Detrimental effects of high molecular-mass polyphenols on olive mill wastewater biotreatment

Research was undertaken to investigate whether low, medium or high molecula r-mass polyphenolics were the most problematic compounds for olive mill was tewater (OMW) biotreatments. For this reason, three polyphenolic fractions were isolated by ultrafiltration of crude OMW and characterized by GC/MS an d gel filtration analysis. When P. chrysosporium was cultivated in the pres ence of Fl polyphenolic fraction (F1<8 kDa), the decolorization/depolymeriz ation was high. However, a very weak decolorization/depolymerization of the F3 fraction (F3 > 60 kDa) was observed. Lignin peroxidase (LiP) was detect ed as traces for the Fl fraction and undetected in the case of F3 one. More over, increasing the molecular-mass of aromatics led to decreases in levels of depolymerization and COD removal by P. chrysosporium cultures. The use of a lignin peroxidase induction medium has a positive effect on the high m olecular-mass fraction decolorization and a high degree of decolorization p aralleled the appearance of Lip activity in the extracellular fluid. By com parison to the synthetic medium used, LiP production was delayed in the pre sence of Fl fraction but strongly inhibited (80% loss) in the presence of F 3 fraction. The Fl fraction was well degraded aerobically by P. putida DSM3 932 (pWWO) and A, eutrophus DSM 4057 (pJP3) or an activated sludge consorti um while F3 resisted degradation by the OMW-acclimated activated sludge. Mo reover, continuous anaerobic biomethanization experiments conducted in para llel with the different fractions showed that at the same hydraulic retenti on time (26 days), the Fl fraction was bioconverted into methane at high yi eld while F3 fraction was poorly biodegraded. (C) 2000 Elsevier Science Ltd . All rights reserved.