodiments of the present invention, the angle to which the third and, if present,

fourth sections of the outlet expand is consistent along their lengths. However, this is not strictly

necessary and the degree of expansion may change along the length of the third (and/or fourth)

section. For example, the degree of expansion at the upstream end of the third section may be

relatively minimal initially but drastically increases as it approaches the downstream end of the

third section. This may have the effect of a more rapid decrease in the pressure of the

effluent/oxygen mixture by the time it reaches the downstream end of this section of the outlet.

It will be appreciated by persons skilled in the art that relative dimensions and cross-sectional areas

of the first, second, third and, if present, fourth section, of the outlet will vary according to the

requirements of the user, the desired throughput of effluent into the effluent tank, and the degree

to which the oxygen is to be entrained within the effluent.

For a high degree of entrainment, certain or all sections of the outlet may be relatively elongate. If

minimal entrainment is preferred, the outlet and its respective sections could be smaller in length.

However, it will be appreciated that the basic concept of accelerating the effluent/oxygen mixture and then decreasing pressure and causing a blasting ettect to help break up and tractionate suspended solids as achieved by the at least three distinct sections of the outlet will be unchanged.

The effluent tank should be understood to include a plurality of effluent conduits and associated

outlets.

In preferred embodiments, the effluent tank includes at least three, and preferably four, effluent

conduits extending towards the centre of the tank and spaced equidistance around its perimeter.

This should be understood to mean that the four effluent conduits of the preferred embodiments

all extend substantially towards the centre of the tank although, as noted above, in some

embodiments the effluent conduits may be at a tangent to the centre. Thus, the effluent/oxygen

mixture is discharged substantially tangentially to the centre of the tank from each effluent inlet,

the flow further increasing the aeration and stirring effect achieved with the invention.

This can create a current within the effluent tank, particularly if is circular. This current can help

keep the organic material suspended and minimises it settling out, hence the applicant's

preference for a circular effluent tank.

However, this is not meant to be limiting and more (or less) effluent conduits may be present and

be orientated at a range of angles relative to the centre of the tank. It will be appreciated that the

effluent conduits may include a jointing or connection system that allows its orientation to be

adjusted according to the preferences of the user.

One suitable location for the jointing system may be the intersection of the aeration vent with the

effluent conduit although this is not meant to be limiting.

Good results have been observed in trials. For example, when the invention was used in an

effluent tank having a diameter of approximately 38 metres, a depth of 0.9 metres, and containing

1,200,000 litres of dairy effluent, dissolved oxygen levels were notably improved after 65 minutes.

Measurements ot dissolved oxygen were taken at three sample points spaced equidistance about

the circumference of the tank at the start of the trials and again after 30 minutes, 35 minutes, and

65 minutes. This data is tabulated in table 1 below.

Sample site Depth below Start DO (mg/L) 30 minutes DO 35 minutes DO 65 minutes DO

surface (mm) (mg/L) (mg/L) (mg/L

1 200 0.01 0.46 0.40 1.00

2 200 0.02 0.21 0.30 0.60

3 200 0.20 0.50 0.40 0.55

Average (mg/L) 0.08 0.39 0.37 0.72

Table 1: Dissolved Oxygen (DO)

It will be seen that there was a significant increase in levels of dissolved oxygen by the end of the

trial. A small decrease between 30 minutes and 35 minutes was put down to consumption of the

dissolved oxygen during the period that the pump motor was shut off (at the 30 minute mark in

order to take the readings).

Pump energy outputs of the invention are favourably comparable to that achieved by paddle

aerators, which are generally considered to supply 0.4 to 0.8 kilograms of oxygen per kilowatt

(calculated by measuring difference between start and end DO, multiplying by volume of effluent

to give a total of oxygen in milligrams/litre (mg/L) injected. When this value is divided by the pump

kilowatt this gives a pump energy value). The invention achieved 0.9 kilograms of oxygen per

kilowatt but without the attendant risks of rotating parts and electrical hazards.

Furthermore, turbidity was considered to be uniform across the tank. It was also noted that after

running the invention for 30 minutes, a blanket of sludge that was previously present in the bottom o the tank was no longer detectable. I his sludge was now in suspension, thereby contributing to a reversal in turbidity profile.

Further advantages become apparent when the effluent is applied to pasture.

Firstly, the aeration treatment applied to the raw dairy shed effluent with the present invention

means that the available organic matter, total carbon and the carbon to nitrogen ratio are all

higher. There is improved cation exchange potential and nutrient availability to support herbage

(grass) growth.

