Microbial characteristics in a fixed-biofilm BNR process for treatment of low organic sewage

Abstract

Microbial characteristics of a fixed-biofilm process packed with hollow-type ceramic media were studied for treating low organic level sewage (average ratio=3.4), and an easy monitoring method such as a bio-index was suggested. The fractions of autotrophs and heterotrophs were directly affected by changing the organic surface loads in the aerobic reactors. After 90 days of operation, the amount of attached biomass was maintained constantly with a stable nitrification rate and low effluent concentration. At this point, the dominant diatoms observed were Fragilaria sp. in the second anoxic reactor, Cyclotella sp. in the second anoxic and aerobic reactors, and Navicula sp. in the first aerobic reactor. Specific protozoa (Euglypha sp., Arcella sp. and Colepus sp.), which were considered predators of nitrifiers, were observed under high nitrification rate and were used as a bio-index and indicators of nitrifying biofilm formation and low effluent concentration in the fixed-biofilm BNR process.

Keywords:

• bio-index
• diatom
• fixed-biofilm BNR process
• nitrifiers
• protozoa

Acknowledgements

The authors would like to acknowledge financial support by Hyundai MOBIS and the management of Pusan National University IETI (Institute of Environmental Technology and Industry, 97-10-21-99-B-2 and 97-10-21-99-B-3).