Integration of coagulation and electro-activated HSO5− to treat pulp and paper wastewater

Pulp and paper wastewater (PPW) is classified as complex wastewater that contains high concentrations of recalcitrant pollutants. In this study, the integration of coagulation process and electro-activated peroxymonosulfate (PMS) were tested to treat PPW. FeCl3, aluminum sulfate and poly aluminum chloride were examined for chemical oxygen demand (COD) removal from PPW. Amongst the coagulants, FeCl3 showed higher performance compared to other coagulants in which 55% of COD was removed under the conditions of natural pH of 6.9 and FeCl3 dosage of 100 mg L−1. Coagulation-treated wastewater by FeCl3 was treated by electro-activated PMS. Under the condition of 0.75 mA cm−2 current density, 6.0 mM PMS and 60 min reaction time, 53% of COD was further eliminated. To compare with electro-Fenton, electro-activated PMS provided higher COD removal and specific oxidant efficiency. Integration of coagulation (FeCl3) and electro-activated PMS enhanced the biodegradability of PPW based on biochemical oxygen demand/COD index. The results showed that integrated chemical and electrochemical processes can be used as a pretreatment for biological process.