Insight into dissolved organic nitrogen transformation and characteristics: Focus on printing and dyeing wastewater treatment process

Textile industry discharges large amounts of printing and dyeing wastewater (PDW) containing high concen-tration of refractory dissolved organic nitrogen (DON). However, the DON transformation and characteristics during PDW treatment, and its potential environment impact receive little concern. Treatment groups of dyeing wastewater (G-RB5), printing wastewater (G-Urea) and domestic wastewater (G-NH4Cl) with Reactive Black 5 (RB5), Urea and NH4Cl as influent nitrogen species were set to compare the DON behavior during the hydrolytic acidification-aerobic-anoxic process. G-RB5 exhibited higher DON concentrations with greater fluctuations, and its effluent dominated low molecular weight (LMW) and hydrophilic DON, showing high bioavailability (67.6%) and low biodegradation (8.0%). In the aerobic section, the concentration of microorganism-derived DON in G-RB5 was higher but the nitrogen species were fewer than G-Urea and G-NH4Cl. Grey relational analysis revealed that Proteobacteria and Thauera were the common bacteria strains showing high association degree (gamma > 0.9) with biodegradable DON (ABDON) in all groups; while microbes related with biodegradable DON (BDON) varied between groups. The higher contents of DON, ABDON, LMW-DON and hydrophilic DON induced by RB5 highlight the importance of controlling DON from textile industry to mitigate the potential risk like algae growth stimulation, which needs more attention in future.

Automated summary

The textile industry discharges printing and dyeing wastewater containing high levels of refractory dissolved organic nitrogen (DON), but little attention has been focused on its transformation and characteristics during treatment, as well as its potential environmental impact.