BOD-SystemOxiDirect®
Instruction Manual GB
Content
1. The system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51.1 Principle of operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51.2 Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51.3 Illustrations/Equipment supplied . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2. The method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62.1 Biochemical oxygen demand (BOD) . . . . . . . . . . . . . . . . . . . . . . . . . . . 62.2 BOD sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62.3 Principle of measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. BOD measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73.1 Sample volume . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73.2 Preparing the water sample . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83.3 Preparing the sample / brief summary . . . . . . . . . . . . . . . . . . . . . . . . . 10
4. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114.1 Buttons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114.2 Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114.3 Technical terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124.4 Displays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134.5 Setting up the unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144.6 Switching on . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144.7 Switching off . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144.8 Reading out measurement values . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154.9 Starting measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154.10 Parameter menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164.10.1 Setting date and time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164.10.2 Autostart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174.10.3 Replacing batteries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
5. Interpreting the results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
6. Checking the measurement system . . . . . . . . . . . . . . . . . . . . . . . . 19
7. Replacing the batteries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
8. Care and maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
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Content
9. Inductive stirring system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209.1 User instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219.1.1 Correct use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219.1.2 Instruction symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219.2 Safety considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229.3 Equipment description and function . . . . . . . . . . . . . . . . . . . . . . . . . . 249.4 Start-up procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249.5 Magnetic stirring rods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259.6 Stirring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259.7 Maintenance and cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269.8 Problems during operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269.8.1 The magnetic stirring rod rotates unevenly . . . . . . . . . . . . . . . . . . . . . . 269.8.2 The stirring rod swerves back and forth . . . . . . . . . . . . . . . . . . . . . . . . 26
10. Technical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2710.1 BOD system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2710.2 Inductive stirring system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
11. Accessories and spare parts list . . . . . . . . . . . . . . . . . . . . . . . . . . 29
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1. The System
1.1 Principle of operationBOD is determined by measuring the pressure difference within a closed system(respirometric BOD). The integrated memory saves a BOD value automatically every24 hours for a test period of more than 2 days. For a period of 1 day a value is savedevery hour, for 1 to 2 days, every 2 hours.
1.2 ApplicationsDetermination of BOD5 and BOD7, OECD 301F / biological degradability.Other bio-technological applications.
1.3 Illustrations / Equipment supplied
� 1 x BOD measuring device with integral bottle rack
� 6 x BOD sensor
� 6 x BOD bottles
� 6 x seal cups (Gasket)
� 6 x magnetic stirring rods
� 1 x stirring system drive
� 1 x stirring system controller
� 1 x nitrification inhibitor (ATH)
� 1 x potassium hydroxide solution (KOH solution, 45%)
� 2 x overflow measurement flasks (157 ml and 428 ml)
� 1 x instruction manual
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2. The Method
2.1 Biochemical Oxygen Demand (BOD)The biochemical oxygen demand (BOD) of waste water, industrial effluents and surfacewater is an expression for the amount of oxygen consumed by the decomposition oforganic matter in a biochemical process. BOD measurement is an important analyticaltool in determining the effects of effluents on water treatment plants and surface watersystems.
2.2 BOD SensorsThe OxiDirect® is a respirometric BOD measurement system, where BOD is determinedin the bottle itself, without prior dilution. This method offers a range of advantages,compared with the so-called dilution method. The sample can be tested undilutedform; the measurement range is wider; the amount of work involved is significantlyless.
2.3 Principle of MeasurementThe BOD measurement unit, consisting of the sample bottle and the BOD sensor,represents a closed system. In the bottle, above the sample itself, is a defined airspace. During the BOD measurement the bacteria in the sample consume the dissolvedoxygen in the sample. This is replaced by oxygen out of the air within the bottle, abovethe sample. The carbon dioxide released at the same time is chemically bounded bythe potassium hydroxide in the seal gasket. This generates a decrease of pressurewithin the system. This is measured by the BOD sensor and displayed as a BOD valuein mg/l O2.
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3. BOD Measurement
3.1 Sample VolumeThe sample volume is related to the expected BOD value. The OxiDirect® is designedto operate over the measurement ranges and sample volumes shown in the followingtable, allowing for BOD measurement ranges of 0 - 4000 mg/l, without any dilution ofthe sample.
