Performance appraisal of the A2/O process in domestic wastewater treatment replacing the anaerobic unit with UASB

Abstract

Feasibility of a combined system consisting of an anaerobic up-flow anaerobic sludge blanket (UASB) followed by anoxic unit then aerobic activated sludge (AS) was investigated. The system was fed with normal domestic wastewater, then medium loading wastewater using activated sludge from El Berka WWTP, then high strength sewage having a chemical oxygen demand (COD) of 2635 mg COD/L. The organic loading rate (OLR) was increased gradually from 0.5 to 4.43 kg COD/m 3 /day. The HRT was changed for each loading from 10.5 to 15 h. The internal recirculation (IR) was tested at 100%, 200% and 300% for each loading run. The return activated sludge was adjusted to maintain a mixed liquor suspended solids of greater than 2500 ppm. At steady state conditions, the UASB reactor achieved removal efficiency up to 79.13% of the total COD. The combined system performed an excellent organic removal pushing the overall removal efficiency of the total COD, TN and TP to 95.87%, 84.95% and 87.59%, respectively. When the OLR increased to 4.43 kg COD/m 3 /day, the effluent quality of the UASB deteriorated reaching a percent of 48.20 for COD removal efficiency dropped to 62.90%, 29.90% and 46.90% respectively. The optimum operational conditions for the system on different organic loadings were HRT = 15 h and the IR = 200%.

Effectiveness of Anaerobic Technologies in the Treatment of Landfill Leachate

“…Montalvo et al [47] found that treatment of leachate via UASB was capable of removing 92.4% nitrate, whereas a study conducted by Liu et al [48] reported that leachate treatment by UASB could achieve removal of NH 3 -N, TN and COD as high as 99.3%, 85.4% and 90.3%, respectively. In support of this, Moharram et al [49] also found out that UASB could achieve 50 to 75% of COD removal. Lu et al…”