Combining electro-bioremediation of nitrate in saline groundwater with concomitant chlorine production

Groundwater pollution and salinization have increased steadily over the years. As the balance between water demand and availability has reached a critical level in many world regions, a sustainable approach for the management (including recovery) of saline water resources has become essential. A 3-compartment cell configuration was tested for a new application based on the simultaneous denitrification and desalination of nitrate-contaminated saline groundwater and the recovery of value-added chemicals. The cells were initially operated in potentiostatic mode to promote autotrophic denitrification at the bio-cathode, and then switched to galvanostatic mode to improve the desalination of groundwater in the central compartment. The average nitrate removal rate achieved was 39±1 mgNO3-N L−1 d−1, and no intermediates (i.e., nitrite and nitrous oxide) were observed in the effluent. Groundwater salinity was considerably reduced (average chloride removal was 63±5%). Within a circular economy approach, part of the removed chloride was recovered in the anodic compartment and converted into chlorine, which reached a concentration of 26.8±3.4 mgCl2 L−1. The accumulated chlorine represents a value-added product, which could also be dosed for disinfection in water treatment plants. With this cell configuration, WHO and European legislation threshold limits for nitrate (11.3 mgNO3-N L−1) and salinity (2.5 mS cm−1) in drinking water were met, with low specific power consumptions (0.13±0.01 kWh g−1NO3-Nremoved). These results are promising and pave the ground for successfully developing a sustainable technology to tackle an urgent environmental issue. 

Additional Info

  • Year: 2021
  • Authors: Puggioni G., Milia S., Dessì E., Unali V., Pous N., Balaguer M.D., Puig S., Carucci, A.
  • Reference: Water Research, Volume 2061, November 2021, Article number 117736

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