Treatment of olive mill wastewater using an anaerobic sequencing batch reactor

Wastewater from olive mills in Jordan has been characterized and treated using a lab scale anaerobic sequencing batch reactor (ASBR). It was found that this wastewater has an average COD:N:P ratio of about 900:5:1.7. At this ratio, the wastewater was found to have sufficient nutrients that it was not necessary to add nutrients or combine it with other wastewaters. For effective treatment it was necessary to reduce the strength of the wastewater with an average COD value of about 97 g/L, to about 16 g/L by keeping part of the treated wastewater in the reactor when a new batch of wastewater was added. This achieved more than 80% COD removal at 3 d hydraulic retention time and at an organic load of about 5.3 kg COD/m3/d provided that alkalinity was added to adjust the pH to near 7. The specific substrate utilization rate, and observed biomass yield were about 0.37 kg COD removed/kg VSS/d, and 0.06 kg VSS/kg of COD degraded, respectively.