Effect of zero-valent iron and granular activated carbon on nutrient removal and community assembly of photogranules treating low-strength wastewater

Traditional wastewater treatment processes with high energy consumption and greenhouse gas emissions are not suitable for rural areas with low sewage strength and wide distribution. In this study, a microalgae-bacteria synergistic photogranules system was developed under the impetus of green chemical additives to address these challenges. The results showed that zero-valent iron (ZVI) or granular activated carbon (GAC) addition made successful photogranulation treating low-strength wastewater with excellent settleability and stability performance (settling velocity: 14–22 m h−1; integrity coefficient: 0.81–6.62%), while systems without light or additives failed due to the bio-granules disintegration caused by the overgrowth of predators or phototrophic species. A better nutrient removal performance (TN