1, ORP is generally measured online. Have you calibrated the instrument? If it is an instrument problem, it may cause a problem of dose control.
2. It is necessary to measure the chromium concentration in the inlet and outlet water to see if the change of process production leads to the change of inlet water quality.
3, ferrous sulfate reagent should also be tested. I am also engaged in environmental protection, and often help the owners to purchase reagents. Because of the purchase cost or operation cost, when purchasing chemicals, sometimes the effect of chemicals is very different, which will also affect the normal process effect of wastewater station.
4. The two electroplating projects I made myself both used NaHSO3 as reducing agent, and the treatment effect was good. Really can't. You can try changing the dressing.