Start-up phase assessment of a UASB-Septic tank system treating domestic septage

Abstract

About 65% of the annual domestic wastewater in Palestine is currently collected in cesspits, where inadequate disposal might cause cumulative public health risks and annual environmental degradation. This research presents the preliminary results for the start-up period of a pilot-scale UASB-septic tank system treating domestic septage of Birzeit town. Under different operational conditions, the performance of the pretreatment system for the removal of organic matter and nutrients was evaluated. Initial results showed that organic pollutants removal was mainly due to biophysical processes including sedimentation and microbial degradation. During the start-up phase, the system attained removal efficiency for CODtotal of about 80% compared to the removal for CODcol, and CODdis of 71% and 43%, respectively. Similarly, the continuous operation mode demonstrated that the system was quite effective in removing organic pollutants. Operational experience from the initial results revealed that seeding the UASB reactor with activated sludge during the start up period was not practical. Finally, the advantages of the UASB–septic tank application appeared to be achievable if adequate system operation and control over a long monitoring period were maintained.