Note
The expected results should be in the upper half of the range. For example, if theexpected BOD value is 250 mg/l, select a measurement range of 0 - 400 mg/l and,therefore, a sample volume of 157 ml, for best results.
For domestic waste it is generally safe to consider a BOD5 value which is approximately80 % of the COD value.
Range BOD mg/l Sample volume in ml Drops ATH
0 – 40 428 10
0 – 80 360 10
0 – 200 244 5
0 – 400 157 5
0 – 800 94 3
0 – 2000 56 3
0 – 4000 21.7 1
Table 1
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3.2 Preparing the Water Sample1. Check the pH value of the effluent sample. The optimum pH value for biochemical
oxidation is between pH 6.5 and 7.5. If the pH value of the sample is higher or lower, itshould be pre-adjusted. Any significant deviation will result in a lower BOD value. If thepH value is too high, it can be reduced by adding dilute hydrochloric acid (1 mol/l) ordilute sulphuric acid (1 mol/l). If the pH value is low, it can be adjusted with a sodiumhydroxide solution (1 mol/l).
2. Mix the water sample well and allow to settle for a short while. It may also be advisableto filter or homogenise the sample.
Depending on the nature of the effluent to be examined (e.g., paper mill effluents,surface water, dairy wastes) the sample will need to be pre-treated. Samples containingfibres should be homogenised; samples containing algae should be filtered. BODmeasurements will not be comparable unless the same pre-treatment is used. In theevent of different results, the pre-treatment should be checked.
3. Measure out precisely the sample volume required, using the appropriate overflowmeasurement flask and pour the sample into the sample bottle (it may be helpful to usea funnel for this). Ensure that the sample in the bottle contains a representative portionof any solids in suspension. It is recommended that each sample should be testedtwice or three times. It is essential to measure the sample volumes very precisely;otherwise, significant measurement errors may occur. Where two samples are generallythe same but have different amounts of suspended solids, different results may beexpected. If the difference between results is significant, the measurements should berepeated.
Note
The OxiDirect® measurement system is designed to operate with the sample volumesshown in Table 1 and the sample bottles supplied with the system (or as spare parts).Different volumes or wrong sample bottle will lead to false results. We thereforerecommend strongly that you always measure the samples with the overflowmeasurement bottle supplied. You should also use a funnel to transfer the sample tothe BOD bottle.
4. To inhibit nitrification, we recommend the addition of nitrification inhibitor B( = Allyl Thiourea, or ATH). This is particularly important for the low measurement rangeof 0 - 40 mg/l (for example, when checking discharges from effluent treatment plants).The ideal volume of nitrification inhibitor B to be added will depend on the measurementrange - see Table 1.
Note
Nitrifying bacteria also consume oxygen. This consumption can occur within the first 5days and is more likely with samples with low BOD levels. As a general rule, the BODmeasurement should not include the oxygen consumption caused by nitrifying bacteriaand this can be inhibited by using nitrification inhibitor B. This inhibitor suppresses theactivity of the bacteria by enzymatic inhibition, so that only the breakdown of organicsubstances in the sample will be measured as the BOD value.
If it is desired to measure oxygen consumption resulting from nitrification (N-BOD),carry out measurements of samples both with and without the use of nitrification inhibitorand compare the results. The difference between the two BOD values will represent theoxygen demand of the nitrifying bacteria.
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5. Add a clean magnetic stirring rod to each sample bottle and add 3-4 drops of 45%potassium hydroxide solution to the seal gasket (this will absorb the carbon dioxide).Then insert the seal gasket in the rack of the bottle.
Important
The sample must never come in contact with the potassium hydroxide solution.Never use grease or any other lubricants as an additional sealing agent, for the BODsensors or for the seal gasket. Products of this kind may contain solvents which willattack the sensor, resulting in severe damage to the plastic housing and even to afailure of the sensor. The use of sealing greases and lubricants is not covered by ourguarantee !
6. Before measurement begins, the prepared sample must be brought to the desiredtemperature (e.g. BOD5, 20 °C ). This can be achieved by placing the sample in athermostatically controlled cabinet, while stirring the sample continuously with theinductive stirring system.
