Treatment of compound pollution in simulated livestock and poultry wastewater by algae-bacteria symbiosis system

Abstract

Livestock and poultry breeding wastewater contains a large number of heavy metals and antibiotics; the volume is huge, and it is difficult to treat, which causes serious pollution of the environment. Some studies have shown that symbiotic systems can effectively improve the efficiency of sewage treatment, but there is still a lack of research on the treatment of livestock and poultry wastewater. This experiment not only provides a more in-depth discussion of previous studies, but also demonstrates the feasibility of symbiotic treatment of livestock and poultry wastewater and explores the survival mode and operation mechanism of algal and bacterial symbiosis. The results show that the presence of bacteria greatly promoted the growth of microalgae, with production of 0.50-0.59 g/L biomass and 17.5% lipid content. Lipid levels in the algae from the symbiotic system were 1.3 times higher than for the system of pure algae, which is attributed to the bacteria releasing extracellular substances to promote their own growth and providing small molecules of organic matter and other essential elements which can be used by microalgae. In addition, during the removal of complex pollutants in the symbiotic system we found that the main contributor to the removal of heavy metal ions was the adsorption by Chlorella, while the decomposition of antibiotics mainly originated from bacteria. Furthermore, in the context of this experiment was obtained the highest removal rate of SM2 reached 28.8%, while the removal rate of Cu(II) reached 60.6%-66.7%. The technology of symbiotic treatment of wastewater from livestock and poultry breeding fills a gap and lays a theoretical foundation for the improvement of wastewater treatment.

Keywords: Algal-bacterial interactions; Bacterial community structure; Composite pollutants; Lipid accumulation; Pollutant removal.