Anaerobic wastewater treatment of concentrated sewage using a two-stage upflow anaerobic sludge blanket- anaerobic filter system

Abstract

A two-stage pilot-scale upflow anaerobic sludge blanket – anaerobic filter (UASB-AF) reactors system treating concentrated domestic sewage was operated at 23°C and at hydraulic retention times (HRT) of 15 and 4 h, respectively. Excess sludge from the downstream AF stage was returned to the upstream UASB reactor. The aim was to obtain higher sludge retention time (SRT) in the UASB reactor for better methanization of suspended COD. The UASB-AF system removed 55% and 65% of the total COD (COD_tot) and suspended COD (COD_ss), respectively. The calculated SRT in the UASB reactor ranged from 20–35 days. The AF reactor removed the washed out sludge from the first stage reactor with average COD_ss removal efficiency of 55%. The volatile fatty acids concentration in the effluent of the AF was 39 mg COD/L compared with 78 mg COD/L measured for the influent. The slightly higher COD_tot removal efficiency obtained in this study compared with a single stage UASB reactor was achieved at 17% reduction in the total volume.

Keywords:

• Two-stage system
• anaerobic filter
• UASB reactor
• HRT
• concentrated sewage
• domestic wastewater

Acknowledgment

The authors would like to thank the International Arid Land Consortium (IALC) for the grant PO# Y432976 provided to run the research. The authors are also grateful to Water Authority of Jordan (WAJ) and Miyahuna Company for the permissions given for University of Jordan to have their experimental set up at Abu-Nusier Wastewater treatment plant.

Notes

* OLR is the organic loading rate.

⁺ HUSB: Hydrolytic upflow sludge bed digester.^{[ 6 ]}

□ Calculated based on data presented by Seghezzo.^{[ 12 ]}

♦ Calculated based on data presented by Alvarez et al.^{[ 18 ]}