If a metering pump is being used to feed DTC into the pretreatment system, a mathematical calculation may be used to drop the residual DTC concentration down to an acceptable level. It’s usually a good idea to maintain a “safety margin” of residual DTC within the waste stream of about 100 ppm. If a test of the effluent water yields a DTC concentration of 250 ppm, for instance, and the metering pump is running at a rate of 100 BPM, turn down the pump to the 100 ppm level by using the following equation:
New Pump Speed = Current Pump Speed X 100 ppm / 250 ppm
New Pump Speed = 40 BPM
It’s also recommended to run lab jar tests (beaker tests) on samples of wastewater in order to determine the accurate volume of DTC to add prior to running the batch.