The soil itself is potentially improved following application of treated effluent; there is lower

nitrogen and phosphorous which reduces the load the soil has to absorb thereby reducing the risk

of leaching into waterways. There is also a reduced need for lime to buffer the pH of the soil and as

a consequence herbage mineral content may be better balanced.

The present invention has a number of advantages including:

• a reduction in the odour caused by the presents of anoxic and anaerobic bacteria;

• acts as an aeration as well as a stirrer system;

• acts to help in the breakup and fractionation of suspended solids, thereby reducing

turbidity and improving oxygen uptake;

• does not require any fans, blades or other rotating parts to stir the effluent;

• does not require a power supply into the effluent tank;

• reduces the adverse effects of the effluent when it is applied to pasture and soil as an

organic fertiliser; or

* at the very least offers the public a useful choice.

Ihe invention may also be said broadly to consist in the parts, elements and teatures referred to or

indicated in the specification of the application, individually or collectively, in any or all

combinations of two or more of said parts, elements or features.

Where in the foregoing description reference has been made to integers or components having

known equivalents thereof, those integers are herein incorporated as if individually set forth.

It should be noted that various changes and modifications to the presently preferred embodiments

described herein will be apparent to those skilled in the art. Such changes and modifications may

be made without departing from the spirit and scope of the invention and without diminishing its

attendant advantages. It is therefore intended that such changes and modifications be included

within the present invention.

BRIEF DESCRIPTION OF DRAWINGS

Further aspects of the present invention will become apparent from the following description

which is given by way of example only and with reference to the accompanying drawings in which:

Figures la, 1b, and Ic are perspective views of an exemplary embodiment of the invention

including an effluent tank with effluent conduits;

Figures 2a and 2b are perspective views of a second exemplary embodiment of the invention

including an effluent tank with effluent conduits;

Figure 3 is a perspective view of a third exemplary embodiment of the invention including

an effluent tank with effluent conduits;

Figures 4a and 4b are perspective and side cross-sectional views of part of the effluent

conduit, including its outlet, of the embodiment of Figures 2a and 2b; and

Figure 5 is a cross-sectional view of the effluent conduit of an exemplary embodiment of the invention, including its outlet with representations ot ettluent and oxygen tlow.

DETAILED DESCRIPTION OF THE INVENTION

In an exemplary embodiment illustrated in Figures la, 1b, and 1c, the invention (generally

indicated by arrow 100) includes an effluent tank (101), and three effluent conduits (102) which

enter the tank through suitably configured sealed openings (103) in the sides of the tank. Figures

la and lb shows the external arrangement in which pipes (105) are connected to the effluent

conduit (102) and pass through the tank (101).

Each effluent conduit includes an aeration vent (104); this is simply a pipe extending vertically from

the effluent conduit (102) and, as shown in Figure 1c, is positioned such that it opens at its upper

end (104a) at a height which is higher than the tank (101).

Effluent (not shown) is provided to the effluent conduits (102) via pipes (105) and discharged into

the tank via outlets (106).

It will be noted that in this embodiment, the centre (107) of the tank (101) is configured with a

drainage pipe (108) to allow it to be emptied if desired. However, this is not an essential part of the

invention (100).

An alternative embodiment of the invention (200) is depicted in Figures 2a and 2b. As with the

previous embodiment, it includes an effluent tank (201) and effluent conduits (202).

However, as shown in Figure 2b, a detail view, the effluent conduits enter over the top of the walls

(201a) of the tank. The effluent conduit includes an upright component (202a) running up the wall

of the tank (201). It will also be noted that the aeration vent (204) includes a bracket (204b) for

external support.

An alternative arrangement aeration vent (205) is shown in Figure 2c. In this figure, the ettluent

conduit (202) is as previously depicted but the aeration vent is in the form of a flexible hose. The

lower end (205a) is connected to a hub (206) on the effluent conduit while the upper end (205b) is

connected to an opening (not visible) in below the top of the wall (201a) of the tank (201). This is

more practical for use with tanks having a floating roof or cover (207).

Returning now to Figure 2a, it will be seen that the effluent conduits (202) are spaced substantially

equidistance around the interior perimeter of the effluent tank (201).

Each effluent conduit (202) includes an outlet (208), which extends substantially towards the

centre (209) of the tank such that the effluent (not shown) emitted by the outlets is in the path of

the effluent discharge from the other outlets.

