Advanced oxidation of a pulp mill bleaching wastewater

Area of Science:

• Environmental Chemistry
• Water Treatment Technologies
• Industrial Effluent Management

Background:

• Pulp mill Extended Chlorination (ECF) bleaching generates effluents with low initial biodegradability.
• The organic matter in these effluents poses environmental challenges due to its recalcitrant nature.
• Effective treatment methods are crucial for reducing the environmental impact of pulp and paper industries.

Purpose of the Study:

• To investigate the efficacy of various advanced oxidation processes (AOPs) in degrading pulp mill ECF bleaching effluent.
• To assess the impact of AOPs on the biodegradability of the effluent's organic matter.
• To compare the performance of different AOPs, including ozonation and UV-based systems.

Main Methods:

• Effluent samples were subjected to ozonation and five AOPs: O3/UV, O3/UV/ZnO, O3/UV/TiO2, O2/UV/ZnO, and O2/UV/TiO2.
• Biodegradability was estimated using the BOD5/COD ratio.
• Chemical Oxygen Demand (COD), Total Organic Carbon (TOC), and toxicity were measured before and after treatment.
• Activated sludge treatment was used as a comparative biological method.

Main Results:

• Initial biodegradability (BOD5/COD) of the effluent was low at 0.3.
• AOPs treatments, particularly O3/UV, significantly increased effluent biodegradability.
• The O3/UV system demonstrated the highest efficiency in converting organic matter into more biodegradable forms within five minutes.
• Reductions in COD, TOC, and toxicity correlated well with enhanced biodegradability after AOPs.

Conclusions:

• Advanced oxidation processes are effective in enhancing the biodegradability of pulp mill ECF bleaching effluent.
• The O3/UV system shows superior performance among the tested AOPs for improving effluent treatability.
• AOPs offer a viable approach to pre-treat recalcitrant industrial wastewater, facilitating subsequent biological treatment and reducing environmental pollution.