title: 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.
abstract: 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.
authors.affiliation: University of Pretoria, Water Utilisation Division, Pretoria 0002, South Africa E-mail: emrava@buckman.com.
authors.forename: E
authors.initials: E
authors.lastname: Rava
authors.affiliation: University of Pretoria, Water Utilisation Division, Pretoria 0002, South Africa E-mail: emrava@buckman.com.
authors.forename: E
authors.initials: E
authors.lastname: Chirwa
mesh_terms: D000641:Ammonia / Q000378:metabolism; D052818:Autotrophic Processes; D001419:Bacteria / Q000254:growth & development*; D018441:Biofilms; D057919:Biological Oxygen Demand Analysis; D019149:Bioreactors; D003031:Coal; D052836:Heterotrophic Processes; D007220:Industrial Waste; D058465:Nitrification; D009584:Nitrogen / Q000737:chemistry / Q000378:metabolism*; D010636:Phenols / Q000378:metabolism; D014865:Waste Disposal, Fluid / Q000379:methods; D062065:Wastewater / Q000737:chemistry*
chemical_list: D000641:Ammonia; D003031:Coal; D007220:Industrial Waste; D009584:Nitrogen; D010636:Phenols; D062065:Wastewater