Aspergillus niger P6 and Rhodotorula mucilaginosa CH4 used for olive mill wastewater (OMW) biological treatment in single pure and successive cultures

Abstract

The aim of this study was to investigate the Rhodotorula mucilaginosa CH4 and Aspergillus niger P6 abilities to purify olive mill wastewater (OMW) in single pure and mixed cultures during the treatment. Both fungi were molecularly identified. OMW was used at five dilutions from 5% to 30% with chemical oxygen demand (COD) ranging from 11,600 to 24,600 mg L⁻¹. Firstly, each fungus was used separately, then they were successively used to treat the OMW. In single pure culture, A. niger showed a better efficiency in OMW purification than R. mucilaginosa. Furthermore, when successively used, the two studied strains exhibited improvements in the decrease of COD, polyphenolic compounds concentration and effluent colour. COD removals were 95.68–56.71% by R. mucilaginosa and 98.02–69.51% by A. niger for OMW dilutions varying from 5% to 30%. Both strains showed an important polyphenolic compounds removal of 83–45% by R. mucilaginosa and 94–58% by A. niger, in accordance with the OMW COD initially used. The COD and phenolic compound removals fitted simple equation models, with high regression coefficients. The strains’ growth kinetics decreased according to the OMW concentration, but, when successively used, fungal growth was improved, allowing efficient effluent treatment.

Keywords:

• olive mill wastewater
• Aspergillus niger
• Rhodotorula mucilaginosa
• COD reduction
• decolorization

Acknowledgements

The authors are indebted to Mr. Ahmed Ayadi, the General Manager of the Tunisian Service Society, for providing the material and allowing exploration of the site. They are also grateful to Mrs Hela Chaabouni Fourati from Sfax, for proofreading.