Abstract

Tannery wastewater and breeding wastewater both contain high concentrations of total nitrogen (TN), and their direct discharge leads to water eutrophication. The TN removal rate for both tannery wastewater and breeding wastewater treated with the bioflocculant modified by sm-A3 amphoteric starch was optimised using the TN removal rate as the indicator in this study. Single-factor and orthogonal experiments were conducted to investigate the effects of initial pH, initial TN concentration, flocculant dosage and flocculation time. Results showed that for tannery wastewater, the highest TN removal rate (81.62%) was achieved under optimal conditions: initial p 8.0, initial TN concentration 150mg/L, flocculant dosage 0.06g/100mL, and flocculation time 8 min. For aquaculture wastewater, the optimal conditions were initial pH 7.0, initial TN concentration 125mg/L, flocculant dosage 0.07g/100mL, and flocculation time 16min, yielding a TN removal rate of 82.68%. Orthogonal experiments revealed that pH and flocculant dosage significantly impacted the TN removal (p<0.01). The modified bioflocculant outperformed unmodified bioflocculant and amphoteric starch alone in the TN removal. This work provides an environmentally friendly solution for treating high-nitrogen wastewater, supporting potential industrial applications.