This helps to maximise turbulence in this area of the effluent tank (201) and creates a stirring

effect, keeping the contents of the tank in relatively constant motion.

A further embodiment of the invention (300) is illustrated in Figure 3. As with the embodiments

previously described it includes a tank (301) and effluent conduits (302). However, in this

arrangement the effluent conduits, which come over the top of the wall (301a) of the tank in a

manner similar to the embodiment of Figures 2a and 2b, are arranged such that their respective

outlets (303) are at a tangent relative to the centre (306) of the tank.

The connection between the aeration vent (307) and effluent conduits (302) may be configured to

allow the effluent conduit to be pivoted or other ways moved towards or away from the centre

(306) of the tank (301) according to the preference of the user.

Turning now to Figures 4a and 4b, a perspective cross-sectional and side cross-sectional view

respectively of the effluent conduit (202) of Figure 2a, and its associated outlet (205), are shown.

It will be seen that the ettluent conduit (202) consists ot two pipes, an outer pipe (202b), which

carries the oxygen (not shown) to be introduced and entrained into the effluent (not shown) going

into the tank (not shown), and an inner pipe (202c), through which effluent is discharged into the

tank. The oxygen is carried in the space (401) between the inner and outer pipes.

It will be seen that the outlet (205) is divided substantially into four distinct sections (205a, 205b,

205c and 205d), each with its own specific aspect ratio which may be determined by its relative

diameters and/or lengths.

The first section (205a), one end of which is proximate the outlet (206) of the inner pipe (202b)

carrying the oxygen (not shown), tapers from a large cross-sectional area to a smaller cross-section

area as it progresses towards the opening (207) of the outlet (205). This has the effect of increasing

fluid pressure and velocity, beginning an initial cavitation effect, as the effluent passes through this

portion of the outlet and is mixed with oxygen bubbles that begin to implode with the increase in

pressure and velocity. This process may be aided by a gentle reduction in cross-sectional area of

the outlet of the inner pipe.

The second section (205b) of the outlet (205) is of a constant cross-sectional area along its length.

This provides an opportunity for the oxygen (not shown) flowing through the exterior housing

(202a) to become entrained with the effluent (not shown) exiting the internal housing (202b) and

implode, continuing the cavitation effect that begun in the previous section

The third section (205c) of the outlet (205) which, at its upstream end has a cross-sectional area

the same as that of the second section (205b), expands towards a larger cross-sectional area. This

reduces the pressure of the effluent (not shown) passing through this portion of the outlet and

consequently more of the air bubbles (not shown) that has been entrained within the flow of

effluent implode.

Ihis process cavitates, blasts and tractionates the organic matter present in the ettluent and mixes

the oxygen into the effluent. Collectively, these two sections (205b and 205c) can be thought of as

a blasting and/or fractionation zone.

The cavitation effect is further enhanced due to the relatively large fourth section (205d) of the

outlet (205) which includes the opening (207) from which the effluent/oxygen mixture (not shown)

enters the tank (not shown).

The flow of the effluent and oxygen can be better appreciated in Figure 5. In this figure, the

effluent is depicted by blue bubbles, passing through the internal housing (202c) while the oxygen

is depicted by the bubbles with an X.

It will be seen that the oxygen flows in the space (401) between the external (202b) and internal

housings (202c) and begins mixing with the effluent as it exits the opening (206) of the internal

housing. This implodes and fractionates some effluent (brown bubbles with irregular outline).

The first section (205a) of the outlet (205) is tapered to pressurise the effluent and oxygen, as will

be appreciated from the relatively congested passage, which becomes entrained in the second

section (205b). The expansion of the third and fourth sections (205c, 205d respectively) causes a

decrease in pressure and results in some oxygen bubbles imploding (brown bubbles) as they exit

the fourth section. This contributes to a cavitation effect that helps the break up and fractionation

of any suspended solids within the effluent.

Aspects of the present invention have been described by way of example only and it should be

appreciated that modifications and additions may be made thereto without departing from the

scope of the appended claims thereof.

WHAT WE CLAIM IS:

1. An aeration and fractionation mixing system for an effluent tank, wherein the system

includes:

a plurality of effluent conduits for the tank, wherein each conduit includes:

an external housing;

an aeration vent connected or otherwise linked to the external housing;

an internal housing disposed within the external housing, and

an outlet for the external housing, wherein the outlet has adjacent first, second, and third

sections;

characterised in that

the internal housing terminates in the first section of the outlet, proximate the upstream

end of the first section, and wherein the second section is of reduced cross sectional area

relative to the first section, and the third section has an increased cross sectional area

relative to the second section,

wherein the first section of the outlet tapers inwardly to a reduced diameter relative to the

external housing,

and wherein the aeration vent is connected or otherwise linked to the external housing

upstream of the termination of the internal housing.

