WO2005027624A1

WO2005027624A1 - Test on cleaning result

Info

Publication number: WO2005027624A1
Application number: PCT/SE2004/001332
Authority: WO
Inventors: Johan Jakobsson; Epke Bosma
Original assignee: Delaval Holding Ab
Priority date: 2003-09-19
Filing date: 2004-09-15
Publication date: 2005-03-31
Also published as: SE525860C2; SE0302342D0; SE0302342L

Abstract

The present invention comprises cleaning means for cleaning surfaces in an milking apparatus coming in contact with milk, the cleaning means uses a fluid for cleaning said surfaces. The milking apparatus comprises means for diverting at least a portion of said fluid to a measurement chamber, means for measuring a value of the chemical oxygen demand (COD) for the fluid in the measurement chamber, and means for comparing the measured value with a threshold and performing an action if the measured value is above the threshold.

Description

TEST ON CJαESHING .EESUET TECHNICAL ≤FIEIiD The present invention relates to a milking apparatus comprising means for measuring the amount of pollution in a 5 cleaning fluid used for cleaning the milking apparatus and a method therefore. More specifically the present invention relates to a milking machine comprising means for measuring a COD value of a cleaning fluid and a method therefore.

BACKGROUND OF THE INVENTION

10 Both biological and physical methods are known for measurement of RBCOD. Physical methods involving COD measurement of ⁾ membrane filtered samples have given poor correlation with biological methods.

The three main biological methods are 15 1) the short sludge age, step fed reactor, 2) the batch aerobic reactor and 3) the batch anaerobic reactor.

These are described in some detail by Dold et. al. "Comparison of Measurement Methods for Readily Biodegradable COD Fraction

..20 in Municipal Wastewater", IWPC, Durban, South Africa (1985) .

The short sludge - age step fed reactor method has been reported as not giving consistent results and as being -:^' -tedious, difficult to operate and unsuitable for the determination of in situ generated RBCOD. Furthermore, to 25 obtain an RBCOD value representative of a 24-hour period, a large refrigerated composite sample would have to be collected each day. Long periods, for example 24 hours, are required for each measurement. Although measurement times can be reduced to about two hours with a batch aerobic reactor, the sampling and 30 sample storage requirements for use of these reactors limit their applicability. The usefulness of anaerobic batch reactors is also limited by their sampling requirements. Furthermore RBCOD measurements based on limited sampling may not provide an accurate profile of the RBCOD of a waste stream because of wide variations over the diurnal cycle.

5 An alternative method for periodically determining the readily biodegradable chemical oxygen demand (RBCOD) in a wastewater stream or feed comprises: i) continuously feeding a sample representative of the •_ι real-time wastewater stream or feed to a sample-volume

10 whereby the feed rate is controlled to ensure an hydraulic retention time (HRT) in the sample volume sufficient for substantially complete oxidation of the readily biodegradable compounds, ii) periodically passing air for predetermined periods 15 through the sample volume, iii) determining the oxygen consumption in the sample volume by measuring a change in the dissolved oxygen content while not passing air through the sample volume, and iv) calculating an RBCOD value from each oxygen consumption ^•JO measurement.

The disclosure also provides an apparatus for monitoring a wastewater stream or feed comprising:

^ i) a bio-reactor suitable for maintaining a completely mixed sample volume and for continually receiving a 25 sample representative of the real-time wastewater feed, ii) air injection means which may be periodically operated to pass air for a predetermined period through a waste water sample when contained in the bio-reactor, iii) means for measuring the dissolved oxygen content of a sample within the bio-reactor to determine the oxygen consumption of the sample from which the readily biodegradable chemical oxygen demand (RBCOD) is 5 calculable.

The bio-reactor (that is, the sample volume in the method) is completely mixed and as the hydraulic retention time (HRT) is chosen to ensure the RBCOD is substantially oxidised in the reactor, then the concentration of RBCOD within the reactor at ''^•"iO any point in time will be close to zero. (There will be some oxygen demand by the bacteria just for them to survive - this is called endogenous oxygen uptake, which may be assumed to be constant. )

It follows then that the oxygen consumption at any point in 15 time is due to the incoming feed (plus the assumed constant endogenous demand) .

