Guide for sampling and analysis of bisphenol A (BPA) in industrial effluent: chapter 4

Chapter 4

4.0 Sampling Type

• 4.1 Intermittent Process
• 4.2 Continuous Process

As discussed previously, the individual collecting the samples should be aware of production processes at the industrial facility to ensure that representative samples are collected.

There are two basic collection techniques (grab sampling or composite sampling) that can be used when sampling industrial effluent containing BPA. It is imperative for facilities to determine their activities associated with the manufacture, use and release of BPA in order to identify whether a grab sample or composite samples will be required. Please refer to Figure 1 for a flow chart illustrating the appropriate sampling options.

Initially, the individual collecting the samples must know if the facility is continuously releasing BPA into effluent. If the BPA-contributing process is not continuous, the sample collector can treat it as an intermittent process and choose the appropriate sampling technique based on the duration of the BPA-contributing process.

The guidance below is recommended for BPA sampling under normal operating conditions. However, in some specific instances it may be acceptable to collect a grab sample of a facility’s effluent when a composite sample would normally be required. This can occur if the facility collects all of the effluent prior to final discharge, such as in a retention or collection tank. Facilities may also use a composite sampling when the effluent content is highly variable, and use a grab sample when effluent content remains consistent during discharge. Also, if known, facilities can use grab samples at the precise moment when BPA releases are at their highest level at the final discharge point.

The individual collecting the samples should work with site contacts to understand and choose the best method to ensure that the samples are as representative as possible of BPA releases.

Figure 1: Sampling Decision Flowchart

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4.1 Intermittent Process

Example #1 Composite Sample is appropriate for facilities that have an intermittent process which operates for more than four hours and contributes to the presence of BPA in the effluent. Composite sample at the final discharge point is recommended for the length of time that BPA is present in the effluent. Note: The facility may need to evaluate an appropriate lag time to ensure the BPA wastewater reaches the final discharge point prior to sampling.

Example #2 Grab Sample is appropriate for facilities that have an intermittent process which operates for less than four hours consecutively and contributes to the presence of BPA in the effluent. This situation may be experienced at a facility that uses a dry process, but which requires a cleaning or sanitation work shift. A grab sample of effluent at the facility’s final discharge point is recommended during the four-hour cleaning or sanitation work shift.

Example #3 Grab Sample is appropriate for facilities that have an intermittent process which contributes to the presence of BPA in the effluent, but the wastewater is captured in a retaining tank prior to discharge. This situation may be experienced at a facility that captures wastewater for a few days prior to a discharge. It is recommended to collect a grab sample from the retaining tank prior to discharge and take a grab sample at the final discharge point after the retaining tank has been emptied to validate results. During tank sampling it is important to ensure that this tank is well mixed to ensure sample homogeneity and that no other effluent is released downstream from the final discharge point.

4.2 Continuous Process

Example #4 Composite Sample is appropriate for facilities that have a continuous process which operates for less than 24 hours per day and contributes the presence of BPA in the effluent. This situation may be experienced at a facility that operates during the day and has a sanitation work shift that washes equipment in contact with BPA. A composite sample is recommended for the duration of the facility’s operation and the sanitation work shift.

Example #5 Composite Sample is appropriate for facilities that have a continuous process which operates for 24 hours per day and contributes to the presence of BPA in the effluent. This situation may be experienced at a facility that operates three production work shifts per day where BPA is processed or used for a full 24 hours. A 24-hour composite is recommended in this example.