The Algal-Bacterial System (MAS), composed of microalgae and activated sludge, has garnered considerable attention for its simple construction and efficient removal of pollutants such as nitrogen, phosphorus, and Chemical Oxygen Demand (COD) from wastewater. In wastewater treatment, Hydraulic Retention Time (HRT) is a crucial factor directly influencing treatment performance, operational costs, and microbial community composition. However, there has been limited research on the role of HRT in the resourceful treatment of actual wastewater using MAS systems.
Recently, a collaboration between researchers from the Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences led by Dr. Shunni Zhu and Prof. Huu Hao Ngo from the University of Technology Sydney has made progress in the research on resourceful treatment of dairy farm anaerobic digestate using the MAS system. This research was supported by the National Natural Science Foundation of China and the National Key Research and Development Program and the findings have been published in the Journal of Chemical Engineering.
The researchers applied the MAS system, comprising of microalgae and activated sludge, to treat dairy farm anaerobic digestate under three different HRT conditions (4 days, 6 days, and 8 days) for four cycles to investigate the role of HRT in resourceful treatment using MAS for dairy farm anaerobic digestate. The results showed that at HRTs of 4-8 days, the biomass growth of MAS was primarily attributed to microalgae. Longer HRTs facilitated biomass accumulation and nitrogen-phosphorus removal, with the highest biomass production (2.20-2.52 g/L) and nutrient removal (87.68±4.57% for total nitrogen and 100% for total phosphorus) achieved at an HRT of 8 days.
Analysis of the microbial community revealed that HRT significantly influenced the abundance and diversity of bacterial communities, with the highest abundance and diversity observed at an HRT of 6 days. The growth of microalgae selectively enriched specific bacteria, with Proteobacteria and Bacteroidetes being the predominant phyla across all treatment systems. While HRT affected the biochemical composition of MAS biomass, its impact on the calorific value of MAS biomass was not significant. Longer HRTs led to lipid accumulation in biomass due to nutrient deficiency, while shorter HRTs provided sufficient nutrients, resulting in faster MAS growth and accumulation of more polysaccharides.
This research elucidates the influence of HRT on biomass production, pollutant removal, bacterial communities, and biochemical composition of MAS biomass during the resourceful treatment of dairy farm anaerobic digestate. It holds significance for the practical application of MAS systems and the construction of algal-bacterial consortia in continuous treatment processes.
For more information, please refer to the related paper: DOI: 10.1016/j.cej.2024.149538.
