The establishment of a microalgae-bacteria co-culture system for real anaerobic digestion piggery effluent treatment

A microalgae-bacteria co-culture system was established by combining in-situ activated sludge bacteria ( ASB ) with Chlorella vulgaris ( C. vulgaris ) for the treatment of real anaerobic digestion piggery effluent (ADPE). The results suggest that the optimal strategy for establishing the co-culture system is an initial inoculation with ASB for one day, followed by C. vulgaris , with an inoculation ratio of 1:1. Subsequently, a custom-designed C. vulgaris - ASB biofilm photobioreactor was employed for scale-up testing under semi-continuous operation. This photobioreactor demonstrated competitive performance in treating ADPE, achieving removal efficiencies of approximately 60 %, 70 %, 98 % and 66 % for total phosphorus (TP), total nitrogen (TN), ammonia nitrogen (NH 4 + -H) and chemical oxygen demand (COD), respectively. Interestingly, a higher renewal rate of ADPE contributed to more efficient COD removal, which is typically considered the most challenging parameter in wastewater treatment. Benefiting from the effective COD reduction, the effluent under 30 % renewal conditions met the discharge standards for pollutants from livestock and poultry breeding (GB18596–2022, China). Microbiome analysis reveals that higher ADPE renewal rates were correlated with increased microbial biodiversity. This study highlights the great potential of the C. vulgaris-ASB consortia system to treat real ADPE while simultaneously facilitating microalgal biomass recovery. • A co-culture of activated sludge bacteria and Chlorella vulgaris treated real ADPE. • Optimizing inoculation sequence and ratio improves co-culture system performance. • Treated ADPE met the discharge requirements of Chinese national standards. • Metagenomics revealed microbial community shifts, interactions, and dynamic changes.