Soluble microbial products and performances assessment during OMW biological treatment by an activated sludge pilot

Olive mill wastewater (OMW) is currently one of the most serious environmental pollution problems, because of its high potential to contaminate surface and ground waters. Untreated OMWW is a major problem for the wastewater treatment plants (WWTP) based on activated sludge because of its phenolic compounds content which inhibit microbial activity and growth. This paper aims to assess the soluble microbial products (SMP) and treatment performances in activated sludge pilot plant (ASPP) depending the increasing OMW mass ratio F/M. The results highlight optimal performances of the system during the experiment. Indeed, the biomass concentration in bioreactor of ASPPwas high and reached5.71 g(MLSS).L-1 for mixed liquor suspended solids (MLSS) and 4.86 g(MLVSS).L(-1)for mixed liquor volatile suspended solids (MLVSS), the respirometric activity was very promising of about 9.95 mg(O2.gmlvss)(-1).h(-1)which indicates good promptness of the biomass against the OMW increasing feedings. Theresults showalso an important abatement of COD and polyphenols which both reached more than 90%. Moreover, HPLC analysis shows an important abatement of the most toxic polyphenols present in OMW, hydroxtyrosol and tyrosol. The SMP have a crucial importance for biological wastewater treatment systems because of their significant impacts on both treated effluent quality and treatment efficiency. In this study, their concentrations were significantly influenced by OMW increasing mass ratio F/M. Consequently, they reacheda stable concentrations at end of the experimental study of 8 mg.L-1 for proteins and 17 mg.L-1 for polysaccharides.