The OxiDirect® has an optional “Auto-Start” function, which enables it to start withsamples at temperatures from 15° to 20°C. When this “Auto-Start” function is switchedon, the system checks at specific intervals to detect whether there has been a fall inpressure in the BOD bottle and will not start the timer until a pressure drop is detected(the timer will start to run at latest 3 hours after the BOD sensor has been initiated,whether or not a fall in pressure has been noted).
7. Place the BOD sensors on the sample bottles and tighten carefully. This is extremelyimportant – the system must be completely air-tight. Then place the BOD bottle, withthe sensor screwed in position, into the bottle rack. This can be done in thethermostatically controlled cabinet itself.
Alternatively, because of the user-friendly design of the OxiDirect®, you can remove theentire BOD unit, with its integral bottle rack, from the thermostatically controlled cabinet,while leaving the inductive stirring system in the cabinet. There is no need to disconnectthe cabling. Once the BOD bottles have been placed in the rack, the system is positionedover the inductive stirring system so that the 4 adjustment screws engage in theassociated recesses in the stirring system drive.
8. Start the measurement process (see Section 4).
9. Incubate the sample in accordance with the instruction (e.g. BOD5 for 5 days at 20 °C).
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3.3 Preparing the Sample / Brief Summary• Estimate the measurement range for the sample under test and select the volume of
the sample (see Table 1).
• Carry out any essential pre-treatment of the sample (e.g., setting the pH value; filtering; etc.).
• Measure the volume of the sample precisely, using the overflow measurement flaskand transfer it to the BOD bottle, with the aid of a funnel. If necessary, add nitrificationinhibitor (see Table 1).
• Insert the magnetic stirring rod in the BOD bottle.
• Place 3-4 drops of KOH solution into the seal gasket. Then insert the gasket in the rackof the bottle.
• Screw the BOD sensors to the sample bottles.
• Place the sample bottles in the bottle rack.
• Start the measurement process (see Section 4).
• Incubate the sample in accordance with the instructions (e.g. BOD5 for 5 days at 20 °C)
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4. Operation
4.1 Buttons
ESC
Start
Read
+
– Enter
ESC - switch the unit on and off- quit sub-menus- shut down an application
START - start measurements
READ - read and display the current value (this is not saved !)
+ - select the next completed / available head- increase parameters
- - go back one head- reduce parameters
ENTER - confirm input- switch to next stage in a menu
4.2 NotesFlicker of the display is normal. To ensure correct measurements the measuringtasks got a higher priority than the routine serving the display.
If bottles have been added to the rack while switched off, the unit must be switched ononce for starting the measurement.
If bottles have been removed permanently from the rack while the electronics were off,the unit should be switched on and off once, so that these places do not affect the lifespan of the batteries.
The unit will switch itself off after approximately 45 seconds. To prolong battery life, theunit should always be switched off immediately, after the current task has beencompleted. For taking the required measurements the unit will work in the “background”mode, with only the centre “minus” in the upper display being illuminated. Once themeasurement is completed, the unit will switch itself off again.
The battery capacity is monitored continuously. If the batteries are closed to the end oftheir effective life, the display show “Lo” ”bAt”. At this point, the batteries should bereplaced (see : “Replacing Batteries”). Because a reliable evaluation of the battery levelcannot take place until the unit has been switched on for approximately 15 seconds,the “switch off” sequence, during which “OFF” is displayed, may take a little longer ifthe unit is switched off very shortly after it has been switched on.
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4.3 Technical Terms
Rapid read-out mode Operating condition, in which the OxiDirect® displays the lastmeasurement value which has been stored and the period ofmeasurement of a head.
Read-out mode Operating condition, in which all stored measurement values for anindividual head can be displayed, together with the time ofmeasurement.
Start mode Operating condition, in which measurements can be started
Completed head A head which has completed its series of measurements
Free head A heads, where the series of measurements has been completedand at least one values has been displayed in “read-out” mode(see : “Reading Out Measurement Values”).
Background mode The OxiDirect® is carrying out measurements, or is waiting just beforea measurement execution time. However, the display is switchedoff, except for the centre “minus” in the upper display. Before switchingon the unit, wait until the “background” mode has finished and thedisplay is completely blank.
