Growing Chlorella vulgaris on thermophilic anaerobic digestion swine manure for nutrient removal and biomass production

Growing Chlorella vulgaris on mixed wastewaters for biodiesel feedstock production and nutrient removal

“…Swine manure and centrate used in this study were collected from the University of Minnesota Southern Research and Outreach Center (Waseca, MN, USA) and the Metropolitan Wastewater Treatment Plant (Saint Paul, MN, USA), respectively. Prior to use, the SM and centrate were pretreated according to the methods described previously . Briefly, the SM was digested with the method of thermophilic anaerobic digestion; and then ammonia and solid particles were removed from the SM using the methods of thermal‐vacuum stripping (55 °C, 63.5 cm Hg, 2 h) and centrifugation (10 000 × g , 25 °C, 10 min), respectively.…”

“…Thus, low cost alternative water and nutrients resources must be used to reduce the production cost of algae cultivation. Previous studies showed that the integration of algae cultivation and wastewater treatment is likely to be one of the most viable strategies for sustainable production of algae‐based biodiesel and bio‐based products because wastewaters provide not only the water source but also most of the necessary nutrients for algal growth …”

“…Some animal manures were found to be suitable media for microalgae cultivation because their nutrient profiles were similar to that of conventional algal culture media . However, high ammonia (NH 4 + ‐N) concentration (3.0–4.0 g L −1 ) and salinity (30.0–50.0 ppt) are two of the major issues during microalgae cultivation using animal manures because they exceed the tolerance levels of microalgae for NH 4 + ‐N concentration and salinity, and would inhibit algal growth . Although the two issues could be addressed through diluting the manures 20–100 times with freshwater, this would consume a large quantity of freshwater and increase the cost of microalgae cultivation.…”

“…Although the two issues could be addressed through diluting the manures 20–100 times with freshwater, this would consume a large quantity of freshwater and increase the cost of microalgae cultivation. To further mitigate these problems, an innovative thermal‐vacuum stripping process was developed and performed in a previous study, where about 90% of NH 4 + ‐N was removed from swine manure (SM) within 2 h . At present, there are no more effective methods to decrease the salinity of SM, except dilution.…”

“…At present, there are no more effective methods to decrease the salinity of SM, except dilution. Results of the previous study showed that after ammonia stripping, a green freshwater microalga, Chlorella vulgaris (UTEX 2714), grew very well on the SM minimally diluted with distilled water (2–4 times), in which the salinity was in the range 6–12 ppt . Instead of freshwater, centrate (concentrated municipal wastewater) was selected to dilute the SM in this study because centrate was the best municipal wastewater stream for cultivating algae, with a very low salinity of 1.33 ppt, which served dual purposes: to further reduce the use of freshwater and to balance the profile of nutrients in the culture media.…”