Algal-bacterial symbiosis system treating high-load printing and dyeing wastewater in continuous-flow reactors under natural light

Abstract

This study investigated the symbiotic structure relationship between mixed algae and activated sludge while treating high-load printing and dyeing wastewater under natural light. The effects of hydraulic retention time (HRT) (12 h, 16 h and 20 h) and aeration rate (0.1-0.15, 0.4-0.5 and 0.7-0.8 L/min) on algal-bacterial symbiosis (ABS) and conventional activated sludge (CAS) systems. Experimental results showed that the ABS system exhibited the best removal performance for chemical oxygen demand (COD), ammonia nitrogen (NH4+-N) and total phosphorus (TP), which was increased by 12.5%, 23.1% and 10.5%, respectively, and reduced colour 80 times compared with the printing and dyeing wastewater treatment plant. Algae growth could be promoted under lower dissolved oxygen (DO), and the addition of algae could provide more DO to the ABS system. The particle size distribution of sludge in the ABS system was stable, which guaranteed a stable treatment effect. In addition, the COD and colour could be further degraded under the conditions of no external carbon source and longer HRT. It is expected that the present study will provide a foundation for the practical application of the ABS system, and new insights for the treatment of printing and dyeing wastewater.