Environmental biology

Enhanced biological nutrient removal by the alliance of a heterotrophicnitrifying strain with a nitrogen removing ecosystem

Naeem ud din Ahmad , XU Haiying , CHEN Liping , LIU Zhipei , LIU Shuangjiang


Received April 20, 2007,Revised July 16, 2007, Accepted , Available online

Volume 20,2008,Pages 216-223

  • Summary
  • References
  • Related Articles
Nitrogen removal from synthetic wastewater was investigated in an airlift bioreactor (ALB), augmented with a novel heterotrophic nitrifier Pseudonocardia ammonioxydans H9T under organic carbon to nitrogen ratios (Corg/N) ranging from 0 to 12. E ect of the inoculated strain was also determined on the settling properties and the removal of chemical oxygen demand (COD). Two laboratory scale reactors were set up to achieve a stable nitrifying state under the same physicochemical conditions of hydraulic retention time (HRT), temperature, pH and dissolved oxygen (DO), and operated under the sequencing batch mode. The level of DO was kept at 0.5– 1.5 mg/L by periodic stirring and aeration. Each specific Corg/N ratio was continued for duration of 3 weeks. One of the reactors (BR2) was inoculated with P. ammonioxydans H9T periodically at the start of each Corg/N ratio. Sludge volumetric index (SVI) improved with the increasing Corg/N ratio, but no significant di erence was detected between the two reactors. BR2 showed higher levels of nitrogen removal with the increasing heterotrophic conditions, and the ammonia removal reached to the level of 82%–88%, up to10% higher than that in the control reactor (BR1) at Corg/N ratios higher than 6; however, the ammonia removal level in experimental reactor was up to 8% lower than that in control reactor at Corg/N ratios lower than 2. The COD removal e ciency progressively increased with the increasing Corg/N ratios in both of the reactors. The COD removal percentage up to peak values of 88%–94% in BR2, up to 11% higher than that in BR1 at Corg/N ratio higher than 4. The peak values of ammonia and COD removal almost coincided with the highest number (18%–27% to total bacterial number) of the exogenous bacterium in the BR2, detected as colony forming units (CFU). Furthermore, the removal of ammonia and COD in BR2 was closely related to the number of the inoculated strain with a coe cient index (R2) up to 0.82 and 0.85 for ammonia and COD, respectively. These results suggest that it was more e cient for both the ammonia and carbon nutrient removals in a reactor inoculated with a heterotrophic nitrifier at high Corg/N ratio, inferring that the heterotrophic nitrifers would be practically more available in the treatment of wastewater with high level of ammonia and COD.

Copyright © Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.京ICP备05002858号-3