Decentralized wastewater treatment in an urban setting: a pilot study of the circulating fluidized bed bioreactor treating septic tank effluent

ABSTRACT

To meet the increasing wastewater treatment demand while minimizing the land footprint of the treatment systems and plants, more efficient and compact processes are needed. The circulating fluidized bed bioreactor (CFBBR) has been proven to achieve high levels of biological nutrient removal. Past studies at the lab and pilot scale achieved 94% COD removal and 80% nitrogen removal at HRT's of 2–4 h. A collaborative project between Western University and the Guangzhou Institute of Energy Conversion (GIEC), in Guangzhou, China, further explored the treatment of municipal wastewater with the CFBBR. A pilot CFBBR, with aerobic and anoxic columns for nitrification and denitrification, was constructed at the GIEC for in-situ treatment of septic tank effluent from a residential building. Due to high concentrations of ammonia (NH₄-N), the wastewater had a COD/N ratio of 2–3. Thus, operating at a longer HRT and supplementing COD, in the form of glucose, was necessary to achieve a high nitrogen removal efficiency. The system was run both with and without supplemental COD at HRT's between 16 and 21 h, treating approximately 1000–1270 L/d. Overall, a COD removal efficiency of at least 92%, ammonia removal of 97%, and nitrogen removal of 82% was achieved. The CFBBR system achieved an effluent with BOD and NH₄-N concentrations both below 5 mg/L, a NO₃-N concentration below 15 mg/L, and a total nitrogen concentration below 25 mg/L. The compact design of this pilot-CFBBR, coupled with its high BNR performance make it an excellent option for decentralized treatment of urban wastewaters.

GRAPHICAL ABSTRACT

KEYWORDS:

• Biological nutrient removal
• attached growth process
• high-efficiency process
• decentralized treatment
• in-situ treatment

Disclosure statement

No potential conflict of interest was reported by the authors.

Data availability

The data that support the findings of this study are not available publicly due to their being part of a larger, ongoing study at the Guangzhou Institute of Energy Conversion.

Additional information

Funding

This work is supported by grants from the Technology Planning Project of Guangzhou City (grant numbers 201508020049); and the Guangdong Key Laboratory of New and Renewable Energy Research and Development (grant numbers Y609jj1001).