An RBCOD value for each oxygen consumption measurement is calculated by multiplying the oxygen consumption measurement by a constant. Thus, soon after the start of an air-off period 20 a first dissolved oxygen concentration measurement (DOχ) is

' ^') taken and after a fixed period of time t_p a second dissolved oxygen concentration measurement (D0₂) is taken from which the oxygen uptake consumption in the reactor in time t_p is given . by:

25 (DOi - D0₂) x V =ΔDO x V mg where V (litres) is the sample volume.

The RBCOD may be calculated from the change in dissolved oxygen concentration over the set measuring period by multiplying the value obtained by an apparatus constant which 30 may be determined by calculation from the parameters of the system which are held fixed or by calibration using acetate solutions of known concentration.

Thus RBCOD = ADO x constant.

The value for the constant includes a conversion factor of 3 5 for converting oxygen, consumption to RBCOD (as suggested by Dold et al, supra) and factors relating the oxygen consumption in the bio-reactor over time t_p to oxygen consumption in the quantity of the feed that enters the reactor. These factors j include the feed rate into the bio-reactor, a constant 10 measurement period t_p and the bio-reactor volume.

In automatic milking systems milk is carried in tubing and stored in tanks or containers. Between milking runs milk residues settle in the tubing and cleaning of the automatic milking system is therefore of vital importance. This is to 15 ensure high milk quality by preventing milk residues from previous milking runs, having high bacteria content, to pollute the fresh milk from later milking runs.

Cleaning in an automatic milking system is also an automatic feature involving a number of different cleaning steps .

.20 According to prior art systems there is no test to identify ^•) problems in the cleaning process. Thus, in case of failure of the cleaning the farmer may be of the impression that the

... cleaning was successful and continue with the next milking v run. This, in turn, would mean that the new milk would be

25 polluted with old milk residues resulting in high bacteria count in the milk, which may not be discovered until a bacteria test is taken on the milk, possibly as late as in the dairy.

Thus, it would be beneficial if the farmer could be notified 30 of the success or failure of the cleaning of an automatic milking system. This is specifically important in an automatic robotic milking system since these systems are left unattended for long periods, and the farmer has an even smaller possibility to discover eventual problems with the cleaning system.

5 Detergents used in cleaning of automatic milking systems are often highly reactive substances, which may have environmental impact. It would be beneficial if the amount of detergents could be optimal with respect to achieving a thorough cleaning with minimal environmental impact. -)

10 SUMMARY OF THE INVENTION

It is a main object of the present invention to provide such apparatus and method that at least alleviate the above problems .

It is in this respect a particular object of the invention to 15 provide such apparatus and method that is able to perform an action if the cleaning of an automatic milking apparatus fails.

It is still a further object of the invention to provide such apparatus and method that uses an optimal amount of detergents Ϊ0 in cleaning of an automatic milking apparatus.

These objects among others are, are according to a first .ά aspect of the present invention, attained by a milking apparatus comprising cleaning means for cleaning surface's in said milking apparatus coming in contact with milk, said

25 cleaning means uses a fluid for cleaning said surfaces. Said apparatus comprises means for diverting at least a portion of said fluid to a measurement chamber, means for measuring a value of the chemical oxygen demand (COD) for said fluid in said measurement chamber, and means for comparing said

30 measured value with a threshold and performing an action if said measured value is above said threshold. T e above objects among others are, according to a second aspect of the present invention, attained by a method for cleaning a milking apparatus comprising cleaning means for cleaning surfaces in said milking apparatus coming in contact 5 with milk, said cleaning means uses a fluid for cleaning said surfaces. The method comprises the steps of diverting at least a portion of said fluid to a measurement chamber, measuring a value relating to the chemical oxygen demand (COD) for said fluid in said measurement chamber, comparing said measured

,10 value with a threshold, and performing an action if said measured value is above said threshold.

By measuring the COD value after cleaning of the automatic milking apparatus an indication is achieved as to whether the cleaning was successful or failed. If the cleaning failed the 15 COD values will be high since the fluid will contain milk residues. The milk residues will consume oxygen, hence the increased value^'. If the COD value is higher than a threshold an action is taken

The action may 'for instance be sounding an alarm, performing 20 an extended cleaning cycle, performing a new cleaning, or register said value in a database etc.

