Efficient integrated processes for pulp and paper wastewater treatment and phytotoxicity reduction: Permanganate, electro-Fenton and Co3O4/UV/peroxymonosulfate

Pulp and paper wastewater (PPW) is a high strength effluent which requires advanced treatments for achieving the discharge standards. Integrated processes were used for the first time to treat PPW including permanganate (PM), electro-Fenton (EF) and Co3O4/Peroxymonosulfate/UV (sulfate radical, SR). The main operating parameters of each process were investigated on chemical oxygen demand (COD) removal. The results showed that the combination of PM, EF and SR processes could provide the discharge standard in a way that COD was reduced from 1450 to 62 mg/L. Moreover, the biodegradability of effluents obtained from EF and SR was improved. As an important result, pH of the wastewater was adjusted for one time at first process (PM) and final effluent reached neutral condition. Phytotoxicity of the effluents obtained in each process was evaluated by germination index. Their results showed that phytotoxicity was dramatically reduced for four plants species in final effluent. The sequence of the processes was assessed in case of COD removal. The results indicated that the sequence of processes (PM + EF + SR) was the best choice for PPW treatment. The sludge of PM and EF was evaluated by FTIR analysis. Finally, these combinations of the chemical, electrochemical and photochemical processes were proposed as an excellent option for treatment of PPW. (C) 2016 Elsevier B.V. All rights reserved.