What are the new perspectives on free nitrous acid uses for sustainable wastewater management?

The high-quality development of a country cannot be separated from environmental protection and improving water use efficiency, among which sustainable wastewater management plays an important role. Free nitrous acid (FNA) has been widely applied in urban wastewater management, including sewer networks, wastewater treatment processes, and sludge treatment processes. However, these applications are associated with great costs to produce FNA at the required levels, leaving many enterprises can’t bear the heavy load. In a recently published paper, researchers proposed a new approach to facilitating in situ FNA generation by acid-tolerant ammonia oxidizers.

The paper was published in Frontiers of Environmental Science & Engineering on December 5.

Researchers make a lot of efforts to reduce negative impacts of FNA on wastewater treatment, improve the efficiency of FNA treatment, increase FNA production, and lower the cost. Yet, challenges like high-strength wastewater are unavailable for many wastewater treatment facilities demand solutions. A researcher at National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology and Engineering Research Center of Beijing, Beijing University of Technology, Beijing, China, proposed a new approach to producing FNA in situ from low-strength of wastewater and said “We focus on the concept of in situ FNA generation facilitated by acid-tolerant ammonia oxidizers and highlight the multiple benefits it creates, after a brief review of the historical development of FNA-based technologies.”

“The acid-tolerant AOB offers the possibility of achieving in situ FNA accumulation through operating sewage and sludge treatment units in acidic operations. First, it allows for the achievement of FNA concentrations at ppm levels even in low-strength municipal wastewater. Second, compared to the periodic treatment of biomass with FNA generated ex situ, the high in situ FNA concentration ensures the continuous exposure of the entire system to the harsh conditions, theoretically maximizing the benefits.” said Zuo.

Researchers also highlight the multiple benefits of in situ FNA self-sustained by acid-tolerant AOB for wastewater management from the perspective of robust nitridation in mainstream treatment of domestic wastewater, acidic sludge treatment for reduction, stabilization, and toxic metal removal.

“We propose broader possibilities through the utilization of acid-tolerant AOB to enhance wastewater management,” said Zuo. The FNA produced in situ could simultaneously remove micropollutants. In addition, FNA-induced cell lysis could support pathogen inactivation. Moreover, using acid-tolerant AOB, a high FNA level could be generated, which is expected to mitigate membrane fouling. Furthermore, the utilization of acid-tolerant AOB led to FNA being self-sustained and optimizing Algae-Based Wastewater Treatment.

In the future, researchers will leverage the potential of acid-tolerant ammonia oxidizers to discuss how wastewater systems can be made more energy-efficient and sustainable.

Contributors include Zhiqiang Zuo and Yongzhen Peng of Beijing University of Technology, Min Zheng of Australian Centre for Water and Environmental Biotechnology (the University of Queensland), Liu Tao of the Hong Kong Polytechnic University, and Zhiguo Yuan of City University of Hong Kong. Zhiqiang Zuo and Liu Tao are also affiliated with the University of Queensland; Min Zheng is affiliated with University of New South Wales.

The International Postdoctoral Exchange Fellowship Program (China), the National Natural Science Foundation of China, Australian Research Council (ARC) Industry Fellowship, an ARC DECRA Fellowship, and the Government of the Hong Kong Special Administrative Region, China supported this research.