Effects of sodium acetate, glucose, and Chlorella powder as carbon source on enhanced treatment of phenolic compounds and NO2–-N in coal pyrolysis wastewater

Large amount of phenols and nitrogen in coal pyrolysis wastewater have become a major bottleneck that restricts industrial development. There are few studies on enhanced phenol treatment and short-cut denitrification with dried Chlorella powder as carbon source in coal pyrolysis wastewater treatment. This study aimed to explore the effects of sodium acetate, glucose, and Chlorella powder as carbon source on enhanced treatment of phenolic compounds and NO2−-N in coal pyrolysis wastewater. The appropriate dosage of Chlorella powder was 180 mg/L in the reactor. The corresponding removal ratios of chemical oxygen demand (COD), total phenol (TPh), NO2−-N, and total nitrogen were 96.91%, 98.60%, 99.50%, and 98.60%, respectively. The pH of influent in reactor with Chlorella powder should be maintained between 6.5 and 7.5, whereas the hydraulic retention time (HRT) should be maintained above 8 h. Sodium acetate, glucose, and Chlorella improved the stability and sedimentation of sludge. Addition of Chlorella powder in the reactor resulted in the enrichment of Comamonas (5.83%), Povalibacter (9.53%), Acidaminobacter (13.41%), Youngiibacter (8.81%), Flavobacterium (5.09%), and Gemmobacter (5.03%). Among these, Comamonas, Povalibacter, Youngiibacter, Flavobacterium, and Gemmobacter are phenolic compounds degrading functional bacteria, whereas Povalibacter, Flavobacterium, and Gemmobacter are short-cut denitrification functional bacteria. Combined with economic analysis, the results revealed that Chlorella powder has advantages of good treatment effect, easy addition, low direct cost, and low operation and maintenance cost. Thus, Chlorella powder can be used as an alternative carbon source for phenol degradation and short-cut denitrification of coal pyrolysis wastewater.