Potential of free nitrous acid (FNA) for sludge treatment and resource recovery from waste activated sludge: A review

• Published in: Journal of environmental management 2024-06, Vol.360, p.121170-121170, Article 121170
• Main Authors: Jiang, Tan, Li, Xiaodi, Yang, Jiayi, Wang, Lu, Wang, Wen, Zhang, Li, Wang, Bo
• Format: Article
• Language: English
• Subjects: Free nitrous acid; Resource recovery; Sludge dewatering; Sludge reduction; Waste activated sludge
• ISSN: 0301-4797; 1095-8630
• DOI: 10.1016/j.jenvman.2024.121170

The escalating production of waste activated sludge (WAS) presents significant challenges to wastewater treatment plants (WWTPs). Free nitrous acid (FNA), known for its biocidal effect, has gained a growing focus on sludge dewatering, sludge reduction, and resource recovery from WAS due to its eco-friendly and cost-effective properties. Nevertheless, there have been no attempts made to systematically summarize or critically analyze the application of FNA in enhancing treatment and resource utilization of sludge. In this paper, we provided an overview of the current understanding regarding the application potential and influencing factors of FNA in sludge treatment, with a specific focus on enhancing sludge dewatering efficiency and reducing volume. To foster resource development from sludge, various techniques based on FNA have recently been proposed, which were comprehensively reviewed with the corresponding mechanisms meticulously discussed. The results showed that the chemical oxidation and interaction with microorganisms of FNA played the core role in improving resource utilization. Furthermore, current challenges and future prospects of the FNA-based applications were outlined. It is expected that this review can refine the theoretical framework of FNA-based processes, providing a theoretical foundation and technical guidance for the large-scale demonstration of FNA. •RNS generated by FNA induces cell lysis and EPS decomposition of sludge.•FNA concentration and contact time affect the sludge dewatering and sludge reduction.•Resource recovery is improved as more soluble substrates are released from WAS by FNA.•FNA and its derivative can prominently affect the microbial community abundance.•The current challenges and future studies based on FNA are proposed and discussed.