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4.4 Displays
LoAd OxiDirect® has not located Provided at least one head isa valid head available, check the contacts
LEDs These display the position of the head,to which the values in the display apply
LED perma- Measurement completednently lit
LED flashes Measurement not yet completed
UFL “Underflow “ the BOD is lower Check that the sample bottlethan the allowed range is fully sealed against(meaning below 0) the measurement head
Check tempering of the system
OFL “Overflow” the BOD exceeds theupper limit of the chosenmeasurement range
Lo bAt End of battery life Replace batteries
Measurement No valid preasure condition found for Check that the sample bottlevalue flashes a start during the “Autostart” time is fully sealed with the
window measurement headCheck tempering of the system
F 1 No measurement value available yet
F 2 No “start” value available yet,so no current figure can be calculated
F120 A fault has occurred during “Start” Do not remove a bottle or changetheir places during the “Start”procedure
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4.5 Setting up the UnitThe batteries are not in place for shipment. If necessary, take all samples from the rack,turn the rack around and open the battery compartment. Place the three alkali-manganese “Baby” cells (C-Size) in the battery compartment, making sure of correctpolarity. The unit should then be started automatically and will be in the “Date-Time”sub-menu (see “Setting Date & Time”). If the unit does not switch on, or is not in thissub-menu, switch to the “Date-Time” sub-menu as described in the instructions. Setdate and time and switch the unit off. Switch it on again and the unit will go into “RapidRead-Out” mode. Then switch the unit off again.
4.6 Switching OnSwitch the unit on by pressing the “ESC” button. The OxiDirect® will now be in “RapidRead-Out” mode and will display the final value of the first completed measurementwhich it finds (the “Position” LED will illuminate to indicate the position). If no completedmeasurement is available, the “Position” LED will flash. The upper display will show thetime span (e.g., “ 5d” for BOD5, while the lower display will show the last value whichhas been stored. If the display shows “F 1”, there is no stored value jet available. If novalue could be measured at the specified time, the display will show “-F- ”.
The “ + ” button is used to switch over to the position of the next completedmeasurement, while the “ - ” button is used to select any head required. Positionswithout a bottle in places cannot be selected.
4.7 Switching OffThe unit is switched off by pressing the “ESC” button, if it is in the “Rapid Read-Out”mode. During the switch-off sequence, the upper display will show “OFF” followed bythe centre “minus”. During this time, no bottles must be taken from or added to therack. The switch-off sequence is finished when the display no longer shows “OFF” andthe centre “minus” has also disappeared. Do not push the “ESC” button during thissequence. If you wish to switch the unit on again, it is essential to wait until at least twoseconds after the display is completely off.
If the unit is not in the “Rapid Read-Out” mode, it will be necessary to press the “ESC”a number of times in order to switch off.
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4.8 Reading Out Measurement ValuesSet the unit to “Rapid Read-Out” mode, select the desired position and press the“ENTER” button. The unit will switch to “Read-Out” mode for the bottle you haveselected. The upper display will show the time of the measurement, the lower displaywill show the corresponding stored measurement value. If the measurement period isone or two days (for BOD1 and BOD2) the time of the measurement will be shown inhours. If the measurement period is longer than 2 days (BOD3, BOD4...) the figureshown in the display will read in days. Time in hours is displayed in the form of “hxx” (forexample, “h48” for the last measurement value for BOD2). Time in days is displayed as“dxx” (for example, “d 5” for the last measurement value for BOD5).
4.9 Starting MeasurementStarting a new measurement will delete all stored data for the sensor!
Press the “START” key. The unit will switch to “Start” mode. It will then seek the firstfree position. The lower display will show the measurement range which was used lasttime, while the upper display will show the necessary sample volume. Use the “ + ” and“ - ” key to change the position (the “ + ” key will select the next free position, while the“ - ” key can be used to select any position).
Press “ENTER”. The “ + ” and “ - ” keys can now be used to select the measurementrange. Confirm the range selected by pressing “ENTER” again. The unit will now displaylast used measurement time span. If this is not changed within 3 seconds (use the “ + ”and “ - ” keys) this previous measurement duration is automatically adopted and themeasurement will start. Following a modification, this automatic start will no longeroperate. The “start” procedure can be stopped by pressing the “ESC” key.
If the unit does not find a free position, it will select some head. In this case, the displaywill show “dEL ”. If you wish this head to be used, press the “START” key again. Theunit then changes to the selection of the measurement range.
