Australian Centre for Water
and Environmental Biotechnology

Project Dates: 2014 to 2017


This project aims to substantially reduce the cost of wastewater treatment by developing a technology, and the underpinning science, that will reduce sludge production, improve biological nutrient removal and enhance renewable energy production. A wastewater treatment plant should be operated to achieve satisfactory biological nutrient removal, maximum bioenergy recovery and minimum sludge production. However, the achievement of the above goals is often hindered by the low biodegradability of secondary sludge. The project team has found that free nitrous acid (FNA) was strongly biocidal to secondary sludge. Also, FNA was found to be more biocidal to ammonium oxidizing bacteria than to nitrite oxidizing bacteria (NOB).

Based on these findings, we developed a sludge pre-treatment strategy based on FNA to enhance methane production through anaerobic digestion of secondary sludge and to reduce sludge production during aerobic digestion of secondary sludge. Also, we developed an FNA-based sludge treatment strategy to selectively eliminate NOB and achieve nitrogen removal via the nitrite pathway. Collectively, the FNA-based sludge pre-treatment approach can be used to improve biological nutrient removal, enhance methane production and reduce sludge production simultaneously in a wastewater treatment plant. 




  • ARC Linkage Project