The researchers tested different methods to clean up wastewater from pulp and paper factories. They tried using ozone, Fenton, hydrogen peroxide, and photo-Fenton treatments alone and combined with biological methods. They found that combining biological treatment with advanced oxidation processes improved the efficiency of removing color and chemical oxygen demand (COD) from the wastewater. Ozone and photo-Fenton treatments were particularly effective, with ozone removing 41-46% of color and 88-96% of COD. Fenton and hydrogen peroxide treatments also showed good results, with Fenton removing over 26% of color and 84-86% of COD, and hydrogen peroxide removing 28-39% of color and 85-87% of COD. Overall, combining biological treatment with advanced oxidation processes can make wastewater treatment more effective and cost-efficient for pulp and paper industries.