Once a measurement has been started, the unit will indicates the next free position.Pressing the “ESC” key will cause the unit to quit the “Start” mode and return to the“Rapid Read-Out” mode.
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4.10 Parameter MenuPress the “ENTER” key and keep it pressed. Switch the unit on. Once the lower displayhas flashed 3 decimal points for approximately 3 seconds, release the “ENTER” key.The unit is now in the “Parameter” menu and will initially display the “Date-Time” sub-menu. Use the “ + ” and “ - ” keys to switch between the “Date-Time”, the “Autostart”and the “Replace Batteries” sub-menu. Press the “ENTER” key to select the requiredsub-menu. Leave the ”Parameter” menu by pressing the “ESC” key and return to the“Rapid Read-Out” mode.
4.10.1 Setting Date & Time
Switch the unit to the “Parameter” menu and select the “Date-Time” sub-menu :“Set” ”dAtE”. The unit will display “ dA” and the current year setting. Press the “ENTER”key. The unit will now display “ dA” and the current date setting in the form of “MM.TT”(MM = month and TT = day). Press the “ENTER” key. The unit will display “ ti” and thetime in the form of “hh.mm” (hh = hours and mm = minutes). Press the “ENTER” key.The upper display of the unit will flash “JJ” and the lower display will show the year. Usethe “ + ” and “ - ” keys to increase or decrease the figures and store by pressing the“ENTER” key.
Using the same method, set the figures for the month (the display shows “Mo”), theday (the display shows “ dd”), the hour (the display shows “hh”), the “tens of minutes”(the display shows “M”) and the single minutes (the display shows “m”). Finally, pressthe “ENTER” key in order to execute. The unit will set its internal clock to these figuresand, if there was no fault, the display will show “iS” ” Set”.Before finally confirming by pressing the “ENTER” key, you can go back by pressing the“ESC” key or quit the “Date-Time” menu.
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4.10.2 Autostart
The “Autostart” function can be switched on or off. The setting which is selected willapply to all the heads on the rack from now on.
In particular, when the “Autostart” function is switched off, an automatic start will alsotake place immediately for those heads which had been initiated by the “Autostart”function when it was switched on, but for which the “start” condition had not yet beenachieved. To change the setting go to the “Parameter” menu and select the sub-menu: “Set” ”Auto”. The “ + “ key is then used, in the “Autostart” sub-menu, to switch on the“Autostart” function. With the function switched on, the unit will display “On” ”Auto”and can be switched off with the “ – “ key. Once the selection has been made, you mayquit the sub-menu by pressing the “ESC” key. This causes the new setting to becomeeffective.
4.10.3 Replacing Batteries
In order to replace the batteries without missing an intermediate measurement, makesure the tool required to open the battery compartment is to hand, as well as the newbatteries (3 alkali-manganese “baby” cells (C-Size)).
Set the unit to the “Parameter” menu and select the “Replace Batteries” sub-menu“Set” ”bAt”. Activate the menu by pressing the “ENTER” key. The unit will display “bAt”.Press the “ENTER” key again. The display will flash, showing “bAt” ”chg”. Wait until thedisplay becomes dark - this may take up to 6 minutes. At this point the unit hasswitched off.
The batteries must be replaced within the next 4 minutes : the unit should not bewithout battery power for more than one minute. Take all the samples from the rack,turn the rack around and open the battery compartment. As soon as the old batterieshave been removed, the new batteries must be inserted, so that they are in place andable to power the unit within one minute. Then close the battery cover, replace all thesamples and switch the unit on. Once the unit has reached the “Rapid Read-Out”mode, it can be switched off again.
If the unit goes automatically into the “Date-Time” menu after the batteries have beenreplaced, this indicates that the power supply was interrupted for too long. It will thenbe necessary to reset the date.
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5. Interpreting the Results
Start 1. Day 2. Day 3. Day 4. Day 5. Day
300
250
200
150
100
50
0
1. The BOD value on any particular day must be higher than that measured on the previousday.
2. BOD values do not increase in a linear manner. The increase is always smaller than thatof the previous day.
3. If the BOD results increase in a linear manner, the sample has a higher BOD value thanexpected when the sample was prepared.