^' By sounding an alarm, which may be performed in a multitude of different ways such as by ringing a bell, flashing a light, ;) print a specific alarm text on a display etc, the farmer is 25 alerted and informed of the higher COD values and may then take appropriate actions.

A somewhat higher COD value may also indicate that the present cleaning program was not efficient enough and the action may thus be to invoke a more elaborate cleaning program, possibly 30 involving stronger detergents and/or longer cleaning steps. The values may also be stored in a computer for later analysis.

According to a preferred embodiment the automatic milking apparatus comprises means for performing a washing step using a washing fluid comprising a detergent, and a post-rinsing step using a post-rinsing fluid without detergent, and at least a part of said post-rinsing fluid is diverted into said measurement chamber.

_.-ι Even though the COD measurement and analysis may be performed 10 during any sequence in the cleaning process, it is advantageous to perform the COD analysis on the last rinsing ") water as this will give a clear indication whether the complete cleaning was successful or failed.

According to a preferred embodiment the pre-rinsing and/or the 15 post-rinsing fluid is water and said washing fluid is water with added detergent.

According to a preferred embodiment the automatic milking apparatus comprises means for registering several consecutive values of said measurement values of the COD of said fluid in 20 a database and performing an action based on several of said values..

By registering values in a database or in a computer trend ^'&) . analysis may be performed. These trend analysis could indicate faults which do not immediately result in a significantly 25 higher COD value but nevertheless indicates a less satisfactory cleaning.

Further characteristics of the invention and advantages thereof will be evident from the following detailed description of embodiments of the invention. -BRIEF DESCRIPTION OF THE -DRAWINGS

The present invention will become more fully understood from the detailed description of embodiments of the present invention given herein below and the accompanying Figs. 1-3, 5 which are given by way of illustration only, and thus are not limitative of the present invention.

Figure 1 shows a schematic drawing of an automatic milking apparatus including cleaning means according to a preferred embodiment of the invention.

10 Figure 2 shows schematic drawing of a bio-chamber for measuring COD values. ) Figure 3 shows a schematic flow diagram for the operation of a preferred embodiment according to the invention.

PREFERRED EMBODIMENTS

15 In the following description, for purposes of explanation and not limitation, specific details are set forth, such as particular techniques and applications in order to provide a thorough understanding of the present invention. However, it will be apparent to one skilled in the art that the present 20 invention may be practiced in other embodiments that depart from these specific details. In other instances, detailed

;>?, descriptions of well-known methods and apparatuses are omitted so as not to obscure the description of the present invention with unnecessary details.

25 Figure 1 shows a schematic drawing of a cleaning means for cleaning teat cups and tubing in an automatic milking apparatus. Only a single teat cup 101 is disclosed but it will be apparent for the skilled man that ' several more teat cups may be cleaned simultaneously. For a robotic milking system 30 several teat cup may be placed side by side for cleaning and where a teat cup claw is present four teat cups may be cleaned together with the claw.

In a first step according to the present embodiment of the invention a pre-rinsing is performed. The container 102 is 5 filled with lukewarm water and the pump 103 pumps the water from the container 102 to the teat cup 101, through the milk meter 103, the air-fluid separator 104 and further to the waste. Thus, the pre-rinsing water is only passed once through the automatic milking system. The pre-rinsing water may 10 alternatively be sucked through the system by a vacuum system.

In a following washing step, the container 102 is filled with •) warm water and detergents are added. This step involves circulation so the water is not directly diverted to the waste but rather back to the container 102 for circulation. The 15 water may be warmed during the washing step or may be allowed to cool off during the washing. The washing is performed for 6-7 minutes and the water holds a temperature of approximately 70-80 degrees Celsius, at least at the beginning of the washing step.

20 After washing a post-rinsing step is performed using cold ^' ₎ water. Instead of passing all of the post-rinsing water to the waste some is directed to bio-chamber 105 where COD measurements is performed and recorded in a computer 106. If

?j the value of the COD measurement is above a threshold the 25 computer sounds an alarm indicating to the farmer that the cleaning has failed.

