An integrated bioaugmentation/electrocoagulation concept for olive mill wastewater management and the reuse in irrigation of biofuel plants: a pilot study.

A consortium of highly degrading microorganisms was used in an integrated bioaugmentation/electrocoagulation process for treating olive mill wastewater. The system was investigated for treating 1 m day, at a pilot scale, for 2 years; hydraulic loading rate and organic loading rate were 2880 l m day and 37,930 g COD m day, respectively. Average removal efficiency for COD, oils, and total phenols was 63.9%, 85.2%, and 43.6%, respectively. The olive mill consortium, OMC, consisted of seven actinomycete strains. The strains were confirmed, by 16S rDNA analysis, to belong to five Streptomyces, one Kitasatospora, and one Micromonospora strains, at 100-99.06% similarities. Hydrolytic enzyme activities of OMC strains were remarkably higher for degrading cellulosic and lipid constituents (enzyme-cumulative indices, 14-16.1), than the phenolic constituents (indices, 4.1-6.5). The establishment of actinomycetes in the treatment system was indicated by their increased counts in the biofilm at the end of the biofilter, reaching 13-fold higher than that in the control bed. The treated effluent was toxic to the seedlings of Jatropha curcas (Jatropha) and Simmondsia chinensis (Jojoba). Though its application in irrigation of 3-year-old Jatropha shrubs, significantly, enhanced the fruit yield up to 1.85-fold higher than the control, without affecting the seed oil content, after 3-month application, the irrigated soil showed insignificant changes in its biochemical properties. This developed bioaugmentation/electrocoagulation process can treat wastewater with extremely high organic strength, while its approximate construction and operational costs are limited to 0.03 and 0.51 US$ m, respectively. It produces a treated effluent that can be reused in irrigation of specific plants. Graphical abstract.