Biodegradation of pretreated olive mill effluent in mixture with a domestic sewage or compatible wastewater stream

BACKGROUND: The study focused on the biodegradation of pretreated olive mill wastewater (OMW) properly diluted in and mixed with a biodegradable substrate and/or domestic sewage stream. It utilized the permeate of a chemically conditioned two-stage ultrafiltration/nanofiltration system with COD of 5700 mg L⁻¹ and a total phenol content of 100 mg L⁻¹. Peptone mixture with similar characteristics to domestic sewage was adopted as the biodegradable synthetic substrate. The study relied on two sets of microbial culture; one acclimated to peptone and the other to a mixture of peptone and domestic sewage. Respirometric analyses were conducted on pretreated OMW diluted in the selected substrate using corresponding biomass seeding. RESULTS: Model evaluation of the oxygen uptake rate profiles indicated that the pretreated OMW was fully consumed in the respirometric tests. There were no inhibitory/toxic impacts of OMW dosing on the biomass. The entire biomass participated in the utilization of OMW/substrate with no metabolic adjustment problems. CONCLUSION: Experimental results provided conclusive evidence that co-treatment with a domestic sewage stream is a viable option for OMW management, after a chemically conditioned two-stage filtration used as the pretreatment step. Pretreatment removes the recalcitrant nature of the wastewater, which becomes fully biodegradable under appropriate dilution and mixing conditions.