4. If BOD results rise suddenly in the course of measurement, this may be the result ofnitrification.
5. If BOD results fall suddenly in the course of measurement, this may indicate that thereis an air leak in the system.
The information given in the previous pages refers in all cases to normal samples(municipal wastes) and the normal behaviour of bacteria in the course of a BODmeasurement. However, special events are always possible, depending on the relevantcircumstances. For example, if there is a reading of zero after 5 days, this may meanthat there is a leak in the system, or severe inhibition.
In the case of industrial effluents, special circumstances will often occur. Effluents ofthis kind may contain toxic substances and these must be removed from the sample,or the sample must be diluted so that the measurement results are not too low. Inaddition, nutrients (nitrogen; phosphate) and trace elements such as iron must bepresent in sufficient concentrations; otherwise bacterial growth may be limited andartificially low BOD values may be recorded. Where problems of this kind occur in thecourse of measurement, each individual case must be considered and resolved on itsown particular merits.
For further information, please ask for our application reports.
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6. Checking the Measurement System
The following test systems are available for checking the OxiDirect® measurement system:
1) Quick-test-equipmentThe Quick-test unit for BOD sensors is a test unit which enables a BOD sensor to besubjected to a defined vacuum. It can therefore be used to carry out a speedy andsimple check on the correct operation of individual BOD sensors.
2) Calibration SetThe calibration Set enables a check to be carried out on all the components of theOxiDirect®. It consists of special reagent tablets, which generate a defined vacuum inthe sealed BOD bottle. With the calibration Set, it is therefore possible to check theentire OxiDirect® system for functionality and correct sealing.
7. Replacing the Batteries
When the batteries are low, “Lo” ”bAt ” will appear in the lower display. To change thebatteries, loosen the two security screws and remove the cover to the batterycompartment. Replace the old batteries with three new batteries (Type: Baby/C/LR14,Alkali-Manganese) according to the procedure given in chapter “Operation -->Parameter-Menu --> Replacing Batteries”.
All calibration data remain secure while the batteries are being changed.
8. Care and Maintenance
High-quality metal alloys are used for the contacts between the BOD sensors and thebottle rack. If necessary, the contacts may be cleaned carefully with a soft cloth.
To compensate for any irregularities and to ensure optimum contact between the BODsensor and the bottle rack, the BOD measurement system has 4 levelling screws on itsbase.
If necessary, the BOD base unit (including the bottle rack) and the BOD sensors can becleaned carefully with a soft cloth.
All parts which come into contact with the sample (BOD bottles; seal cups; magneticstirring rod) must be cleaned thoroughly after each measurement. The bottles must beemptied completely and washed several times in hot water.
Where any cleaning agents, washing up liquids, etc., are used, the parts must berinsed thoroughly ! The residues of such agents can interfere with BOD measurements.
20
9. Inductive Stirring System
Fig. 1: Inductive stirring drive with stirring controller
� Stirring place
� Stirring drive
� Stirring controller
� Plug out
� Control cable
�
�
�
�
�
21
9.1 User Instructions
9.1.1 Correct use
This inductive stirring system has been designed for stirring liquids in BOD bottles.
9.2.2 Instruction symbols
The following instruction symbols are used in this operating manual:
DANGER!
This sign refers to dangerous voltages
DANGER!
This sign refers to hazardous situations.Risks to human life are indicated by the term ”LIFE HAZARD”
����� CAUTION!
This sign indicates risks to equipment and machinery
����� INFORMATION
This sign indicates easier working practices
* Indicates an operating step
Indicates alternatives
22
9.2 Safety ConsiderationsFor your own safety, you should observe the following safety warning signs.
The safety warnings indicate a possible sources of danger. At the same time theycontain information on how correct action can avert danger. You will always find warningsigns attached to points of possible danger.
DANGER!
Magnetism.Magnetic or metallic parts (e.g. data carriers, pacemakers, watches ...) can beaffected by magnetic fields.Keep such parts away from the magnetic stirrer (2) and the magnetic stirringrods
DANGER!
Supply voltage and supply frequency must be within the range specified forthe control unit (3)
����� CAUTION!
Do not use in hazardous locations
����� CAUTION!
General ambient conditions :Stirring drive (2): -10 to +56 °C at 100% humidity.Control unit (3): 0 to +40 °C at max. 80% humidity.Avoid extreme temperature changes.The control unit (3) must not be run in humid rooms, or set up in areas wherewater may splash!
