Optimization of parameters for treatment of livestock farming wastewater by algal-bacterial symbiosis

Abstract

Pig farm biogas slurry is high in color and turbidity with high content of nitrogen and phosphorus. The use of microalgae-bacteria symbiosis can simultaneously and efficiently remove carbon，nitrogen and phosphorus，save energy and reduce consumption，and recover resources，meeting the needs of the new era for wastewater treatment. In this study，the three parameters of light intensity，aeration intensity and the proportion of microalgae and bacteria were optimized from the perspectives of pollutant removal and microbial growth. It was found that the amount of aeration had the greatest impact on nitrogen removal，while the three parameters had little impact on carbon and phosphorus removal. After weighted evaluation，the sequence of three factors followed aeration amount>light intensity>inoculation proportion，and the optimal parameter combination is light intensity at 550 μmol/（m2·s），aeration rate at 0.2 L/min，microalgae-bacteria inoculation ratio at 1∶1. The concentrations of TP，COD，TN and NH4+-N in the group with the best comprehensive score were 0.48，219.2，125.2，64 mg/L respectively，and the removal rates were 95.46%，88.58%，61.58% and 80.21% respectively. The particle size of microalgae-bacteria flocs in each group increased，and decreased with the increase of the microalgae-bacteria proportion.

Keywords

• pig farm biogas slurry
• microalgae-bacteria symbiosis
• parameters optimization
• nitrogen and phosphorus removal