BOD-System OxiDirect - panwell-tech. To inhibit nitrification, we recommend the addition of nitrification

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  • 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

  • 4

    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

  • 5

    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

  • 6

    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.

  • 7

    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

  • 8

    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 shou