Enhancement of nitrate removal under limited organic carbon with hydrogen‐driven autotrophic denitrification in low‐cost electrode bio‐electrochemical reactors

Abstract

BACKGROUND Nitrate‐contaminated water is a concerning environmental and health problem in agricultural areas. Due to its low organic carbon content, such water cannot be purified using a conventional bioreactor with heterotrophic denitrification. Low‐cost bio‐electrochemical reactors were established with the aim of enhancing denitrification performance by cooperation of heterotrophic and hydrogenotrophic denitrification. RESULTS At the lowest C/N ratio of 1.0, the bioreactor reached only 67.4% for NO3‐N removal and 47.5% for total N removal (total N removal rate of ca 1.2 mg L−1 h−1), whereas the Cu reactor (bio‐electrochemical reactor using copper wire as cathode) achieved the best efficiencies of 73.7% and 53.8% for NO3‐N and total N removal (total N removal rate of ca 1.3 mg L−1 h−1), and followed by the SS reactor (bio‐electrochemical reactor using stainless steel wire as cathode). On the other hand, the greatest total organic carbon (TOC) removal efficiency was observed for the bioreactor and followed by the SS reactor and the Cu reactor. The low TOC consumption of 1.2–1.4 mg‐TOC (mg‐N)−1 in the Cu reactor and the SS reactor indicated the enhanced denitrification from coexisting hydrogenotrophic denitrification. In addition, the performance of hydrogenotrophic denitrification was improved by increasing the applied current from 10 to 30 mA. CONCLUSIONS The abundance of autotrophic denitrifying bacteria (identified as hydrogenotrophs) was higher than that of heterotrophic denitrifying bacteria in both the Cu reactor and the SS reactor. Archromobacter and Flavobacterium were the most dominant genera in the biofilm of the Cu reactor cathode and in the suspended sludge, respectively. Hydrogenophaga were detected in both biomass samples, but were absent from the biomass samples of the conventional bioreactor. © 2021 Society of Chemical Industry (SCI).

Research progress of novel bio-denitrification technology in deep wastewater treatment

“…This has resulted in the development of economically and environmentally friendly bio-denitrification technologies that hold great promise. Examples include partial short-cut nitrification ANAMMOX (PN-ANAMMOX; Qiu et al, 2021 ; Wang Z., 2021 ; Shang et al, 2023 ; Yuan et al, 2023 ), ANAMMOX-SND ( Yu Y. et al, 2022 ), sulfur autotrophic-iron autotrophic denitrification ( Yang et al, 2023 ), iron autotrophic-hydrogen autotrophic denitrification ( Liang et al, 2022 ), and bioelectrochemical denitrification ( Huang et al, 2020a ; Prarunchaya et al, 2021 ). In this context, the focus will primarily be on the short-range nitrification anaerobic ammonia oxidation process and the bioelectrochemical system.…”

“…Section 2.2 introduces several novel bio-denitrification coupling technologies, and Table 2 provides data on denitrification and carbon removal performance during the application of selected coupling denitrification technologies. As demonstrated in Table 2 , the actual wastewater treated by these new biological denitrification coupling processes includes landfill leachate ( Wang Z., 2021 ), domestic wastewater ( Huang et al, 2020a ; Prarunchaya et al, 2021 ; Qiu et al, 2021 ; Liang et al, 2022 ; Shang et al, 2023 ; Yang et al, 2023 ; Yuan et al, 2023 ), and chemical wastewater ( Wang et al, 2022 ; Yu D. Y. et al, 2022 ; Jia et al, 2023 ), closely resembling the wastewater types addressed by the new biological denitrification technologies in Table 1 . PN-ANAMMOX technology has emerged as the most prevalent coupling method in recent years, showcasing its versatility in handling a wide range of nitrogen loads and consistently achieving robust denitrification efficiency exceeding 90% ( Qiu et al, 2021 ; Wang Z., 2021 ; Shang et al, 2023 ; Yuan et al, 2023 ).…”

“…Transportation safety risks associated with H 2 limit the application of hydrogen autotrophic denitrification ( Zhang Y. H. et al, 2014 ). However, BES with external electric fields can produce hydrogen in situ , providing a local source of H 2 for hydrogen autotrophic denitrification ( Prarunchaya et al, 2021 ). Nevertheless, the extra electricity needed for this coupled technology increases its operational costs, to some extent, restricting its large-scale practical application.…”

Development of Bio-Electrochemical Reactor for Groundwater Denitrification: Effect of Electric Current and Water Hardness

“…Due to previous studies, the water hardness (e.g., Ca 2+ , Mg 2+ ) was able to deposit on the cathode surface during electrolysis. This chemical deposition adversely affected the cathodic electrolysis, and directly impacted the microbial activity, leading to a decline in NO 3 -N removal by autohydrogenotrophic denitrification [13,14]. The electrochemical method was applied to remove the hardness.…”