Immobilization-mediated algae-bacteria interactions improve swine wastewater treatment and microalgal biomass energy...

Swine wastewater contains extremely high levels of chemical oxygen demand, nitrogen, phosphorus, and other pollutants, posing serious risks to farm ecosystems and public health. Traditional treatment methods often fail to simultaneously achieve high pollutant removal and resource recovery. This study systematically elucidated the mechanisms underlying swine wastewater treatment and enhanced resource conversion efficiency by Chlorella pyrenoidosa, with particular focus on algae-bacteria interactions regulated in different COD loading by immobilization. The results indicate that immobilization restructures microbial competition and facilitates algal dominance at COD₀ = 1000 mg L^-1, enabling C. pyrenoidosa to maintain higher cell activity, photosynthetic capacity, and biomass production compared with suspended cultures, which effectively enhances the removal and conversion efficiency of pollutants. After immobilization of C. pyrenoidosa, conversion efficiencies of carbon, nitrogen, and phosphorus in wastewater reached 83.43%, 97.99%, and 91.87%, representing 1.41-, 3.40-, and 2.67-fold increases over the suspended state, respectively. Consequently, lipid and total protein production were enhanced by 4.0- and 1.2-fold. The immobilization has potential functions in promoting the expression of stress resistance-related proteins and genes of bacterial community, thereby enhancing its tolerance to wastewater and improving treatment efficiency. Dehydrogenase activity and chlorophyll content increased by 47% and 101.66%, respectively, further supporting enhanced physiological performance. This study reveals the mechanism of C. pyrenoidosa in swine wastewater treatment and provides a theoretical basis for designing high-performance immobilized algal systems, offering a promising approach for integrated wastewater treatment and resource recovery in swine wastewater.