Effect of polyphenols on activated sludge biomass during the treatment of highly diluted olive mill wastewaters: biomass dynamics and purifying performances

This study aims to investigate the feasibility of treating olive mill waste water (OMWW) by activated sludge pilot (AS) after its high dilution (1%) by urban waste water (UWW) and to study the effect of polyphenol compounds on the biomass during the treatment. Specific oxygen uptake rate (SOUR), mixed liquor volatile suspended solids (MLVSS), chemical oxygen demand (COD) and total polyphenols, were followed up over 100 days. In spite of the polyphenols' high concentration (up to 128 mg·L−1), successful biomass growth of 7.12 g MLVSS.L −1 and activity were achieved. Most of the bacteria (Pseudomonas sp., Klebsiella oxytoca, Citrobacter fereundii, Escherichia coli and Staphylococcus sp.) and fungi (Trichoderma sp., Rhizopus sp., Aspergillus niger, Penicillium sp., Fusarium sp., Alternaria) identified in the aerobic basin during the stabilization stage were known to be resistant to OMWW and showed effective adaptation of the biomass to polyphenols in high concentration. COD and polyphenols were highly eliminated (90%, 92% respectively). The sludge volume index in the pilot settling tank was almost constant at around 120 mL.g −1. This suggests the possibility of managing OMWW by simple injection at a given percentage in already functioning conventional AS treating UWW.