Application of digester-sludge based biochar on ammonia nitrogen removal

  • Author / Creator
    Tang, Yao
  • Water contamination by ammonium ions presents huge risks to the ecosystems. This work evaluated the potential application of digested sludge pyrolyzed biochar on ammonium removal. Anaerobic digester sludge was collected from a municipal wastewater treatment plant in Alberta, Canada and pyrolyzed separately from 350 ℃ to 550 ℃ with 50 ℃ temperature interval. The characteristics of biochar were analyzed by elemental analysis, scanning electron microscopy (SEM), BET surface area analysis, and fourier transform infrared spectroscopy (FTIR). It was observed that the biochar yield decreased with an increase in the pyrolysis temperature. Biochar produced at 450℃ (BC450) had the highest ammonium remval capacity due to the incereased surface area and function groups. The Langmuir isotherm best described the relation between digested sludge biochar and ammonium removal capacity at the equilibrium point, indicating that monolayer chemical adsorption was the dominating mechanism. Biochar ammonium removal capacity was 1.2mg NH4-N/g biochar in municipal wastewater, which is lower than that in the synthetic ammonium solution (1.4 mg NH4-N/g biochar). Our results demonstrate that the digester sludge biochar is a promising adsorbent for ammonium removal. Aiming to enhance the biochar ammonium removal capacity, biochar-alginate beads were introduced. By combined sodium alginate as the other kind of supporting material with biochar powder under previous treatment condition, biochar-alginate beads were formatted. Based on ammonium adsorption experiment, 1.5% (w/w) of sodium alginate was the optimal concentration of formatting beads and ammonium adsorption. 3% (w/w) of biochar powder concentration was selected as the best concentration of biochar-alginate beads, which enhanced biochar-alginate beads the ammonium capacity increase about 15% from 2.38 mg/g to 2.74 mg/g. The FTIR results also showed that compared to alginate beads and biochar powder alone, the acidic and oxygen surface functional groups have enhanced after the biochar-alginate beads were formatted, which were two important functional groups for ammonium adsorption. Mass transfer and mechanical property results showed that biochar-alginate beads are able to transfer nutrients inside and have better resistance under hash operation condition. After bacteria was imbedded inside biochar-alginate beads, a change of mechanism was observed after 24 hours’ contact time, which indicated that only the adsorbents remove ammonium from aqueous system rather than bacteria gets involved. The 72 hours’ contact time adsorption results showed that biochar-alginate beads imbedded with bacteria were able to uptake 75% of total ammonium. The results indicated biochar-alginate beads can provide a suitable condition for bacterial growth and able to transport nutrients and contaminants inside biochar-alginate beads. Thus, the biochar-alginate beads, the system combined with physisorption, chemisorption and biological removal were established and ready for the further experiments.

  • Subjects / Keywords
  • Graduation date
    Fall 2017
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • 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.