Discussion: View Thread

  • 1.  Wastewater composite sampling and BOD get effected

    Posted 10-14-2018 09:09 AM
    Edited by Tirza Austin 10-14-2018 09:09 AM
    Hello everyone
    Scenario of work
    I am making a composite sampling with respect to time (2 hr) and proportional to flow
    I prepare 6 bottles for 12 hr sampling and note the flow before each sample collection (1 bottle is one sample of single point)
    Then I mix all the six bottle to a new bottle, quantity sample proportional to flow.
    My question regarding this scenario working is that,
    While transferring the sample into a new bottle is BOD (biochemical oxygen demand) get effected or not? 
    If effected what can we do to minimize the effect?
    (During transferring we use measuring cylinder pipette tube and new bottle for composite sample)

    Syed Alvi M.ASCE
    junior engineer
    Techno Consult International

  • 2.  RE: Wastewater composite sampling and BOD get effected

    Posted 10-15-2018 03:00 PM
    Edited by Tirza Austin 10-15-2018 02:59 PM
    The info below is from the USGS:

    Samples can degrade significantly during extended storage. To minimize sample degradation, and thus avoid negative bias in the measurement of BOD5, analyze samples promptly or store chilled without freezing (maintain a temperature from 1 to 4°C). Chilling the sample is not necessary if the analysis begins within 2 hours of collection (American Public Health Association and others, 1995).
    If a sample is refrigerated prior to analysis, allow the sample to warm to 20°C before starting the test. A sample may be removed from an ice chest or refrigerator during transit to allow it to warm to 20°C before analysis begins.
    It is optimum to start the BOD5 analysis immediately after sample collection to minimize changes in bacterial
    The maximum holding time of a sample to be analyzed for BOD is 24 hours

    Bevin Beaudet P.E., M.ASCE
    Bevin A. Beaudet, P.E., LLC.
    West Palm Beach FL