Treatment of high-strength wastewater by Fe(2+)-activated persulphate and hydrogen peroxide

Ferrous ion-activated persulphate and hydrogen peroxide were studied for the treatment of real high-strength industrial effluent. The Fenton process demonstrated greater organic load removal, biodegradability improvement and toxicity reduction as well as lower treatment cost than the activated persulphate system. However, the use of an activated persulphate process was more favourable due to the exothermic effect intrinsic to the Fenton reaction, which resulted in a rapid increase in the temperature of the high-strength wastewater along with excessive foam formation. Overall, for the H2O2/Fe(2+) and [Formula: see text] processes, the application of a chemical oxygen demand (COD)/oxidant/Fe(2+) weight ratio of 1/0.4/0.075 resulted in a COD removal of 58 and 50%, a 7-day biochemical oxygen demand/COD ratio increase from 0.14 to 0.3 and 0.23, and an increase in the EC50 (Daphnia magna) by 6.5-fold and 2.9-fold, respectively. The stepwise addition of the oxidant and activator was favourable for the Fenton process and resulted in negligible improvement in the wastewater treatment efficacy in the activated persulphate system.