The purpose of this study was to determine the effect different biofilm carrier filling ratios would have on biofilm morphology and activity and bacterial diversity in a hybrid fixed-film bioreactor treating high strength coal gasification wastewater (CGWW) for the removal of chemical oxygen demand (COD), phenols and ammonia-nitrogen. Results showed that a carrier fill of 70% formed a ‘compact’ biofilm, a 50% fill formed a ‘rippling’ biofilm and a 30% fill formed a ‘porous’ biofilm. The highest microbial activity was obtained with a 50% carrier fill supporting a relatively thin biofilm. The highest level of biofilm bound metals were aluminium, silicon, calcium and iron in the ‘compact’ biofilm; nitrogen, magnesium, chloride, sodium and potassium in the ‘rippling’ biofilm, and copper in the ‘porous’ biofilm. The bioreactor improved the quality of the CGWW by removing 49% and 78% of the COD and phenols, respectively. However, no significant amount of ammonia-nitrogen was removed since nitrification did not take place due to heterotrophic bacteria out-competing autotrophic nitrifying bacteria in the biofilm. The dominant heterotrophic genera identified for all three carrier filling ratios were Thauera, Pseudaminobacter, Pseudomonas and Diaphorobacter.
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Research Article|
February 25 2016
Effect of carrier fill ratio on biofilm properties and performance of a hybrid fixed-film bioreactor treating coal gasification wastewater for the removal of COD, phenols and ammonia-nitrogen
E. Rava;
1University of Pretoria, Water Utilisation Division, Pretoria 0002, South Africa
E-mail: [email protected]
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E. Chirwa
E. Chirwa
1University of Pretoria, Water Utilisation Division, Pretoria 0002, South Africa
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Water Sci Technol (2016) 73 (10): 2461–2467.
Article history
Received:
July 29 2015
Accepted:
February 11 2016
Citation
E. Rava, E. Chirwa; Effect of carrier fill ratio on biofilm properties and performance of a hybrid fixed-film bioreactor treating coal gasification wastewater for the removal of COD, phenols and ammonia-nitrogen. Water Sci Technol 18 May 2016; 73 (10): 2461–2467. doi: https://doi.org/10.2166/wst.2016.108
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