Evaluation of ozonation applicability to pulp and paper streams for a sustainable wastewater treatment

Pulp and paper wastewater ozonation was tested at pilot-scale in a medium-potentiality wastewater treatment plant (143,000 population equivalent). Single wastewater lines (bleaching and process water), as well as wastewater mixture (before and after secondary biological treatment) were investigated to evaluate the best ozonation conditions. The aim of the work was to evaluate the feasibility of substituting current tertiary physicochemical treatment with an ozonation unit, reducing operating costs and improving management operations. The tests were useful to identify the ozone dosage required to achieve the desired COD abatement. Ozone effectiveness was more pronounced in process water (60% COD removal), rather than bleaching water (28% COD removal); ozone showed a significantly higher efficiency on pulp and paper wastewater mixture after biological treatment (up to 81% COD removal) rather than before biological process (46% mean COD abatement). COD removal efficiency at a dosage of 100 mg O-3/L was comparable to existing physicochemical treatment (mean 50%); a good TSS abatement (up to 20-30 mg/L) was observed as well. Toxicity analysis revealed that ozonation treatment did not modify treated effluent toxicity characteristics (mean Daphnia Magna mortality of 23.3%). Economic analysis proved that ozonation installation cost would be 1.5-2.0 M(sic), for total flowrate to be treated of 1200 m(3)/h. Ozonation would lead to an economic saving of about 300,000 (sic)/y compared to actual physicochemical treatment and the investment cost could be recovered in about 7 years. The proposed innovative approach, including plant analysis, pilot-ozonation tests, data regression, respirometric fractionation, toxicity and economic analysis, could be exported to other industrial wastewater treatment plants to allow an increased advanced oxidation processes diffusion. (C) 2020 Elsevier Ltd. All rights reserved.