Effect of Methylene Blue on the Properties and Microbial Community of Anaerobic Granular Sludge

Basic dyes, which are widely used in industry, can cause serious damage to the environment if they are discharged to waterways. If directly discharged into water, they can cause serious damage to the environment due to their deep color and low degradation rate. The results showed that the average chemical oxygen demand removal rate from the wastewater was greater than 60%, while the methylene blue removal rate was greater than 90%. Anaerobic granular sludge can remove methylene blue and organic matter simultaneously. Candidatus Cloacimonetes was not detected when the methylene blue concentration was 0 mg/L, 2 mg/L, or 4 mg/L. When the methylene blue concentration was 6 mg/L, 8 mg/L, and 10 mg/L, more Candidatus Cloacimonetes was detected in the sludge as the concentration of methylene blue increased. The Candidatus Cloacimonetes content was found to be 1.02%, 1.08%, and 2.11% in these samples, respectively.