2. The system as claimed in claim 1, wherein the tank is at least partially defined by a base

and a wall.

3. The system as claimed in claim 2, wherein at least one of the effluent conduits is: a) configured to enter the tank by passing through the wall; or b) configured to enter the tank by passing over the wall.

4. The system as claimed in any one of claims 2 to 3, wherein at least a portion, including the

outlet, of one of the effluent conduits is configured to run substantially along or proximate

the base of the tank.

5. The system as claimed in any one of claims 1 to 4, wherein the internal housing is

configured to be connected to an effluent supply.

6. The system as claimed in any one of claims 1 to 5, wherein the aeration vent is an elongate

pipe extending vertically from the effluent conduit.

7. The system as claimed in any one of claims 1 to 6, wherein the outlet is an open end of the

external housing.

8. The system as claimed in any one of claims 1 to 7, wherein the angle of the taper of the

first section of the outlet is consistent along its length.

9. The system as claimed in any one of claims 1 to 8, wherein the second section of the outlet

has a substantially consistent cross-sectional area along its length.

10. The system as claimed in any one of claims 1 to 9, wherein the third section of the outlet

tapers outwardly to an enlarged diameter relative to the second section.

11. The system as claimed in claim 10, wherein the angle of the taper of the third section of

the outlet is consistent along its length.

12. The system as claimed in any one of claims 1 to 11, wherein the third section includes the

opening of the outlet.

13. The system as claimed in any one of claims 1 to 11, wherein the outlet includes a fourth

section adjacent the third section, and wherein the fourth section includes the opening of

the outlet.

14. A kitset for an aeration and fractionation mixing system for an effluent tank, wherein the

system includes:

a tank to contain effluent;

a plurality of effluent conduits into the tank, wherein each conduit includes:

an external housing;

an aeration vent connected or otherwise linked to the external housing;

an internal housing disposed within the external housing, and

an outlet, wherein the outlet has adjacent first, second, and third sections;

characterised in that

the internal housing terminates in the first section of the outlet, proximate the upstream

end of the first section, and wherein the second section is of reduced cross sectional area

relative to the first section, and the third section has an increased cross sectional area

relative to the second section,

wherein the first section of the outlet tapers inwardly to a reduced diameter relative to the

external housing,

and wherein the aeration vent is connected or otherwise linked to the external housing

upstream of the termination of the internal housing.

15. An effluent conduit for a fractionating mixing and aeration system for an effluent tank, the

Claims (1)

1. effluent conduit including:

   an external housing;

   an aeration vent connected or otherwise linked to the external housing;

   an internal housing disposed within the external housing, and

   an outlet, wherein the outlet has adjacent first, second, and third sections;

   characterised in that

   the internal housing terminates in the first section of the outlet, proximate the upstream

   end of the first section, and wherein the second section is of reduced cross sectional area

   relative to the first section, and the third section has an increased cross sectional area

   relative to the second section,

   wherein the first section of the outlet tapers inwardly to a reduced diameter relative to the

   external housing,

   and wherein the aeration vent is connected or otherwise linked to the external housing

   upstream of the termination of the internal housing.

   16. The conduit as claimed in claim 15, wherein the angle of the taper of the first section of the

   outlet is consistent along its length.

   17. The conduit as claimed in either claim 15 or claim 16, wherein the second section of the

   outlet has a substantially consistent diameter along its length.

   18. The conduit as claimed in any one of claims 15 to 17, wherein the third section of the

   outlet tapers outwardly to an enlarged diameter relative to the second section.

   19. The conduit as claimed in claim 18, wherein the angle of the taper of the third section of the outlet is consistent along its length.

   20. The conduit as claimed in any one of claims 15 to 19, wherein the third section includes the

   opening of the outlet.

   21. The conduit as claimed in any one of claims 15 to 19, wherein the outlet includes a fourth

   section adjacent the third section, and wherein the fourth section includes the opening of

   the outlet.

   FIGURE 1a

   FIGURE 1b

   1/6 FIGURE 1c

   FIGURE 2a

   FIGURE 2b

   2/6 FIGURE 2c

   FIGURE 3

   3/6

   FIGURE 4a

   4/6

   FIGURE 4b

   5/6

   FIGURE 5

   6/6