Study on the treatment of livestock and poultry wastewater using algae-bacteria symbiotic system: effect of inoculation proportion and performance

In order to solve the problems of poor tolerance of traditional algal-bacterial symbiosis system to high ammonia wastewater and biomass recovery, a new symbiosis system combining biological agents of nitrifying bacteria and ordinary <i>Chlorella vulgaris</i> was proposed. The results showed that adjusting the volume ratio of algae and bacteria had an effect on the wastewater treatment performance, microalgae growth and flocculation effect. At the optimal algal-bacterial volume ratio of 1:3, the TN, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mrow><mml:mi>NH</mml:mi></mml:mrow><mml:mn>4</mml:mn><mml:mo>+</mml:mo></mml:msubsup></mml:math>-N and COD removal rates were 50%, 70%and 83%, respectively. The high concentration of ammonia nitrogen would have some inhibitory effect on microalgal photosynthesis, but the appropriate inoculation ratio could alleviate this pressure and improve the growth rate of microalgae. Under the optimal inoculation ratio, the PN and PS contents of extracellular polymers were 125.16 and 73 mg/L, respectively, which induced a stronger protective mechanism and enhanced the synergistic effect between algae-bacteria. In addition, the flocculation efficiency of the algal-bacterial system increased from 15% to 30% with the decrease of the initial inoculum of microalgae. The results provided a theoretical basis for the construction of an efficient algal-bacterial symbiosis system for the treatment of livestock and poultry wastewater as well as the efficient flocculation of the algal-bacterial system.