23
����� CAUTION!
Do not place hot stirring vessels on top of the magnetic stirrer (2).Maximum temperature : 56 °C.
����� CAUTION!
In case of repair, the equipment must only be opened by an authorised serviceagent. Disconnect from mains before opening !
����� CAUTION!
Do not allow the magnetic stirring rod to come to rest in an alternating magneticfield (e.g. in an unfilled stirring vessel when the stirring or mixing mode isselected). Do not subject the magnetic stirring rod to a strong inverse magneticfield or to strong impact shocks (e.g. by dropping it). This may result indestruction of the magnetic stirring rod.
����� INFORMATION
The length of the magnetic stirring rod must not exceed 40 mm.Do not use elliptical stirring rods with a round cross-section.
24
9.3 Equipment Description and FunctionThe stirring system has been designed for stirring liquids in standard BOD bottles. Itconsists of an ultra-slim stirring drive (2) with 6 stirring points (1) and a separate stirringcontroller (3). All the bottles can be removed from the rack without disturbing the stirringdrive (2). Several stirring drives (2) can be installed next to each other, saving space.
The stirring drive has no motor and is therefore wear-free. It is particularly suited tocontinuous stirring in a incubator. It is hermetically sealed (fully protected from splashingwater) and can be used even in the roughest environments. The wide space betweenthe stirring points (1) ensures good ventilation of the stirring containers, even in aincubator. The stirring drive (2) is controlled by a controller (3) with a pre-set speed.When turned on, the soft start feature ensures a uniform start of the magnetic stirringrods at half speed.
Every 40 seconds, the electronically controlled automatic monitor reduces the stirringspeed by 50%, re-centring the magnetic stirring rod in the middle of the bottle forseveral seconds. This means that individual bottles may be “hot-swapped” or the rackinstalled during operation.
The magnetic stirring rods are operated synchronously, preventing practically anyinterference between them.
9.4 Start-up procedure
DANGER!Supply voltage and supply frequency must be within the range specified forthe control unit (3)
DANGER!Magnetism. Magnetic or metallic parts (e.g. data carriers, pacemakers,watches ...) can be affected by magnetic fields. Keep such parts away fromthe magnetic stirrer (2) and the magnetic stirring rods.
�����CAUTION!Do not use in hazardous locations
�����CAUTION!General ambient conditions:Stirring drive (2): -10 to +56 °C at 100% humidity.Control unit (3): 0 to +40 °C at max. 80% humidity.Avoid extreme temperature changes.The control unit (3) must not be run in humid rooms, or set up in areas wherewater may splash !
The control unit (3) does not have an on-off switch. It is ready for use as soonas it is plugged in.
* Connect the control cable (5) from the stirring drive (2) to the outputsocket (4) of the control unit (3) while tightening the thumb-wheel. * Plug the control unit (3) into the mains socket.
25
9.5 Magnetic stirring rodsWe recommend the use of PTFE-coated magnetic stirring rods.
����� INFORMATION
The length of the magnetic stirring rod (8) must not exceed 40 mm.
9.6 Stirring
����� CAUTION!
Do not place hot stirring vessels on top of the magnetic stirrer (2).Maximum temperature : 56 °C.
* Fill the bottles with the sample.
* Place a magnetic stirring rod into every bottle.
* Place bottles in the BOD rack.
The control unit (3) is preset to operate at 320 rpm. The electronically controlledautomatic monitor reduces the stirring speed to about 200 rpm, re-centringeach magnetic stirring bar in the middle of the bottle for several seconds. Thismeans that individual bottles may be “hot-swapped” or the rack installed duringoperation.
If you want to stop the stirring process:
* Disconnect the control unit (3) from the mains socket.
26
9.7 Maintenance and CleaningThe stirring drive (2) is maintenance-free.
The magnetic drive inside the housing is embedded in synthetic resin and is completelywatertight. Clean the surface of the stirring drive (2) at regular intervals. It may becleaned under running water. Alternatively, you may clean the stirring drive (2) with adisinfectant solution suitable for use on PVC. Wipe the surface of the stirring controller(3) using a damp cloth.
����� CAUTION!
