Multiple Microbial Processes in Membrane Aerated Biofilms Studied Using Microsensors

• Author / Creator

  Tan, Shuying

• Membrane aerated biofilms (MABs) have exhibited unique advantages over conventional biofilms for wastewater treatment. However, due to the limited available technology to probe the internal biofilms, the information for multiple microbial processes inside the MABs is quite inadequate. Microsensor techniques make it feasible to detect chemical gradients and herein explore the microbial activities of processes inside biofilms. In this work, multiple microbial processes including sulfate reduction, sulfide oxidation, nitrification and denitrification inside the MABs were investigated using microsensor techniques. O2, pH, H2S, ORP, NH4+ and NO3- microsensors were successfully fabricated and implemented to measure in situ the corresponding chemical gradients inside the MABs. The amperometric H2S microsensor was further developed and displayed linear response within the range of 0 - 600 μM (20.4 mg·L-1) total sulfide concentration with a high sensitivity up to 1.21 pA·μM-1. The response time could be less than 1 second. This H2S microsensor was used to measure the change of H2S concentrations from the low to high and from the high to low. The simultaneous occurrence of multiple microbial processes inside a piece of MAB has been revealed using microsensor techniques. The multiple microbial processes were stratified: sulfate reduction followed by denitrification and sulfide oxidation near the bulk liquid-biofilm interface; nitrification in the middle; and aerobic oxidation near the membrane. These results were promising in providing multi-functional biofilms for engineering applications. COD/SO42- ratios of 1 and 2 at constant COD concentration were examined to evaluate the effects of COD/SO42- ratios on the ability of simultaneous multiple microbial processes. The results showed that under the two conditions, the activity of sulfate reduction at COD/SO42- ratio of 1 was higher. COD/NH4+ ratios of 4 and 10 at constant COD concentration were investigated to check the effects of COD/NH4+ ratio on the occurence of simultaneous multiple microbial processes. It was found that nitrification and denitrification activities at a COD/NH4+ ratio of 4 were higher than those at a COD/NH4+ ratio of 10. The biofilm structures were observed using scanning electron microscopy. Microscopic observations showed the denser structure near the bulk liquid-biofilm interface and porous structure near the membrane.

• Subjects / Keywords

  • Multiple Microbial Processes
  • Microsensors
  • Membrane Aerated Biofilm

• Graduation date

  Fall 2012

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R32D44

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.