Chemical and toxic evaluation of a biological treatment for olive-oil mill wastewater using commercial microbial formulations

Olive-oil-mill wastewater (OMW) has significant polluting properties due to its high levels of chemical oxygen demand (COD), biochemical oxygen demand (BOD), and phenols. In the present study, different commercial bacterial formulations were used in the biological treatment of OMW. COD and toxicity testing using primary consumers of the aquatic food chain (the rotifer Brachionus calyciflorus and the crustacean Daphnia magna) were employed to evaluate abatement of the organic load and reduction of the toxic potential. In addition, the four most active formulations were tested mixed pair-wise on the basis of their unique characteristics in order to evaluate the improvement of treatment. The effect of treatment was assessed by measuring COD removal, reduction of total phenols, and decreased toxicity. The results obtained with the mixed formulations showed that the maximum removal of the organic load was about 85%, whereas phenols were reduced by about 67%. The toxicity for rotifers decreased by 43% and for crustaceans by about 83%.