In case of repair, the equipment must only be opened by an authorised serviceagent. Disconnect from mains before opening !
9.8 Problems during Operation
9.8.1 The magnetic stirring rod rotates unevenly:
Some ageing of the stirring rod in time cannot be avoided. This may reduce itsmagnetisation.
����� CAUTION!
Do not allow the magnetic stirring rod to come to rest in an alternating magneticfield (e.g. in an unfilled stirring vessel when the stirring or mixing mode isselected). Do not subject the magnetic stirring rod to a strong inverse magneticfield or to strong impact shocks (e.g. by dropping it). This may result indestruction of the magnetic stirring rod.
* Replace it by a new one.
9.8.2 The stirring rod swerves back and forth:
Swerving movements of the magnetic stirring rod may be caused by irregularly shapedforms of the bottle. This may occur, for instance, in the case of BOD bottles with aconvex bottom if the bottom is shaped irregularly or asymmetrically.
* Replace the bottle by a new one.
27
10. Technical Data
10.1 BOD System
Type OxiDirect®
Measurement principle Manometric; mercury-free; electronic pressure sensor
Ranges 0 - 40, 0 - 80, 0 - 200, 0 - 400, 0 - 800, 0 - 2000, 0 – 4000 mg/l[mg/l O2]
Applications BSB5, BSB7, OECD 301 F ...
Result display BSB [mg/l]; 4 - digits; 7 - segment LED
Measurement BOD-range, volume, duration, display time of measurementparameter display
Measurement period User-selectable, between 1 and 28 days
Auto result storage up to 28 results, depending on measurement period
Storage intervall – hourly (1 day);– every 2 hours (2 days);– daily (3-28 days)
Automatic start function – After temperature equalisation of samples– can be switched off
Power supply 3 alkaline-manganese batteries
Battery life 1 year (normal use as BOD5 meter – max. one reading a day);early warning before battery fails
Clock Real-time clock
Protection class IP54 (sensor head)
Dimensions 375 x 195 x 230 mm(L x W x H) included stirring unit
Housing ABS
Approval CE
28
10.2 Inductive Stirring System
Type Inductive Stirring System
Stirring volume 6 BOD bottles
Stirring power 7 W
Rotation speed 320 rpm(briefly reduced to 200 rpm every 40 s)
Dimensions (W x D x H) 270 x 180 x 25 mm
Distance between 88 mmstirring points
Weight (stirring drive) 1800 g
Housing material PVC
General Ambient Conditions -10 to +56 °C at 100 % humidity
Operating voltage 20 V max.
Control cable 2 m
Protective system IP 68 (DIN 40050)
Stirring controller230 V version 220 – 240 V / 10 V / 50 - 60 Hz, protection class II,
Thermosicherung, CE-Zeichen115 V version 110 – 120 V / 10 V / 50 - 60 Hz, protection class II,
thermal featurePermanent ambient conditions 0 to + 40 °C at max. 80 % humidityProtection class IP 20 (DIN 40050)
29
11. Accessories and Spare Parts List
Article Order code
Replacement BOD sensor 444430
Replacement BOD base unit 444433
Stirring controller 444413
Inductive stirring drive 444401
Quick-test-equipment 418327
Calibration Set 418328
Potassium hydroxide solution (50 ml) 418634
Nitrification inhibitor B (50 ml) 418642
BOD sample bottle 418644
Seal cup (gasket) 418636
Diagram pad 418663
Magnetic stirring rod 418637
Magnetic stirring rod remover 418638
Overflow measuring flask, 428 ml 418660
Overflow measuring flask, 360 ml 418659
Overflow measuring flask, 244 ml 418658
Overflow measuring flask, 157 ml 418657
Overflow measuring flask, 94 ml 418656
Overflow measuring flask, 56 ml 418655
Overflow measuring flask, 21, 7 ml 418664
Thermostatically controlled incubators see general catalogue
Thermostatically controlled incubators with glass door see general catalogue
Technische Änderungen vorbehalten.Printed in Germany 09/03
We reserve the right to alter or amendany of the items contained hereinwithout prior notice.
AQUALYTIC®
P.O. Box 41 02 5344272 Dortmund
Germany
Telefon: (+49) (0)2 31/9 45 10 - 755Telefax: (+49) (0)2 31/9 45 10 - 750
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