Figure 2 shows the bio-chamber in greater detail comprising a bioreactor 201, air injection means 202 and a dissolved oxygen-measuring probe 203. Post-rinsing water is fed to the 30 bio-chamber through inlet 204. The bio-chamber also comprises a temperature regulating means in the form of a water bath^' 205. Figure 3 shows a flow diagram of the operation according to a preferred embodiment of the invention. In a first step 301 a COD-value is measured by the bio-chamber disclosed in connection with figure 2. A test 302 is performed by the 5 computer 106 to compare the measured COD value with a threshold. If the test is positive the computer takes an action 303, in this preferred embodiment sounds an alarm. The operation continues with recording the measured COD value in a step 304 irrespective of the result of the test for later ■jlO analysis. The system is then ready for another COD measurement .

It will be obvious that the invention may be varied in a plurality of ways. Such variations are not to be regarded as a departure from the scope of the invention. All such 15 modifications as would be obvious to one skilled in the art are intended to be included within the scope of the appended claims.

Claims

CI-AIMS 1. A milking apparatus comprising cleaning means for cleaning surfaces in said milking apparatus coming in contact with milk, said cleaning means uses a fluid for 5 cleaning said surfaces, characterised in - means for diverting at least a portion of said fluid to a measurement chamber, - means for measuring a value of the chemical o.xygen

'10 demand (COD) for said fluid in said measurement chamber, and - means for comparing said measured value with a _j threshold and performing an action if said measured value is above said threshold.

15 2. A milking apparatus according to claim 1, wherein said action is selected from a group of actions including: sounding an alarm, performing an extended cleaning cycle, performing a new cleaning, register said value in a database etc.

20 3. A milking apparatus according to claim 1, wherein - said cleaning means comprises means for performing a washing step using a washing fluid comprising a detergent, and a post-rinsing step using a post-rinsing fluid without detergent, and -25 ' - wherein at least a part of said post-rinsing fluid is diverted into said measurement chamber.

4. A milking machine according to claim 3, wherein - said cleaning means further comprises means for performing a pre-rinsing step using a pre-rinsing fluid

30 without detergent before said washing step.

5.. A milking apparatus according to claim 3 or 4, wherein - said pre-rinsing and/or said post-rinsing fluid is water and said washing fluid is water with added detergent .

6. A milking apparatus according to claim 1, wherein - said milking machine comprises means for registering 5 several consecutive values of said measurement values of the COD of said fluid in a database and performing an action based on several of said values.

7. A milking apparatus according to any of the claims above, ^■:•) wherein 10 - said milking apparatus is an automatic robotic milking apparatus . ^•)

8. A method for cleaning a milking apparatus comprising cleaning means for cleaning surfaces in said milking apparatus coming in contact with milk, said cleaning 15 means uses a fluid for cleaning said surfaces, characterised in the steps of - diverting at least a portion of said fluid to a measurement chamber, - measuring a value relating to the chemical oxygen 20 demand (COD) for said fluid in said measurement chamber, - comparing said measured value with a threshold, and - performing an action if said measured value is above said threshold. .

9. A method according to claim 8, wherein said action is

25 selected from a group of actions including: sounding an alarm, performing an extended cleaning cycle, performing a new cleaning, register said value in a database etc.

10. A method according to claim 8, comprising the further steps:

30 - performing a washing step using a washing fluid comprising a detergent, and - performing a post-rinsing step using a post-rinsing fluid without detergent, and - wherein at least a part of said post-rinsing fluid is diverted into said measurement chamber.

5 11. A method according to claim 10, comprising he further step of: - performing a pre-rinsing step using a pre-rinsing fluid without detergent before said washing step.

,,

12. A method according to claim 10 or 11, wherein 10 - said pre-rinsing and/or said post-rinsing fluid is water and said washing fluid is water with added •) detergent .

13. A method according to claim 8, comprising the further steps of: 15 - registering several consecutive values of said measurement values of the COD of said fluid in a database, and - performing an action based on several consecutive of said values.

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