Computer vision-assisted sorting and selective cultivation of high-activity anammox granules

Anaerobic ammonium oxidation (anammox) granular sludge is a rapidly developing biological wastewater treatment technology characterized by high nitrogen removal efficiency, and now is being at the stage of engineering application and process optimization. Both laboratory and full-scale observations have consistently shown that anammox sludge comprises granules with distinct color variations, typically ranging from yellow to red. Our previous study demonstrated that red-colored granules exhibit significantly higher biochemical activity at the single-granule level. Building upon this insight, the present study introduces a computer vision-assisted fluidic sorting technique capable of selectively separating red granules from heterogeneous sludge populations. Extended cultivation of the sorted granules revealed superior nitrogen removal performance and biomass proliferation compared to unsorted granules. In addition, the red granule-enriched reactor demonstrated enhanced biological stability, maintaining and even improving metabolic activity over time. This approach not only accelerates the acclimation, enrichment, and startup of anammox systems but also provides a scalable strategy for advancing high-rate and sustainable nitrogen removal in environmental biotechnology.