Using graphene oxide to enhance the activity of anammox bacteria for nitrogen removal

Graphene oxide (GO) was applied in this study to enhance the activity of anaerobic ammonium oxidation (anammox) bacteria for nitrogen removal. A GO dose-dependent effect on anammox bacteria was observed through batch tests. The results showed that the activity increased as the GO dose was varied within 0.05–0.1 g L−1. A maximum 10.26% increase of anaerobic ammonium oxidizing activity was achieved at 0.1 g L−1 GO. Analysis of extracellular polymeric substances (EPS) indicated that the highest carbohydrate, protein, and total EPS contents (42.5, 125.7, and 168.2 mg (g volatile suspended solids)−1, respectively) were obtained with 0.1 g L−1 GO. Appropriate GO dose stimulated EPS production to promote the activity of anammox bacteria. Transmission electron microscopy showed the large surface area of GO benefited cell attachment. These findings proved that the application of GO was an effective approach to enhancing the activity of anammox bacteria.