Effect of cathode material and charge loading on the nitrification performance and bacterial community in leachate treating Electro-MBRs

• Published in: Water research (Oxford) 2020-09, Vol.182, p.115990-115990, Article 115990
• Main Authors: Roy, Dany, Drogui, Patrick, Rahni, Mohamed, Lemay, Jean-François, Landry, Dany, Tyagi, Rajeshwar D.
• Format: Article
• Language: English
• Subjects: Ammonia nitrogen; Electro membrane bioreactor; Electro-coagulation; Leachate; Microbial community; Nitrification
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2020.115990

Electro-MBR technology, which combines an electrocoagulation process inside the mixed liquor of a membrane bioreactor, was studied for the treatment of a high-strength ammonia leachate (124 ± 4 mg NH4-N L−1). A lab-scale aerobic Electro-MBR was operated with a solid retention time of 45 days, hydraulic retention times of 24h and 12h, and charge loading ranging from 100 to 400 mAh L−1. At 400 mAh L−1, with a combination of a Ti/Pt cathode and a sacrificial iron anode, removal percentages for ammonia nitrogen, total organic carbon, and total phosphorus were 99.8%, 38%, and 99.0%, respectively. At 400 mAh L−1, the estimated ferric ion dosage was 325 mg Fe3+ L−1. Experiments conducted with different cathode materials showed that previously reported inhibition phenomena may result from a cathodic nitrate reduction into ammonia nitrogen. Conventional cathode materials, such as graphite, have electrochemical nitrate reduction rates of −0.03 mg NO3-N mAh−1. By comparison, when using Ti/Pt, the rate was −0.0045 mg NO3-N mAh−1(85% lower than graphite due to its low hydrogen overpotential). Charge loading tested in this study had no significant impact on both nitrification performance and microbial population diversity. However, the relative abundance of the mixed liquor’s Nitrosomonas increased from 4.8% to 8.2% when the charge loading increased from 0 to 400 mAh L−1. Results from this study are promising for future applications of the Ti/Pt - Iron Electro-MBR in various high-strength ammonia wastewater treatment applications. [Display omitted] •Nitrate cathodic reduction rate depends on the cathode material’s hydrogen overpotential.•Ferric ion dosage of 82–325 mg Fe L−1 has shown no nitrification inhibition phenomena.•Nitrification inhibition is avoided by the use of a platinized titanium cathode.•Nitrosomonas relative abundance is positively correlated to the charge loading.•A Ti/Pt-Fe Electro-MBR can simultaneously remove >99% of NH4 and Ptot at 400 mAh L−1.