Removal of organic load from olive washing water by an aerated submerged biofilter and profiling of the bacterial community involved in the process.

The present work aims to use a biofilter technology (aerated submerged filters) for the aerobic transformation at laboratory-scale of olive washing water (OWW) generated in the first steps of olive oil processing, as well as the genetic profiling and identification to the species level of the bacteria involved in the formation of the biofilm, by means of TGGE. Chemical parameters, such as biological oxygen demand at five days (BOD5) and chemical oxygen demand (COD), decreased markedly (up to 90 and 85%, respectively) by the biological treatment, and the efficiency of the process was significantly affected by aeration and inlet flow rates. The total polyphenol content of inlet OWW was only moderately reduced (around 50% decrease of the inlet content) after the biofilter treatment, under the conditions tested. Partial 16S rRNA genes were amplified using total DNA extracted from the biofilm and separated by TGGE. Sequences of isolated bands were mostly affiliated to the alpha-subclass of Proteobacteria, and often branched in the periphery of bacterial genera commonly present in soil (Rhizobium, Reichenowia, Agrobacterium, and Sphingomonas). The data obtained by the experimentation at laboratory scale provided results that support the suitability of the submerged filter technology for the treatment of olive washing waters with the purpose of its reutilization.