physico-chemical and biological treatment of olive mill wastewater by rotating biological contactor (rbc) reactors

the removal performance of total poly phenols and orthodiphenols (o-diphenols) content in olive mill waste (omw) was investigated with a three stages cross flow laboratory scale rotating biological contactor (rbc) in the present study. due to high cod and other pollutant in the original omw, physico-chemical treatment was effected for cod and other pollutant reduction prior to biological treatment of omw by the rbc system. inoculation of rbc was effected by sludge from olive oil factory. in biological treatment, effect of operating parameters such as hydraulic loading (hl) and influent cod were examined. the study of the  physico-chemical treatment before biological treatment of omw showed,  that about 9.1% of total poly phenols, 3.2% of o-diphenols and 12% of cod were removed by physical treatment. the effect of chemical treatment by different coagulants, alum, bentonite and zeolite at different ph and concentrations showed that bentonite at ph 6.5 and 15g/l resulted in the best removal efficiency of 20% for poly phenols and o-diphenols. the experimental results in rbc system show that at low hl, significant removal efficiency was observed for poly phenols and o-diphenols, at the first stage, but with increasing hl, other stages took part in removal efficiency. also, decreasing cod from 5000 to 2500 at different hl caused an increase in poly phenols and o-diphenols  removal efficiency.