Batch reactor In the batch reactor, flow is neither entering nor leaving the reactor(i.e, flow enters, is treated, and then is discharged and the cycle repeats) The bod test is carried out in a batch reactor that are often used to blend chemicals or to dilute concentrated chemicalsBatch Reactor In the batch reactor, flow is neither entering nor leaving the reactor (i.e, flow enters, is treated, and then is discharged, and the cycle repeats). The BOD test is carried out in a batch reactor that are often used to blend chemicals or to dilute concentrated chemicals