Enhancing Nitrate Removal from Waters with Low Organic Carbon Concentration Using a Bioelectrochemical System—A Pilot-Scale Study

Abstract

Assessments of groundwater aquifers made around the world show that in many cases, nitrate concentrations exceed the safe drinking water threshold. This study assessed how bioelectrochemical systems could be used to enhance nitrate removal from waters with low organic carbon concentrations. A two-chamber microbial electrosynthesis cell (MES) was constructed and operated for 45 days with inoculum that was taken from a municipal wastewater treatment plant. A study showed that MES can be used to enhance nitrate removal efficiency from 3.66% day−1 in a control reactor to 8.54% day−1 in the MES reactor, if a cathode is able to act as an electron donor for autotrophic denitrifying bacteria or there is reducing oxygen in a cathodic chamber to favor denitrification. In the MES, greenhouse gas emissions were also lower compared to the control. Nitrous oxide average fluxes were −639.59 and −9.15 µg N m−2 h−1 for the MES and control, respectively, and the average carbon dioxide fluxes were −5.28 and 43.80 mg C m−2 h−1, respectively. The current density correlated significantly with the dissolved oxygen concentration, indicating that it is essential to keep the dissolved oxygen concentration in the cathode chamber as low as possible, not only to suppress oxygen’s inhibiting effect on denitrification but also to achieve better power efficiency.

Effect of Cathode Material and Its Size on the Abundance of Nitrogen Removal Functional Genes in Microcosms of Integrated Bioelectrochemical-Wetland Systems

“…Bioelectrochemical systems can be considered to be an effective conjugated system to constructed wetlands for the removal of N from polluted water [7][8][9]. In addition, these systems can be very efficient for removal of organic matter in wastewater treatment [10].…”

“…No previous studies could be found on functional genes of other N transformation processes such as dissimilatory nitrate reduction to ammonia (DNRA), anaerobic ammonia oxidation (ANAMMOX), and complete ammonia oxidation (COMAMMOX) in MFC-CWs. Likewise, only few studies have considered greenhouse gas fluxes in MFC-CWs [9,[22][23][24]26,27].…”

Single-chamber microbial electrosynthesis reactor for nitrate reduction from waters with a low-electron donors’ concentration: from design and set-up to the optimal operating potential

“…The main goal of this study was to achieve a long-term stable NO 3 reduction by denitrification in the constructed MESR for treating wastewater with a low electron donor concentration. However, in our previous study (Lust et al, 2020), where a twochamber MESR was used, the NO 3 reduction rate was relatively low, and a lack of electroactive bacteria was thought to be the cause. The use of two-chamber MESR caused the pH to drift and therefore needed constant neutralizing.…”

“…( 2)) (di Capua et al, 2016;Pang and Wang, 2021;Szekeres et al, 2002). A description and graphical representation of the process have been published previously, where NO 3 reduction was studied in a two-chamber microbial electrosynthesis reactor (MESR) (Lust et al, 2020).…”

A Review on the Use of Membrane Technology Systems in Developing Countries

“…Contamination of nitrate in water resources has become significant, and it can be from the discharge of industrial wastewater or nitrogen fertilizers used in agriculture. The maximum allowable concentration of nitrates in drinking water has been set up at around 50 mg NO 3 − /L as higher than that, will be toxic to humans [51]. RO has been used to treat borehole waters in rural areas in South Africa, and it was found to be effectively suitable for water denitrification where the nitrate-nitrogen was reduced from 42.5 mg/L to only 0.9 mg/L in the permeate [52].…”