Treatment of pulp mill wastewater by Cryptococcus podzolicus and solar photo-Fenton: A case study

• First report on PMW treatment combining Cryptococcus podzolicus and solar photo-Fenton.
• Cr. podzolicus yeast isolated showed a COD removal of 68% and 27% of total polyphenols.
• Solar photo-Fenton demonstrates excellent ability to treat the remaining pollutant load of the PMW.
• Combination of Cr. podzolicus and solar photo-Fenton can achieve DOC removal greater than 90%.

This study evaluated a combination of biological and physical–chemical processes for pulp mill wastewater (PMW) treatment. Biological tests were performed with various yeasts to find out their capacity for growth at different temperatures in the effluent under study. Of the 8 yeast isolates, Cryptococcus podzolicus (AGG 691) proved to be the most appropriate for the aims pursued. After 32 h of incubation, the AGG 691 monoculture had removed 68% of the chemical oxygen demand (COD) and 27% of total polyphenols (TP). This was followed by evaluation of a physical–chemical polishing step.First, coagulation/flocculation was evaluated. Since this was found to be ineffective, two Advanced Oxidation Processes (AOPs), dark-Fenton and solar photo-Fenton, were then studied.Solar photo-Fenton experiments were performed with 10, 20 and 50 mg/L concentrations of Fe2+. Although all the solar photo-Fenton experiments showed over 90% dissolved organic carbon (DOC) removal, the experiment with 10 mg Fe2+/L was selected as the best treatment option considering the lowest consume of iron and H2O2. Treatment with Cr. podzolicus (AGG 691) yeast followed by solar photo-Fenton was able to ensure that pulp mill wastewater discharged into natural waters met legal requirements.

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