Superiority of basalt fibers with different modifications in contact oxidation reactor for wastewater treatment: Exploration of microbial community and underlying mechanism

Modified basalt fiber (MBF) has been employed as biological carrier to strengthen wastewater treatment. However, few studies focused on the superiority of different MBFs and their microbial mechanisms. In this study, after surface coating and chemical grafting, four MBFs and BF were applied as carriers in contact oxidation reactors. Surface roughness and area of MBFs increased in relation to original BF. Compared to BF group, MBFs could improve nutrients removal performance and stability, probably owing to impacts on microbial community structure. Specifically, calcium coating (Ca-MBF) contributed to the highest ammonium removal in average (72.25%), due to the relative more stimulation on Nitrosomonas and Nitrospira. Improvement on nitrification in Ca-MBF group resulted in the most significant increase of total nitrogen removal by 9.72% (p < 0.05) compared to BF. In contrast, chemical grafting was more inclined to enhance denitrification, particularly in PEI-MBF group, which was 34.62% higher (p < 0.05) than BF. The most enrichment on denitrification bacteria was also observed in PEI-MBF group (51.29%), including Zoogloea, Flavobacterium, and Acinetobacter, causing promotion on microbial denitrification. Besides, chemical grafting brought about more phosphate accumulating organisms like Thauera, Acinetobacter, and Pseudomonas, increasing total phosphorus removal compared to BF by 4.27–18.53%. Nevertheless, the highest phosphorus removal was discovered with Ca modification, inconsistent to the lowest microbial abundance, suggesting that more physical absorption sites by Ca modification was the major reason for enhancement on phosphorus removal. This work provided insights into application potential of different modified BFs for wastewater treatment.