Resource recovery from biological wastewater treatment system and biosolids

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Biological wastewater treatment is an established cost-effective treatment option to remove wastewater pollutants. Currently, the International Water Association considers aerobic granular sludge (AGS) as one of the most promising biological municipal wastewater treatment technologies of the 21st century. Aerobic granules, with a size range of 0.2-5 mm, are a dense colony of different strains of microorganisms held together by extracellular polymeric substances (EPS) secreted by the bacterial cells under special operational conditions. Both municipal and different industrial wastewaters have been effectively treated using AGS biotechnology. In addition to efficient wastewater treatment, AGS offers the opportunity to recover high-value products from the wastewater. This is due to the high EPS content in the granule matrix and the biochemical reactions that take place in the granule matrix. Four high-value products are presently recovered from sludge from AGS reactors: phosphorus, polyhydroxyalkanoates, alginate-like exopolysaccharides, and tryptophan. Recently, curdlan, tyrosine and phenylalanine have also been identified in the sludge from AGS systems. Xanthan is widely applied as a supplement in the food industry and for viscosity control in the oil industry. The xanthan gum market was estimated at US$987.7 million in 2020. Curdlan is used in the food (thickening agent), cosmetic (moisturizing increase, and incense agents), and biomedical/pharmaceutical (antitumor or anti-HIV) industries. With the approval of curdlan by the US Food and Drug Administration for use in the food industry in 2005, there is a growing market demand for curdlan. Tyrosine is used as a food supplement and in the production of medicines. Phenylalanine is used as a feed and food supplement, a building block for the production of the artificial sweetener aspartame, and in agriculture for postharvest preservation. To date, the recovery of xanthan, curdlan, tyrosine, and phenylalanine from the sludge generated by AGS systems has not been explored. Since the EPS in the sludge is naturally occurring and an eco-friendly alternative material, and in view of the high market demand for xanthan, curdlan, tyrosine, and phenylalanine, the proposed research aims at optimizing their production in the matrix of aerobic granules while maintaining wastewater treatment. Effective extraction protocols from sludge and recovery protocols applicable to each of these resources will also be developed. The outcomes of this research have the potential to advance Canada's economic interests. Resource recovery will open a new market for economic success and create a competitive advantage for local wastewater management industries. Resource recovery from the sludge produced by AGS systems will lead the way to attaining a circular economy, and enhancing economic prosperity. Additionally, highly qualified personnel will also be thoroughly trained in the research program for the Canadian workforce.