Performance and mechanism of sacrificed iron anode coupled with constructed wetlands (E-Fe) for simultaneous nitrogen and phosphorus removal

Electrochemically enhanced micro-electrolytic ceramic substrate infiltration system as an efficient approach for treatment of imidacloprid wastewater

In this study, an electrochemically coupled micro-electrolytic technology-enhanced soil infiltration system (E-ME-SIS) was proposed to address the problem of the high cost of traditional soil infiltration system (SIS) and the difficulty of removing imidacloprid (IMI) wastewater efficiently by a single treatment process. Micro-electrolytic ceramic substrates (MECS) were prepared from iron, activated carbon, aluminum, and fly ash and combined with an external power source to optimize the electrochemical and micro-electrolytic synergy and investigate their effectiveness in treating IMI wastewater. The results showed that MECS had a rough surface with a specific surface area of 2.682 m2/g, combining strong adsorption capacity (maximum adsorption of 1.149 mg/g) and wear resistance (24 h wear rate of 6.4%). The removal of total nitrogen (TN), total phosphorus (TP), and IMI by E-ME-SIS was stabilized at 99%, 98%, and 98%, respectively, at a current density (CD) of 0.625 mA/cm2 and influent C/N (COD/N) = 5. This study significantly enhanced the removal of difficult-to-degrade pollutants by SIS through an electrochemically enhanced micro-electrolysis reaction, which provides an energy-saving and stable technical reference for the efficient treatment of IMI wastewater with a potential for engineering applications.

Mechanisms and mitigation control of clogging in constructed wetlands: Insight into the enhancement of the bioelectrochemical systems

Constructed wetlands (CWs), a cost-effective and eco-friendly wastewater treatment technology, are extensively applied in various types of wastewater treatment. There is a series of strong impacts on CWs performance by the accumulation of clogging matters which attribute to physical, chemical, and biological processes after the long-term operation. This paper summarizes the mechanism of clogging formation, which can be classified into physical, chemical, and biological clogging. Moreover, it analyzes the typical measures for preventing and controlling clogging in CWs. The integration of bioelectrochemical systems (BES), including microbial fuel cells (MFCs) and microbial electrolysis cells (MECs) into CWs is proposed as a safe and efficient way to alleviate substrate clogging on-site, owing to the fact that BES can easily automate the control or adjustment of its internal electric field form. The mechanism of clogging control by CW-BES is comprehensively described and analyzed. With the help of BES, the clogging substances obtained optimized occurrence form, reduced hydrophobicity and advantageous spatial distribution. Besides, the microbial community achieved promoted structure, accelerated rates of electron transfer and more diverse metabolic pathway. Compared to traditional methods for evaluating the clogging of CWs, the MFC sensor offers the advantages of being fast, enabling in-site detection, and being non-destructive. Future research should be focused on the theoretical underpinnings for putting CW-BES into practical use. Additional, efforts should be made to ensure the stable, long-term operation of CWs.

Fulvic acid impact on constructed wetland-microbial electrolysis cell system performance: Metagenomic insights

This study explores the roles of fulvic acid (FA) in both a conventionally constructed wetland (CCW) and a newly constructed wetland-microbial electrolysis cell (ECW). The results showed that FA increased the average removal efficiency of chemical oxygen demand, total phosphorus, total nitrogen, and ammonia nitrogen in ECW by 8.6, 46.2, 33.0, and 27.9 %, respectively, compared to CCW, and reduced the global warming potential by > 60 %. FA promoted the proliferation of electroactive bacteria (e.g., Chlorobaculum and Candidatus Tenderia) and FA-degrading bacteria (e.g., Anaerolineaceae and Gammaproteobacteria) and reduced methanogens (e.g., Methanothrix) via type-changing. The study's findings suggest that FA influences pollutant removal and microbiome dynamics by altering dissolved oxygen levels and redox potential. In summary, FA and ECW enhanced the efficiency of constructed wetlands by facilitating electron transfer and consumption, and supporting microbial growth and metabolism.

Autotrophic denitrification based on sulfur-iron minerals: advanced wastewater treatment technology with simultaneous nitrogen and phosphorus removal

Autotrophic denitrification technology has many advantages, including no external carbon source addition, low sludge production, high operating cost efficiency, prevention of secondary sewage pollution, and stable treatment efficiency. At present, the main research on autotrophic denitrification electron donors mainly includes sulfur, iron, and hydrogen. In these autotrophic denitrification systems, pyrite has received attention due to its advantages of easy availability of raw materials, low cost, and pH stability. When pyrite is used as a substrate for autotropic denitrification, sulfide (S2-) and ferrous ion (Fe2+) in the substrate will provide electrons to convert nitrate (NO3-) in sewage first to nitrite (NO2-), then to nitrogen (N2), and finally to discharge the system. At the same time, sulfide (S2-) loses electrons to sulfate (SO42-) and ferrous ion (Fe2+) loses electrons to ferric iron (Fe3+). Phosphates (PO43-) in wastewater are chemically combined with ferric iron (Fe3+) to form ferric phosphate (FePO4) precipitate. This paper aims to provide a detailed and comprehensive overview of the dynamic changes of nitrogen (N), phosphorus (P), and other substances in the process of sulfur autotrophic denitrification using iron sulfide, and to summarize the factors that affect wastewater treatment in the system. This work will provide a relevant research direction and theoretical basis for the field of sulfur autotrophic denitrification, especially for the related experiments of the reaction conversion of various substances in the system.