Nutrient removal and biogas upgrading by integrating freshwater algae cultivation with piggery anaerobic digestate liquid treatment

Abstract

An integrated approach that combined freshwater microalgae Scenedesmus obliquus (FACHB-31) cultivation with piggery anaerobic digestate liquid treatment was investigated in this study. The characteristics of algal growth, biogas production, and nutrient removal were examined using photobioreactor bags (PBRbs) to cultivate S. obliquus (FACHB-31) in digestate with various digestate dilutions (the concentration levels of 3200, 2200, 1600, 1200, 800, and 400 mg L(-1) chemical oxygen demand (COD)) during 7-day period. The effects of the level of pollutants on nutrient removal efficiency and CO2 removal process were investigated to select the optimum system for effectively upgrade biogas and simultaneously reduce the nutrient content in digestate. The treatment performance displayed that average removal rates of COD, total nitrogen (TN), total phosphorous (TP), and CO2 were 61.58-75.29, 58.39-74.63, 70.09-88.79, and 54.26-73.81 %, respectively. All the strains grew well under any the dilution treatments. With increased initial nutrient concentration to a certain range, the CO4 content (v/v) of raw biogas increased. Differences in the biogas enrichment of S. obliquus (FACHB-31) in all treatments mainly resulted from variations in biomass productivity and CO2 uptake. Notably, the diluted digestate sample of 1600 mg L(-1) COD provided an optimal nutrient concentration for S. obliquus (FACHB-31) cultivation, where the advantageous nutrient and CO2 removals, as well as the highest productivities of biomass and biogas upgrading, were revealed. Results showed that microalgal biomass production offered real opportunities to address issues such as CO2 sequestration, wastewater treatment, and biogas production.

Enhancement of nutrient removal from swine wastewater digestate coupled to biogas purification by microalgae Scenedesmus spp.

“…Concomitantly, CO 2 and other undesirable compounds present in the biogas, such as the toxic and corrosive H 2 S, could be removed (Bahr et al, 2014), ultimately adding value to filtered biomethane. Xu et al (2015) demonstrated the effects of desulphurized biogas on increased nutrient removal by axenic culture of microalgae Scenedesmus obliquus. Nonetheless, considering that H 2 S present in the biogas (up to 5000 ppm; Kao et al, 2012a) could exert some inhibitory effects on microalgae, further studies using raw biogas is warrant to anticipate field scale performance.…”

Microalgal cultivation with waste streams and metabolic constraints to triacylglycerides accumulation for biofuel production

“…employed swine waste‐water‐derived biogas to growth native microalgal strains and found that CO 2 was completely removed from raw biogas at 219.4 ± 4.8 mg L −1 d −1 , with a biomass yield of 1.1 ± 0.2 g L −1 and growth rate of 141.8 ± 3.5 mg L −1 d −1 . Similar studies also demonstrated that microalgal‐based waste‐water treatment processes could benefit from in situ CO 2 ‐rich biogas . However, the photosynthetic production of oxygen could potentially lead to the explosion of the gas mixture and would therefore necessitate oxygen separation .…”

The interactions of an algae–fungi symbiotic system influence nutrient removal from synthetic wastewater

“…Similar to the conventional activated sludge process, algal systems have traditionally been employed for wastewater treatment, relying on their ability to assimilate nutrients such as nitrogen and phosphorus from the wastewater and use them for their growth. [1][2][3][4] A previous study showed that a combination of algae with activated sewage obtained good nutrient removal rates and promoted algal growth. 5 This suggests that microbes from activated sewage promote nutrient removal and benefit algal growth.…”