Chemical oxygen demand and tannin/lignin removal from paper mill wastewater by electrocoagulation combined with peroxide and hypochlorite treatments

The present investigation sought to assess the practicality of utilizing a combined pre-treatment approach comprising electrocoagulation, peroxide, and hypochlorite treatments for the removal of chemical oxygen demand (COD) and tannin/lignin from paper mill wastewater. The study aimed to optimize the operating parameters with a view to maximizing the removal efficiencies while minimizing energy consumption. A pair of iron electrodes were used as anode and cathode in the study, and the main operating parameters were determined as initial pH, applied current, treatment time and oxidant dosage/COD ratio. Response surface methodology (RSM) was used to evaluate the effect of these parameters on COD and tannin/lignin removals. The primary findings of the investigation indicated that the integration of electrocoagulation with peroxide and hypochlorite treatments exhibited efficacy in removing COD, tannin/lignin, colour, phenol, and turbidity from paper mill wastewater. The optimized conditions resulted in COD removal efficiencies of 48.13 +/- 2.2% and 29.53 +/- 1.4% for EC with H2O2 and Ca(OCl)(2), respectively. Tannin/lignin removal efficiencies were 92.59 +/- 3.6% and 94.09 +/- 1.8% for EC-H2O2 and EC-Ca(OCl)(2), respectively. The specific energy consumption (SEC) values showed that EC-Ca(OCl)(2) required 7 times more energy than EC-H2O2 for removing 1 kg COD. The principal deduction drawn from the study was that EC-H2O2 pre-treatment demonstrated superior COD removal efficiency and lower energy consumption, while EC-Ca(OCl)(2) pre-treatment exhibited greater efficiency in removing toxic and recalcitrant pollutants. In future studies, it would be useful to conduct research to increase COD removal efficiency in addition to tannin/lignin removal in EC-Ca(OCl)(2) process.

Automated summary

This study aimed to assess the feasibility of using a combined pre-treatment approach for removing COD and tannin/lignin from paper mill wastewater, and to optimize the operating parameters for maximum removal efficiency and minimal energy consumption. The results showed that the integration of electrocoagulation with peroxide and hypochlorite treatments effectively removed various pollutants from the wastewater, with EC-H2O2 pre-treatment demonstrating superior COD removal efficiency and lower energy consumption.